ASCO GU 2018: The Probability of Indolent Versus Aggressive Histology Based on Renal Tumor Size: Implications for Surveillance and Treatment

San Francisco, CA ( Dr. Bimal Bhindi and colleagues from the Mayo Clinic presented their results today at the GU ASCO 2018 poster session assessing the probability of indolent versus aggressive histology based on renal tumor size. While the probability of benign versus malignant histology based on renal tumor size has been described, this alone does not sufficiently inform decision-making in the modern era of surveillance for indolent malignant tumors. Thus, the objective of this study was to characterize the probability of indolent versus aggressive histology based on radiographic tumor size.

The authors evaluated 2,650 patients who underwent radical or partial nephrectomy at Mayo Clinic for a pT1-2, pNx/N0, M0 solid renal tumor between 1990-2010. Pathology was reviewed by one genitourinary pathologist. Benign tumors, low grade (1-2) clear cell and papillary renal cell carcinoma (RCC), and any chromophobe, clear cell papillary, mucinous tubular and spindle cell, SDH-B deficient, and tubulocystic RCC were considered indolent. All other histologies were considered aggressive, as were any malignancies with necrosis or sarcomatoid differentiation. Cancer-specific survival (CSS) was estimated using the Kaplan Meier method. Logistic regression models were used to estimate the probability of malignant and aggressive histology based on tumor size, in addition to performing gender-stratified analyses.

Among the 2,650, there were 1,773 patients (66.9%) with indolent tumors (303 benign; 1470 malignant) and 877 (33.1%) with aggressive tumors. Ten-year CSS was 96% for indolent malignant tumors and 82% for aggressive tumors. The predicted probabilities of any malignant histology and aggressive malignant histology increased with tumor size:

Screen Shot 2018 02 11 at 4.59.13 PM

For any given tumor size, men had a greater probability of aggressive histology than women.

Dr. Bhindi concluded that tumor size-based estimates predict the probability of aggressive histology for renal masses. Ultimately, this information should be useful for patient counseling and treatment decision-making.

Speaker: Bimal Bhindi, Mayo Clinic, Rochester, MN

Co-Authors: Robert Houston Thompson, Christine M. Lohse, Ross Mason, Igor Frank, Stephen A. Boorjian, John C. Cheville, Bradley C. Leibovich

Written by: Zachary Klaassen, MD, Urologic Oncology Fellow, University of Toronto, Princess Margaret Cancer Centre, Twitter: @zklaassen_md, at the 2018 American Society of Clinical Oncology Genitourinary (ASCO GU) Cancers Symposium, February 8-10, 2018 - San Francisco, CA