A Phase II Study Assessing Stereotactic Radiotherapy in Therapeutic Strategy of Oligoprogressive Renal Cell Carcinoma Metastases

Every year, 12500 primary renal cell carcinoma (RCC) are diagnosed in France. Metastases occur in half of RCC patients. Management of metastatic RCC is based on systemic treatments (targeted therapies/immunotherapy). However, resistance to systemic treatment is frequent. In case of progression, usual therapeutic attitude is initiating another systemic therapy. Because of the emergence of resistant tumor clonal cells, some patients progress only on few sites while the rest of tumor burden is controlled. In this setting named oligoprogressive disease \[isolated progression of \<3-5 metastase(s)\], ablative treatments of these evolving metastatic sites could allow a disease control and a reduced risk of new metastases occurrence by tumor-cell reembolization. Such strategy is challenging to prolong ongoing systemic treatment and delay further lines. Although RCC was considered radioresistant and radiotherapy with conventional fractionation was mainly used for palliation of symptoms, stereotactic radiotherapy (SRT), by delivering high dose in one or few fractions, allows local control for about 90% of RCC metastases through various radiobiological pathways. Furthermore, some data suggest that high-dose focal irradiation of RCC could induce a systemic antitumor response mediated by immunologic effectors(1). This phenomenon ("abscopal effect") could be enhanced in patients under immunotherapy, including anti-PD1. Several retrospective studies and one non-randomized phase-II study highly suggest the interest of SRT as focal ablative treatment in RCC oligometastases with excellent local control rates and low toxicity(2,3). Furthermore, the multicentric retrospective study the sponsor recently conducted within the GETUG group among 101 metastatic RCC patients with oligoprogression under systemic therapy highlighted that SRT on progressive sites provided a median of 8.6-month progression-free survival and allowed to continue current systemic line for 10.5 months. However