A 52-year-old postmenopausal woman presents with postmenopausal bleeding and pelvic pain. Transvaginal ultrasound shows an endometrial mass with myometrial invasion up to the inner third. MRI confirms FIGO stage IB endometrial cancer. She undergoes total abdominal hysterectomy with bilateral salpingo-oophorectomy and pelvic lymph node dissection. Histopathology reveals grade 2 endometrioid adenocarcinoma with lymphovascular space invasion (LVSI). Pelvic lymph nodes are negative. Which of the following is the most appropriate adjuvant treatment?

Explanation

## Clinical Context This patient has FIGO stage IB endometrial cancer (myometrial invasion to inner/middle third) with grade 2 histology and **lymphovascular space invasion (LVSI)** — a critical intermediate-risk factor. ## Risk Stratification According to **NCCN and GOG-99 trial data**, endometrial cancer risk is stratified as: - **Low-risk:** Stage IA, grade 1–2, no LVSI - **Intermediate-risk:** Stage IB, grade 1–2, OR grade 3 with myometrial invasion, OR any grade with LVSI - **High-risk:** Stage II–IV, grade 3, or non-endometrioid histology ## Evidence Base The **GOG-99 trial** (2009) demonstrated that for intermediate-risk disease, **vaginal brachytherapy alone** reduces vaginal recurrence but does NOT improve overall survival compared to observation. However, **LVSI is a strong predictor of occult systemic disease** and nodal metastasis. The **GOG-165 trial** and subsequent data show that **combined EBRT + chemotherapy** is superior to EBRT or brachytherapy alone in reducing both locoregional and distant recurrence in intermediate- to high-intermediate-risk disease, particularly when LVSI is present. ## Key Point: **LVSI presence elevates the risk profile toward high-intermediate risk** and warrants systemic therapy. Combined EBRT (pelvic ± para-aortic) with concurrent and adjuvant chemotherapy (cisplatin-based) is the standard of care for this patient. ## Mnemonic: **LVSI = Systemic Risk** → Add chemotherapy to locoregional therapy.