Browsing by Author "Onal, Cem"

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Bone Only Oligometastatic Renal Cell Carcinoma Patients Treated with Stereotactic Body Radiotherapy: A Multi Institutional Study
(2022) Onal, Cem; Guler, Ozan Cem; Hurmuz, Pervin; Yavas, Guler; Tilki, Burak; Oymak, Ezgi; Yavas, Cagdas; Ozyigit, Gokhan; 0000-0002-2742-9021; 35695908; D-5195-2014
Purpose This study aimed to analyze the prognostic factors associated with overall survival (OS) and progression-free survival (PFS) in patients with bone-only metastatic renal cell carcinoma (RCC) who have five or fewer lesions treated with stereotactic body radiotherapy (SBRT). Methods The clinical data of 54 patients with 70 bone metastases undergoing SBRT treated between 2013 and 2020 with a dose of at least 5 Gy per fraction and a biologically effective dose (BED) of at least 90 Gy were retrospectively evaluated. Results The majority of lesions were located in the spine (57.4%) and had only one metastasis (64.8%). After a median follow-up of 22.4 months, the 1- and 2-year OS rates were 84.6% and 67.3%, respectively, and median OS was 43.1 months. The 1- and 2-year PFS rates and median PFS were 63.0%, 38.9%, and 15.3 months, respectively. In SBRT-treated lesions, the 1-year local control (LC) rate was 94.9%. Age, metastasis localization, and number of fractions of SBRT were significant prognostic factors for OS in univariate analysis. In multivariate analysis, patients with spinal metastasis had better OS compared to their counterparts, and patients who received single-fraction SBRT had better PFS than those who did not. No patient experienced acute or late toxicities of grade 3 or greater. Conclusion Despite excellent LC at the oligometastatic site treated with SBRT, disease progression was observed in nearly half of patients 13 months after metastasis-directed local therapy, particularly as distant disease progression other than the treated lesion, necessitating an effective systemic treatment to improve treatment outcomes.
Cardiac angiosarcoma treated with 1.5 Tesla MR-guided adaptive stereotactic body radiotherapy-Case report and review of the literature
(2022) Noyan, Asli; Yavas, Guler; Arslan, Gungor; Yavas, Cagdas; Onal, Cem; 0000-0002-2742-9021; 36027835; D-5195-2014
Introduction: Cardiac angiosarcoma is a very rare disease. As a result of their nonspecific presentation symptoms, and the lack of consensus in treatment, caution should be taken in both diagnosis and treatment. The role of radiotherapy (RT) is debatable due to the continuous movement of the heart, which makes it difficult to safely deliver high radiation doses to the target volume.Presentation of case: The case of a 16-year-old boy with cardiac angiosarcoma that recurred one year after surgery and was treated with chemotherapy is presented. The patient received high field 1.5-Tesla (magnetic resonance) MR-Linac treatment in 5 fractions with a dosage of 25 Gy to the tumor bed and 30 Gy to the recurrent nodules using the simultaneous integrated boost technique. The patient tolerated the treatment well and had stable disease two months later. Discussion: MR-guided radiotherapy, particularly in the case of cardiac malignancies, allows for direct tumor visualization with high soft tissue image resolution capacity. Furthermore, modern RT techniques allow for the full therapeutic window to be used by achieving superior dose distributions, allowing for dose escalation stra-tegies with tolerable toxicity rates.Conclusion: Magnetic resonance guided RT allows direct visualization of the target during treatment delivery, allowing for higher-dose administration with less damage to healthy tissue near the tumor. This treatment strategy is a viable option in selected patients with cardiac angiosarcoma.
