A 25-year prospective cohort study at the National Cancer Institute evaluated 89 patients with sporadic bilateral multifocal (BMF) papillary RCC (no confirmed germline variant) to characterize tumor growth kinetics, oncologic outcomes, and renal functional impact, with active surveillance assessed in 105 tumors from 44 patients over ≥6 months of serial imaging (median follow-up 50 months).
Metastatic disease developed in 6 of 89 patients (6.7%), exclusively in those whose largest tumor exceeded 3 cm — zero metastatic events occurred when the largest tumor was <3 cm. Median tumor growth rate was 1.55 mm/yr (IQR 1.24–1.81); 64% of surveilled tumors showed interval growth. Repeat ipsilateral partial nephrectomy caused a significant eGFR decline (80.9 → 63.5 ml/min/1.73 m²; p = 0.002).
Single-institution cohort from a tertiary referral center (National Cancer Institute), which may limit generalizability. Germline testing completeness is not fully described, raising the possibility of missed hereditary cases. Relatively small sample size (n=89) limits precision of rare-outcome estimates.
For sporadic BMF pRCC with the largest tumor <3 cm, active surveillance appears safe — no metastases were observed in this group. When surgery is needed, avoid repeat ipsilateral partial nephrectomy if possible, as it carries a meaningful risk of permanent renal function loss.
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