Top Line: What is oligometastatic disease?
The Studies: Oligometastatic disease (OMD) has exploded onto the scene over the past few years. And while it’s obviously a spectrum of disease, we need concrete definitions to generate meaningful data and guide appropriate use of aggressive forms of treatment. Here, ESTRO and EORTC provide their classification of OMD. In addition, ASTRO and ESTRO are accepting public comment until January 13 on their proposed consensus definition of OMD as it applies more specifically to radiation oncology. We’ll blend the two here. Overall, the groups stop short of using an arbitrary number of lesions to define OMD--instead basing that recommendation (when it comes to local therapy) on the feasibility of treating all sites. The major break point in overall classification is whether disease presents in an oligometastatic state (genuine OMD) or a polymetastatic state (induced OMD). This is an important biological distinction as it represents different disease capacities for further metastatic spread. The former is divided into de novo and repeat OMD with the latter being a state of limited disease after prior treatment of de novo OMD. Furthermore, de novo OMD can be synchronous (think single bone met within 6 months of treatment) or metachronous (think single bone met 5 years after treatment). Lastly, we get to these states through events like oligorecurrence, oligoprogression, and oligopersistence. Excepting de novo OMD, aggressive focal therapy would be aimed at reversing these events. Put another way, the goal of local therapy is to maintain the oligometastatic state by preventing progression to polymetastatic disease. Now all we need is an ICD-10 update for OMD.
TBL: Using a common framework for classifying OMD will help us generate and interpret more meaningful data as we venture further into a new era in cancer therapy. | Guckenberger, Lancet Oncol 2020 and Lievens, ASTRO 2020


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