Surgical resection of a primary malignancy, while critical for cure, results in postoperative immune suppression, characterized by MDSC mediated inhibition of NK cell killing. In preclinical models the causal link between this immune suppression and the formation of postoperative metastases is undeniable. Fortunately, this postoperative immune suppression is preventable using modulators of MDSC and NK cell function. In this Phase Ib study the hypothesis is that simultaneous administration of perioperative tadalafil, to prevent MDSCs from suppressing NK cells, and influenza vaccine, to directly activate NK cells will safely and effectively reverse the effects of surgical stress on NK cell cytotoxicity. This is a necessary first step towards demonstrating that this re-purposed perioperative regimen can reduce the formation of postoperative metastatic disease in cancer surgery patients.

In this proposed Phase I trial a carefully selected promising perioperative immunomodulatory regimen, which includes tadalafil and influenza vaccination, for rapid clinical translation. The proposal is to re-purpose these drugs, they already have ample safety data associated with their use but neither agent has been systematically administered immediately prior to surgery. This trial will allow us to not only establish the safety of this regimen but will permit a rigorous assessment of its ability to reverse surgery-induced suppression of NK cells. If this regimen can effectively prevent postoperative NK cell dysfunction without any regimen limiting toxicity then this will provide the necessary data required to undertake a randomized efficacy study in a specific cancer subtype, with cancer recurrence as the primary endpoint.