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Item There Is No Doubt About The Winner Of The Lion-Rabbit Fight(2022) Onal, Cem; Oymak, Ezgi; Guler, Ozan C.; https://orcid.org/0000-0002-2742-9021; 35652580; D-5195-2014Item Stereotactic body radiotherapy for oligoprogressive lesions in metastatic castration-resistant prostate cancer patients during abiraterone/enzalutamide treatment(2021) Onal, Cem; Kose, Fatih; Ozyigit, Gokhan; Aksoy, Sercan; Oymak, Ezgi; Muallaoglu, Sadik; Guler, Ozan C.; Tilki, Burak; Hurmuz, Pervin; Akyol, Fadil; 0000-0002-2742-9021; 33905131; D-5195-2014Background Metastasis-directed therapy (MDT) utilizing stereotactic body radiotherapy (SBRT) for oligoprogressive lesions could provide a delay in next-line systemic treatment (NEST) change while undergoing androgen receptor-targeted agents (ARTA) treatment. We evaluated prognostic factors for prostate cancer-specific survival (PCSS) and progression-free survival (PFS) to characterize patients receiving treatment with ARTA who may benefit from MDT for oligoprogressive lesions. The impact of MDT on delaying NEST and the predictive factors for NEST-free survival (NEST-FS) were also assessed. Materials and Methods The clinical data of 54 metastatic castration-resistant prostate cancer patients with 126 oligoprogressive lesions receiving abiraterone (1 g/day) or enzalutamide (160 mg/day) before or after systemic chemotherapy were analyzed. A median of three lesions (range: 1-5) were treated with MDT. The primary endpoints were PCSS and PFS. The secondary endpoints were time to switch to NEST and NEST-FS. Results The median follow-up time was 19.1 months. Univariate analysis showed that the number of oligoprogressive lesions treated with SBRT and the time between the start of ARTA treatment and oligoprogression were significant prognostic factors for PCSS, and the timing of ARTA treatment (before or after chemotherapy) and the prostate-specific antigen (PSA) response after MDT were significant prognostic factors for PFS. Multivariate analysis showed that early MDT for oligoprogressive lesions delivered less than 6 months after the beginning of ARTA and higher PSA levels after MDT were significant predictors of worse PCSS and PFS. The median total duration of ARTA treatment was 13.8 months. The median time between the start of ARTA treatment and the start of MDT for oligoprogressive lesions was 5.2 months, and MDT extended the ARTA treatment by 8.6 months on average. Thirty-two (59.3%) patients continued ARTA treatment after MDT. ARTA treatment after chemotherapy, early oligoprogression requiring MDT, and lower radiation doses for MDT were independent predictors of NEST-FS in multivariate analysis. Conclusions MDT for oligoprogressive lesions is effective and may provide several benefits compared to switching from ARTA treatment to NEST. Patients with early progression while on ARTAs and inadequate PSA responses after MDT have a greater risk of rapid disease progression and poor survival, which necessitates intensified treatment.Item Retrospective correlation of (68)ga-psma uptake with clinical parameters in prostate cancer patients undergoing definitive radiotherapy(2020) Onal, Cem; Torun, Nese; Oymak, Ezgi; Guler, Ozan C.; Reyhan, Mehmet; Yapar, Ali F.; 0000-0001-6908-3412; 0000-0001-8550-3368; 0000-0003-1715-4180; 0000-0002-2742-9021; 0000-0002-5597-676X; 32221791; AAC-5654-2020; AAJ-5242-2021; AAI-8973-2021; D-5195-2014; AAE-2718-2021Objective The aim of the study is to investigate the correlation between the intensity of prostate-specific membrane antigen (PSMA) uptake in primary tumor and clinico-pathological characteristics of non-metastatic prostate cancer patients treated with definitive radiotherapy (RT). Methods Using the clinical data of 201 prostate cancer patients who were referred for (68) Ga-PSMA-positron emission tomography (PET/CT) for staging and RT planning, we analyzed