Vaginal dose de-escalation in image guided adaptive brachytherapy for locally advanced cervical cancer.

PURPOSE: Vaginal stenosis is a major problem following radiotherapy in cervical cancer. We investigated a new dose planning strategy for vaginal dose de-escalation (VDD).

MATERIALS AND METHODS: Fifty consecutive locally advanced cervical cancer patients without lower or middle vaginal involvement at diagnosis from 3 institutions were analysed. External beam radiotherapy was combined with MRI-guided brachytherapy. VDD was obtained by decreasing dwell times in ovoid/ring and increasing dwell times in tandem/needles. The aim was to maintain the target dose (D90 of HR-CTV⩾85Gy EQD2) while reducing the dose to the surface of the vagina to <140% of the physical fractional brachytherapy dose corresponding to a total EQD2 of 85Gy.

RESULTS: The mean vaginal loading (ovoid/ring) was reduced from 51% to 33% of the total loading with VDD, which significantly reduced the dose to the vaginal dose points (p<0.001) without compromising the target dose. The dose to the ICRU recto-vaginal point was reduced by a mean of 4±4Gy EQD2 (p<0.001), while doses to bladder and rectum (D2cm(3)) were reduced by 2±2Gy and 3±2Gy, respectively (p<0.001).

CONCLUSIONS: VDD significantly reduces dose to the upper vagina which is expected to result in reduction of vaginal stenosis.