Does Thermoplastic Mask Alleivates Skin Sparing Effect of Photons in Head and Neck Cancer Patients: A Pilot study

Abstract

Introduction: Head and Neck tumors are mainly treated with concurrent chemoradiation. Treatment delivery with Megavoltage beam has the advantage of skin sparing effect but still skin reactions have been a major side effect since 2D era. Initially these reactions were due to the delivery with bilateral opposed portals but with advent of IMRT/ VMAT, it has been possible to escalate the tumor dose with the need of strict immobilization with thermoplastic mask. This thermoplastic mask may have a bolus effect and can result in increase in surface dose resulting in skin reactions. The aim of this study was to evaluate if any bolus effect of thermoplastic mask exists. Materials and Methods: A total of 15 patients of histologically proven carcinoma oropharynx and hypopharynx were taken. Patients were scanned for planning CT with thermoplastic mask. Another scan was taken in the same position but without thermoplastic mask. Same contouring and planning were done on both the scans. Plans were made and ascertained that all OAR’s and target volumes should get similar doses. Skin contoured on both the scans was evaluated for the dose received. Results: Mean dose received by skin in patients with thermoplastic mask was 48.15 GY while Mean dose received by skin in patients without thermoplastic mask was 43.18 GY. A paired t-test was applied on the dataset which revealed a statistically significant difference between the skin doses with and without mask with a p value of < 0.05. Conclusion: Increase in skin dose can be attributed of the bolus effect of thermoplastic mask. This bolus effect should be considered once high dose to skin is observed during planning or patient develops skin reaction.

The Remove-the-Mask Open-Source head and neck Surface-Guided radiation therapy system

“…Mask related anxiety can also lead to long-term mental health impacts such as symptoms of post-traumatic stress and recurrent nightmares [17] , [18] . Immobilisation masks also partially negate the skin-sparing effect of megavoltage RT and increase skin dose by up to 18 % [19] , [20] on average for coplanar RT and up to 58 % for non-coplanar, non-isocentric beam delivery [21] . Furthermore, the level of immobilisation that thermoplastic masks can achieve degrades with weight-loss induced changes in head anatomy [22] , [23] , [24] .…”