Defining oligometastatic disease from a radiation oncology perspective: An ESTRO-ASTRO consensus document

Abstract

Background: Recognizing the rapidly increasing interest and evidence in using metastasis-directed radiotherapy (MDRT) for oligometastatic disease (OMD), ESTRO and ASTRO convened a committee to establish consensus regarding definitions of OMD and define gaps in current evidence. Methods: A systematic literature review focused on curative intent MDRT was performed in Medline, Embase and Cochrane. Subsequent consensus opinion, using a Delphi process, highlighted the current state of evidence and the limitations in the available literature. Results: Available evidence regarding the use of MDRT for OMD mostly derives from retrospective, singlecentre series, with significant heterogeneity in patient inclusion criteria, definition of OMD, and outcomes reported. Consensus was reached that OMD is largely independent of primary tumour, metastatic location and the presence or length of a disease-free interval, supporting both synchronous and metachronous OMD. In the absence of clinical data supporting a maximum number of metastases and organs to define OMD, and of validated molecular biomarkers, consensus supported the ability to deliver safe and clinically meaningful radiotherapy with curative intent to all metastatic sites as a minimum requirement for defining OMD in the context of radiotherapy. Systemic therapy induced OMD was identified as a distinct state of OMD. High-resolution imaging to assess and confirm OMD is crucial, including brain imaging when indicated. Minimum common endpoints such as progression-free and overall survival, local control, toxicity and quality-of-life should be reported; uncommon endpoints as deferral of systemic therapy and cost were endorsed. Conclusion: While significant heterogeneity exists in the current OMD definitions in the literature, consensus was reached on multiple key questions. Based on available data, OMD can to date be defined as 1-5 metastatic lesions, a controlled primary tumor being optional, but where all metastatic sites must be safely treatable. Consistent definitions and reporting are warranted and encouraged in ongoing trials and reports generating further evidence to optimize patient benefits.

Chemoradiotherapy by intensity-modulated radiation therapy with simultaneous integrated boost in locally advanced or oligometastatic non-small-cell lung cancer—a two center experience

“…Some patients in our study had oligometastatic disease not exceeding two extrathoracic metastases. It has been shown that patients with limited metastatic disease benefit from (chemo)radiotherapy of the primary tumor in combination with metastasis-directed local treatment with regard to PFS and OS [27][28][29][30][31]. In our cohort we observed a median PFS of 7.0 months and a median OS of 19.6 months for the subgroup of UICC stage 4 patients.…”

Oligometastatic Disease Management: Finding the Sweet Spot

“…Over the past year, growing efforts have been undertaken to define oligometastatic disease and its different states in order to standardize reporting thereof (20,21). As a result, the following two conditions must be met: the maximum number of five metastases should not be surpassed, and all of them must be safely treatable, whereas a controlled primary is optional (21). According to the timing of its appearance, several distinct clinical presentations, discussed further in the text, are recognized (20)(21)(22).…”

“…As a result, the following two conditions must be met: the maximum number of five metastases should not be surpassed, and all of them must be safely treatable, whereas a controlled primary is optional (21). According to the timing of its appearance, several distinct clinical presentations, discussed further in the text, are recognized (20)(21)(22). Since a standard approach has not been determined in these situations, all patients who could potentially be considered for a local approach should be discussed in multidisciplinary tumor boards.…”

Stereotactic ablative body radiotherapy (SABR) combined with immunotherapy (L19-IL2) versus standard of care in stage IV NSCLC patients, ImmunoSABR: a multicentre, randomised controlled open-label phase II trial

“…Metastasized NSCLC patients with oligo-metastatic disease showed a benefit in progression free survival (PFS) when local ablative therapy was added to systemic therapy (chemotherapy ( [6][7][8]) or tyrosine kinase inhibitor ( [7,8])); one trial also demonstrated an improved overall survival (OS) [7]. Oligometastatic disease is usually defined as "limited metastasis" (NCCN guideline [9]), up to three metastases (ESMO guideline [5]) or up to five metastases (European Organization for the Research and Treatment of Cancer (EORTC) lung cancer group consensus definition [10][11][12] and most clinical trials [13][14][15]). These guidelines advise to treat these patients with a combination of systemic therapy and local ablative therapy, preferably within a clinical trial.…”