Scopus Kapalı Erişimli Yayınlar

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Author: search.filters.author.Guler, Ozan CemSubject: search.filters.subject.Prostate cancer

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    The prognostic value of mean apparent diffusion coefficient measured with diffusion-weighted magnetic resonance image in patients with prostate cancer treated with definitive radiotherapy
    (2022) Onal, Cem; Erbay, Gurcan; Guler, Ozan Cem; Oymak, Ezgi; 35753556
    Purpose: To assess the correlation between initial tumor apparent diffusion coefficient (ADC) values and clinicopathological parameters in prostate cancer (PCa) patients treated with definitive radiotherapy (RT). Additionally, the prognostic factors for freedom from biochemical failure (FFBF) and progressionfree survival (PFS) in this patient cohort were analyzed. Materials and methods: The clinical data of 503 patients with biopsy-confirmed PCa were evaluated retrospectively. All patients had clearly evident tumors on diffusion-weighted magnetic resonance imaging (DW-MRI) for ADC values. Univariable and multivariable analyses were used to determine prognostic factors for FFBF and PFS. Results: The median follow-up was 72.9 months. The 5-year FFBF and PFS rates were 93.2% and 86.2%, respectively. Significantly lower ADC values were found in patients with a high PSA level; advanced clinical stage; higher ISUP score, and higher risk group than their counterparts. Receiver operating characteristic (ROC) curve analysis revealed an ADC cut-off value of 0.737 x 10-3 mm2/sec for tumor recurrence. Patients who progressed had a lower mean ADC value than those who did not (0.712 +/- 0.158 vs. 1.365 +/- 0. 227 x 10-3 mm2/sec; p < 0.001). There was a significant difference in 5-year FFBF (96.3% vs. 90%; p < 0.001) and PFS rates (83.8% vs. 73.5%; p = 0.002) between patients with higher and lower mean ADC values. The FFBF and PFS were found to be correlated with tumor ADC value and ISUP grades in multivariable analysis. Additionally, older age was found to be a significant predictor of worse PFS. Conclusions: Lower ADC values were found in patients with high-risk characteristics such as a high serum PSA level, stage or grade of tumor, or high-risk disease, implying that ADC values could be used to predict prognosis. Lower ADC values and higher ISUP grades were associated with an increased risk of BF and progression, implying that treatment intensification may be required in these patients. (c) 2022 Elsevier B.V. All rights reserved. Radiotherapy and Oncology 173 (2022) 285-291
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    Stereotactic radiotherapy to oligoprogressive lesions detected with Ga-68-PSMA-PET/CT in castration-resistant prostate cancer patients
    (2021) Onal, Cem; Ozyigit, Gokhan; Oymak, Ezgi; Guler, Ozan Cem; Tilki, Burak; Hurmuz, Pervin; Akyol, Fadil; 0000-0002-2742-9021; 33693965; D-5195-2014
    Purpose We assessed the outcomes of stereotactic body radiotherapy (SBRT) to treat oligoprogressive castration-resistant prostate cancer (CRPC) patients with <= 5 lesions using gallium prostate-specific membrane antigen-positron emission tomography (Ga-68-PSMA-PET/CT). Methods The clinical data of 67 CRPC patients with 133 lesions treated with Ga-68-PSMA-PET/CT-based SBRT were retrospectively analyzed. All of the patients had oligoprogressive disease during androgen-deprivation therapy (ADT). The prognostic factors for overall- (OS) and progression-free survival (PFS) and the predictive factors for switching to next-line systemic treatment (NEST) and NEST-free survival (NEST-FS) were analyzed. Results With a median follow-up of 17.5 months, the 2-year overall survival (OS) and PFS rates were 86.9% and 34.4%, respectively. The PSA response was observed in 49 patients (73.1%). Progression was observed in 37 patients (55.2%) at a median of 11.0 months following SBRT. A total of 45 patients (67.2%) remained on ADT after SBRT, and 22 patients (32.8%) had a NEST change at a median of 16.4 months after metastasis-directed treatment (MDT). Patients with a NEST change had higher post-SBRT PSA values and fewer PSA nadirs after MDT than their counterparts. In multivariate analysis, higher pre-SBRT PSA values were the only significant predictor for worse OS and NEST-FS, and no significant factor was found for PFS. No serious acute or late toxicities were observed. Conclusion This study demonstrated the feasibility of MDT using SBRT to treat oligoprogressive lesions by Ga-68-PSMA-PET/CT in CRPC patients is efficient and well-tolerated, prolonging the effectiveness of ADT by delaying NEST.
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    Incidental testicular doses during volumetric-modulated arc radiotherapy in prostate cancer patients
    (2020) Onal, Cem; Bozca, Recep; Dolek, Yemliha; Guler, Ozan Cem; Arslan, Gungor; 0000-0001-6908-3412; 0000-0002-2742-9021; 32125635; AAC-5654-2020; D-5195-2014
    Purpose To compare the incidental testicular doses during volumetric-modulated arc therapy (VMAT) in patients receiving prostate-only and pelvic lymphatic irradiation. Materials and methods Testicular doses in 40 intermediate- and high-risk prostate cancer patients were determined on treatment planning system (TPS) using the VMAT technique at 6 MV. Scattered testicular doses were also measured by MOSFET detectors placed on testis surface. The testicular doses of patients treated with prostate-only and pelvic field irradiation were compared. Results The median testicular doses measured per 200 cGy fraction by TPS and MOSFET detectors were 1.7 cGy (0.7-4.1 cGy) and 4.8 cGy (3.6-8.8 cGy), respectively. The TPS doses and MOSFET readings showed a significant strong correlation (Pearson r = 0.848, p < 0.001). The testicular doses measured by TPS (1.34 +/- 0.36 cGy vs. 2.60 +/- 0.95 cGy; p < 0.001) and MOSFET (4.52 +/- 0.64 cGy vs. 6.56 +/- 1.23 cGy; p < 0.001) were significantly lower in patients with prostate-only irradiation than in those with pelvic field irradiation. The mean cumulative scattered dose for prostate-only field delivering 78 Gy was 1.8 Gy and that for pelvic field irradiation was 2.6 Gy, consistent with the reported findings. Conclusions The patients with prostate-only irradiation received lower testicular doses than those with additional pelvic field irradiation possibly due to the increased scattered doses in large field irradiation using the VMAT technique. The clinical response to increased incidental testicular doses due to pelvic field irradiation remains unknown, and it warrants further investigation.