ESTRO 2024 - Abstract Book

S2490

Clinical - Urology

ESTRO 2024

MRI-based robotic SBRT microboost with nodal irradiation in treatment of aggressive prostate cancer

Jonathan W. Lischalk 1 , Vianca F. Santos 1 , Meredith Akerman 2 , Astrid Sanchez 1 , Christopher Mendez 1 , Todd J. Carpenter 1 , Moses M. Tam 1 , Angela Tong 3 , Mary K. O'Keeffe 4 , David R. Wise 5 , Samir Taneja 6 , Aaron Katz 7 , Anand Mahadevan 8 , Herbert Lepor 6 , Michael J. Zelefsky 8 , Jonathan A. Haas 1 1 Perlmutter Cancer Center at New York University Langone Hospital - Long Island, Department of Radiation Oncology, New York, USA. 2 New York University Long Island School of Medicine, Division of Health Services Research, Mineola, USA. 3 New York University Grossman School of Medicine, Department of Radiology, New York, USA. 4 New York University Long Island School of Medicine, Department of Medicine, Mineola, USA. 5 New York University Grossman School of Medicine, Department of Medicine, New York, USA. 6 Perlmutter Cancer Center at New York University Grossman School of Medicine, Department of Urology, New York, USA. 7 New York University Long Island School of Medicine, Department of Urology, Mineola, USA. 8 Perlmutter Cancer Center at New York university Grossman School of Medicine, Department of Radiation Oncology, New York, USA The publication of POP-RT has renewed interest in the use of prophylactic nodal irradiation for more aggressive prostate cancer. Moreover, the results of ASCENDE-RT offer an innovative approach of dose escalation to the prostate utilizing a brachytherapy boost. A novel method of escalating radiation dose to the prostate utilizes SBRT rather than a brachytherapy boost. Further efforts of dose escalation have focused on an MRI-directed intraprostatic nodule microboost, which has demonstrated favorable oncologic outcomes based on the FLAME trial. Herein, we marry the use of pelvic nodal irradiation followed by an SBRT 3-fraction boost to the prostate and seminal vesicles with a simultaneous MRI-directed focal intraprostatic lesion ablative microboost (MIB). An institutional registry of patients undergoing pelvic nodal radiation followed by an SBRT boost to the prostate and seminal vesicles from April 2021 to March 2023 was evaluated. All patients were treated with pelvic nodal irradiation utilizing conventional fractionation followed by a 3-fraction SBRT boost to a total dose of 1800 to 2100 cGy. In a sub-cohort of this group, a simultaneous MIB was performed with SBRT to a total prescription dose of 2100 to 2400 cGy. Toxicity was reported utilizing the CTCAE version 5.0. Patient reported EPIC quality of life summary and subscale scores were evaluated for the genitourinary (GU) and gastrointestinal (GI) domains. Quality of life endpoints were evaluated at 0, 3, 6, 9, and 12+ months. The minimally important difference (MID) was utilized to assess a clinically significant change in these measures from baseline, and was set as half a standard deviation (SD). The GU and GI EPIC summary and subscale scores were assessed using generalized linear mixed models, including the main effects of time (0, 3, 6, 9, and 12 months), boost group, and the difference in groups across time. A result was considered significant at p < 0.05. Purpose/Objective: Material/Methods:

Results:

Forty-two patients underwent pelvic nodal irradiation followed by an SBRT boost to the prostate with a median follow up of 12.4 months and a distribution of risk grouping as follows: intermediate 11.90% (n = 5), high 42.86% (n = 18), very high 28.57% (n = 12), and regional 16.67% (n = 7). The majority of patients received ADT as a component of the treatment (92.86%, n = 39). Prostate SBRT boost dose was predominately 2100 cGy in three fractions (90.48%, n = 38). Fifteen patients (35.71%) also received an MIB in concert with their 3-fraction prostate boost, most