Postoperative radiation therapy for extramammary Paget's disease.

ABSTRACT

BACKGROUND: Extramammary Paget's disease (EMPD) is a rare cutaneous malignancy that is usually treated with surgery. Patients with positive surgical margins require adjuvant therapy, but there have been few reports on the use of radiation therapy. OBJECTIVES: To investigate the effectiveness of postoperative radiation therapy in EMPD. MATERIALS AND METHODS: Twenty-one patients with EMPD involving the genitalia underwent radiation therapy as adjuvant therapy after surgery. Ten patients had inguinal lymph node involvement before radiation therapy, but none had distant metastases. A median total dose of 59·4 Gy (range, 45-64·8 Gy) was delivered to the tumour bed in 30 fractions (range, 23-36 fractions). RESULTS: At a median follow-up period of 38 months, all patients had local control. However, six patients had developed distant metastases 6-43 months after radiation therapy. The distant metastasis-free rates were 66% at 3 years and 55% at 5 years. Inguinal lymph node involvement was a significant risk factor for distant metastases. Four patients died 33-58 months after irradiation; the causes of death were tumour progression in three patients and infectious pneumonia in one. The overall and cause-specific survival rates were both 92% at 3 years, and 62% and 71% at 5 years, respectively. No therapy-related toxicities of grade ≥ 3 were observed. CONCLUSIONS: Postoperative radiation therapy is safe and effective in maintaining local control in patients with EMPD.