3316 - Impact of Pre-Therapy PSA Kinetics on Overall Survival of Prostate Cancer Patients Treated with Lu-177 PSMA 617
Presenter(s)
V. Prasad1, J. M. Michalski2, M. Reimers3, H. Kim4, A. K. Bhatt5, F. Dehdashti6, B. Roth7, J. Picus7, C. Swingle5, A. Jahromi5, R. Pachynski7, and H. A. Gay2; 1Washington University School of Medicine in St. Louis, St. Louis, MO, 2Department of Radiation Oncology, Washington University School of Medicine, St. Louis, MO, 3Washington University in St. Louis, St. Louis, MO, 4WashU Medicine, Department of Radiation Oncology, St. Louis, MO, 5Washington University in Saint Louis, Saint Louis, MO, 6Washington University School of Medicine, St. Louis, MO, 7Department of Medicine, Division of Hematology and Oncology, Washington University School of Medicine, St. Louis, MO
Purpose/Objective(s): [177Lu]Lu-PSMA-617 (Lu-177 PSMA) is approved for treatment of patients with metastatic castration resistant prostate cancer (mCRPC). We retrospectively evaluated the impact of PSA kinetics on overall survival (OS) of mCRPC patients referred for Lu-177 PSMA therapy in our center.
Materials/Methods: Patient electronic records were retrospectively reviewed and data collected in an institutional database. A multidisciplinary theranostics tumor board (TTB) consisting of radiation oncologists, nuclear medicine, and medical oncologists assessed the indication for Lu-177 PSMA therapy. Wherever feasible, patients underwent post-therapy PSMA SPECT/CT after every cycle. The following data were analyzed for the study: age, time of first cycle, time since first diagnosis, time since PSMA PET, interval from first treatment to last follow-up (FU), PSA up to 4 months prior to first cycle, PSA at baseline (within 4 weeks of first cycle), PSA after 2nd cycle, PSA after the last cycle, PSA response defined as PSA50 i.e. (> 50% drop in PSA at the end of last cycle and after 2nd cycle), number of cycles, dose modification (if any), survival status, and date of last FU. To assess the impact of pretherapy PSA kinetics on OS, patients were divided into two categories: patients with or without rapid pretreatment PSA rise (rise was defined as difference between PSA 4 weeks and PSA at 4 months prior to first cycle; rapid defined as > 50% increase in PSA or > 100 ng/mL rise prior to first cycle). All statistical analyses were performed using software. p-value < 0.05 was considered as statistically significant.
Results: Out of 114 patients discussed in TTB, 90 patients (mean age of 71.4 ± 8.0 years) were found to be eligible to receive Lu-177 PSMA. PSA50 response was observed in 41.4% and 43.2% after the 2nd and last cycles, respectively. Median follow-up duration was 13.5 months. Thirty-three (36.7%) died during follow-up. Median OS was 19.1 months (95% CI 15.7-22.5, figure 1). Patients achieving PSA50 response after the last cycle had significantly higher OS compared to those that did not (median not reached vs 17.5 months; log rank p=0.006). Patients not showing a PSA50 after 2 cycles were found to have lower OS (19.1 months vs. median not reached; log rank p=0.031). Patients with rapid pretherapy PSA increase had significantly lower OS as compared to those without (median not reached vs. 16.8 months, 95% CI 10.8-23.5, p=0.021).
Conclusion: In our single center experience, median overall survival was found to be approximately 4 months higher than OS reported in VISION trial. Patients with rapid pretherapy PSA rise or not meeting a PSMA50 have shorter OS.