Oligometastatic cancer

Refers to a distinct stage of cancer with an option for therapeutic approaches that could enable long-term disease management similar to other chronic conditions or have curative potential.

Oligometastatic disease is conceptualized as an intermediate state between limited, organ-confined primary malignancy and diffuse, polymetastatic disease.

Differentiating between oligometastatic and systemic metastatic disease is essential to pursue active treatment or palliative care.

Oligometastatic disease needs to be differentiated from oligo-recurrence, in which the oligometastases occur while the primary tumor is controlled or oligo-progression, in which a lesion exhibits disease progression even as the majority of tumor burden responds to therapy.

A quantitative definition suggests up to 3-5 lesions.
Oligometastatic disease may be present at the initial time and diagnosis of the primary tumor and is called synchronous, or separated by an interval of time for recurrence since the initial diagnosis or treatment of the primary tumor, called metachronous.
Patient with metachronous oligometastases, particularly those with a long delay to recurrence have a better prognosis than tumors with metastatic disease at the time of presentation.

Aggressive local therapy of oligometastatic lesions has the potential to improve outcomes and allow the patient to be treated as a chronic disease over long periods of time.

Options for oligometastatic disease include surgery, stereotactic body radiation therapy, or radio frequency ablation.

A major objective of treating oligometastatic metastatic cancer is to achieve local tumor control while minimizing or eliminating systemic therapy associated with serious side effects.

In the STAMPEDE  study arm H, added radiation to patients with low volume metastatic prostate cancer with minimal associated toxicity and decreased doses of 55Gy in 20 fractions administered to the prostate.

An abscopal effect may be beneficial in patients with metastatic disease, when the primary tumor is treated.

The use of stereotactic ablative radiotherapy in patients with oligometastasis is associated  with less than 5% grade three or higher toxic effects (Olson R).

A proposed biological mechanism for improved clinical outcomes with local therapy is the reduction of total tumor burden, where  higher tumor burden is associated with greater expression of cancer stem cell markers.
Local consolidative therapy clinical benefits have been validated in Lung, Colorectal, Prostate colorectal and breast cancer and a range of metastatic sites including the brain, lungs, bone, and liver: demonstrable benefit with stereotactic ablative body radiotherapy.

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