J. C. Hurwitz1, J. A. Haas2, C. Mendez3, A. Sanchez4, V. Santos2, F. M. Deng5, S. Niglio6, M. P. Economides6, T. J. Carpenter2, W. Huang7, J. Kaminetsky7, A. J. Evans8, S. Taneja7, A. Katz9, M. J. Zelefsky10, and J. W. Lischalk2; 1Department of Radiation Oncology, New York University Long Island School of Medicine, Mineola, NY, 2Department of Radiation Oncology, Perlmutter Cancer Center at New York University Langone Hospital - Long Island, Mineola, NY, 3Department of Radiation Oncology, Perlmutter Cancer Center, NYU Long Island, Mineola, NY, 4NYU Langone Health - Long Island, Mineola, NY, United States, 5Department of Pathology, New York University Grossman Long Island School of Medicine, New York, NY, 6Department of Medicine, Perlmutter Cancer Center at NYU Langone Medical Center, New York, NY, 7Department of Urology, Perlmutter Cancer Center at New York University Grossman School of Medicine, New York, NY, 8Department of Radiation Oncology, NYU Langone Health and Perlmutter Cancer Center, New York, NY, 9Department of Urology, Perlmutter Cancer Center at New York University Langone Hospital - Long Island, Mineola, NY, 10Department of Radiation Oncology, Perlmutter Cancer Center at New York University Langone Hospital, New York, NY
Purpose/Objective(s): High-volume (= 50%) biopsy core involvement is an independent factor for unfavorable intermediate risk stratification by NCCN guidelines. The bulk of the data demonstrating elevated radio-recurrence in high-volume disease were established in an age of conventional fractionation and often without dose escalation. In the era of ultra-hypofractionation, we explore the value of this pathologic criteria specifically in intermediate risk disease treated with SBRT monotherapy. Materials/
Methods: A large institutional database was reviewed to identify patients diagnosed with localized intermediate risk (grade group [GG] 2 and 3) prostate cancer treated with 5-fraction SBRT without ADT. Pathology reports were reviewed to determine detailed percent core involvement and grade group. High-volume biopsy core involvement was defined as = 50% per NCCN. Percent core involvement was analyzed (1) traditionally with all positive cores (regardless of GG) given equal weight, (2) a positive core of GG1 to GG3 given a linearly increased weight (1x, 2x, 3x), and (3) a positive core of GG1 to GG3 given an exponentially increased weight (e0, e1, e2). Prostate volume was defined based on pretreatment MRI. Oncologic outcomes were analyzed for association with core involvement using standard Kaplan-Meier survival and Cox regression analysis. Results: From 2009 to 2018, a total of 939 patients diagnosed with intermediate risk prostate cancer were treated with SBRT monotherapy to a median total dose of 3500 cGy in 5 fractions. The majority were diagnosed with GG2 (68%) with the remainder GG3. Gland size was modest with mean (SD) prostate volume 44cc (22.6). High-volume biopsy core involvement was present in the minority of cases (33%) and was inversely related to prostate volume (p < 0.001). Biochemical disease-free survival (bDFS) was not significantly associated with unweighted high-volume biopsy core involvement in the entire cohort (p = 0.4) nor in the GG2 (p = 0.3) and GG3 (p = 0.8) sub-cohorts. Similarly, when additional weight was given to a core with higher grade disease, whether analyzed linearly or exponentially, there was no significant association with bDFS. Finally, even when controlling for prostate volume, bDFS remained unassociated with biopsy core involvement, irrespective of weighting or GG. Conclusion: With a median follow up of 4.1 years, high-volume biopsy core involvement was not associated with an increased risk of bDFS following SBRT monotherapy regardless of GG in intermediate risk patients. Additional patients and longer follow up should confirm whether high-volume core involvement is irrelevant in risk classification in the era of ablative radiotherapy.