Clinical characteristics of relapsed ovarian cancer patients with striking response to the bevacizumab at first relapse
(2020) Kose, Fatih; Alemdaroglu, Songul; Mertsoylu, Huseyin; Besen, Ali Ayberk; Guler, Ozan Cem; Simsek, Seda Yuksel; Erbay, Gurcan; Onal, Cem; Celik, Husnu; 0000-0002-2742-9021; 0000-0003-4335-6659; 0000-0001-6908-3412; 0000-0002-0156-5973; 0000-0002-7862-0192; 0000-0002-1932-9784; D-5195-2014; AAI-8400-2021; AAC-5654-2020; G-4827-2016; AAD-6910-2021; M-9530-2014
Background: Ovarian cancer is fifth leading cause of the cancer related death in women. Platin based doublet regimen plus bevacizumab is standard treatment in relapse. The primary aim of this study is to define clinicopathological characteristics of the relapsed ovarian cancer who derived unexpectedly long benefit from bevacizumab treatment. Methods: Total number of 106 patients with relapsed ovarian cancer and treated with bevacizumab (bevacizumab is not reimbursed as a part of adjuvant treatment in Turkey) on their first relapse were included. For the purpose of the study, the patients were placed into two groups, Group A and B, selected on the basis of the rate of PFS 1 (time between first day of adjuvant chemotherapy and first radiological progression) to PFS 2 (time between first day of second line treatment and second radiological progression). The patients included into Group A if PFS 1 greater than PFS 2 and Group B vice versa. Results: Group A and B were consisted of 67 (63%) and 39 (37%) patients. At a median follow-up of 32.1 months (5.3-110.8), 56 (52.8%) patients were died. Significant number of patients (78.4%) treated with primary surgery without neoadjuvant treatment and 59 (57.8%) out of the 102 patients had debulking surgery when their cancer relapsed. PFS 1 and 2 were estimated as 16.5 mo (14.1-18.9) vs. 13.7 mo (9.9-17.5) and 13.4 mo (8.0-18.6) vs. 29.7 mo (21.5-38.0) in group A and B, respectively (p < 0.001 and p < 0.001). Only parameter that show significant difference between groups was the rate of platin resistant patients; Group A: 13 (19.4%) out of 67 patients vs. Group B: 15 (38.6%) out of 39 patients with ap value of 0.041. Binary logistic regression indicates PFS1 is significant inverse predictor (shorter PFS-1 means greater chance of being in group B) of entering Group B [Chi-Square = 16.5, df = 6 and p = 0.011 (< 0.05)]. PFS1 is significant at the 5% level [ PFS1 wald = 4.33,p = 0.038 (p < 0.05)]. In multivariate analysis, cox-regression proportional hazard, cytoreductive surgery at second relapse (yes or no) (p: 0.028; HR: 0.3, 0.02-0.7, 95% CI) showed significant effect on PFS-2. On the other hand, platin resistance (< 6 mos; yes or no) (p: 0.04; HR: 4.0, 1.1-14.4, 95% CI) and secondary surgery outcome (no visible vs. visible) (p: 0.003; HR: 0.2, 0.07-0.58, 95% CI) showed significant effect on OS. Bevacizumab related adverse effects with greater than grad 3 detected in 13 (15%) and 10 (25%) in group A and B (p: 0.77). Conclusions: Our findings indicate that bevacizumab produced strikingly high PFS (over 24 months) in significant portion of relapsed ovarian cancer patients whom were mostly platin resistant cases with short PFS-1. This gain specifically achieved in patients who had aggressive secondary surgery with no-visible surgical outcome.
Clinical parameters and nomograms for predicting lymph node metastasis detected with Ga-68-PSMA-PET/CT in prostate cancer patients candidate to definitive radiotherapy
(2021) Onal, Cem; Ozyigit, Gokhan; Oymak, Ezgi; Guler, Ozan Cem; Hurmuz, Pervin; Tilki, Burak; Reyhan, Mehmet; Tuncel, Murat; Akyol, Fadil; 0000-0002-2742-9021; 33949694; D-5195-2014
Background Defining the extent of disease spread with imaging modalities is crucial for therapeutic decision-making and definition of treatment. This study aimed to investigate whether clinical parameters and nomograms predict prostate-specific membrane antigen (PSMA)-positive lymph nodes in treatment-naive nonmetastatic prostate cancer (PC) patients. Materials and Methods The clinical data of 443 PC patients (83.3% high-risk and 16.7% intermediate-risk) were retrospectively analyzed. Receiver operating characteristic (ROC) curves with areas under the curve (AUC) were generated to evaluate the accuracy of clinical parameters (prostate-specific antigen [PSA], T stage, Gleason score [GS], International Society of Urological Pathology [ISUP] grade) and nomograms (Roach formula [RF], Yale formula [YF], and a new formula [NF]) in predicting lymph node metastasis. The AUCs of the various parameters and clinical nomograms were compared using ROC and precision-recall (PR) curves. Results A total of 288 lymph node metastases were identified in 121 patients (27.3%) using Ga-68-PSMA-11-positron emission tomography (PET)/computed tomography (CT). Most PSMA-avid lymph node metastases occurred in external or internal iliac lymph nodes (142; 49.3%). Clinical T stage, PSA, GS, and ISUP grade were significantly associated with PSMA-positive lymph nodes according to univariate logistic regression analysis. The PSMA-positive lymph nodes were more frequently detected in patients with PSA >20 ng/ml, GS >= 7 or high risk disease compared to their counterparts. The clinical T stage, serum PSA level, GS, and ISUP grade showed similar accuracy in predicting PSMA-positive metastasis, with AUC values ranging from 0.675 to 0.704. The median risks for PSMA-positive lymph nodes according to the RF, YF, and NF were 31.3% (range: 12.3%-100%), 22.3% (range: 4.7%-100%), and 40.5% (range: 12.3%-100%), respectively. The AUC values generated from ROC and PR curve analyses were similar for all clinical nomograms, although the RF and YF had higher accuracy compared to NF. Conclusion The clinical T stage, PSA, GS, and ISUP grade are independent predictors of PSMA-positive lymph nodes. The RF and YF can be used to identify patients who can benefit from Ga-68-PSMA-11 PET/CT for the detection of lymph node metastasis. Together with nomograms, Ga-68-PSMA-11 PET/CT images help to localize PSMA-positive lymph node metastases and can thus assist in surgery and radiotherapy planning.
