A Comparative Study between Open-faced and Closed-faced Masks for Head and Neck Cancer in Radiation Therapy

Abstract

The standard of care for the immobilization of head and neck (HN) radiotherapy (RT) patients is the full head thermoplastic mask. However, full head thermoplastic masks can cause discomfort for many patients, in some instances triggering anxiety that can disrupt radiotherapy. Development of new open-face masks allows an alternative immobilization equipment for HN radiotherapy, with the aim of increased comfort with comparable, if not increased reproducibility. As such, the study aims to determine the setup reproducibility in the radiation treatment of HN patients using open face head and shoulder masks (OHSM) with customized headrest (HR) versus standard closed head and shoulder masks (CHSM) and to determine the patient’s level of comfort and satisfaction for both masks. Forty patients were prospectively randomized into two groups using simple random sampling with Microsoft Excel. Group 1 was subjected to a CHSM, immobilized with a standard HR (SHR) and Group 2, to an OHSM, with a customized HR (CHR). Cone beam computed tomography (CBCT) was taken the first 3 days, followed by weekly CBCT (prior treatment) with the results registered to the planning CT to determine the translational and rotational inter-fraction shifts and to verify accuracy. Systematic and random setup errors of the 2 arms in the anterior, superior, lateral and rotational directions were computed. Absolute shift values and proportional treatment accuracy were compared between the 2 groups using both parametric (independent t-test) and non-parametric (Mann-Whitney U test) tests. Patient’s comfort and satisfaction were assessed both at CT-scan time and at RT using 4 Likert-type scale questions including tightness of the mask, perceived anxiousness, neck and shoulder comfort and overall satisfaction; for each item, scores were compared between the two masks using Mann-Whitney U test. Analysis used the Statistical Package for Social Sciences, Version 21.0 for Windows (SPSS Inc., Chicago IL, USA). The absolute shifts in the vertical, lateral and longitudinal direction as well as Z/roll axis were not significantly different between the two masks. X/yaw and Y/pitch rotational shifts were significantly greater in Group 2 versus Group 1, for both systematic (p=0.031 and 0.021 respectively) and random settings (p=0.026 and 0.040 respectively) but still within three degrees. In terms of proportional accuracy, OHSM had a tendency to be more accurate than the CHSM in lateral (37.1% versus 28.6%), longitudinal (25.0% versus 19.1%) and vertical (33.3% versus 28.6%) planes at ±0.05cm accuracy cutoff, respectively; however, these results were not statistically significant (p>0.05). Patients reported greater neck and shoulder comfort (p=0.020) and overall satisfaction (p=0.026) using the OHSM with the CHR versus the CHSM with the SHR during CT simulation. Open masks with CHR provide comparable yet comfortable immobilization to closed masks with SHR, for HN radiotherapy.