To find the optimal dose weighting for a combination of three-dimensional conformal radiotherapy (3DCRT) and hybrid volumetric modulated arc therapy (hVMAT) plans for thoracic oesophageal cancer radiation therapy.

This retrospective study involved fourteen patients diagnosed with carcinoma of the oesophagus previously treated with VMAT radiotherapy techniques. Four hVMAT plans were developed for each patient, with a prescribed dose of 50.4 Gy delivered over 28 fractions. The plans incorporated varying ratios of 3DCRT and VMAT techniques: hVMAT-1(33% 2F 3DCRT/67% VMAT), hVMAT-2 (33% 3F 3DCRT/67% VMAT), hVMAT-3 (67% 2F 3DCRT/33% VMAT), and hVMAT-4 (67% 3F 3DCRT/33% VMAT). Dose volume histograms were used to assess the coverage of the planning target volume (PTV) and to analyse dosimetric parameters, including the doses received by organs at risk.

In the four hVMAT techniques, statistically insignificant differences were observed in PTV doses, conformity index and homogeneity index. Notably, monitor unit values differed significantly in three techniques, except for hVMAT-1(p = 0.358). hVMAT-3 demonstrated lower lung mean dose and lung V20Gy values (14.5±3.97, 21.09 ± 9.02) compared to other techniques. There were statistically significant differences in heart mean doses between hVMAT-1 and hVMAT-2, or hVMAT-3 and hVMAT-4 plans (p = 0.462, p = 0.542). However, a significant difference in spinal cord Dmax was found only in hVMAT-1(p = 0.024).

The hVMAT -1 and hVMAT-2 techniques (33% 2F 3DCRT/67% Arc) appear to be the most suitable weighting for the hybrid VMAT technique, offering optimal sparing of the lungs and heart while ensuring adequate coverage of the planning target volume.