Comment on Hunt et al, "Feasibility of magnetic resonance guided radiotherapy for the treatment of bladder cancer"
(2021) Yavas, Guler; Yavas, Cagdas; Arslan, Gungor; Onal, Cem; 33912694
Comment on: Role of 68-Ga-PSMA-PET/CT in pelvic radiotherapy field definitions for lymph node coverage in prostate cancer patients, by Onal C et al response
(2021) Onal, Cem; 0000-0002-2742-9021; 32980383; D-5195-2014
The Comparision of Breast Cancer in the Young and Elderly Patients
(2019) Petek Erpolat, Ozge; Yuce Sari, Sezin; Ergen, Sefika Arzu; Aydin, Barbaros; Akkus, Berna; Gultekin, Melis; Copan Oksuz, Didem; Arican, Zumre; Onal, Cem; Gursel, Bilge; Akmansu, Muge; Ozyigit, Gokhan; Bilkay Gorken, Ilknur; Yildiz, Ferah
OBJECTIVE To compare the tumor characteristics, treatment approaches, recurrence patterns and survival results rates of young and elderly patients with breast cancer. METHODS In this study, Between between 2000-2013, a total of 779 patients were treated for breast cancer at nine radiation oncology departments were evaluated retrospectively. Three-hundred eight four of these patients were young (<= 35 years), and 395 of those the patients were elderly (>= 70 years). RESULTS Young patients were more likely to present with aggressive tumor features. They were more often received comprehensive lymphatic irradiation, tumor bed boost and intense chemotherapy. No difference was found for 5 and 10-year loco-regional recurrence- free survival rates were (96% and 93% for young, 97% and 97% for elderly). The 5 and 10-year distant recurrence- free survival rates were lower in the young patients (77% and 67% for young, 85% and 85% for elderly, p<0.0001). No difference was found in 5 and 10-year breast cancer- specific survival (91% and 79% for young, 92% and 87% for elderly). The 5 and 10-year overall survival rates were higher in the young patients (92% and 78% for young, 78% and 63% for elderly, p<0.0001). CONCLUSION The reason for the similarity between the age groups in terms ofregarding loco-regional recurrence- free survival can be more comprehensive lymphatic irradiation and tumor bed boost, the young patients received. The distant recurrence- free survival rates rates were significantly lower in the young patients even though they received more intensive chemotherapy. Future studies aimed at more effective systemic regimens to decrease distant recurrence in young patients are warranted.
Comparison of Helical and TomoDirect Techniques with Simultaneous Integrated Boost in Early Breast Cancer Patients
(REPORTS OF PRACTICAL ONCOLOGY AND RADIOTHERAPY, 2023) Onal, Cem; Bozca, Recep; Oymak, Ezgi; Guler, Ozan Cem
Background: The aim of the study was to perform dosimetric comparisons of helical (H) and TomoDirect (TD) plans for whole-breast irradiation (WBI) with simultaneous integrated boost (SIB) in early-stage breast cancer patients undergoing breast conserving surgery.Materials and methods: Fifty patients, 25 with left-side and 25 with right-side tumors, were determined for a treatment planning system for a total dose of 50.4Gy in 1.8Gy per fraction to WBI, with a SIB of 2.3Gy per fraction delivered to the tumor bed. The planning target volume (PTV) doses and the conformity (CI) and homogeneity indices (HI) for PTV(breast )and PTVboost, as well as organ-at-risk (OAR) doses and treatment times, were compared between the H and TD plans.Results: All plans met the PTV coverage criteria for the H plan, except for mean V107 of PTVbreast for TD plan. The H plan yielded better homogeneity and conformity of dose distribution compared to the TD plan. The ipsilateral mean lung doses were not significantly different between the two plans. The TD plans is advantageous for mean doses to the heart, contralateral breast and lung, spinal cord, and esophagus than the H plans. In both the H and TD plans, the right-sided breast patients had lower heart dose parameters than the left-sided breast patients. The TD plan is superior to the H plan in sparing the contralateral breast and lung by decreasing low-dose volumes.Conclusions: While the OAR dose advantages of TD are appealing, shorter treatment times or improved dose homogeneity and conformity for target volume may be advantageous for H plan.
