Radiotherapy (RT) is a highly effective breast cancer treatment. However, RT can deliver radiation dose to the healthy tissues of the shoulder, increasing the potential for long-term shoulder morbidity. This study compared the dose delivered to key shoulder muscles between common RT techniques and patient positioning.

The treatment plans of 54 patients were analysed, including those treated in the prone and supine positions. Eight shoulder muscles were contoured on each patient’s computer tomography scan. The following breast treatment techniques were analysed: hybrid-intensity-modulated RT (hybrid IMRT), wedged field, two partial arcs volumetric-modulated arc therapy (VMAT), hybrid VMAT, and 3-field supraclavicular technique. Moreover, the effect of patient positioning was also evaluated (supine versus prone). Muscle radiation exposure was compared for the mean dose and the percent muscle volume exposed to V15 Gy and V30 Gy.

The mean dose and exposed volume for the pectoralis major and pectoralis minor were similar between hybrid IMRT, wedged field, VMAT, and hybrid VMAT. VMAT and hybrid VMAT delivered a greater mean dose to most posterior shoulder muscles compared to hybrid IMRT, though overall exposure remained generally low for these muscles. The 3-field supraclavicular technique increased radiation exposure to all shoulder muscles, particularly to the pectoralis major, the pectoralis minor and the supraspinatus. Prone positioning significantly reduced V15 Gy and V30 Gy exposure for both anterior and posterior shoulder muscles.

Shoulder muscle exposure was similar between hybrid IMRT, wedged field, VMAT and hybrid VMAT. The anterior shoulder muscles were consistently exposed to radiation with all RT techniques investigated in this study. In comparison, the 3-field supraclavicular technique substantially increased the radiation exposure to the posterior shoulder muscles. Lastly, delivering radiation in the prone position spared the anterior and posterior shoulder muscles. These findings inform treatment planning decisions aimed at mitigating the risk of long-term shoulder dysfunction.

To evaluate the extent to which intensity-modulated arc therapy (IMAT) for high-grade gliomas is comparable with three-dimensional conformal radiotherapy (3DCRT) in relation to the dose delivered to normal brain tissue (NBT), planning target volume (PTV) conformity and the dose delivered to brainstem and optic chiasma.

A total of 16 randomly selected 3DCRT treatment plans of grade 3 gliomas were re-planned using an IMAT planning technique and dose–volume histograms were compared. Primary outcomes were maximum, mean, 1/3 and 2/3 doses to NBT outside the PTV. Also the maximum, mean, D50 and D20 doses to PTV. Secondary outcomes were maximum and mean doses to the brainstem and optic chiasm. Wilcoxon signed rank test was used to compare data.

IMAT led to a statistically significant increase in mean dose to NBT (34·4 versus 33·3 Gy, (p=0·047) but a statistically significant reduction in maximum dose to NBT (62·7 versus 63·8 Gy, p=0·004) compared with 3DCRT. IMAT led to statistically significant reductions in maximum, D50 and D20 doses to the PTV (63·3 versus 64·7 Gy, p=0·001; 60·0 versus 60·7 Gy, p=0·001 and 60·5 versus 61·8 Gy, p=0·002, respectively). No statistically significant differences were seen in doses to brainstem and optic chiasm.

IMAT is at least comparable with 3DCRT in relation to minimising dose to NBT and ensuring good PTV conformity. Doses delivered to organs at risk using IMAT were also comparable with 3DCRT. This study supports the continued use of IMAT for the treatment of high-grade gliomas.