Metastatic breast cancer isn’t a uniform disease but a diverse spectrum of clinical and molecular characteristics. One subset of metastatic breast cancer, called oligometastatic breast cancer, is characterized by having only a few tumor sites beyond the breast.
While the exact number of lesions that defines oligometastatic breast cancer is debated, the maximum cutoff is generally five metastatic lesions. Due to its limited growth, oligometastatic breast cancer is often considered to be more treatable than widespread metastatic cancer.
Characteristics of oligometastatic breast cancer
Oligometastatic breast cancer isn’t rare—upwards of 20% of individuals diagnosed with metastatic breast cancer will have oligometastatic disease. Many experts view it as an intermediate stage towards metastasis: It has grown beyond the primary tumor site but remains somewhat contained.
There are three main types of oligometastatic breast cancer, characterized by the time of detection:
- Synchronous oligometastatic breast cancer: Individuals with this form, also known as de novo oligometastatic breast cancer, have metastases on initial diagnosis.
- Oligorecurrent breast cancer: This form is identified after an earlier stage, non-metastatic tumor has already been successfully treated.
- Oligoprogressive breast cancer: In this type, patients with metastatic breast cancer respond to systematic therapy, but some tumor sites continue to progress.
Even though oligometastatic breast cancer is somewhat common, it’s heavily under-researched. As a result, there is no agreed-upon definition or biomarker of the disease.
Read more about breast cancer types
Diagnosing oligometastatic breast cancer
Currently, there are no standard guidelines for diagnosing oligometastatic breast cancer. In a 2020 consensus paper, the European Society for Radiotherapy and Oncology American Society for Radiation Oncology recommend positron emission tomography/computed tomography (PET/CT) to diagnose oligometastatic cancer.
Depending on suspected metastatic sites, patients may also undergo chest, abdominal or pelvic CT scans or magnetic resonance imaging (MRI) scans of the brain and spine.
Treatment considerations
When treating oligometastatic breast cancer, complete remission is often the goal. Individuals may undergo systemic therapy via chemotherapy or immunotherapy.
Another treatment approach, known as stereotactic body radiation therapy (SBRT), has emerged as a potential treatment option. This noninvasive method delivers high doses of radiation to tumors throughout the body. It’s extremely precise, meaning the surrounding healthy tissues aren’t targeted. However, evidence regarding the effectiveness of SBRT in oligometastatic breast cancer is mixed.
In some cases, surgical removal of the primary breast tumor can help curb the spread of the cancer and improve outcomes.
Prognosis of oligometastatic breast cancer
Overall, individuals with oligometastatic breast cancer have better prognoses than those with more widespread disease, especially when treated quickly and aggressively. As with any form of breast cancer, though, prognosis will depend on several factors including receptor status and response to therapy.
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