Correlation of Clinical Risk Factors with Diffusion-Weighted Magnetic Resonance Images in Prostate Cancer Patients Treated with Definitive Radiotherapy
(2015) Erbay, Gurcan; Onal, Cem; Guler, Ozan C.; Karadeli, Elif; Koc, Zafer
This study is aimed to correlate apparent diffusion coefficient (ADC) values and clinical T-stage, serum PSA, pathology Gleason scores. We also further analyzed whether ADC values could be used to appropriately define the risk groups. 135 biopsy-proven, radiotherapy-(RT)-treated, prostate cancer patients who underwent pre-RT DW-MRI and standard T2W pelvic MRI were included. ADC and normalized ADC (nADC) values were calculated from DW-MRI delivered a median 8.1 weeks after prostate biopsy. ADC values were correlated with clinical risk factor values by using Pearson correlation test. ADCs in low-, intermediate-, and high-risk patients were 0.873 +/- 0.122X10(-3) mm(2)/s, 0.763 +/- 0.124X10(-3) mm(2)/s, and 0.701 +/- 0.132X10(-3) mm(2)/s (p = 0.001), respectively. Patients with preRT PSA <10 ng/mL had significantly higher ADCs than patients with preRT PSA 10-20 ng/mL (p = 0.02) or >20 ng/mL (p < 0.001). Mean ADC for patients with Gleason score <7 was significantly higher than patients scoring 7 (p = 0.001) or >7 (p < 0.001). Clinical stage
Daily Workflow and Workload of Radiation Oncology Specialists in Turkey
(2015) Akman, Fadime; Kamer, Serra; Onal, Cem; Agaoglu, Fulya; Guney, Yildiz; Hicsonmez, Ayse; Koc, Mehmet; Colpan Oksuz, Didem; Ozyigit, Gokhan; Ozkok, Serdar; 0000-0002-2742-9021; D-5195-2014
OBJECTIVES This study aimed to research the effort required by patient evaluation, radiotherapy planning and treatment processes in the daily applications of radiation oncology in terms of time, and to use this effort as the primary source for human power and infrastructure planning required in radiotherapy. METHODS The surveys carried out by Turkish Radiation Oncology Association Proficiency Board, Curriculum Preparation and Evaluation Commission on Education Institutions, Surveys delivered to the officers of the center via electronic mail, were answered and evaluated in accordance with the data of 2012. RESULTS 26 University and 8 Ministry of Health Hospitals participated in the study. The total number of specialists employed in the participant centers, were 227. For per specialist, 383 hours in a year were spent for the patients at follow-up, 334 hours were spent for the patients that were in treatment, and 950 hours were spent for planning and treatment set-ups. It was determined that the time spent for per patient in intensity modulated radiotherapy technique, was 2-3 times more when compared to the location of tumor, which is a conformal technique. It was observed that this duration was much longer in special radiotherapy applications such as brachytherapy, total body irradiation and radiosurgery. CONCLUSION Technological advancements in radiotherapy, require more effort and working time for new job descriptions and in daily practice.
Definitive Brachytherapy in Inoperable Endometrial Cancer
(2019) Onal, Cem
In elderly patients with medical comorbidities that increase perioperative risks, surgery cannot be performed, and definitive radiotherapy (RT) is a therapeutic option. Although staging for endometrial cancer is based on surgical findings, clinical and radiological imaging has not been standardized yet. For a radiological evaluation of inoperable endometrial cancer, magnetic resonance imaging (MRI) is preferred for local tumor infiltration, and positron emission tomography is accepted as the most accurate modality for assessing lymph node and distant metastases. External RT alone is inadequate, and intracavitary brachytherapy with or without external RT is recommended depending on the disease stage in patients with inoperable endometrial cancer. However, there is currently no standard treatment approach for patients with inoperable endometrial cancer. For patients with inoperable endometrial cancer treated with definitive RT, there are some problems including the RT technique, treatment volumes, and systemic treatment. Based on clinical practice, image-based brachytherapy using computed tomography and magnetic resonance imaging is highly recommended.
