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 ⩾ 85 Gy 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 85 Gy. 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 ± 4 Gy EQD2 (p < 0.001), while doses to bladder and rectum (D_2cm ³) were reduced by 2 ± 2 Gy and 3 ± 2 Gy, respectively (p < 0.001). Conclusions VDD significantly reduces dose to the upper vagina which is expected to result in reduction of vaginal stenosis.