Session Item

Tumour growth dynamics – growth rate combined with metastatic seeding efficiency – is the single most important biological feature determining the likelihood of success of local ablative treatment (LAT) in an individual patient. This can be assessed using appropriate clinical imaging. In particular, when it is applied as serial imaging, metastatic lesion doubling times can be calculated, and volume changes of lesions predicted. In the context of selection criteria for LAT, detecting metastases at the edge of image resolution contains essential diagnostic information that might trigger reluctance to use, or postponing LAT. Countability of lesions could thus be a better basic parameter for LAT than number of lesions.

The entity of LAT as a treatment option in metastatic disease might best be defined not as a single procedure at one point in time, but as a series of treatments that can be given in a single or multiple sessions to different lesions. Translated into clinical practice, newly appearing lesions that remain amenable to LAT without triggering the start of a new systemic treatment, a change in systemic therapy, or initiation of best supportive care, should thus not constitute failure of LAT from an oncological perspective. In analogy with systemic therapies, failure of LAT would have to be decided when newly appearing lesions could no longer be treated with LAT and are thus progressing beyond LAT. This would have consequences for the definition of endpoints in clinical trials and registries, as a progression-of-disease event entailing failure of LAT would have to be redefined as progression beyond further options of LAT. Progression of an already locally treated metastatic lesion would constitute failure from a technical as opposed to an oncological perspective, needed when comparison of different LAT-modalities is at stake.