title: The impact of temporal presentation on clinical and pathological outcomes for patients with sporadic bilateral renal masses.
abstract: 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.
  
  
  METHODS
  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.
  
  
  METHODS
  Patients underwent surgical resection of bilateral renal tumors.
  
  
  METHODS
  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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Department of Urology, Mayo Medical School and Mayo Clinic, 200 First Street SW, Rochester, MN 55905, USA.
authors.forename: Stephen A
authors.initials: SA
authors.lastname: Boorjian
authors.forename: Paul L
authors.initials: PL
authors.lastname: Crispen
authors.forename: Christine M
authors.initials: CM
authors.lastname: Lohse
authors.forename: Bradley C
authors.initials: BC
authors.lastname: Leibovich
authors.forename: Michael L
authors.initials: ML
authors.lastname: Blute
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002292:Carcinoma, Renal Cell / Q000175:diagnosis* / Q000401:mortality / Q000601:surgery*; D005260:Female; D006801:Humans; D007680:Kidney Neoplasms / Q000175:diagnosis* / Q000401:mortality / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D009378:Neoplasms, Multiple Primary / Q000175:diagnosis* / Q000401:mortality / Q000601:surgery*; D016609:Neoplasms, Second Primary / Q000175:diagnosis* / Q000401:mortality / Q000601:surgery*; D015996:Survival Rate; D055815:Young Adult