Case series of patients treated with the oral fluoropyrimidine S-1 after capecitabine-induced coronary artery vasospasm

Fluoropyrimidines are widely used in cancer therapy for various solid tumours. Cardiotoxicity is an infrequent but relevant fluoropyrimidine-related toxicity, with a reported incidence in larger studies between 1.2% and 5.9% [1,2]. Its symptoms can be serious and often necessitate treatment discontinuation, thereby compromising the outcome of treatment. The most well-known fluoropyrimidine-related cardiotoxicity is coronary artery vasospasm, which is characterised by intermitting angina-like chest pain. This is observed during intravenous infusion of 5-fluorouracil (5-FU) and oral capecitabine administration. To date, re-challenging fluoropyrimidines has been considered unattractive in view of the high rates of recurrent symptoms [3,4]. The oral fluoropyrimidine S-1 may be promising in this respect, since S-1 results in significantly lower serum concentrations of cardiotoxic 5-FU-metabolites compared to other fluoropyrimidines [5]. Moreover, to date no cases of cardiotoxicity upon treatment with S-1 have been reported in clinical trials. In this case series, we present 7 patients who switched to S-1 after capecitabine-induced coronary vasospasm.