the correlations among intermediate- or high-risk disease based on Gleason score (GS), prostate-specific antigen (PSA) level, D'Amico risk group classification, and maximum standardized uptake (SUVmax) of primary tumor. Results Primary tumor was visualized via (68) Ga-PSMA-PET/CT scan in 192 patients (95.5%). The median SUVmax of primary tumor and metastatic lymph node were 13.2 (range 3.3-83.7) and 11.4 (range 3.6-64.5), respectively. A significant moderate correlation was observed between PSA level and median tumor SUVmax as measured by (68) Ga-PSMA-PET/CT (Spearman = 0.425; p < 0.001). Patients with serum PSA > 10 ng/mL, GS > 7, D'Amico high-risk group classification, and pelvic lymph node metastasis had significantly higher tracer uptake in primary tumor than their counterparts. The median SUVmax of primary tumor was highest in patients with GS 9. The primary tumor detection rates of (68) Ga-PSMA-PET/CT were 83%, 92%, and 99% for patients with serum PSA <= 5.0 ng/mL (14 patients, 7%), PSA 5.1-10.0 ng/mL (45 patients, 22%), and PSA > 10 ng/mL (142 patients, 71%), respectively. Conclusions We demonstrated a correlation between prostate tumor characteristics and PSMA tracer uptake. Patients with serum PSA > 10 ng/mL, GS > 7, D'Amico high-risk group classification, and pelvic lymph node metastasis had significantly higher SUV than their counterparts. In addition, the primary tumor detection rate was higher in patients with serum PSA > 10 ng/mL and GS > 7.Item 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-5654-2020Background/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.Item Effects of bladder distension on dose distribution of vaginal vault brachytherapy in patients with endometrial cancer(2014) Guler, Ozan C.; Onal, Cem; Acibuci, Ibrahim; 25834581Purpose: 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.Item 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, ZaferThis 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 stageItem The role of delineation education programs for improving interobserver variability in target volume delineation in gastric cancer(2017) Onal, Cem; Cengiz, Mustafa; Guler, Ozan C.; Dolek, Yemliha; Ozkok, Serdar; 0000-0002-2742-9021; 0000-0001-6908-3412; 28339289; D-5195-2014; AAC-5654-2020Objective: To assess whether delineation courses for radiation oncologists improve interobserver variability in target volume delineation for post-operative gastric cancer radiotherapy planning. Methods: 29 radiation oncologists delineated target volumes in a gastric cancer patient. An experienced radiation oncologist lectured about delineation based on contouring atlas and delineation recommendations. After the course, the radiation oncologists, blinded to the previous delineation, provided delineation for the same patient. Results: The difference between delineated volumes and reference volumes for pre-and post-course clinical target volume (CTV) were 19.8% (-42.4 to 70.6%) and 12.3% (-12.0 to 27.3%) (p = 0.26), respectively. The planning target volume (PTV) differences pre-and post-course according to the reference volume were 20.5% (-40.7 to 93.7%) and 13.1% (-10.6 to 29.5%) (p = 0.30), respectively. The concordance volumes between the pre-and post-course CTVs and PTVs were 467.1 +/- 89.2 vs 597.7 +/- 54.6cm(3) (p < 0.001) and 738.6 +/- 135.1 vs 893.2 +/- 144.6 cm(3) (p < 0.001), respectively. Minimum and maximum observer variations were seen at the cranial part and splenic hilus and at the caudal part of the CTV. The kappa indices compared with the reference contouring at pre- and post-course delineations were 0.68 and 0.82, respectively. Conclusion: The delineation course improved interobserver variability for gastric cancer. However, impact of target volume changes on toxicity and local control should be evaluated for further studies. Advances in knowledge: This study demonstrated that a delineation course based on current recommendations helped physicians delineate smaller and more homogeneous target volumes. Better target volume delineation allows proper target volume irradiation and preventing unnecessary normal tissue irradiation.Item Adjuvant Small Pelvic Radiotherapy in Patients with Cervical Cancer Having Intermediate Risk Factors Only - Is It Sufficient?