Dose-volume effects in pathologic lymph nodes in locally advanced cervical cancer

Objective

In cervical cancer patients, dose-volume relationships have been demonstrated for tumor and organs-at-risk, but not for pathologic nodes. The nodal control probability (NCP) according to dose/volume parameters was investigated.

Material and methods

Patients with node-positive cervical cancer treated curatively with external beam radiotherapy (EBRT) and image-guided brachytherapy (IGABT) were identified. Nodal doses during EBRT, IGABT and boost were converted to 2-Gy equivalent (α/β?=?10?Gy) and summed. Pathologic nodes were followed individually from diagnosis to relapse. Statistical analyses comprised log-rank tests (univariate analyses), Cox proportional model (factors with p?≤?0.1 in univariate) and Probit analyses.

Results

A total of 108 patients with 254 unresected pathological nodes were identified. The mean nodal volume at diagnosis was 3.4?±?5.8?cm³. The mean total nodal EQD2 doses were 55.3?±?5.6?Gy. Concurrent chemotherapy was given in 96%. With a median follow-up of 33.5?months, 20 patients (18.5%) experienced relapse in nodes considered pathologic at diagnosis. Overall nodal recurrence rate was 9.1% (23/254). On univariate analyses, nodal volume (threshold: 3?cm³, p?α/β10, p?=?.039) were significant for nodal control. The use of simultaneous boost was borderline for significance (p?=?.07). On multivariate analysis, volume (HR?=?8.2, 4.0–16.6, p?

Conclusion

A nodal dose-volume effect on NCP is demonstrated for the first time, with increasing NCP benefit of additional doses to higher-volume nodes.