Stereotactic radiotherapy of oligometastatic disease: a new paradigm for a curative approach

In a seminal paper Hellmann and Weichselbaum [1] described for the first time oligometastasis, i.e. an intermediate state between localized cancer growth and a diffuse metastatic disease, thus challenging both the “halstedian” (“contiguous growth”) and the “systemic disease” paradigm of cancer natural history [1–3]. Characterized by the presence of up to 5 lesions (according to the current definition) [4], oligometastatic disease is an “umbrella” term encompassing different scenarios which has recently been classified into oligo-recurrence, oligo-progression and oligo-persistence, depending on whether it was diagnosed during a treatment-free interval or active systemic therapy or whether it progressed on current imaging or if it persisted after systemic therapy [5]