Loss of BAP1 expression in metastatic tumor tissue is an event of poor prognosis in patients with metastatic clear cell renal cell carcinoma.

Purpose: To evaluate the prognostic impact of the protein expression of both PBRM1 and BAP1 in metastatic tissue of patients with metastatic clear cell renal cell carcinoma (ccRCC).

Patients And Methods: In all 124 consecutive cases of metastatic ccRCC, who underwent metastasectomy or biopsy of metastatic tumor tissue between 2007 and 2016 were selected from the medical records of our institution. Additionally, 38 paired cases with tissue from the primary tumor involving radical or partial nephrectomy for ccRCC were also selected. All cases were reviewed for uniform reclassification and the most representative tumor areas were selected for the construction of a tissue microarray.

Results: PBRM1 nuclear staining of the 124-immunostained metastases of ccRCC specimens showed that 98 (79.0%) had negative expression and 26 (21.0%) positive expression of PBRM1. Regarding BAP1 expression, we observed that 77 (62.1%) specimens were negative and 47 (37.9%) showed positive nuclear staining. When we compared the expression of both markers on primary tumor and tumor metastasis, we found disagreement in half of the cases. Five-year overall survival rates in patients with positive expression and negative expression of BAP1 were 53.2% and 35.1%, respectively (P = 0.004). Five-year progression-free survival rates in patients with positive expression and negative expression of BAP1 were 14.9% and 3.9%, respectively (P = 0.003). Conversely, PBRM1 expression did not significantly influence either overall survival or progression-free survival rates. In multivariate analysis, negative expression of BAP1 tumors also presented higher risks of death (hazard ratio (HR) = 1.913, P = 0.041) and disease progression (HR = 1.656, P = 0.021).

Conclusion: The use of prognostic biomarkers identified in the primary tumor tissue might be not reliable in the metastatic disease scenario. Patients with metastatic ccRCC that present loss of BAP1 expression in metastatic tissue demonstrated poor survival rates and represent a relevant risk group for tumor recurrence and death.