(2017) Onal, Huseyin Cem; Sari, Sezin Yuce; Guler, Ozan C.; Gultekin, Melis; Yildiz, Ferah; 0000-0002-2742-9021; 28848218; D-5195-2014Background: We sought to determine the outcomes of adjuvant small pelvic external beam radiotherapy (EBRT) and prognostic factors for survival and disease control. Patients and Methods: We retrospectively evaluated 113 cervical cancer patients treated with postoperative median 50.4-Gy small pelvic EBRT. We treated the surgical bed, bilateral parametria, paravaginal soft tissues, upper third of the vagina, and presacral lymphatics. Results: Median follow-up of all patients and survivors was 58 and 67 months, respectively. The 2-and 5-year overall survival (OS) and disease-free survival rates were 91 and 82%, and 85 and 74%, respectively. The locoregional failure rate was 10%. Age was a significant predictor for OS and distant metastasis-free survival (DMFS) on univariate analysis. The number of dissected lymph nodes being < 30 negatively affected the pelvic recurrence-free survival. The only independent predictor on multivariate analysis was older age for DMFS. Although no severe acute toxicity was observed, late grade >= 3 toxicity developed in 8 patients. Conclusion: Small pelvic EBRT produces satisfactory survival and locoregional control with acceptable toxicity, and can be an alternative to whole pelvic EBRT in selected cervical cancer patients. (C) 2017 S. Karger GmbH, FreiburgItem Risk Factors for Fatal Pulmonary Hemorrhage following Concurrent Chemoradiotherapy in Stage 3B/C Squamous-Cell Lung Carcinoma Patients(2018) Topkan, Erkan; Selek, Ugur; Ozdemir, Yurday; Besen, Ali A.; Guler, Ozan C.; Yildirim, Berna A.; Mertsoylu, Huseyin; Findikcioglu, Alper; Ozyikan, Ozgur; Pehlivan, Berrin; 0000-0001-6908-3412; 30515211; AAC-5654-2020We aimed to identify the fatal pulmonary hemorrhage- (FPH-) related risk factors in stage 3B/C squamous-cell lung carcinoma (SqCLC) patients treated with definitive concurrent chemoradiotherapy (C-CRT). Medical records of 505 stage 3B/C SqCLC patients who underwent 66 Gy radiotherapy plus 1-3 cycles of concurrent chemotherapy with available pretreatment thoracic computerized tomography scans were retrospectively analyzed. Primary end-point was the identification of FPH-related risk factors. Examined factors included the basal patient and tumor characteristics with specific emphasis on the tumor cavitation (TC) status, tumor size (TS) and cavitation size (CS), tumor volume and cavitation volume (TV and CV), relative cavitation size (RCS = CS/Ts), and relative cavitation volume (RCV=CV/TV). FPH emerged in 13 (2.6%) patients, with 12 (92.3%) of them being diagnosed <= 12 months of C-CRT. All FPHs were diagnosed in patients with TC (N=60): group-specific FPH incidence: 21.6%. TC (P<0.001) was the unique independent factor associated with higher FPH risk in multivariate analysis. Further analysis limited to TC patients exhibited the RCV>0.14 (37.5% versus 11.1% for RCV <= 0.14; P<0.001), major RCS group (31.0% versus 19.0% for minor versus 0% for minimum RCS; P-0.008), and baseline hemoptysis (26.3% versus 13.6% for no hemoptysis; P-0.009) as the independent risk factors for higher FPH incidence. FPH was an infrequent (2.6%) complication of C-CRT in stage 3B/C SqCLC patients, but its incidence increased to 37.5% in patients presenting with TC and RCV>0.14. Diagnosis of >90% FPHs <= 12 months of C-CRT stresses the importance of close and careful follow-tip of high-risk patients after C-CRT for multidisciplinary discussion of possible invasive preventive measures.