3188 - Comparative Analysis of Lymph Node-Only vs. Bone-Only Metastasis-Directed Radiation Therapy in Oligorecurrent Prostate Cancer
Presenter(s)
V. R. Aslot1, S. M. Parker2, E. E. Obi3, S. Patil4, K. L. Stephans3, P. Pendyala3, C. Wee5, A. Nizam5, M. C. Ornstein5, and R. D. Tendulkar2; 1University of Toledo College of Medicine, Toledo, OH, 2Department of Radiation Oncology, Cleveland Clinic Foundation, Cleveland, OH, 3Department of Radiation Oncology, Taussig Cancer Institute, Cleveland Clinic, Cleveland, OH, 4Department of Quantitative Health Sciences, Cleveland Clinic Foundation, Cleveland, OH, 5Department of Hematology and Oncology, Cleveland Clinic Foundation, Cleveland, OH
Purpose/Objective(s): Oligorecurrent prostate cancer (ORPC) encompasses a heterogenous subgroup of patients with oligometastatic progression following prior definitive management of localized prostate cancer. Metastasis directed therapy (MDT) with radiation is often utilized to treat oligorecurrence. However, among patients with ORPC the prognostic significance of oligometastatic disease limited to lymph nodes compared to bone remains unclear.
Materials/Methods: This retrospective analysis identified ORPC patients with lymph node (LNO) or bone only (BO) oligometastatic disease treated with MDT at a single institution since 2016. ORPC was defined as development of oligometastatic disease (5 or fewer lesions) greater than 6 months from initial curative-intent treatment. Patients with visceral, prostate bed, or combination of bony/lymph node metastatic disease were excluded. Primary endpoint was radiographic progression free survival based (PFS). We also evaluated recurrence rates for oligometastases limited to the pelvis versus suprapelvic nodes. Kaplan Meier method was used for survival analysis.
Results: There were 120 patients with LNO (56%) or BO (44%) oligorecurrence. Median follow up was 25 months (IQR, 16 – 37). The most common Gleason score was 7 (50%) at initial diagnosis, and patients underwent primary treatment with radical prostatectomy (68%) or radiation therapy (RT) alone (18%). At recurrence, most patients had a single oligometastasis (83%), most commonly detected by PSMA PET (58%) or fluciclovine PET (30%). Among LNO, 85% of patients had metastases limited to the pelvis versus 15% in extrapelvic nodes. Rates of concurrent ADT use were similar in LNO (69%) and BO (62%) groups. Median duration of ADT was 21.9 months (IQR, 6.9 – 25.4) in BO and 20.3 months (IQR, 6.1 – 25.3) in LNO. Among the total 178 sites treated, median BED1.5 was 230 Gy (range, 132 – 287 Gy) and MDT was delivered with SBRT (83%) or IMRT (17%). Among LNO treatments, 24 were delivered with conventional fractionation/moderate hypofractionation (33%) whereas 49 treatments were delivered with SBRT (67%). Patients with BO ORPC treated with MDT had a significantly lower 3-year PFS compared to those with LNO metastases (48% vs. 77%, p=0.024). Among LNO patients, 3-year PFS was worse in the extrapelvic compared to the intrapelvic group (100 vs. 73%, p=NS), although this comparison was limited by small sample size in extrapelvic group (n=10).
Conclusion:
ORPC limited to bone have significantly lower PFS than patients with lymph node limited oligometastatic disease after MDT. These results can inform risk-stratification for future clinical trials of ORPC based on metastatic site.