Beth Israel Deaconess Medical Center Boston, MASSACHUSETTS, United States
N. Aghdam, N. Bhargava, M. Hurwitz, L. Bennett, J. A. Aronovitz, D. R. Schmidt, and I. D. Kaplan; Department of Radiation Oncology, Beth Israel Deaconess Medical Center, Boston, MA
Purpose/Objective(s):SBRT is a standard of care treatment for localized prostate cancer. Intra-prostatic boost (IPB) may improve biochemical control. Additionally, the prognostic impact of early PSA nadir has been described by ICECaP collaborative. In the present series, we report early PSA kinetics for patients with intermediate risk disease who received IPB treated with SBRT with and without short course of hormone therapy. Materials/
Methods: From October 2018 to June 2023, 280 patients with intermediate risk prostate cancer were treated with a robotic stereotactic body radiotherapy platform with fiducial tracking. Intra-prostatic nodules were delineated using diagnostic and treatment planning MRI by the treating radiation oncologist. Patients received the standard dose of 36.25Gy to the prostate and proximal seminal vesicles with isotropic expansion margin of 5mm, except posteriorly towards the rectum, where the margin was 3mm. GTV received 40 Gy. For assessing PSA kinetics, each patient’s PSA value at diagnosis and follow-up, defined as 6-12 months after completion of treatment, were considered. PSA values were retrospectively extracted from each patient’s medical records and the percentage of patients with PSA values <0.1 ng/mL, <0.2 ng/mL, and <0.5 ng/mL within 6-12 months of completion of treatment was determined. Patients were compared based on the use of short term (4-6 months) hormone therapy with SBRT. Results: Of 280 patients, 157 patients received hormone therapy and 123 did not. The median and ranges of PSA values at diagnosis for each group were 6.9 (0.8-19.5) and 6.8 (2-19.9), respectively.Of patients who received hormone therapy with SBRT and IPB, 36.9% achieved PSA<0.1ng/mL compared to 1.6% for those who did not receive hormone therapy. Respectively, 58.0% and 4.1% achieved PSA<0.2mg/mL and 86.0% and 15.4% achieved PSA<0.5ng/mL within 12 months of treatment completion. Conclusion: SBRT is a safe and effective treatment for patients with localized prostate cancer. To our knowledge, this report is the largest series describing early PSA kinetics for patients treated with SBRT with IPB in the context of established PSA nadirs reported by ICECaP collaborative group. Long-term follow up is needed to determine the prognostic significance of these findings.
