Small renal masses with tumor size 0 to 2 cm : A SEER-based study and validation of NCCN guidelines

Background: The NCCN Clinical Practice Guidelines in Oncology for Kidney Cancer recommend active surveillance as an option for initial management of T1a 0- to 2-cm renal lesions, in addition to partial nephrectomy, radical nephrectomy, and focal ablation. However, contemporary data regarding the distribution of patient and renal cell carcinoma characteristics within this special patient group are scarce. Methods: Within the SEER database (2002-2016), 13,364 patients with T1aNanyMany 0- to 2-cm renal lesions treated with nephrectomy were identified. Data were tabulated according to histologic subtype, Fuhrman grade (FG1-2 vs FG3-4), age category, and sex. In addition, rates of synchronous metastases were quantified. Results: Overall, clear-cell (69.3%), papillary (21.4%), chromophobe (6.9%), multilocular cystic (2.0%), sarcomatoid dedifferentiation (0.2%), and collecting-duct histologic subtypes (0.2%) were identified. Advanced age was associated with a lower rate of FG1-2 clear cell histologic subtype (70.8%-50.3%) but higher rates of FG1-2 papillary (11.1%-23.9%) and chromophobe histologic subtypes (6.2%-8.5%). Overall, 14.5% individuals harbored FG3-4 clear cell (9.8%) or FG3-4 papillary histologic subtypes (4.8%), and both were more prevalent in men. FG3-4 clearcell and FG3-4 papillary histologic subtypes increased with age,more so in women than in men. The overall rate of synchronous metastases was 0.4% and ranged from 0 in the multilocular cystic subtype to 0.9% in the FG3-4 papillary histologic subtype, respectively, except for 13.8%in the sarcomatoid dedifferentiation histologic subtype. Conclusions: Most T1a 0- to 2-cm renal cell carcinoma represents the low-grade clear-cell or low-grade papillary histologic subtype, with an FG3-4 minority. Even in patients with the FG3-4 histologic subtype, rates of synchronous metastases are virtually zero.