Watchful waiting is possible option for renal masses

Chicago-In patients with a contrast-enhancing renal mass, delayed intervention after watchful waiting does not adversely affect pathologic outcomes, results of a retrospective study designed to gain insight into the natural history of "incidentalomas" indicate. This holds true even for some lesions that are relatively large at diagnosis or found on follow-up to be rapidly growing, researchers from University of North Carolina at Chapel Hill reported at the American College of Surgeons clinical congress.

The study included 43 patients with 46 masses who had planned expectant management because of choice or comorbidity. Thirteen patients with 14 renal masses eventually underwent surgery, usually after convalescence from a condition existing at the time of renal mass diagnosis. Mean period of surveillance was 32.8 months for patients who had no intervention and 43.5 months for the intervention group. Eleven of the masses were relatively large at initial diagnosis, ranging from >4 to 6.6 cm, and three exhibited a rapid growth rate (>3 standard deviations above the group mean).

At surgery, 12 of the masses were diagnosed as renal cell carcinoma, one was a benign cyst, and one was an angiomyolipoma. The RCCs were all stage 1. Two lesions were Fuhrman grade 1, eight were grade 2, and two were grade 3. Notably, no patient had upstaging of disease secondary to delay in treatment and no patient had evidence of disease after a mean follow-up of 32 months post-surgery, reported Daniel McRackan, MD, a UNC urology resident working with senior author Raj Pruthi, MD.

"The natural history of small renal masses remains a mystery, and the population of patients reported to have been managed expectantly remains small, consisting only of about 350 patients. However, the results of our study are consistent with limited existing reports in suggesting that watchful waiting may be an appropriate option for renal masses in carefully selected patients, especially for those with competing comorbidities," Dr. McRackan said.

Larger masses included

The patients included in the current retrospective study had contrast-enhancing masses consistent with RCC. Any cystic component was classified as Bosniak IV. They were followed every 3 months with CT or MRI. Patients with known or suspected von Hippel-Landau disease were excluded.

The patients had a mean age of 67 years. Those who eventually came to surgery were significantly younger than those who did not receive intervention (56 vs. 71 years).

The mean initial mass size (maximum cross-sectional diameter) of 2.9 cm was not significantly different between the intervention and non-intervention subgroups. Mean annual growth rate was 0.70 cm/year. While it tended to be slower in the non-intervention group than in the patients who had surgery (0.61 vs. 0.90 cm/year), the difference was not statistically significant.

When the patients were stratified by age into two groups (≤60 and >60 years), the tumor growth rate was faster in the younger patients (0.7 vs. 0.4 cm/year), but the difference was not significant.

"Our study has a relatively small number of patients, but we also performed a meta-analysis including all patients in published series, and the findings showed a significant inverse correlation between age and growth rate," Dr. McRackan said.

A subset analysis of growth rate and outcomes was also performed considering the 11 masses in the series that were more than 4 cm at initial measurement. Compared with smaller lesions, the larger masses had a faster mean growth rate (0.9 vs.0.4 cm/year), but a slower median growth rate (0.5 vs. 0.6 cm/year). Three of the larger masses exhibited no growth during a median follow-up of 11 months.

"The masses followed on most other studies are under 4 cm, but in one report including five larger masses followed for a mean of 31 months, no patient had evidence of metastasis and one lesion also showed no growth," Dr. McRackan said. "While these findings suggest larger masses may also be managed expectantly, some studies show 5 cm may be the best cutoff for predicting 5-year survival and likelihood of progression of RCC. Therefore, caution is certainly warranted in this situation."

For the three rapidly growing masses in the intervention group, the calculated annual growth rates ranged from 1.9 to 2.7 cm/year. However, in all cases, the rapid size increase was noted at the first follow-up scan, and the patients have no evidence of disease after a mean postoperative follow-up of 20 months.