Metastases-directed local therapies (MDT) beyond genuine oligometastatic disease (OMD): Indications, endpoints and the role of imaging

• Published in: Clinical and translational radiation oncology Vol. 45; p. 100729
• Main Authors: Widder, Joachim, Simek, Inga-Malin, Goldner, Gregor M., Heilemann, Gerd, Ubbels, Jan F.
• Format: Journal Article
• Language: English
• Published: Ireland Elsevier B.V 01.03.2024; Elsevier
• Subjects: LAT; Locally ablative therapy; MDT; Metastasectomy; Metastases-directed therapy; Oligometastases; Oligometastatic disease; SABR; SBRT; Special Issue on Current status and innovations in SBRT; Edited by Marta Scorsetti, Nicolaus Andratschke; Stereotacic ablative radiotherapy; Stereotactic body radiotherapy; Stereotactic body radiotherapy; Metastasectomy; Metastases-directed therapy; Oligometastases; SBRT; SABR; Stereotacic ablative radiotherapy; Locally ablative therapy; MDT; Oligometastatic disease; LAT
• ISSN: 2405-6308; 2405-6308
• DOI: 10.1016/j.ctro.2024.100729

•The concepts of oligometastatic state of disease and indications for metastases-directed local treatment (MDT) should be investigated independently from each other.•Replacing the criterion of a certain numerical upper limit of metastases (usually three or five) with the criterion of countability of lesions over the entire course of metastatic disease should be considered.•The technical endpoint of local recurrence of treated metastatic lesions should be distinguished from the oncological endpoint: appearance of uncountable lesions indicating polymetastatic disease. To further personalise treatment in metastatic cancer, the indications for metastases-directed local therapy (MDT) and the biology of oligometastatic disease (OMD) should be kept conceptually apart. Both need to be vigorously investigated. Tumour growth dynamics – growth rate combined with metastatic seeding efficiency – is the single most important biological feature determining the likelihood of success of MDT in an individual patient, which might even be beneficial in slowly developing polymetastatic disease. This can be reasonably well assessed using appropriate clinical imaging. In the context of considering appropriate indications for MDT, detecting metastases at the edge of image resolution should therefore suggest postponing MDT. While three to five lesions are typically used to define OMD, it could be argued that countability throughout the course of metastatic disease, rather than a specific maximum number of lesions, could serve as a better parameter for guiding MDT. Here we argue that the unit of MDT as a treatment option in metastatic cancer might best be defined not as a single procedure at a single point in time, but as a series of treatments that can be delivered in a single or multiple sessions to different lesions over time. Newly emerging lesions that remain amenable to MDT without triggering the start of a new systemic treatment, a change in systemic therapy, or initiation of best supportive care, would thus not constitute a failure of MDT. This would have implications for defining endpoints in clinical trials and registries: Rather than with any disease progression, failure of MDT would only be declared when there is progression to polymetastatic disease, which then precludes further options for MDT.