Purpose: Few studies have evaluated the growth pattern of renal cell carcinoma (RCC) in patients with delayed treatment. This report investigated the growth rate and stage progression of incidentally discovered RCC following a long period of active surveillance.
Methods: Thirty-two patients who did not receive immediate surgical treatment for renal solid masses that later proved to be RCC were reviewed retrospectively. Annual tumor growth rates were calculated according to changes in the maximal diameter on CT or MRI. Clinical and pathological characteristics associated with tumor growth rate and stage progression were analyzed.
Results: The median tumor size grow from 2.14 (range, 0.30-6.70) cm to 4.33 (range, 1.40-8.80) cm after a median 46.0 months observation period. The average tumor growth rate was 0.80 (range, 0.16-3.80) cm/year. Clear cell carcinoma (0.86 cm/year) tended to grow faster than papillary cell carcinoma (0.28 cm/year) (P = 0.066). The mean growth rate of grade 2 tumors (0.88 cm/year) was faster than that of grade 1 tumors (0.36 cm/year) (P = 0.041). Thirteen tumors (40.6%) were upstaged at a median 48 months after initial presentation. Cox regression analysis revealed initial tumor size as the only risk factor for upstaging (P = 0.018). No local and systemic recurrences were noted in our cohort after the intervention at a median of 47 (range, 6-248) months of follow-up.
Conclusions: RCCs were found to be slow growing in a group of untreated renal cell carcinoma patients. However, some tumors progressed in stage under observation. The growth rate of RCC tended to correlate with histologic grade and histologic subtype.