Image-based three-dimensional conformal brachytherapy for medically inoperable endometrial carcinoma

Area of Science:

• Gynecologic Oncology
• Radiation Oncology
• Medical Physics

Background:

• Definitive radiotherapy is an option for medically inoperable early-stage endometrial cancer.
• Image-based brachytherapy (BT) presents a potential treatment modality.

Purpose of the Study:

• To evaluate the feasibility and early outcomes of image-based BT for medically inoperable early-stage endometrial cancer.
• To assess local control, survival, and toxicity in patients treated with definitive BT.

Main Methods:

• Retrospective analysis of 38 patients with clinical Stage I endometrial adenocarcinoma treated with definitive BT (with or without external beam radiotherapy) from 2007-2013.
• High-dose-rate BT utilized MRI- or CT-based planning, with dose prescribed to the clinical treatment volume (CTV) and gross tumor volume (GTV) contoured on MRI.
• Equivalent 2 Gy doses (EQD2) were calculated for CTV and GTV coverage.

Main Results:

• Two-year actuarial local control and overall survival were 90.6% and 94.4%, respectively, with a median follow-up of 15 months.
• No Grade 2-5 late toxicities were observed.
• Mean CTV D90 EQD2 was 48.6 Gy for BT alone and 72.4 Gy for combined therapy; mean GTV D90 EQD2 was 172.3 Gy and 138.0 Gy, respectively.

Conclusions:

• Image-based BT is a feasible and effective treatment for medically inoperable early-stage endometrial cancer, yielding excellent early results.
• High doses delivered to the gross tumor volume (GTV) via BT likely contribute to the observed high local control rates.
• Development of evidence-based guidelines for image-based planning in endometrial cancer is needed to define risk-adapted target volumes and differential dose prescriptions.