Renal cell carcinoma with metastasis to the pancreas: a model for oligometastasis, oligoprogression and metastatic organotropism.

Metastatic cancer has been considered uniformly fatal in the past with very poor outcomes for most cancer sites. However, novel systemic and targeted therapies have rendered unique responses with longer survival across several cancer types and metastatic sites. In addition, improved surgical experience and safety with good outcomes has made metastasectomy as an alternative curative-intent treatment across multiple organ sites. The pancreas is an uncommon site for metastasis, even if >30 different primary tumor entities have been described to metastasize to the pancreas. More than half of all resected metastasis in the pancreas are from renal cell carcinoma (RCC). RCC demonstrates a particular capacity to metastasize to nearly any site in the body-including uncommon sites like the tongue, salivary glands, spleen, testes, and pancreas-and, have remarkable plasticity and specific molecular trajectories with clinical implications. Cancer cells have a propensity to metastasize to specific organ sites, such as the lungs, liver or skeleton, called "organotropism" and the inherent tumor biology as well as the concept of 'oligometastatic' disease is still controversial and conflicting. Pancreatic metastasis has a very different biology from other RCC metastatic sites. Clinical observations suggest an indolent biology that warrants further investigation. Survival times are very long and approaching up to 10 years in recent series. In this paper we discuss the specific situation of pancreatic metastasis from RCC, the relation to oligometastasis and organotropism and how this can be viewed as a model to better understand cancer biology.