OBJECTIVES: To compare cancer-specific mortality in patients with unclassified
renal cell carcinoma (URCC) vs clear cell RCC (CRCC) after nephrectomy, as URCC
is a rare but very aggressive histological subtype.
PATIENTS AND METHODS: Eighty-five patients with URCC and 4322 with CRCC were
identified within 6530 patients treated with either radical or partial
nephrectomy at 18 institutions. Of 85 patients with URCC, 55 were matched with
166 of 4322 for grade, tumour size, and Tumour, Node and Metastasis stages.
Kaplan-Meier and life-table analyses were used to address RCC-specific survival.
Subsequently, multivariate Cox regression analyses were used to test for
differences in RCC-specific survival in unmatched samples.
RESULTS: Of patients with URCC, 80% had Fuhrman grades III or IV, vs 37.8% for
CRCC. Moreover, 36.5% of patients with URCC had pathologically confirmed nodal
metastases, vs 8.6% with CRCC. Finally, 54.1% of patients with URCC had distant
metastases at the time of nephrectomy, vs 16.8% with CRCC. Despite these
differences in the overall analyses, after matching for tumour characteristics,
the URCC-specific mortality rate was 1.6 times higher (P = 0.04) in matched
analyses and 1.7 times higher (P = 0.001) in multivariate analyses.
CONCLUSIONS: These findings indicate that URCC presents with a higher stage and
grade, and even after controlling for the stage and grade differences,
predisposes patients to 1.6-1.7 times the mortality of CRCC
