This E-Learning module elaborates in a concise way different issues important for making advances in oligometastatic disease in solid tumours, such as understanding oligometastasis hypothesis, biological spectrum, problems with definition, precision in targeting oligometastasis in terms of imaging, treatments and biomarkers.
The module elaborates management strategies through the illustration of newer techniques, but also in different tumour sites and argues for a need of randomised clinical trials in oligometastatic disease. It also provides a prospect in terms of clinical outcomes and promises from future research in combining local ablative techniques and immunotherapy.
Only a tiny proportion of cancer cells have clonogenic potential to successfully colonise secondary organs. Specific mechanisms of oligometastasis are relatively underinvestigated. There are different reasons behind, like the use of different definitions of oligometastases, insufficient tumour models, limited human clinical trials and relevant databases.
Patients with metastasis limited in number and organ site might be cured by ablative therapies. The aim is to replace, delay, or complement the introduction of systemic treatments, relieve symptoms and/or extend overall and disease-free survival. Newer radiotherapy techniques combined with advancements in imaging and systemic therapy can allow the use of radiation as an effective local ablative treatment.
Stereotactic body radiotherapy can treat metastases in multiple organs in a patient, including some metastases not eligible for surgery. Some patients achieve long-term survival after ablative treatment and local control benefit. The authors urge that the randomised trials should be conducted now, before increasing clinical experience and expert opinion alter the balance of equipoise and render accrual impossible.
There is an open question, if the treatment of patients with oligometastatic disease extends the survival, or whether their long survival is merely due to the presence of slow-growing, indolent disease. Furthermore, better predictive and prognostic biomarkers are urgently required to determine which patients harbour micrometastases that will progress and render the treatment futile.
One potential solution to the problem of disease burden and heterogeneity within metastasis is ablative types of treatments combined with systemic treatments. There is a potential synergic effect between immunotherapy and ablative radiotherapy within the tumour microenvironment. Improvements in the molecular staging of metastasis, immunotherapy strategies, and radiotherapy delivery techniques could lead to improved disease outcomes.