Definitive Chemoradiation Therapy Following Surgical Resection or Radiosurgery Plus Whole-Brain Radiation Therapy in Non-Small Cell Lung Cancer Patients With Synchronous Solitary Brain Metastasis: A Curative Approach
(2014) Parlak, Cem; Mertsoylu, Huseyin; Guler, Ozan Cem; Onal, Cem; Topkan, Erkan; https://orcid.org/0000-0001-6170-0383; https://orcid.org/0000-0002-1932-9784; https://orcid.org/0000-0001-6908-3412; https://orcid.org/0000-0002-2742-9021; https://orcid.org/0000-0001-8120-7123; 24495594; B-3671-2014; M-9530-2014; AAC-5654-2020; HOC-5611-2023; AAG-2213-2021
Purpose/Objectives: The aim of this study was to evaluate the impact of definitive thoracic chemoradiation therapy following surgery or stereotactic radiosurgery (SRS) and whole-brain radiation therapy (WBRT) on the outcomes of patients with non-small cell lung cancer (NSCLC) with synchronous solitary brain metastasis (SSBM). Methods and Materials: A total of 63 NSCLC patients with SSBM were retrospectively evaluated. Patients were staged using positron emission tomography-computed tomography in addition to conventional staging tools. Thoracic radiation therapy (TRT) with a total dose of 66 Gy in 2 Gy fractions was delivered along with 2 cycles of cisplatin-based chemotherapy following either surgery plus 30 Gy of WBRT (n = 33) or SRS plus 30 Gy of WBRT (n = 30) for BM. Results: Overall, the treatment was well tolerated. All patients received planned TRT, and 57 patients (90.5%) were also able to receive 2 cycles of chemotherapy. At a median follow-up of 25.3 months (7.1-52.1 months), the median months of overall, locoregional progression-free, neurological progression-free, and progression-free survival were 28.6, 17.7, 26.4, and 14.6, respectively. Both univariate and multivariate analyses revealed that patients with a T1-T2 thoracic disease burden (P = .001), a nodal stage of N0-N1 (P = .003), and no weight loss (P = .008) exhibited superior survival. Conclusions: In the present series, surgical and radiosurgical treatments directed toward SSBM in NSCLC patients were equally effective. The similarities between the present survival outcomes and those reported in other studies for locally advanced NSCLC patients indicate the potentially curative role of definitive chemoradiation therapy for highly selected patients with SSBM. (C) 2014 Elsevier Inc.
Definitive Chemoradiotherapy in Elderly Cervical Cancer Patients: A Multiinstitutional Analysis
(2017) Guler, Ozan Cem; Sari, Sezin Yuce; Birgi, Sumerya Duru; Gultekin, Melis; Yildiz, Ferah; Onal, Cem; https://orcid.org/0000-0002-2742-9021; 28604459; D-5195-2014
Objective The aim of the study was to investigate the prognostic factors for survival and treatment-related toxicities in older (65 years) cervical cancer patients treated with definitive chemoradiotherapy. In addition, we sought to compare the outcomes between the older elderly (75 years) and their younger old counterparts (age, 65-74 years). Materials and Methods We retrospectively reviewed medical records from 269 biopsy-proven nonmetastatic cervical cancer patients treated with external radiotherapy and intracavitary brachytherapy at the departments of radiation oncology in 2 different universities. The prognostic factors for survival, local control, and distant metastasis (DM) were analyzed. Results The median follow-up time was 38.8 months (range, 1.5-175.5 months) for the entire cohort and 70.0 months (range, 6.1-175.7 months) for survivors. The 2- and 5-year overall survival (OS), disease-free survival (DFS), and cause-specific survival rates were 66% and 42%, 63% and 39%, and 72% and 55%, respectively. Patients 75 years or older showed significantly worse OS compared with patients aged 65 to 74 years but showed no significant difference in DFS. The 2- and 5-year local control rates were 86% and 71%, respectively. The incidences of DMs at 2 and 5 years were 22% and 30%, respectively. In multivariate analysis, vaginal infiltration and lymph node metastasis were predictive of OS, DFS, local recurrence, and DM. Concomitant chemotherapy was predictive of OS, DFS, and local recurrence, and larger tumor (>4 cm) was a significant prognostic factor for local recurrence. None of the patients had toxicity that necessitated the discontinuation of radiotherapy. All patients were evaluable for acute toxicity, and no grade higher than 3 adverse events occurred during external beam radiation therapy or brachytherapy. Conclusions Although age limited the delivery of aggressive treatment, concurrent chemoradiotherapy in elderly patients associated with improved outcomes similar as in younger counterparts without increasing serious acute and late toxicities.
