Radiation therapy for extramammary Paget's disease: treatment outcomes and prognostic factors

Extramammary Paget's disease (EMPD) is a relatively rare malignancy, and there are few reports related to radiation therapy. In the present study, we investigated the outcome of radiation therapy for EMPD.

Forty-one patients with EMPD in the genitalia underwent radiation therapy with curative intent. Fifteen patients had regional lymph node metastases before radiation therapy, but none had distant metastasis. Total doses of 45-80.2 Gy (median, 60 Gy) were delivered to tumor sites in 23-43 fractions (median, 33 fractions).

At a median follow-up period of 41 months, 16 patients had developed recurrences, including 5 with local progression within the radiation field and 12 with lymph node or/and distant metastases outside the radiation field. The local progression-free and disease-free rates were 88% and 55% at 3 years, and 82% and 46% at 5 years, respectively. Nine patients died at 6-73 months after irradiation; the causes of death were tumor progression in five patients, infectious pneumonia in two, renal failure in one and old age in one. The overall and cause-specific survival rates were 93% and 96% at 3 years, and 68% and 84% at 5 years, respectively. Tumor invasion into the dermis and regional lymph node metastasis were significant prognostic factors for both distant metastasis and survival. No therapy-related toxicities of grade ≥3 were observed.

Radiation therapy is safe and effective for patients with EMPD. It appeared to contribute to prolonged survival owing to good tumor control, and to be a promising curative treatment option.