SUO 2017: The Probability Of Indolent Versus Aggressive Histology Based On Renal Tumor Size: Implications For Surveillance And Treatment

Washington, DC (UroToday.com) The probability of benign versus malignant histology based on renal tumor size has been well-described. However, tumor size alone does not sufficiently inform decision-making in the modern era, since indolent malignant tumors can often be surveilled. Thus, we sought to characterize the probability of indolent versus aggressive histology based on radiographic tumor size.

Methods:
The authors evaluated patients who underwent radical or partial nephrectomy at Mayo Clinic for a unilateral, sporadic, pT1-2, pNx/0, M0 solid renal tumor between 1990-2010. Pathology was reviewed by a single genitourinary pathologist. Along with benign tumors, malignant tumors considered as indolent included the following: low grade (1-2) clear cell renal cell carcinoma (RCC), papillary RCC, and translocation-associated RCC, and any chromophobe RCC, clear cell papillary RCC, mucinous tubular and spindle cell RCC, SDH-B deficient RCC, and tubulocystic RCC. On the contrast, malignant tumors with necrosis or sarcomatoid differentiation were considered aggressive. All other histologies were also considered aggressive. The validity of the classification was confirmed by comparing Kaplan-Meier cancer-specific survival (CSS) estimates. Logistic regression models were used to characterize the predicted probability of malignant and aggressive histology based on tumor size. Sex-stratified analyses were also performed.

Results:
Overall 2650 patients were included. Out of these, there were 1774 patients with indolent tumors (303 benign; 1471 malignant) and 876 with aggressive tumors. Ten-year CSS was 96% for indolent malignant tumors and 82% for aggressive tumors. The probabilities of any malignant histology and aggressive malignant histology increased with tumor size. The authors gave an example, stating that the estimated probability of malignant histology for a 2.5cm renal tumor is 86%, while the estimated probability of aggressive histology is only 23%. For any given tumor size, males had a greater probability of aggressive histology than females.

Conclusion:
Estimates of the probability of aggressive histology based on tumor size can be informative for treatment decision making and patient counselling for newly diagnosed renal tumors.

Presented by: Bimal Bhindi, Rochester, MN, USA

Written by: Hanan Goldberg, MD, Urologic Oncology Fellow (SUO), University of Toronto, Princess Margaret Cancer Centre, @GoldbergHanan, at the 18th Annual Meeting of the Society of Urologic Oncology, November 29-December 1, 2017 – Washington, DC
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