Prognostic value of lymph node-to-primary tumor standardized uptake value ratio in endometrioid endometrial carcinoma

To determine whether the relative metabolic activity of pelvic or para-aortic LN compared with that of primary tumor measured by preoperative [¹⁸F]FDG PET/CT scan has prognostic value in patients with endometrioid endometrial carcinoma.

We retrospectively reviewed patients with endometrioid endometrial carcinoma who underwent preoperative [¹⁸F]FDG PET/CT scans. Prognostic values of PET/CT-derived metabolic variables such as maximum standardized uptake value (SUV) of the primary endometrial carcinoma (SUV_Tumor) and LN (SUV_LN), and the LN-to-endometrial carcinoma SUV ratio (SUV_LN / SUV_Tumor) were assessed.

Clinico-pathological data, imaging data, and treatment results were reviewed for 107 eligible patients. Median post-surgical follow-up was 23 months (range, 6-60), and 7 (6.5%) patients experienced recurrence. Regression analysis showed that SUV_LN / SUV_Tumor (P < 0.001), SUV_LN (P = 0.003), International Federation of Gynecology and Obstetrics (FIGO) stage (P = 0.006), and tumor grade (P = 0.011) were risk factors of recurrence. Multivariate regression analysis revealed that FIGO stage (P = 0.034) was the independent risk factor of recurrence. SUV_LN / SUV_Tumor showed significant correlation with FIGO stage (P < 0.001), LN metastasis (P < 0.001), lymphovascular space invasion (P < 0.001), recurrence (P = 0.001), tumor grade (P < 0.001), and deep myometrial invasion of tumor (P = 0.022). Patient groups categorized by SUV_LN / SUV_Tumor showed significant difference in progression-free survival (Log-rank test, P = 0.001).

Preoperative SUV_LN / SUV_Tumor measured by [¹⁸F]FDG PET/CT was significantly associated with recurrence, and may become a novel prognostic factor in patients with endometrioid endometrial carcinoma.