Risk factors and prognostic implications for pathologic upstaging to T3a after partial nephrectomy

BACKGROUND: Performing partial nephrectomy (PN) on a cT1 tumor, which postoperatively is upgraded to pT3a can possibly lead to compromise of cancer specific mortality. We therefore aimed to identify risk factors for pathologic T3a upstaging of cT1 tumors and to analyze the association between upstaging, positive surgical margins (PSM) and overall survival (OS). METHODS: The present study included patients who underwent PN for a clinically localized T1 renal mass from two datasets: 1) 1298 patients from a prospectively maintained multi-center database (MCDB); and 2) 7940 patients from the National Cancer Database (NCDB). Multivariable logistic regression models within each cohort were used to identify predictors of cT1 to pT3a upstaging and its association with PSM. Cox proportion hazards regression models were used to compare overall survival in the NCDB cohort. RESULTS: The rate of pT3a upstaging was 5.7% (N.=74) in the MCDB and 1.9% (N.=156) in the NCDB cohort. Older age (MCDB OR=1.04, P=0.001; NCDB OR=1.04, P=0.001) and larger tumor size (MCDB OR=1.89, P<0.001; NCDB OR=1.38, P<0.001) increased the likelihood of upstaging. PSM was found to be more likely for pT3a upstaged patients in both cohorts (MCDB 14.9% vs. 3.5%, P<0.001; NCDB 14.8% vs. 8.3%, P=0.006), even when adjusting for tumor size. At short term follow-up (NCDB median follow-up 27.3 months), pT3a upstaging was associated with worse OS in univariable (HR=1.89; 95% CI=1.00, 3.55; P=0.049) but not multivariable analysis (HR=1.63; 95% CI=0.86, 3.08; P=0.131). OS was 93.0% vs. 95.8% at 3 years for those with and without pT3a upstaging, respectively. CONCLUSIONS: Larger tumor size and increased age are associated with pathological upstaging to T3a for clinical T1 tumors treated with partial nephrectomy. Steps to improve identification of occult pT3a disease are necessary as its occurrence significantly increased the likelihood of a PSM, both in a high-volume multicenter cohort, as well as, a national data registry.