Omer Sager's research while affiliated with Ankara University Faculty of Sport Sciences and other places

Background There is a paucity of data on the management of recurrent lymph nodes after primary or adjuvant radiotherapy (RT) for prostate cancer (PCa). In this study, we report our tertiary cancer center experience with stereotactic body radiotherapy (SBRT) for the management of pelvic lymph node recurrences after adjuvant or primary RT for PCa. Materials and Methods Patients who underwent SBRT for pelvic lymph node metastases from PCa between 2013 and 2019 were retrospectively assessed for local control (LC), androgen deprivation treatment-free survival (ADT-FS), and toxicity outcomes. The primary endpoint was LC and ADT-FS. The secondary endpoint was late treatment toxicity. Results Twenty-two lesions of 18 patients receiving SBRT for pelvic lymph node recurrences for PCa between February 2013 and March 2019 were evaluated. At a median follow-up duration of 29.5 months (range: 9–54 months), LC was 95.5% vs. 90.2% at 1 and 2 years, respectively. Ten patients received palliative ADT following SBRT after a median period of 14.5 months (range: 6–31 months). ADT-FS was 72.2% and 54.3% at 1 and 2 years, respectively. Comparative analysis of biologically effective dose (BED) values revealed that higher BED10 values were associated with higher ADT-FS ( P = 0.008). ADT-FS was 55.6% and 88.9% for BED10 <50 Gy and for BED10 >50 Gy, respectively ( P = 0.008). Assessment of late toxicity outcomes revealed that the most common toxicity was urinary toxicity and fatigue; however, no patient had ≥ grade 3 toxicity. Conclusion Our tertiary cancer center experience confirms the safety and efficacy of SBRT for the management of pelvic lymph node recurrences from PCa.

Background: Adaptive radiation therapy (ART) refers to redesigning of radiation therapy (RT) treatment plans with respect to dynamic changes in tumor size and location throughout the treatment course. In this study, we performed a comparative volumetric and dosimetric analysis to investigate the impact of ART for patients with limited-stage small cell lung cancer (LS-SCLC). Methods: Twenty-four patients with LS-SCLC receiving ART and concomitant chemotherapy were included in the study. ART was performed by replanning of patients based on a mid-treatment computed tomography (CT)-simulation which was routinely scheduled for all patients 20-25 days after the initial CT-simulation. While the first 15 RT fractions were planned using the initial CT-simulation images, the latter 15 RT fractions were planned using the mid-treatment CT-simulation images acquired 20-25 days after the initial CT-simulation. In order to document the impact of ART, target and critical organ dose-volume parameters acquired from this adaptive radiation treatment planning (RTP) were compared with the RTP based solely on the initial CT-simulation to deliver the whole RT dose of 60 Gy. Results: Statistically significant reduction was detected in gross tumor volume (GTV) and planning target volume (PTV) during the conventionally fractionated RT course along with statistically significant reduction in critical organ doses with incorporation of ART. Conclusion: One-third of the patients in our study who were otherwise ineligible for curative intent RT due to violation of critical organ dose constraints could be treated with full dose irradiation by use of ART. Our results suggest significant benefit of ART for patients with LS-SCLC.

Background: Liver metastases may occur during the course of several cancer types and may be associated with significant morbidity and mortality. There is paucity of data regarding the utility of Active Breathing Control (ABC) guided Stereotactic Ablative Body Radiotherapy (SABR) for management of Liver Metastases from Colorectal Cancer (LMCC). Our aim is to investigate the role of ABC guided SABR for management of liver metastases. Patients and methods: 42 liver metastases of 29 patients treated with ABC guided SABR between February 2015 and October 2018 were retrospectively assessed for local control (LC), overall survival (OS), and toxicity outcomes. Primary endpoint was LC. Secondary endpoints were OS and treatment toxicity. Results: At a median follow up duration of 16 months (range: 9-74 months), median OS was 20 months and 3 patients were still alive at last follow up. 1-year OS was 83% and 2-year OS was 28%. LC rates were 92% and 61% at 1 and 2 years, respectively. Comparative analysis of Biological Effective Dose (BED) values revealed that higher BED10 values were associated with higher LC rates (p=0.007). While LC rates for BED10 ≥ 100 Gray (Gy) were 94% and 86% at 1 and 2 years, corresponding LC rates for BED10 < 100 Gy were 89% and 36%, respectively with statistical significance (p=0.007). Assessment of acute and late toxicity outcomes revealed that most common toxicity was fatigue, however, no patients had ≥ grade 3 toxicity. Conclusion: ABC guided SABR is an effective and safe treatment modality for LMCC management.

Pilocytic astrocytoma (PA) may be seen in both adults and children as a distinct histologic and biologic subset of low-grade glioma. Surgery is the principal treatment for the management of PAs; however, selected patients may benefit from irradiation particularly in the setting of inoperability, incomplete resection, or recurrent disease. While conventionally fractionated radiation therapy has been traditionally utilized for radiotherapeutic management, stereotactic irradiation strategies have been introduced more recently to improve the toxicity profile of radiation delivery without compromising tumor control. PAs may be suitable for radiosurgical management due to their typical appearance as well circumscribed lesions. Focused and precise targeting of these well-defined lesions under stereotactic immobilization and image guidance may offer great potential for achieving an improved therapeutic ratio by virtue of radiosurgical techniques. Given the high conformality along with steep dose gradients around the target volume allowing for reduced normal tissue exposure, radiosurgery may be considered a viable modality of radiotherapeutic management. Another advantage of radiosurgery may be the completion of therapy in a usually shorter overall treatment time, which may be particularly well suited for children with requirement of anesthesia during irradiation. Several studies have addressed the utility of radiosurgery particularly as an adjuvant or salvage treatment modality for PA. Nevertheless, despite the growing body of evidence supporting the use of radiosurgery, there is need for a high level of evidence to dictate treatment decisions and establish its optimal role in the management of PA. Herein, we provide a concise review of radiosurgery for PA in light of the literature.