The Impact of Temporal Presentation on Clinical and Pathological Outcomes for Patients with Sporadic Bilateral Renal Masses

Background: The origin of bilateral renal masses has not been definitively established to date. As limited studies on the genetics of bilateral tumors exist, defining the clinical behavior of these lesions remains important. Objective: To evaluate the impact of synchronous versus metachronous presentation on clinicopathological outcomes of patients with bilateral renal masses. Design, Setting, and Participants: We identified 310 patients who were treated at the Mayo Clinic for sporadic bilateral renal masses between 1970-2003, including 148 (47.7%) with synchronous tumors and 162 (52.3%) with metachronous lesions. Intervention: Patients underwent surgical resection of bilateral renal tumors. Measurements: Clinicopathological features of synchronous and metachronous tumors were compared. Survival rates for patients with synchronous (n = 92) and metachronous (n = 100) renal cell carcinoma (RCC) were estimated using the Kaplan-Meier method and compared with the log rank test. Results and Limitations: Metachronous tumors had a greater degree of pathological concordance than synchronous lesions, with 87.7% of metachronous tumors representing bilateral RCC, compared to 69.2% of synchronous masses (p = 0.002). Patients with synchronous RCC tended to have an increased incidence of papillary RCC compared to patients with metachronous RCC, who were more likely to have bilateral clear-cell RCC (p = 0.076). A longer interval between tumors was inversely associated with the risk of cancer death for patients with metachronous RCC (HR 0.90, 95% CI 0.81-0.99, p = 0.039). Compared to patients with metachronous RCC, patients with synchronous bilateral RCC had similar 10-yr CSS (70.5% vs. 69.4%, p = 0.51) and OS (47.5% vs. 51.2%, p = 0.58). We nevertheless recognize that these findings may be limited by the study's retrospective, single-institution design. Conclusions: Metachronous bilateral solid renal masses have a greater degree of pathological concordance and were more likely to represent malignancy. Surgical resection may provide durable cancer control for patients with bilateral RCC, with no difference in survival noted between synchronous and metachronous cancers.