To evaluate cause-specific mortality among patients diagnosed with kidney cancer before age 40 from 2000 to 2020 using the Surveillance, Epidemiology, and End Results incidence database.

Standardized mortality ratios (SMRs) with 95% confidence intervals (CI) were calculated for 1323 patients relative to the general population. Analyses were stratified by time from diagnosis, cancer subtype, and stage. Limitations include the use of registry data and potential coding inaccuracies.

Among all kidney cancer patients, regardless of stage, primary kidney cancer accounted for the majority of deaths (n = 882, SMR 1475.7, 95% CI 1379.9-1576.3). Patients with any type of kidney cancer, regardless of stage, had significantly higher risk of non-cancerous death (n = 312, SMR 2.44, 95% CI 2.18-2.73). Non-Wilms tumor/non-renal cell carcinoma tumors and low-stage cancers had the largest SMRs for non-cancer causes of death (n <16, SMR 5.77, 95%CI 1.57-14.77 and n = 155, SMR 2.47, 95%CI 2.10-2.90). Nephritic/nephrotic syndromes, septicemia, and accidents, suicides, and homicides were significant causes of non-cancer deaths.

Cancer survival outcomes are potentially limited by fatal later effects of treatment, psychological impacts, or comorbidities from conditions that may predispose to kidney cancers. Potential survivorship strategies could include expanded genetic screening, increased use of nephron-sparing approaches, adoption of less toxic treatment regimens, enhanced monitoring for low-stage disease, and incorporation of routine psychological support.