Objectives American Brachytherapy Society (ABS)-recommended interstitial brachytherapy (IBT) should be considered for bulky vaginal tumor thicker than 5 mm. The aim of this study was to evaluate the ABS consensus guideline for patients with severe vaginal invasion based on our long-term follow-up results.

Methods/Materials The study included 7 patients with vaginal cancer and 14 patients with cervical cancer invading to the lower vagina. Based on prebrachytherapy magnetic resonance imaging findings, patients received intracavitary brachytherapy (ICT) for vaginal tumors 5 mm or less or IBT for vaginal tumors less than 5 mm. Nine patients received ICT and the remaining 12 patients received IBT. For dosimetric comparison, an experimental recalculation as the virtual IBT for patients actually treated by ICT, and vice versa, was performed.

Results The 5-year local control rate for all tumors was 89.4%. No differences in local control between ICT- and IBT-treated groups were observed (P = 0.21). One patient experienced a grade 3 rectal complication. There were no significant differences in the CTV D90 and rectum D2cc between the 2 groups (P = 0.13 and 0.39, respectively). In the dosimetric study of ICT-treated patients, neither the actual ICT plans nor the experimental IBT plans exceeded the limited dose for organs at risk, which were recommended in the guideline published from the ABS. In the IBT-treated patients, D2cc for bladder and rectum of the experimental ICT plans was significantly higher than for the actual IBT plans (P < 0.001 and <0.001, respectively), and 11 experimental ICT plans (92%) exceeded the limited dose for bladder and/or rectum D2cc.

Conclusions Tumor control and toxicity after selected brachytherapy according to vaginal tumor thickness were satisfactory; IBT instead of ICT is recommended for patients with vaginal tumor thickness greater than 5 mm to maintain bladder and/or rectum D2cc.