Relationship Between Distance from the Superior Border of Irradiation Field to the Aortic Bifurcation and Non-Regional Lymph Node Recurrence after Definitive Radiotherapy in Uterine Cervical Cancer.

To evaluate the relationship between the distance from the superior irradiation field border to the aortic bifurcation and non-regional lymph node recurrence (NRLR) in uterine cervical cancer patients treated with definitive radiotherapy. We retrospectively investigated patients with uterine cervical cancer who had received definitive radiotherapy between January 2000 and December 2013 at our hospital. Ninety-four patients were included in this study. According to the International Federation of Obstetrics and Gynecology staging system (FIGO 2008), 14 patients were in stage I, 37 patients were in stage II, 33 patients were in stage III, and 10 patients were in stage IV. Thirty-two patients (34 %) had pelvic lymph node metastasis (N1) at the time of diagnosis. Fifty-three patients (56.4 %) were treated with concurrent chemoradiotherapy. Each external beam radiotherapy field was reviewed and the distance from the superior border of the irradiation field to the aortic bifurcation was measured. The non-regional lymph node recurrence-free survival rate (NRFS) was calculated by the Kaplan-Meier method, and differences in NRFS were evaluated by the log-rank test. All tests were two-sided, and a p value < 0.05 was considered statistically significant. The median follow-up time was 64 months (range 2 – 188 months). There were 35 patients (37.2 %) whose bifurcations were above L4 - L5 interspace. The irradiation field superior border was L4 – L5 interspace in 81 patients (86.2 %). When comparing the superior border to the level of the aortic bifurcation, the border was 1 cm or more caudal in direction to the bifurcation in 28 patients (lower group) (29.8 %) and 1cm or more cranial in direction in 20 patients (21.3 %). NRLR occurred in 19 patients. Of these, 9 patients were initially pelvic node negative (N0), and the rest of the 10 patients were N1. The 5-year NRFS was 83.2 % for the N0 and 64.7 % for the N1, respectively (p = 0.04). With regard to the superior border of the irradiated field to the level of the aortic bifurcation, the 5-year NRFS was 68.5 % in the lower group and 80.9 % in the other group (non-lower group) (p = 0.21). When limited to the N0 group, the 5-year NRFS was significantly worse in the lower group than in the non-lower group (67.5 % versus 91.3 %, p = 0.02). The N1 group had higher NRLR compared to the N0 group. In the N0 group, it could prove prudent to keep a sufficient superior margin of the irradiation field to the aortic bifurcation.