External Beam Radiotherapy of Extramammary Paget Disease

Extramammary Paget disease (EMPD) is an insidious intraepithelial neoplasm that occurs in areas with a high density of apocrine glands such as the penoscrotal area, the vulva, and occasionally the axillae. It mainly affects patients aged 50 to 80 years.¹ Clinically, EMPD presents as pruritic, nonhealing, red plaques that can be mistaken for eczema. On histology, characteristic Paget cells have abundant pale cytoplasm and atypical nuclear lobuli and are adenocarcinomatous,^1,2 usually infiltrating the epidermis.² In approximately 25% of cases, EMPD is associated with neoplastic disease in adnexal structures or organs with a contiguous epithelial lining.² Therefore, screening for an underlying malignancy when EMPD is first diagnosed is indispensable.

Because EMPD tends to be multifocal, presents in elderly patients, and affects functionally important areas such as the anal canal or genitals, treatment often is difficult.^3,4 Surgery generally is considered as a first-line treatment⁵; however, the rate of positive margins ranges from 36% to 67%, and local recurrence is common.¹

Radiotherapy has been used in EMPD patients mainly when surgery was not an option or was not effective, but several reports have indicated that it should play a more important role in the treatment of EMPD. Luk et al¹ described 6 patients who were treated with different types of radiotherapy. Similar to the results of prior studies,^3,5,6 they concluded that it was an effective treatment of EMPD.¹

We conducted a retrospective study to analyze long-term outcomes in 7 patients who were treated with external beam radiotherapy (EBRT) for EMPD.

Methods

Seven patients (6 men and 1 woman) who had been diagnosed with EMPD and were treated with EBRT at the Department of Dermatology at the University Hospital Zurich in Switzerland (1988-2004) were evaluated. The diagnosis was confirmed by a dermatopathologist or pathologist via histology. Data regarding clinical presentation, EBRT regimen, and side effects were retrieved from the medical records. Long-term outcomes were evaluated by an attending dermatologist (1 case), a general practitioner (5 cases), or the hospital’s outpatient department (1 case). None of the patients showed an associated malignancy at the time of treatment; however, patient 5 had been diagnosed with and treated for a sigmoid colon adenocarcinoma 6 years prior to undergoing EBRT for EMPD. Three patients (patients 3, 5, and 7) received EBRT for local relapse after prior treatment of EMPD (ie, CO₂ laser, multiple local treatments). One patient (patient 2) underwent surgical excision prior to EBRT. The remaining 3 patients had not undergone any prior treatment of EMPD. All patients underwent EBRT with the goal of complete remission.

Six patients received low-energy radiotherapy of 20 to 30 kV at doses of 200 to 400 cGy per day for 2 to 5 days per week until a total dose of 4000 to 5600 cGy was completed. A 0.4- to 0.5-mm aluminum filter was used, and the focus-skin distance (FSD) was 20 cm. One patient was treated with a radiograph of 40 kV at 400 cGy per day for 2 days per week until a total dose of 4800 cGy was completed. A 1.0-mm aluminum filter was used, and the FSD was 10 cm. The field of EBRT included 2-cm margins clear of all visible disease. The treatment parameters for all patients are outlined in the Table.