Extramammary Paget's disease (EMPD) is a rare intraepithelial adenocarcinoma affecting the genitals and axillary regions. As metastasis of these tumours is itself rare, solid disease management strategies have not been established. Serum carcinoembryonic antigen (CEA) and cytokeratin 19 fragment 21‐1 (CYFRA 21‐1) levels have been identified as candidate biomarkers for tumour progression in EMPD; however, neither the accuracy of, nor correlation between, these markers have been examined in EMPD patients.
Serum CEA and CYFRA 21‐1 levels were examined in 30 EMPD patients treated at Keio University Hospital, and compared against clinical information retrospectively. Both assays were performed at the time of diagnosis, during the postoperative observation period, and following systemic treatment in those with confirmed metastasis. Serum levels were then correlated with tumour progression status and treatment responses.
Normal levels for both assays were observed in all 11 primary localised patients (100%). In metastatic patients, the CEA positivity rate was 78·9% (15/19 patients) and 63·1% (11/19 patients) for CYFRA 21‐1. Changes in CEA and CYFRA 21‐1 levels were statistically independent; however, using a combined view, elevated levels of either marker improved the positivity rate to 94·8% (18/19 patients). Use of both markers also correlated well with the treatment responses.
The combination of CEA and CYFRA 21‐1 is useful for predicting metastasis and treatment response in EMPD patients, especially in those who only have elevation of a single marker.