Treatments, Outcomes, and Validity of Prognostic Scores in Patients With Sarcomatoid Renal Cell Carcinoma: A 20-Year Single-Institution Experience

Introduction: Metastatic renal cell carcinoma (RCC) with a sarcomatoid component is a rare disease associated with a poor prognosis. We report the outcomes of 47 patients with metastatic sarcomatoid RCC (SRCC) treated with different modalities including chemotherapy, tyrosine kinase inhibitors, or immunotherapy over 2 decades in a French cancer center. Furthermore, we assessed the validity of prognostic scores in this subset of RCC.

Patients and methods: Patients were retrospectively identified from the database of the pathology department of the University Hospital of Strasbourg. We enrolled all patients with RCC with a sarcomatoid component diagnosed between 1995 and 2016. Patients with nonmetastatic RCC were excluded. Recorded variables included: clinical stage, metastatic sites, pathologic stage, type of treatments, prognostic group, and survival data. The primary end point was overall survival. The institutional ethical committee approved the study protocol.

Results: Of 104 patients with SRCC, 47 patients with metastatic SRCC were included. The median age was 60 years (range, 41-77 years). Median length of follow-up was 34 months (range, 1-180 months). Fifty-five percent of patients had known metastases at diagnosis. Lung represented the first metastatic site (70%) followed by glandular (28%), bone (23%), liver (21%), and brain (6%). Fifteen percent of patients received immunotherapy including cytokine-based therapy (n = 7), or checkpoint inhibitors (n = 2). Moreover, 7 patients received chemotherapy. Five patients received no systemic treatment because of their poor performance status. Of 42 treated patients, 2 patients achieved complete response and 9 partial response (24%). Median overall survival was 13.3 months. International Metastatic Renal Cell Carcinoma Database Consortium (IMDC) and Memorial Sloan Kettering Cancer Center (MSKCC) prognostic groups were valid in this subset of SRCC patients. A sarcomatoid percentage cutoff of 30% had the strongest influence on overall survival.

Conclusion: Despite the arrival of tyrosine kinase inhibitors 10 years ago, metastatic SRCC remains a disease of poor prognosis and difficult to treat. Chemotherapy regimen and targeted therapies showed little activity in SRCC. IMDC score is a relevant prognostic factor in SRCC patients. Additionally, the MSKCC score, the sarcomatoid percentage, the necrotic fraction, and the vascular invasion could prove useful in identifying patients with a more favorable prognosis. These findings could help toward better patient stratification in clinical trials. Prospective trials assessing new drugs including immune checkpoint inhibitors are currently ongoing to improve SRCC survival.