The Road to Dissemination: The Concept of Oligometastases and the Barriers for Widespread Disease.

Over the last years, the oligometastatic disease state has gained more and more interest, and randomized trials are now suggesting an added value of stereotactic radiotherapy on all macroscopic disease in oligometastatic patients; but what barriers could impede widespread disease in some patients? In this review, we first discuss the concept of oligometastatic disease and some examples of clinical evidence. We then explore the route to dissemination: the hurdles a tumoral clone has to overtake before it can produce efficient and widespread dissemination. The spectrum theory argues that the range of metastatic patterns encountered in the clinic is the consequence of gradually obtained metastatic abilities of the tumor cells. Tumor clones can obtain these capabilities by Darwinian evolution, hence early in their genetic progression tumors might produce only a limited number of metastases. We illustrate selective dissemination by discussing organ tropism, the preference of different cancer (sub)types to metastasize to certain organs. Finally we discuss biomarkers that may help to distinguish the oligometastatic state.

Immune checkpoint blockade for organ transplant patients with advanced cancer: how far can we go?

PURPOSE OF REVIEW: Checkpoint inhibitors (CPIs) provide impressive response rates among immunocompetent patients with various solid tumors. So far, organ transplant recipients have been excluded from clinical studies due to the putative risk of allograft rejection however 48 cases of liver and renal transplant patients treated with CPI were already described in literature. RECENT FINDINGS: Here we discuss 19 cases of liver and 29 cases of renal transplant patients who received CPI for advanced cancer. Disease control rate [stable disease, complete response (CR) and partial response (PR) together] was 35% (21% for liver and 45% for kidney transplant patients). Graft rejection was seen in 37% of liver and 45% and kidney transplant patients. Significantly, our analysis shows that an 'ideal' response occurs in 21% of all patients (antitumor response accompanied with durable graft tolerance). SUMMARY: We believe that transplant patients can be treated with CPI in a controlled setting and for well informed patients. To obtain a durable antitumor immune response while avoiding rejection, to be able to adjust immunosuppression and to have the opportunity to develop biomarkers for tumor response and transplant rejection, these patients should be treated according to a clinical care path or a prospective clinical trial.