The utility of squamous cell carcinoma antigen for the follow-up of patients with squamous cell carcinoma of the anal canal.

Background: Thirty-three patients with histologic documentation of squamous cell carcinoma (SCC) of the anal canal underwent prospective serial collection of 234 serum samples for radioimmunoassay of SCC tumor-associated antigen.

Methods: There were 23 female and 10 male patients, with a median age of 55 years. Twenty-two of the 33 patients had multimodality therapy with radiation therapy and chemotherapy as initial treatment.

Results: The median follow-up was 22 months (range, 4-52 months), with a median of 13 serum specimens per patient (range, 1-23 specimens). Twenty-eight patients currently have no evidence of disease, 4 patients are alive with disease, and 1 patient died with disease.

Conclusion: In these 33 patients, the sensitivity of the SCC tumor-associated antigen was 76%, specificity 86%, and positive predictive value 62%.