Oligometastatic Breast Cancer

In oligometastatic breast cancer, the cancer has spread to parts of the body away from the breast, but there are only a few, usually small, metastatic lesions. Oligos means few in Greek.

Oligometastatic disease isn’t limited to breast cancer. Other types of cancer also can be oligometastatic.

Little research has been done on oligometastatic breast cancer, so there are no standards of care and no standard definition. Some doctors consider five or fewer metastatic lesions to be oligometastatic disease. Others limit the definition to no more than three metastatic lesions.

Oligometastatic breast cancer can be de novo, meaning it is the first diagnosis of breast cancer, or it can be synchronous, meaning that it is diagnosed at the same time as cancer in the breast area. Breast cancer also can recur (come back) as oligometastatic disease. In oligoprogression, one or a few metastatic sites grow in otherwise stable metastatic breast cancer.

There is also a condition that doctors call induced oligometastases, which means larger areas of metastatic breast cancer are converted to oligometastatic disease after treatment eliminates most of the larger areas.

Oligometastatic breast cancer is often found incidentally, during other testing, rather than because it’s causing symptoms. Oligometastatic disease tends to be hormone receptor-positive or HER2-positive rather than triple-negative.

Although oligometastatic disease is not well understood, it’s not rare: It’s estimated that up to 20% ¹ of people diagnosed with metastatic breast cancer have oligometastatic disease. Statistics on oligometastatic breast cancer diagnoses aren’t routinely collected. We do know that among people diagnosed with metastatic breast cancer who are part of major phase II and phase III clinical trials studying systemic therapies, about 50% ² have two or fewer metastatic sites.

Systemic therapies are treatments that affect the whole body by going through the bloodstream. Chemotherapy, hormonal therapy, targeted therapy, and immunotherapy are examples of systemic treatments.

The few studies that have been done suggest that people with oligometastatic breast cancer have better outcomes than people with a larger number of metastatic lesions or lesions that are more widespread throughout the body.

In one of the few trials on oligometastatic disease, a study ³ published in 1983 found that people with five or fewer metastatic lesions had better survival than people with more metastatic lesions.

More recent research ⁴ has found that people diagnosed with early-stage breast cancer who develop metastatic disease with five or fewer lesions have better five-year survival rates than people with more than five lesions.

There is no standard treatment approach for oligometastatic breast cancer. In most cases, oligometastatic breast cancer is treated like metastatic breast cancer, with systemic therapies, such as chemotherapy and appropriate hormonal therapies, targeted therapies, or immunotherapy, based on the cancer’s characteristics.

Whether or not to also use local treatments — therapies that affect just the area where the cancer is, such as surgery and radiation — for a few metastatic lesions is a topic of ongoing debate among oncologists and researchers.

Studies on adding local treatments to systemic treatments for oligometastatic breast cancer have offered disappointing results.

The NRG-BR002 study ⁵ presented at the 2022 American Society for Clinical Oncology (ASCO) Annual Meeting, found that adding surgery or high-dose radiation to systemic treatments for oligometastatic breast cancer didn’t improve progression-free survival or overall survival. About 80% of the cancers in the study were hormone receptor-positive and HER2-negative.

Progression-free survival is how long a person lives without the cancer growing. Overall survival is how long a person lives, whether or not the cancer grows.

“The important thing to remember is that everyone’s treatment plan for oligometastatic breast cancer will be different,” explained Brian Wojciechowski, MD, a medical oncologist with Crozer Health and Breastcancer.org medical adviser. “We need a personalized treatment approach to oligometastatic disease, based on the characteristics of the cancer and the location of the metastatic lesions. Local treatments may be appropriate for some people.”

“Local treatment for oligometastatic breast cancer is a controversial issue,” added Jenni Sheng, MD, a medical oncologist at the Johns Hopkins School of Medicine and Breastcancer.org medical adviser. “Local treatments for someone with oligometastatic breast cancer are almost always discussed at a clinic’s tumor board to get input from a variety of specialties.”