MUC1 and head and neck squamous cell carcinoma: Nevertheless, inspired by the results of preclinical studies on mouse tumor models and a few clinical trials on tadalafil, a randomized phase I/II clinical trial (NCT02544880) was initiated by the same investigators in April 2016 to evaluate whether tadalafil treatment increased the efficacy of another anti-tumor vaccine, Anti-MUC1, in patients with resectable (minimal residual) recurrent or second primary HNSCC [55].