Incidence of adolescent and young adult renal cell carcinoma in the modern era.

568 Background: The incidence of solid tumors in adolescents and young adults (AYA) has been reported to be increasing, but contemporary patterns in renal cell carcinoma (RCC) remain underexplored. We hypothesized that the incidence of RCC would be increasing over time. Methods: Using the National Cancer Database, we assessed patients under 30 years old diagnosed with RCC between 2004–2018. We excluded Wilms tumor and retroperitoneal sarcoma diagnoses. We examined the incidence of AYA RCC over time. Multivariable logistic regression was performed to evaluate differences in demographics, tumor characteristics, and treatments across age groups (0–14, 15–21, and 22–30 years) and time periods (2004–2010 vs. 2011–2018). Results: We found 5,172 AYA patients diagnosed with RCC from 2004–2018. The incidence of RCC increased over time with 2,007 patients diagnosed between 2004–2010 and 3,165 patients diagnosed between 2011–2018. The most common AYA RCC histology was clear cell RCC (ccRCC) (46.7%), which increased by 9.8% between the two time periods. Other histologies included RCC not otherwise specified (NOS) (31.9%), chromophobe (11.0%), and papillary (10.4%). The incidence of RCC was highest in the 22–30 age group and they were more likely to have a diagnosis of ccRCC than younger patients. Patients aged 0-14 years were more likely present with papillary (22.0%) or RCC NOS (61.3%) histologies and at higher clinical stages (cT2b: 8.2%, cT3: 20%, and cT4: 5.9%) as compared to older age groups (age 15–21 papillary 15.2%, NOS 43.9% | cT2b: 5.9%, cT3: 7.5%, and cT4: 3%; age 22–30, papillary 9.4%, NOS 29.2% | cT2b: 4%, cT3: 4.6%, and cT4: 1.4%). Tumor size was also larger in 0–14 year olds as compared to those who are aged 15–21 and 22–30 (6.0cm vs 4.1cm vs 3.3cm, respectively). Patients aged 0–14 were more likely to present with node positive disease (33.7% of 0–14, 8.1% of 15–21, and 4.7% of 22–30 year olds) compared to other age groups. Rates of surgical management as first-line therapy remained consistent across age groups and over time (2004–2010: 0–14 (91.8%), 15–21 (83.0%), and 22–30 (92.1%) vs. 2011–2018: 0–14 (91.4%), 15–21 (86.6%), and 22–30 (90.0%). Conclusions: AYA RCC is rare but increasing, with the greatest burden in young adults aged 22–30. Clear cell histology predominates in this group, while younger patients are more likely to present with non–clear cell and NOS variants. Despite differences in stage and histology, rates of surgical management have remained consistent across age groups. These findings highlight the need for a high index of suspicion when evaluating AYA patients and the need to develop age-specific considerations in RCC treatment and surveillance strategies.