Postoperative radiation therapy for extramammary Paget's disease

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.To investigate the effectiveness of postoperative radiation therapy in EMPD.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).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.Postoperative radiation therapy is safe and effective in maintaining local control in patients with EMPD.