3275 - MRI-Defined Prostatic Gross Extracapsular Extension Association with Acute GU and GI Toxicity Following SBRT
Presenter(s)
J. W. Lischalk1,2, B. Vizcaino3, V. Santos1, C. Mendez4, A. Sanchez4, N. Aghdam5, T. J. Carpenter4, A. Tong6, A. Corcoran7, W. Huang8, A. Katz7, and J. Haas4; 1Department of Radiation Oncology, Perlmutter Cancer Center at New York University Langone Hospital - Long Island, New York, NY, 2Department of Radiation Medicine, Georgetown University Hospital, Washington, DC, 3Department of Radiation Oncology, Perlmutter Cancer Center at New York University Grossman School of Medicine,, New York, NY, 4Department of Radiation Oncology, Perlmutter Cancer Center at New York University Langone Hospital - Long Island, Mineola, NY, 5Department of Radiation Oncology, Beth Israel Deaconess Medical Center, Boston, MA, 6Department of Radiology, NYU Langone Health and New York University, Grossman School of Medicine, New York, NY, 7Department of Urology, Perlmutter Cancer Center at New York University Langone Hospital - Long Island, Mineola, NY, 8Department of Urology, Perlmutter Cancer Center at New York University Grossman School of Medicine, New York, NY
Purpose/Objective(s):
Identification of prostatic extracapsular extension (ECE) has become a common entity with the ubiquitous use of MRI in the modern era. MRI defined ECE is likely a precursor to gross clinical ECE based on digital rectal exam and is not technically high-risk disease by standard AJCC guidelines. SBRT is an established radiation modality for low to intermediate prostate cancer and has been shown to be efficacious in a randomized setting relative to conventional fractionation. Moreover, early data now exists for SBRT utility in the setting of high-risk disease. However, it is unclear if the identification of gross ECE on MRI's leads to variable toxicity outcomes following SBRT. In the present study we explore toxicity outcomes in patients with MRI defined gross ECE.Materials/Methods:
An institutional registry was reviewed to identify patients who completed 5-fraction definitive SBRT, or 3-fraction SBRT boost preceded by pelvic nodal irradiation from 2/3/2021 to 8/23/2024. Patients with missing MRI data were excluded. We explored the outcomes of patients with MRI defined gross ECE on diagnostic and/or treatment planning MRIs. Patients with capsular abutment and microscopic rather than gross ECE were excluded. Toxicity was assessed using CTCAE v5.0.Results:
A total of 207 patients were included and 21% demonstrated gross-ECE on MRI. Median prescription dose in the 5-fraction and 3-fraction boost cohort was 3625 and 2100 cGy, respectively. Risk group distribution in the ECE versus non-ECE cohort was as follows: low (5 vs. 9%), intermediate (42 vs. 71%), high (39 vs. 18%), and other (14 vs. 2%) p < 0.001. Pelvic nodal irradiation was more commonly utilized in patients with gross ECE (34 vs. 17%, p = 0.014). Similarly, ADT was more common in the ECE cohort (79 vs. 49%, p < 0.001). With a median follow up of 19.6 months, there was no significant overall grade 2 GU or GI toxicity difference in patients with and without ECE, (40 vs. 34%, p = 0.89; 14 vs. 12%, p = 0.76) respectively. This remained true when specifically analyzing GU toxicity in patients with and without ECE in the 5-fraction cohort (43 vs 36%, p = 0.51) and the pelvic nodal cohort (33 vs 48%, p = 0.34), respectively. Similarly, GI toxicity was not different in patients with and without ECE in the 5-fraction cohort (10 vs 8%, p = 0.66) and the pelvic nodal cohort (20 vs 31%, p = 0.44), respectively.Conclusion:
With early follow up, gross ECE as identified on MRI did not yield excess grade 2 GU or GI toxicity when delivered in a definitive 5-fraction or 3-fraction boost setting. Future research should explore longer term outcomes as well as toxicity in the sexual domain.