735P Metastatic renal medullary and collecting duct carcinoma in the era of antiangiogenic and immune checkpoint inhibitors: A multicentric retrospective study

Collecting duct carcinoma (CDC) and renal medullary carcinoma (RMC) are two rare subtypes of kidney cancer with a poor prognosis in the metastatic setting. Beyond first-line treatment, there are no standard-of-care therapies. This retrospective study assessed the efficacy of treatments after first-line chemotherapy in 57 patients with metastatic (m) CDC (n = 35) or RMC (n = 22) treated between 2010 and 2019 at 11 French centers. The median age was 53 years; overall, 60% (n = 34) of patients were metastatic at diagnosis. After a median follow-up of 13 months, the median overall survival was 12 (95% CI, 11-16) months. All patients received first-line platinum chemotherapy +/- bevacizumab, with a median time to progression of 7.27 (95% CI, 7-100 months and an objective response rate (ORR) of 39% (95% CI, 26-52%). Patients received a median of two (1-5) treatment lines. Subsequent treatments included tyrosine kinase inhibitors (n = 12), chemotherapy (n = 34), and checkpoint inhibitors (n = 20), with ORR ranging 10-15% and disease control rates ranging 24-50%. The duration of response for all treatments was similar to 2 months. Notably, nine patients with CDC were still alive > two years after metastatic diagnosis. Beyond first-line therapy, treatments showed very low antitumor activity in mCDC/RMC. A better understanding of the biology of those rare tumors is urgently needed in order to identify potential targets.