Increased risk and pattern of secondary malignancies in patients with invasive extramammary Paget disease

Extramammary Paget disease (EMPD) is often associated with underlying or distant synchronous malignancies. The prognosis for affected patients is generally favourable; however, the risk of secondary malignancies is unknown.

The goal of the study was to analyse the incidence, prognosis and pattern of secondary malignancies for patients with invasive EMPD using data from the Surveillance, Epidemiology and End Results (SEER) Program.

We searched the SEER Program database for patients diagnosed with invasive EMPD between 1973 and 2008. Demographic data, outcome and secondary malignancies more than 1 year after the initial diagnosis of invasive EMPD were included in the analysis. We calculated the standardized incidence ratio (SIR) and estimated the excess absolute risk (EAR) per 10,000 person-years (PY).

There were 1439 patients who were diagnosed with invasive EMPD. Most patients (80.4%) had localized disease, while 17.1% had locoregional spread and 2.5% presented with distant disease. The SIR for secondary malignancies in patients with invasive EMPD was significantly elevated with an EAR of 97.4 additional malignancies per 10,000 PY. The excess risk was mostly due to a significantly increased incidence of colorectal and anal malignancies. The initial site of disease predicted the site of the secondary malignancies, with patients with colorectal, anal, vulvar and scrotal disease showing an increased risk of colorectal, anal, vulvar and scrotal malignancies, respectively.

Our study identified a long-term increased risk of developing secondary malignancies in patients with invasive EMPD that are mainly related to the site of origin of this disease. Patients with invasive EMPD require prolonged follow-up and screening for these malignancies.