Clinical Outcomes in Patients With Metastatic Papillary Renal-Cell Carcinoma: A Multi-Institutional Study in Japan

Standard treatments have not been established in metastatic papillary renal-cell carcinoma (PRCC). We aimed to investigate treatment outcomes in patients with mPRCC.

This study included 51 patients who were diagnosed with PRCC at 14 institutions. Pathologic slides were reviewed by pathologists. The associations between clinical factors and overall survival (OS) were analyzed.

Final pathologic diagnoses could be determined in 50 patients. Thirty-five tumors were diagnosed as PRCC (type 2 PRCC, 91.4%), and 15 were diagnosed as other histologic types. Targeted therapies (TTs) were provided to 25 mPRCC patients. Patients treated with TT survived significantly longer than those treated before the era of TT (median OS, 22.5 vs. 6.3 months; P = .0035). Median OS of patients who experienced stable disease for ≥ 9 months using single TT was 43.1 months. Patients treated with a tyrosine kinase inhibitor (TKI) as first-line TT survived longer after TT initiation than those treated with an mTOR inhibitor (median, 22.4 vs. 11.7 months; P = .2684). Patients treated with TKIs in both first- and second-line settings had significantly better survival after TT initiation than those treated with a TKI in one therapy line and an mTOR inhibitor in the other (31.4 vs. 12.9 months, P = .0172). Patients treated with a TKI as second-line TT survived significantly longer after second-line TT initiation than did those treated with an mTOR inhibitor (16.2 vs. 7.4 months, P = .0016).

Prognoses of patients with mPRCC were improved by TT, and TKIs appeared to be the treatment of choice in both the first- and second-line settings.