Dosimetric Analysis of Testicular Doses in Prostate Intensity-Modulated and Volumetric-Modulated Arc Radiation Therapy at Different Energy Levels
(2016) Onal, Cem; ArsIan, Gungor; Dolek, Yemliha; Efe, Esma; 0000-0002-2742-9021; 27623736; D-5195-2014
The aim of this study is to evaluate the incidental testicular doses during prostate radiation therapy with intensity-modulated radiotherapy (IMRT) and volumetric-modulated arc radiotherapy (VMAT) at different energies. Dosimetric data of 15 patients with intermediate-risk prostate cancer who were treated with radiotherapy were analyzed. The prescribed dose was 78 Gy in 39 fractions. Dosimetric analysis compared testicular doses generated by 7-field intensity-modulated radiotherapy and volumetric modulated arc radiotherapy with a single arc at 6, 10, and 15 MV energy levels. Testicular doses calculated from the treatment planning system and doses measured from the detectors were analyzed. Mean testicular doses from the intensity-modulated radiotherapy and volumetric-modulated arc radiotherapy per fraction calculated in the treatment planning system were 16.3 +/- 10.3 cGy vs 21.5 +/- 11.2 cGy (p = 0.03) at 6 MV, 13.4 +/- 10.4 cGy vs 17.8 +/- 10.7 cGy (p = 0.04) at 10 MV, and 10.6 +/- 8.5 cGy vs 14.5 +/- 8.6 cGy (p = 0.03) at 15 MV, respectively. Mean scattered testicular doses in the phantom measurements were 99.5 +/- 17.2 cGy, 118.7 +/- 16.4 cGy, and 193.9 +/- 14.5 cGy at 6, 10, and 15 MV, respectively, in the intensity-modulated radiotherapy plans. In the volumetric-modulated arc radiotherapy plans, corresponding testicular doses per course were 90.4 +/- 16.3 cGy, 103.6 +/- 16.4 cGy, and 139.3 +/- 14.6 cGy at 6, 10, and 15 MV, respectively. In conclusions, this study was the first to measure the incidental testicular doses by intensity-modulated radiotherapy and volumetric-modulated arc radiotherapy plans at different energy levels during prostate-only irradiation. Higher photon energy and volumetric-modulated arc radiotherapy plans resulted in higher incidental testicular doses compared with lower photon energy and intensity-modulated radiotherapy plans. (C) 2016 American Association of Medical Dosimetrists.
Dosimetric Comparison of Sequential Versus Simultaneous-integrated Boost in Early-stage Breast Cancer Patients Treated With Breast-conserving Surgery
(2019) Onal, Cem; Efe, Esma; Guler, Ozan C.; Yildirim, Berna A.; 0000-0001-6908-3412; 31662554; AAC-5654-2020
Background/Aim: To compare simultaneous-integrated boost (SIB) versus sequential-boost (SB) delivered in the context of whole-breast irradiation (WBI) via volumetric-modulated arc therapy (VMAT) and helical-tomotherapy (HT). Materials and Methods: Planning target-volume (PTV) dosimetric parameters and organs at risk (OAR) were analyzed for SB plan (50 Gy plus 16 Gy boost) and SIB plan (50.4 Gy WBI and 64.4 Gy tumor bed boost) in VMAT and HT techniques. Results: Conformity and homogeneity for target-volume doses were better in HT plans compared to VMAT plans. There were no significant differences in ipsilateral lung doses between VMAT and HT plans for SB/SIB techniques, except for a significantly higher lung V5 value with VMAT-SB, and lung V13 value with HT-SIB technique. HT provided a statistically significant decrease in contralateral lung mean V5. Conclusion: The SIB technique showed better target-volume dose distribution in both HT and VMAT plans, and better sparing heart in HT compared to the SB technique.
