Late G2 vagina toxicity in post-operative endometrial carcinoma is associated with a 68 Gy dose equivalent to 2 Gy per fraction at 2 cm of vagina.

PURPOSE

To evaluate if the dose equivalent to 2 Gy per fraction (EQD2) at 0.1 cm, 1 cm, and 2 cm of vagina in vaginal-cuff-brachytherapy (VBT) (high-dose-rate [HDR] Ir-source) ± external-beam-irradiation (EBRT) is associated with toxicity in post-operative endometrial carcinoma (P-EC).

MATERIAL AND METHODS

From June 2014 till November 2015, 67 consecutive P-EC patients underwent VBT ± EBRT; 44 patients received EBRT (median, 45 Gy; range, 44-50.4) + VBT (7 Gy), and 23 exclusive-VBT (6 Gy x 3 fractions). The upper 2.5 cm of vagina was delineated on computed tomography (CT). The active-length source was 2.5 cm, and the brachytherapy dose was prescribed at 5 mm from the applicator. D, V, and EQD2 at 0.1 cm, 1 cm, and 2 cm of the most exposed part of the vagina were calculated. Vaginal toxicity assessment was completed with a LENT-SOMA-objective-criteria. Statistics were done with the use of χ and Student's- test.

RESULTS

The mean follow-up was 23.2 months (7.6-46.8). Median D90 was 7.8 Gy. Late toxicity: 8 G1 and 9 G2. Median EQD2 in vagina was 88.6 Gy (62.8-177.6) for 0.1 cm, 72.4 Gy (57.1-130.4) for 1 cm, and 69 Gy (53-113.4) for 2 cm. Exclusive VBT vs. EBRT+VBT showed no differences in vaginal toxicity. There was no relationship between EQD2 at 0.1 cm and 1 cm of vagina with G1-G2 toxicity ( = 0.62 and = 0.58, respectively). G2 toxicity was related to EQD2 at 2 cm ( = 0.03). EQD2 > 68 Gy caused G2 late toxicity in 20.5% patients. All patients presenting G2 toxicity received > 68 Gy EQD2.

CONCLUSIONS

More than 68 Gy EQD2 at 2 cm was related to G2 toxicity in P-EC-VBT. Further studies including larger number of patients are needed to confirm these results. Patients receiving these doses should be informed of the risk of toxicity, with individualized treatment planning and follow-up to reduce G2 toxicity.