Targeting the GTV in medically inoperable endometrial cancer using brachytherapy.

PURPOSE

We aimed to determine the relationship between gross tumor volume (GTV) dose and tumor control in women with medically inoperable endometrial cancer, and to demonstrate the feasibility of targeting a GTV-focused volume using imaged-guided brachytherapy.

METHODS AND MATERIALS

An endometrial cancer database was used to identify patients. Treatment plans were reviewed to determine doses to GTV, clinical target volume (CTV), and OARs. Uterine recurrence-free survival was evaluated as a function of CTV and GTV doses. Brachytherapy was replanned with a goal of GTV D98 EQD ≥ 80 Gy, without regard for coverage of the uninvolved uterus and while respecting OAR dose constraints.

RESULTS

Fifty-four patients were identified. In the delivered plans, GTV D90 EQD ≥ 80 Gy was achieved in 36 (81.8%) patients. Uterine recurrence-free survival was 100% in patients with GTV D90 EQD ≥ 80 Gy and 66.7% in patients with EQD < 80 Gy (p = 0.001). On GTV-only replans, GTV D98 EQD ≥ 80 Gy was achieved in 39 (88.6%) patients. Mean D was lower for bladder (47.1 Gy vs. 73.0 Gy, p < 0.001), and sigmoid (47.0 Gy vs. 58.0 Gy, p = 0.007) on GTV-only replans compared to delivered plans. Bladder D was ≥ 80 Gy in 11 (25.0%) delivered plans and four (9.1%) GTV-only replans (p = 0.043). Sigmoid D was ≥ 65 Gy in 20 (45.4%) delivered plans and 10 (22.7%) GTV-only replans (p = 0.021).

CONCLUSIONS

OAR dose constraints should be prioritized over CTV coverage if GTV coverage is sufficient. Prospective evaluation of image-guided brachytherapy to a reduced, GTV-focused volume is warranted.