Objective Because of the rarity of uterine clear cell carcinoma (UCCC), a National Cancer Data Base analysis was conducted to evaluate practice patterns and implications of adjuvant therapy.

Methods The National Cancer Data Base was queried for UCCC patients diagnosed from 1998 to 2011. Patients receiving neoadjuvant therapy, lacking surgical staging, or having follow-up time shorter than 6 months were excluded. Factors associated with utilization were assessed using logistic regression. To define the probability of receiving chemotherapy and radiotherapy (CT + RT), propensity scores with inverse probability of treatment weighting (IPTW) were calculated using multivariable logistic regression. Log-rank test and multivariable IPTW-adjusted Cox proportional hazards modeling were then conducted.

Results A total of 2504 patients were identified, with a median follow-up of 65.5 months. Most patients had FIGO (International Federation of Gynecology and Obstetrics) stage I to II UCCC (71.4%). Adjuvant RT alone, CT alone, or CT + RT was given in 35.3%, 9.5%, and 11.7%, respectively. Among those receiving RT, external beam was the most common modality (69.4%). Later year of diagnosis (>2005: odds ratio [OR], 4.42; 95% confidence interval [95% CI], 2.44–8.01), higher FIGO stage (IIIA-IIIC2: OR, 6.34; 95% CI, 3.93–10.24), larger tumor size (3.6–5.0 cm: OR, 3.40; 95% CI, 1.76–6.55), and lymph node dissection (OR, 4.22; 95% CI, 1.60–11.15) were associated with a higher chance of receiving CT + RT. With IPTW-adjusted multivariable analysis, CT + RT significantly decreased mortality risk in stage III to IVA patients (hazards ratio, 0.41; 95% CI, 0.22–0.77), trending toward benefit in stage I to II patients (hazards ratio, 0.53; 95% CI, 0.27–1.07).

Conclusions In this hospital-based registry analysis of UCCC, adjuvant CT + RT significantly reduced the risk of death, reaching statistical significance for stage III to IVA patients.