TYMS and squamous cell lung carcinoma: A phase III study reported an inferior activity in terms of overall survival of the combination of cisplatin and PEM compared to cisplatin and gemcitabine for squamous cell lung carcinoma and opposite data for non-squamous non-small cell lung cancer [7] and this differential efficacy was related to TS mRNA expression, being higher in squamous cell carcinoma of the lung [8, 9].