Dosimetric comparison of vaginal vault brachytherapy vs applicator-guided stereotactic body radiotherapy with volumetric modulated arc therapy and helical tomotherapy for endometrium cancer patients
(2019) Yildirim, Berna Akkus; Dolek, Yemliha; Guler, Ozan Cem; Arslan, Gungor; Onal, Cem; 0000-0001-6908-3412; 0000-0001-6661-4185; 0000-0002-2742-9021; 30551844; AAC-5654-2020; D-5195-2014
We performed this dosimetric study to compare a nonstandard volumetric modulated arc therapy (VMAT) and helical tomotherapy (HT) techniques with high-dose rate (HDR) brachytherapy (BRT) plan of vaginal vault in patients with postoperative endometrial cancer (EC). Twelve postoperative patients with early stage EC were included in this study. Three plans were performed for each patient; dosimetric and radiobiological comparisons were made using dose-volume histograms and equivalent dose for determining the planning target volume (PTV) coverages in brachytherapy and external beam radiotherapy, and organs-at-risk (OARs) doses between three different delivery techniques. All the plans achieved adequate dose coverage for PTV; however, the VMAT plan yielded better dose conformity, and the HT plan showed better homogeneity for target volume. With respect to the OARs, the bladder D-2cc was significantly lower in the BRT plan than in the VMAT and HT plans, with the highest bladder D-2cc value being observed in the HT plan. However, no difference was observed in the rectum D-2cc of the three plans. Other major advantages of the BRT plan over the VMAT and HT plans were the relatively lower body integral doses and femoral head doses as well as the fact that the integral doses were significantly lower in the BRT plan than in the VMAT and HT plans. This is the first dosimetric comparison of vaginal vault treatment for EC with BRT, VMAT, and HT plans. Our analyses showed the feasibility of stereotactic body radiotherapy technique as an alternative to HDR-BRT for postoperative management of EC patients. (C) 2018 American Association of Medical Dosimetrists. Published by Elsevier Inc. All rights reserved.
Effect of Adjuvant Extended Temozolamide Treatment in Survival of Patients with Glioblastoma Multiforme
(2018) Yildirim, Berna Akkus; Sumbul, Ahmet Taner; Topkan, Erkan; Ozdemir, Yurday; Besen, Ali Ayberk; Guler, Ozan Cem; Sedef, Ali Murat; Onal, Cem; https://orcid.org/0000-0001-6661-4185; https://orcid.org/0000-0002-5573-906X; https://orcid.org/0000-0001-8120-7123; https://orcid.org/0000-0002-2218-2074; https://orcid.org/0000-0002-7862-0192; V-5717-2017; D-4793-2014; AAG-2213-2021; AAG-5629-2021; AAD-6910-2021; HOC-5611-2023
Purpose: The aim of this retrospective cohort study was to evaluate the prognostic effect extended temozolamide on survival outcomes of glioblastoma multiforme patients who were underwent surgery/biopsy followed treated with definitive chemo-radiotherapy. Materials and Methods: We retrospectively analyzed the datas of 225 patients with gliablastoma multiforme whom admitted to our clinic All patients were completed concomitant chemoradiotherapy with temozolamide and adjuvant temozolamide therapy at least for six months or more. Patients were divided into two groups as standart and extended temozolamid therapy group as using temozolamide therapy for at least 6 months or more. Results: The median follow-up of the whole patients18 (range 2-125) months, 65 patients (56%) were alive. Extended temozolamide (>6) was associated with longer survival, but was not significantly with survival outcomes in the univariate analysis (49.0 vs 68.33 months; p=0.082). However, progression free survival analysis demonstrated that the patient in extended temozolamide group had paramount extended progression free survival (14 vs 9 months) than other group in standart cycle temozolamide. Conclusion: Our study show that extended temozolamide is good tolerated and leads to a significantly increase in progression free survival and overall survival in newly diagnosed patients with glioblastoma multiforme.
