Thermoplastic mask-induced contact dermatitis: a case report

Purpose: A 44-year-old female with a history of squamous cell carcinoma of the right tonsil with multiple enlarged lymph nodes following surgical excision of the right tonsillar mass and ipsilateral neck dissection elected to undergo adjuvant radiation therapy with VMAT technique without concurrent chemotherapy. A thermoplastic mask was issued prior to radiation therapy. Following the mask fitting, the patient developed an allergic contact dermatitis reaction of the head and neck, in areas covered by the mask. Her symptoms worsened with continued use of the thermoplastic mask and radiation therapy (RT). As the patient continued and eventually finished the radiation treatment regimen, the dermatologic symptoms failed to respond with topical facial moisturizer and topical steroid treatment. The contact dermatitis reaction did not completely dissipate until about 3 months following completion of radiation therapy and contact with the thermoplastic mask.

Methodology: Thermoplastic masks have allowed for improved immobilization of the head and neck region to allow for more precise radiation therapy treatment of head and neck cancers by minimizing patient movement, as well as decreasing set-up variability between treatments. Without positional reproducibility patients are at an increased risk of receiving radiation doses to undesired or non-target areas.

Results: Acute radiation-induced dermatitis was considered but was concluded to be unlikely as the rash did not appear to follow a dose-dependent distribution. In addition, its onset followed the CT simulation, before the RT was even started.

The rash was described by dermatology to be a confluent scaly red rash in the distribution of the radiation mask that resembled the patient's previous cutaneous skin rash from lupus but was not responsive to topical steroid treatment. A shave biopsy of skin measuring 0.4 x 0.3 x 0.1 cm was taken. Histopathological findings of the specimen were described as spongiotic psoriasiform hyperplasia accompanied by superficial perivascular infiltrate of lymphocytes and eosinophils. Diagnosis from pathology indicated allergic contact dermatitis.

Thermoplastic masks largely consist of synthetic polymers such as polycaprolactone. There have been few documented cases of allergic contact dermatitis reaction to polycaprolactone recorded, especially pertaining to its composition in a thermoplastic mask.

Conclusions: We present a rare case of acute allergic contact dermatitis to a thermoplastic mask commonly used for immobilization in head and neck radiation therapy treatment. Dermatitis to the head and neck region during radiation therapy can lead to significant alteration in the radiation treatment regimen. Future suspected cases of allergic contact dermatitis to thermoplastic masks should be reported with allergic contact dermatitis patch testing results.

References: Bray FN et al. Acute and Chronic Cutaneous Reactions to Ionizing Radiation Therapy. Dermatol Ther. 2016;6(2):185-206. doi: 10.1007/s13555-016-0120-y

Weltens C, et al. Comparison of plastic and Orfit masks for patient head fixation during radiotherapy. Int J Radiat Oncol Biol Phys. 1995;33:499–507. doi: 10.1016/0360-3016(95)00178-2