Outcomes of stereotactic ablative radiotherapy for extra-cranial oligo-metastatic renal cell cancer.

Abstract

599 Background: Stereotactic ablative radiotherapy (SAbR) is a standard of care for treating renal cell cancer (RCC) cranial metastasis. We describe the effect of SAbR on oligometastatic extra-cranial RCC disease course. Methods: We retrospectively reviewed 49 patients with oligometastatic RCC with 68 extra-cranial lesions. Patients were treated with SAbR with a curative intent from 2007 to 2017. We analyzed local control, systemic therapy free survival (mPFS), and overall survival. Results: With a median follow-up of 28 months (IQR: 16.0-40.3), the 1-year and 2-year overall survival after SAbR was 93.4% (95% CI: 81.0-97.8), and 83% (95% CI: 67.4-91.5) respectively. The median overall survival was not reached. The median time to systemic therapy was 13.4 months from the first SAbR(95% CI: 8.8-27.6). Median times from the first SabR course to second and third line systemic therapy (or death) were 31.8 months and 45 months, respectively. Patients in the favorable risk group by the Heng’s criteria (HR = 8.67, p = 0.04), with nometastatic disease at diagnosis (HR = 10.38, p < 0.01) and with clear cell histology (HR = 6.15, p < 0.01) exhibited better survival, as shown by univariate analysis. Patients with no metastatic disease at diagnosis (HR = 2.56, p = 0.02) and only one metastasis treated with SAbR (HR = 2.36, p = 0.03) also exhibited better systemic therapy-free survival. SAbR had an excellent local control rate of 94% at 2 years with no reported grade 3 or higher toxicity. Conclusions: SAbR is an effective and safe treatment for oligometastatic RCC, offering excellent local control with minimal toxicity. SAbR delayed the start of systemic therapy for this RCC cohort, offering quality of life benefits for patients without adversely affecting the progression on subsequent lines of systemic therapy. These findings call for prospective verification.