Effect of surgical resection of metastatic disease on immune tolerance to cancer. How a systemic disease could be controlled by a local therapy.

Surgery represents the only chance of cure for patients with colorectal liver metastases. The results of expanded indications for surgical treatment revealed that even advanced disease can be cured in a significant percentage of cases. What is the explanation for this systemic impact of a local treatment such as surgery? What is different in those patients who can be cured by resection? In this review we analyse the available evidence of the complex relationship between the growing tumour and the immune system. Special attention is directed to the role of T regulatory cells (Tregs) recruited by the tumour to construct a tolerogenic microenvironment in which to grow. Based on the published data we developed the hypothesis that surgery breaks the tumour immune tolerance status because it not only removes the tumour, but also the protective shield of T regulatory cells.