MR- versus CT-based high-dose-rate interstitial brachytherapy for vaginal recurrence of endometrial cancer

Brachytherapy. 2017 Nov-Dec;16(6):1159-1168. doi: 10.1016/j.brachy.2017.07.007. Epub 2017 Aug 17.

Abstract

Purpose: To compare clinical outcomes of MR-based versus CT-based high-dose-rate interstitial brachytherapy (ISBT) for vaginal recurrence of endometrioid endometrial cancer (EC).

Methods and materials: We reviewed 66 patients with vaginal recurrent EC; 18 had MR-based ISBT on a prospective clinical trial and 48 had CT-based treatment. Kaplan-Meier survival modeling was used to generate estimates for local control (LC), disease-free interval (DFI), and overall survival (OS), and multivariate Cox modeling was used to assess prognostic factors. Toxicities were evaluated and compared.

Results: Median followup was 33 months (CT 30 months, MR 35 months). Median cumulative equivalent dose in 2-Gy fractions was 75.5 Gy for MR-ISBT and 73.8 Gy for CT-ISBT (p = 0.58). MR patients were older (p = 0.03) and had larger tumor size (>4 cm vs. ≤ 4 cm) compared to CT patients (p = 0.04). For MR-based versus CT-based ISBT, 3-year KM rate for local control was 100% versus 78% (p = 0.04), DFI was 69% versus 55% (p = 0.1), and OS was 63% versus 75% (p = 0.81), respectively. On multivariate analysis, tumor Grade 3 was associated with worse OS (HR 3.57, 95% CI 1.25, 11.36) in a model with MR-ISBT (HR 0.56, 95% CI 0.16, 1.89). Toxicities were not significantly different between the two modalities.

Conclusion: Despite worse patient prognostic features, MR-ISBT was associated with a significantly better (100%) 3-year local control, comparable survival, and improved DFI rates compared to CT. Toxicities did not differ compared to CT-ISBT patients. Tumor grade contributed as the most significant predictor for survival. Larger prospective studies are needed to assess the impact of MR-ISBT on survival outcomes.

Keywords: CT; Endometrial cancer; Interstitial brachytherapy; MRI; Radiation therapy.

Publication types

  • Clinical Trial
  • Comparative Study
  • Research Support, N.I.H., Extramural

MeSH terms

  • Adult
  • Aged
  • Aged, 80 and over
  • Brachytherapy / methods*
  • Endometrial Neoplasms / diagnostic imaging
  • Endometrial Neoplasms / pathology
  • Endometrial Neoplasms / radiotherapy*
  • Female
  • Humans
  • Imaging, Three-Dimensional / methods
  • Kaplan-Meier Estimate
  • Magnetic Resonance Imaging / methods
  • Middle Aged
  • Neoplasm Grading
  • Neoplasm Recurrence, Local / diagnostic imaging
  • Neoplasm Recurrence, Local / pathology
  • Neoplasm Recurrence, Local / radiotherapy*
  • Neoplasm Staging
  • Prognosis
  • Proportional Hazards Models
  • Prospective Studies
  • Radiology, Interventional / methods*
  • Radiotherapy Planning, Computer-Assisted / methods
  • Tomography, X-Ray Computed / methods
  • Vaginal Neoplasms / diagnostic imaging
  • Vaginal Neoplasms / pathology
  • Vaginal Neoplasms / radiotherapy*