Clinical and dosimetric impact of adaptive intensity-modulated radiotherapy in locally advanced head-and-neck cancer

Radiotherapy in head-and-neck cancer (HNC) is a challenging task, and the anatomical alterations occurring during the course of intensity-modulated radiotherapy (IMRT) can be compensated by adaptive radiotherapy (ART) which utilizes repeat computed tomography (CT) scans during the treatment course for replanning. In this study, the clinical and dosimetric benefits of ART were compared with the conventional IMRT.Sixty patients with locally advanced HNC were randomized into two arms to receive IMRT up to a curative dose of 70 Gy with concurrent weekly chemotherapy and were prospectively analyzed between March 2018 and March 2019. Repeat CT scan was acquired after the 3rd week of radiation. Patients in the study arm underwent replanning, whereas those in the control arm continued with the first IMRT plan. Assessment was done weekly till the end of treatment and at 1, 3, and 6 months post IMRT for disease response and toxicities. Tumor volume reduction rate (TVRR) and dose reduction to organs at risk were also recorded.Complete response was observed in 90% and 96.7% patients in the control and study arms, respectively, at the end of 6 months. Insignificant differences were found between the two arms in terms of toxicities. Xerostomia was statistically significantly higher in the control arm at 6 months (P = 0.01). TVRR was found to be 31.85%. Dose to spinal cord, ipsilateral, and contralateral parotid reduced by 4.3%, 6%, and 2.2%, respectively, with ART.Mid-treatment adaptive replanning can help in better target coverage and minimize toxicities in HNC patients.