Increase in Carbohydrate Antigen 19-9 Levels without Tumor Progression after Polaprezinc Administration that Induced Deep Vein Thrombosis in a Colon Cancer Patient.

Carbohydrate antigen 19-9 (CA 19-9) is a well-known tumor marker of adenocarcinoma (reference range, 37 U/mL). It can also be used, together with computed tomography, to monitor responses and resistance to chemotherapy in cancer patients. False elevation of CA 19-9 levels is often seen in conditions such as biliary tract obstruction and cholangitis. However, whether medication might induce false elevation of CA 19-9 levels has not yet been reported. A 74-year-old man was treated with third-line CPT-11 (irinotecan) plus panitumumab for stage IV cancer of the ascending colon. The patient developed chemotherapy-induced dysgeusia and was treated with polaprezinc. After polaprezinc administration, his CA 19-9 levels gradually increased from 18.9 to 1,699.4 U/mL. He developed deep vein thrombosis (DVT), although it was not associated with progressive disease or metastasis. Upon discontinuation of polaprezinc, CA 19-9 levels gradually decreased. This case demonstrates that polaprezinc may not only induce false elevation of CA 19-9 levels but also cause development of DVT induced by increased CA 19-9 levels, both of which are very rare events.