The effect of androgen deprivation therapy on Ga-68-PSMA tracer uptake in non-metastatic prostate cancer patients
(2020) Onal, Cem; Guler, Ozan Cem; Torun, Nese; Reyhan, Mehmet; Yapar, Ali Fuat; 0000-0002-5597-676X; 0000-0001-8550-3368; 0000-0003-1715-4180; 0000-0001-6908-3412; 0000-0002-2742-9021; 31732768; AAE-2718-2021; AAJ-5242-2021; AAI-8973-2021; AAC-5654-2020; D-5195-2014
Purpose To evaluate the effect of neoadjuvant androgen deprivation treatment (ADT) on prostate-specific membrane antigen (PSMA) tracer uptake demonstrated in Ga-68-PSMA-positron emission tomography (PET/CT) in non-metastatic hormone-naive prostate cancer (PC) patients. Materials and methods The clinical data of 108 PC patients who received neoadjuvant ADT were retrospectively analyzed. All patients had a baseline Ga-68-PSMA-PET/CT scan, and a second scan was delivered median of 2.9 months after the initiation of ADT. The maximum standardized uptake value (SUVmax) of primary tumor (SUVp) and metastatic lymph nodes (SUVln) as well as PSA response were assessed between pre- and post-ADT Ga-68-PSMA-PET/CT scans. Results There were significant decreases in posttreatment serum PSA, SUVp, and SUVln. A decrease in SUVp was seen in 91 patients (84%) with a median value of 66% (range, 5-100%), while 17 patients (16%) had no change in or an increase in PSMA tracer uptake with a median value of 24% (range, 0-198%). Patients with Gleason score (GS) of 7 had significantly higher metabolic response rates compared to other patients. The disease progression was significantly higher only in patients with GS > 7 disease compared to GS 7 disease. The PSA response to ADT was the lowest in patients with ISUP high-grade tumors. A total of 16 patients (15%) had progressive disease, and in 9 patients (8%), radiotherapy decisions were modified according to posttreatment Ga-68-PSMA-PET/CT scans. Conclusions The current study includes the largest number of patients analyzed to date and demonstrates that ADT causes a significant decrease in serum PSA values and SUVp and SUVln. The authors demonstrate that Ga-68-PSMA-PET/CT may be used as a quantitative imaging modality after neoadjuvant ADT in hormone-naive non-metastatic PC patients.
Effects of bladder distension on dose distribution of vaginal vault brachytherapy in patients with endometrial cancer
(2014) Guler, Ozan C.; Onal, Cem; Acibuci, Ibrahim; 25834581
Purpose: To investigate dosimetric effects of bladder distention on organs at risk (OARs) during treatment of endometrial cancer using 3D image-based planning of postoperative vaginal vault brachytherapy (BRT). Material and methods: Fifteen patients with early-stage endometrial cancer were studied, each undergoing adjuvant BRT of vaginal vault via 3.5 cm diameter cylinder. As treatment, 25 Gy in 5 fractions were delivered to 5 mm depth of the vaginal mucosa. Dose-volume histograms of OARs were generated individually with bladder empty and with bladder inflated by sterile saline (180 ml), to compare doses received. Results: Bladder distention appreciably impacted dosimetry of bladder, sigmoid colon, and small bowel, but dosimetry of rectum was unaffected. With bladder inflated, mean cylinder-to-bowel distance increased significantly (1.69 cm vs. 1.20 cm; p = 0.006). Mean minimum dose to most exposed 2 cc (D-2cc) volume also rose significantly at bladder (5.40 Gy vs. 4.55 Gy [18.7%]; p < 0.001), as opposed to near-significant reductions in D-2cc at sigmoid colon (15.1%; p = 0.11) and at small bowel (10.5%; p = 0.14). A full bladder had no effect on dose to 50% volume (D-50%) of bladder or rectum, and declines seen in mean D-50% values of sigmoid colon (22.7%; p = 0.12) and small bowel (19.0%; p = 0.13) again fell short of statistical significance. Conclusions: The combination of a full bladder and an empty rectum may cause significant unwanted increases in BRT dosing of bladder, without significantly impacting sigmoid colon and small bowel exposures. These findings should be validated through further clinical studies.
Effects of Setup Errors on Dose Distribution for Tangential Wedge Field and Field-in-Field Techniques During Breast Irradiation
(2014) Sonmez, Aydan; Onal, Cem; Sonmez, Serhat; Arslan, Gungor; Parlak, Cem; Topkan, Erkan; Yavuz, Melek
This study is aimed to evaluate the effects of setup errors on dose distribution for target volume and healthy tissue within the irradiated volume and also critical surrounding organs for breast radiotherapy (RT) using both the tangential field and the field-in-field (FIF) technique. Ten patients with breast cancer were enrolled. For each patients two plans were generated; tangential field plan and FIF-plan. The setup errors were simulated for a series of displacements of +/- 5 mm and +/- 10 mm in superior-inferior (x-axis), medial-lateral (y-axis), and anterior-posterior (z-axis) directions and dose volume comparisons were made both between and within groups. The most prominent changes were observed in setup errors at z-axis. In wedge plan, 10-mm setup error at the +z axis caused a significant decrease in tumor coverage compared with the plan with no setup error (96.5% vs. 99.2%; p= 0.01). The 5 and 10 mm setup errors at the +z-axis resulted in significantly higher healthy tissue doses in wedge plans compared with FIF plans. The setup errors along z-axis had a significant effect on the dose distribution for target volume and also to the lungs. The setup error in the isocenter should be kept strictly below 5 mm.