A Case of Advanced Extramammary Paget’s Disease With a High Tumor Mutation Burden That Showed Partial Lymph Node Regression With Pembrolizumab

Pembrolizumab has been found effective against various solid tumors with high tumor mutation burden, but there are no reports of successful treatment with pembrolizumab for extramammary Paget's disease (EMPD) with a high tumor mutation burden (TMB). This report describes a 71-year-old male patient who presented with irregularly shaped erythematous lesions on his scrotum, which had been there for several years. He was diagnosed with EMPD. A gene panel test indicated a high TMB. Six months after radical surgery, many lymph node metastases were found. We started a combination chemotherapy of tegafur-gimeracil-oteracil potassium (TS-1) and docetaxel. After three courses, a CT scan showed reductions in the sizes of all the metastatic lesions. However, the treatment was switched to pembrolizumab at the patient’s request. After four cycles of the pembrolizumab treatment, a CT scan showed further shrinkage in most of the lymph node metastases. As far as we know, the present patient is the first case of advanced EMPD with response to pembrolizumab monotherapy.

Incidence and Survival of Extramammary Paget’s Disease from the Surveillance, Epidemiology, and End Results (SEER) Database

Extramammary Paget’s Disease (EMPD) is a rare intraepithelial neoplasm predominantly affecting the anogenital regions of older, female, and Asian patients. It often progresses insidiously, leading to diagnostic delays spanning years. This study, conducted through a retrospective review of EMPD patients from 22 SEER registries between 2004 and 2020, aimed to analyze contemporary trends in incidence and survival across sexes. The data included various demographics and clinical factors, and age-adjusted incidence rates were calculated over a 20-year period. Survival estimates were assessed using Kaplan-Meier curves, while Cox proportional hazards models were utilized to identify factors associated with all-cause mortality. The study included 3608 patients, with a higher incidence in Asian patients, who had a rate double that of white patients. Notably, the incidence increase was significant only among white patients. Females had a better ten-year survival rate (63.0%) compared to males (53.4%). Multivariable analysis revealed that older age, advanced disease stage, and treatment delays were linked to poorer overall survival, while primary surgical treatment significantly reduced mortality risk compared to no cancer-directed treatment. The study highlights the rising incidence of EMPD and emphasizes the importance of early, complete surgical resection in improving long-term survival outcomes.