Real-World Evaluation of Modern Adjuvant Radiotherapy in Women with Stage IB Endometrial Cancer

SIMPLE SUMMARY: Endometrial cancer is the most common cancers of the female genital tract. However, the optimal adjuvant treatment for stage IB endometrial cancer is not well-defined. We aimed to study the benefit of modern adjuvant radiotherapy for women with stage IB endometrial cancer. We found that adjuvant external-beam radiotherapy significantly improved survival in patients with stage IB endometrial cancer. However, the benefit of adjuvant radiotherapy varied among the patients, suggesting that the treatment should be individualized. ABSTRACT: The optimal adjuvant treatment for stage IB endometrial cancer remains undefined. We investigated the benefit of modern adjuvant radiotherapy for women with stage IB endometrial cancer. We retrospectively reviewed patients with surgically staged, pure stage IB endometrioid adenocarcinoma (2010 to 2018). Adjuvant modern radiotherapy consists of external-beam radiotherapy (EBRT) by intensity, volumetric-modulated arc radiotherapy, or image-guided vaginal brachytherapy (VBT). The study included 180 stage IB patients. Patients with grade 3 diseases had frequent aggressive histology patterns (lymphovascular space invasion (LVSI); low uterine segment involvement) and experienced significantly shorter recurrence-free survival (RFS) and overall survival (OS) than patients with grade 1/2 diseases. Adjuvant modern radiotherapy decreased the incidence of acute/chronic grade ≥2 gastrointestinal toxicity. In IB grade 1/2 patients, EBRT significantly lengthened survival (RFS/OS); patients with age >60 years, myometrial invasion beyond the outer third, or LVSI benefited the most from EBRT. EBRT also significantly improved survival (RFS/OS) in IB grade 3 patients, where patients with bulky tumors or LVSI benefited the most from EBRT. Therefore, EBRT may be beneficial for all stage IB patients.