Stereotactic Radiation for Oligometastatic and Oligoprogressive Stage IV Breast Cancer: A Case-based Review

For decades, the distant progression of breast cancer has been the purview of systemic therapy alone or with low to moderate-dose radiation therapy intended for the palliation of symptomatic metastases. However, for decades there have been anecdotes of long-term disease-free survival with more aggressive local treatment of one or more metastases. The hypothesis of oligometastases is that the treatment of a clinically limited number of distant metastases can change the natural history of stage IV breast cancer. The advance in the technology of stereotactic body radiation (SBRT) has made it more possible to offer a non-invasive, yet potentially disease-modifying, metastases-directed ablative treatment in place of surgery or a palliative radiation regimen. Although there are promising local control and survival outcomes in phase I/II trials, there is still a lack of phase III evidence of ablative SBRT results showing any change in the natural history of metastatic breast cancer. Limited oligometastases may call for an ablative approach with SBRT when definitive long-term local control is needed for the best palliation against symptomatic progression in challenging locations. Some oligometastases that have progression on a certain systemic regimen, while others remain stable or in remission, may also be treated with SBRT in the hopes of prolonging the use of that regimen. Whether SBRT should represent the standard management for stage IV breast cancer of a limited number or of limited progression requires confirmation by phase III data. This review will discuss the data from key clinical trials as it applies to decision making in typical clinical cases considered for potentially ablative SBRT for oligometastases or oligoprogression.

Automated summary

For decades, the treatment of distant metastases in breast cancer has mainly focused on systemic therapy or low to moderate-dose radiation therapy for symptom relief. However, there have been anecdotes suggesting that more aggressive local treatment of metastases could lead to long-term disease-free survival. The hypothesis of oligometastases proposes that treating a limited number of distant metastases can change the natural history of stage IV breast cancer. Stereotactic body radiation (SBRT) technology has advanced, allowing for non-invasive, potentially disease-modifying ablative treatment for metastases. While phase I/II trials show promising local control and survival outcomes, there is still a lack of phase III evidence for ablative SBRT's impact on the natural history of metastatic breast cancer. This review discusses the data from key clinical trials to inform decision-making for potentially ablative SBRT in cases of oligometastases or oligoprogression.