Factors Predictive of Receiving Adjuvant Radiotherapy in High-Intermediate-Risk Stage I Endometrial Cancer

Randomized trials have shown a local control benefit with adjuvant radiotherapy (RT) in high-intermediate-risk endometrial cancer patients, although not all such patients receive RT. We reviewed the National Cancer Data Base to investigate which patient/tumor-related factors are associated with delivery of adjuvant RT.

The National Cancer Data Base was queried for patients diagnosed with International Federation of Gynecology and Obstetrics 2009 stage I endometrioid adenocarcinoma from 1998 to 2012 who underwent surgery +/- adjuvant RT. Exclusion criteria were unknown stage/grade, nonsurgical primary therapy, less than 30 days' follow-up, RT of more than 6 months after surgery, or palliative treatment. High-intermediate risk was defined based on Post Operative Radiation Therapy in Endometrial Carcinoma 2 criteria: older than 60 years with stage IA grade 3 or stage IB grade 1-2.

Seventeen thousand five hundred twenty-four met inclusion criteria, and the 13,651 patients with complete data were subjected to a multiple logistic regression analysis; 7814 (57.2%) received surgery alone, and 5837 (42.8%) received surgery + RT. Receipt of adjuvant RT was more likely among black women and women with higher income, Northeastern residence, diagnosis after 2010, greater than 50% myometrial invasion, and receipt of adjuvant chemotherapy (P < 0.05). Patients older than 80 years or those undergoing lymph node dissection were less likely to receive adjuvant RT (P < 0.05). Of those treated with RT, 44.0% received external beam therapy, 54.8% received vaginal cuff brachytherapy, and 0.6% received both. Among irradiated women, patients older than 80 years and those with Northeastern residence, treatment at academic facilities, diagnosis after 2004, and lymph node dissection were more likely to undergo brachytherapy over external beam radiation therapy (P < 0.05). Overall use of adjuvant RT was 28.8% between 1998 and 2004, 42.0% between 2005 and 2010, and 43.4% between 2011 and 2012; the difference between 1998-2004 and 2005-2010 was not statistically significant.

Fewer than half of patients with high-intermediate-risk endometrial cancer by Post Operative Radiation Therapy in Endometrial Carcinoma 2 criteria received adjuvant RT despite evidence demonstrating improved local control. Both patient- and tumor-related factors are associated with delivery of adjuvant RT and the modality selected.