(UroToday.com) The Poster Session C on the third day of the American Society for Clinical Oncology (ASCO) Genitourinary Cancer Symposium 2022 focused on Renal Cell Cancer; Adrenal, Penile, Urethral, and Testicular Cancers. In this session, Dr. Muddasani presented a poster examining the role of stereotactic body radiation therapy (SBRT) in patients with oligoprogressive metastatic renal cell carcinoma (mRCC). While RCC was historically considered a radioresistant tumor, SBRT in indicated for the management of locally recurrent and oligometastatic mRCC as per National Comprehensive Cancer Network guidelines based on evidence that it provides high rates of local control and minimal toxicity.
The authors undertook a single-institution retrospective study at the City of Hope Comprehensive Cancer Center. The authors identified mRCC patients who experienced oligoprogression (defined as <1 sites of progressive disease) while on an FDA-approved systemic therapy and were concurrently treated with SBRT, while remaining on the same therapy. The authors collected clinicopathologic characteristics and SBRT-related data along with duration of systemic therapy (DOT). DOT was then quantified into two categories which included the duration of systemic therapy prior to oligoprogression (DOT[P]) and duration of systemic therapy after completion of SBRT (DOT[S]). For each patient, the ratio of DOT[S]/DOT[P] was calculated to determine the impact of SBRT on systemic treatment prolongation.
The authors identified 23 eligible patients diagnosed with mRCC , of whom 91% (n = 21) had clear cell histology and 9% (n = 2) had papillary histology. At the time of oligoprogression, 15 patients (65%) were on immunotherapy, 7 patients (30%) were on targeted therapy, and 1 patient (5%) was on combination therapy. We noted the preponderance of patients were on a first-line therapy at the time of oligoprogression (n = 10, 43%). A median of 2 (range, 1-3) lesions were treated per patient, with lung being the most frequent site (n = 14, 40%). The median total dose of SBRT was 30 Gy (range, 27-50 Gy) with a median dose per fraction of 6 Gy (range, 3-12 Gy). SBRT related toxicities, all of which were grade <2, were noted in 5 patients (22%), of which fatigue was the most frequent side effect (n = 3, 13%).
Median DOT[S] was 13.4 months (range, 0.5-37.7 months) and the median DOT[P] was 12.8 months (range, 0.4-46.3 months). Thus, the median DOT[S]/DOT[P] ratio was 1.3 (range, 0.01-25.8).
The authors, therefore, conclude that these data contribute to the growing literature base supporting SBRT in mRCC, with a clinical benefit of prolonging time on systemic therapy for patients oligoprogression on systemic therapy. The use of SBRT may prolong lines of therapy, thereby decreasing additional toxicities associated with exposure to new regimens though prospective trials are warranted.
Presented by; Ramya Muddasani, MD Department of Medical Oncology & Experimental Therapeutics, City of Hope Comprehensive Cancer Center, Duarte, CA