Utilization and Role of Adjuvant Radiotherapy and Chemotherapy for Uterine Clear Cell Carcinoma: A National Cancer Data Base Analysis.

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.