Patterns of lymph node metastases and their implications in individualized radiotherapeutic clinical target volume delineation of regional lymph nodes in patients with endometrial cancer

Purpose: To study the patterns of lymph node metastasis (LNM) of endometrial cancer (EC) and to clarify the individualized clinical target volume delineations of regional lymph nodes (CTVn). Methods: Data from a total of 556 patients with EC who had undergone total hysterectomy associated with bilateral salpingo-oophorectomy (TH/BSO) and systematic lymphadenectomy were retrospectively examined. The clinicopathological factors related to LNM were analyzed using logistic regression analysis. Results: LNM was found in 76 of 556 patients, resulting in a metastasis rate of 13.67%. The rates of LNM in patients with fundus and cornua lesions were 7.56% for para-aortic nodes and 14.41% for pelvic lymph nodes. The rates of LNM in patients with sidewall lesions were 3.15% for para-aortic nodes and 10.22% for pelvic lymph nodes. The rates of LNM in patients with lower uterine segment and cervix lesions were 12.50% for para-aortic nodes and 26.67% for pelvic lymph nodes. Deep myometrial invasion, histological type, histological differentiation, and lymphovascular space invasion (LVSI) emerged as statistically significant risk factors for pelvic LNM of EC (P = 0.008, 0.015, < 0.001, 0.005, respectively). Grade 3 differentiation had a strong influence on LNM to the para-aortic nodes (P = 0.015). Conclusions: Myometrial invasion, histological type, histological differentiation, and LVSI were related to pelvic LNM and grade 3 was associated with para-aortic LNM. These factors should be considered comprehensively to design the CTVn for intensity-modulated radiation therapy (IMRT) of EC. For patients with lower uterine segment/cervix and fundus/cornua lesions, delineating the irradiation field of the para-aortic nodal region may confer a benefit.