The following article features coverage from the American Urological Association (AUA) 2019 meeting. Click here to read more of Renal & Urology News’ conference coverage.

CHICAGO—Patients on active surveillance for renal cell carcinoma (RCC) may be more likely to experience spontaneous tumor shrinkage if they have papillary or chromophobe rather than clear-cell RCC, investigators reported at the 2019 American Urological Association annual meeting.

Using a prospectively maintained kidney tumor active surveillance (AS) database at a single National Comprehensive Cancer Network institute, Shervin Badkhshan, MD, and colleagues at the Roswell Park Comprehensive Cancer Institute in Buffalo, New York, studied 99 patients on AS for RCC: 58 with clear-cell RCC (ccRCC), 29 with papillary RCC (pRCC), and 7 with chromophobe RCC chRCC). For 5 patients, RCC subtype was unclassified. Of the 99 patients, 17 had shrinking tumors (more than 30% shrinkage by volume) and 82 did not, the investigators reported in a poster presentation.

Dr Badkhshan’s team identified shrinkage in 8 (28%) pRCC tumors and 4 (57%) chRCC tumors during AS without any treatment compared with only only 5 (9%) of ccRCC tumors on AS.

Median tumor volume shrinkage was 69% for pRCC, 89% for chRCC, and 46% for ccRCC, Dr Aly’s team reported. Most shrinking pRCC tumors showed extensive macrophage infiltration compared with only moderate, low, or absent levels in all growing pRCC tumors. Shrinking chRCC tumors exhibited diffusely intense eosinophilia in 3 of 4 cases. Shrinking ccRCC tumors had moderate eosinophilia but lacked macrophage infiltration.

“Among the largest series of biopsied RCC tumors on AS to our knowledge, we identified a novel phenomenon of common spontaneous tumor regression among non-clear cell subtypes on AS,” the investigators concluded. “Macrophage infiltration and common timing of shrinkage onset after the biopsy suggest a possible immune etiology despite current understanding of non-clear subtypes as relatively immunoresistant.”

The authors added that spontaneous RCC shrinkage “carries clear implications for AS patient selection, and warrants additional studies to identify clinical, histologic and molecular predictors.”

Read more of Renal & Urology News’ coverage of the AUA 2019 meeting by visiting the conference page.

Reference

Aly AAH, Badkhshan S, Menon A, et al. Spontaneous regression of renal cell carcinoma on active surveillance. Presented at the 2019 American Urological Association annual meeting held May 3-6 in Chicago. Abstract MP14-09.