3333 - SBRT for Oligoprogressive Metastatic Renal Cell Carcinoma: Results of a Single Institution Retrospective Analysis

Purpose/Objective(s):

Oligoprogression (OP) has been defined as limited metastatic progression (1-5 sites). Stereotactic body radiotherapy (SBRT) for selected patients with oligoprogressive metastatic renal cell carcinoma (mRCC) has been shown to improve progression-free survival (PFS) and allow a delay in next systemic therapy without adding significant toxicity. We report on the use of this approach in a series of mRCC patients treated at our institution.

Materials/Methods:

We performed a retrospective analysis of 38 mRCC patients who received a total of 56 courses of SBRT for OP while on first- to fifth-line systemic therapy. Time to next systemic therapy (NEST-free survival), PFS and overall survival (OS) were calculated using the Kaplan-Meier method

Results:

Patients receiving SBRT for OP had a median age of 67; 74% male/ 26% female. At the time of SBRT, 24, 5, and 2 patients were receiving first-, second-, or = third-line systemic therapy, respectively. Seven patients did not receive any systemic therapy. 23 patients received a single course of SBRT; 15 patients received = 2 SBRT courses for serial OP. The most commonly treated metastatic sites were lung (46.3%) , bone (17.9%), lymph nodes (9%), and pancreas (7.5%). At a median follow-up of 16.7 months from the diagnosis of first metastatic progression, the median NEST-free survival was 10.5 months following SBRT for first OP. For all treated courses of SBRT (including both first and subsequent OP), the median NEST-free survival was 9.6 months (range 1.2 – 40.3, SD 10.4). For patients experiencing serial OP receiving > 1 SBRT course, time to next systemic therapy was extended by 15.9, 12.8, and 1.6 months following their first, second, and third courses of SBRT, respectively. For all patients, the median PFS was 10.8 months (range 2.7–37, SD 9.8). Median OS for all patients from initial diagnosis of metastatic progression was 31 months (range 5.5-83.4, SD 17.4).

Conclusion:

Our institutional experience using SBRT for oligoprogressive mRCC supports this approach as a well-tolerated, effective means of delaying time to next systemic therapy and improving PFS. NEST-free survival was meaningfully extended in patients even after first line systemic therapy, demonstrating that repeat SBRT for serial OP may be an effective, patient-centered approach to managing mRCC. Our ongoing work seeks to better characterize which patients will most benefit from SBRT for OP.