Ten-year follow-up of patients (pts) with metastatic renal cell carcinoma (mRCC) treated with interferon alfa-2b (IFN) as first-line therapy: Results from a randomized trial.

Abstract

365 Background: We previously reported on improved tolerability and maintained efficacy of low-dose IFN in pts with mRCC treated in the cytokine era (Tannir, et al. Cancer 2006). Although VEGFR targeted agents have supplanted cytokines for most pts, IFN, in combination with bevacizumab, is a standard front-line therapy for good-risk and intermediate-risk clear-cell RCC. Methods: Between March 2002 and December 2003, a total of 118 pts (59/arm) were randomized to receive IFN 0.5 million units (MU) twice/day [IFN1] or 5 MU/day [IFN5]. Patients who were progression-free and tolerating therapy well continued IFN for a total of 5 years. The primary endpoint was progression-free survival (PFS). Secondary endpoints were objective response rate (ORR), overall survival (OS), safety, and quality of life (QOL). Results of PFS, ORR, safety, and QOL were previously reported. We provide here updated OS and long-term outcome of complete responders (CR). Results: At 10 years of follow-up, >95% of participants have died. There was no significant difference in OS between the 2 arms (HR=1.32, 95% CI: 0.91-1.91), but favored IFN1 (median OS 2.1 years vs. 1.5 years, log-rank test p=0.14). Compared with IFN5, IFN1 was less toxic and was associated with better QOL. Two nephrectomised pts, 1 from each arm, 1 with multiple hepatic and lung metastases, and 1 with multiple lung and mediastinal metastases, performance status 1 and intermediate-risk clear-cell RCC, remain in unmaintained CR 10 years since starting IFN. Among pts who did not respond to IFN but remain alive, 1 patient received high-dose IL-2 and achieved durable CR; the other patient received multiple approved and investigational targeted agents sequentially. All responders to IFN had tumor regression as early as 8 wks, with PR or CR declared at 16 wks. Conclusions: IFN produces durable CRs and potential cure in about 2% of mRCC pts. Our data have implications for the front-line therapy of mRCC and suggest that IFN, like high-dose IL-2, can be discontinued after 16 wks, if a major response is not achieved. Our updated results are of interest, considering the paucity of durable CRs to VEGFR agents.