External beam radiation therapy evaluated in patients with breast cancer with cutaneous mastocytosis.

Abstract

95 Background: Mastocytosis is a rare disease characterized by an excess of mast cells. The most common presentation is cutaneous mastocytosis (CM) presenting with skin lesions of urticaria pigmentosa (UP). There is concern of anaphylactic shock from the interaction of ionizing therapeutic radiation and mast cell activation in these patients. There is very little if anything published regarding radiation treatment of patients with cutaneous mastocytosis. Literature has ranged from radiation possibly causing mastocytosis in breast cancer patients to radiation treating canine mast cell tumors. Two patients are reported in order to explore and document the tolerance and safety of breast radiation in patients with cutaneous mastocytosis. Methods: Two patients with CM presented with early stage breast cancer for radiation treatment. Three dimensional conformal radiation to the breast was given. Epinephrine injection was kept at the patient’s side during treatment. With the initiation of radiation, a steroid and additional anti-inflammatory medicine or antihistamine were taken with the baseline medication, prior to each treatment. Monitoring was performed after treatment. To minimize potential toxicity, radiation started with the boost field to confirm acceptable tolerance. Results: Both patients tolerated the radiation without any unusual acute or late toxicities. There was no anaphylaxis. Both patients showed a decrease in the UP rash in the radiated field. Tryptase levels, a marker for CM, remained stable or decreased. Conclusions: Two patients with cutaneous mastocytosis showed excellent tolerance of breast radiation therapy. In the radiation field, UP improved and may be indicative of mast cells being sensitive to radiation in small volumes. Breast radiation avoids more extensive surgery and anesthesia, which are known to exacerbate CM. Radiation therapy to the breast appears to be safe for patients with cutaneous mastocytosis. Precautions of starting with the boost field, monitoring the patients, and maximizing medical treatment, should be taken given the limited data. This report is the first to document the safety of breast radiation in patients with cutaneous mastocytosis.