According to research from the National Cancer Institute, the number of women being diagnosed with metastatic breast cancer is increasing; at the same time, these women are living longer, especially younger women. Living longer with metastatic breast cancer, a stage of breast cancer which is driven in part by out-of-control production of proteins by cancerous cells, means increased needs for services and research.
While great progress has been made in the treatment of early-stage breast cancer, effective treatments are not yet available for breast cancer that has metastasized to the lungs, the bones, or other organs. Instead, individuals living with metastatic breast cancer use lines of therapies, getting treated with one drug until it eventually fails, and they must move on to the next available drug.
Among the newer metastatic breast cancer treatments that have been developed because of research are these targeted therapies:
- PARP inhibitors: These medicines cause cancer cells to die by preventing them from fixing damaged DNA. PARP inhibitors are approved to treat metastatic breast cancer in people who have an inherited BRCA1 or BRCA2 genetic mutation. Olaparib (Lynparza) is one such PARP inhibitors that is approved for sale in Canada.
- PIK3CA inhibitors: These treatments are approved to treat certain metastatic breast cancers whose tumor cells have a mutation in the PIK3CA gene. PIK3CA inhibitors disrupt the activity of an enzyme called P13 kinase, interfering with cancer cells’ ability to grow. A PIK3CA inhibitor is currently approved for sale in Canada is alpelisib (Piqray).
- Trop-2 antibody-drug conjugates (ADCs): This drug combination targets a protein called Trop-2, often found in triple-negative breast cancers. These treatments combine the Trop-2 antibody and a chemotherapy drug so that chemotherapy can be delivered directly to certain cancer cells. Sacituzumab govitecan (Trodelvy) is a Trop-2-ADC that has been approved for sale in Canada.
In 2019, Marc Miller, Parliamentary Secretary to the Minister of Crown-Indigenous Relations and Member of Parliament for Ville-Marie–Le Sud-Ouest–Île-des-Sœurs, on behalf of the Minister of Health, announced the new Stand Up to Cancer Canada (SU2C)—Canadian Cancer Society Metastatic Breast Cancer Dream Team. This team is focusing efforts to implement advances in metastatic breast cancer research to improve the health of patients.
The Team is composed of world-leading Canadian researchers from various disciplines. Together, they are studying drugs to effectively treat metastatic breast cancer by carrying out a pan-Canadian clinical trial testing a new therapeutic strategy to determine how the drugs work and how future treatments can be improved. The multidisciplinary team will share data, methods, and information among its members with advice from patient advocates to ensure progress.
The Team is investigating a new way to treat metastatic breast cancer by interrupting the ability of breast cancer cells to manufacture the proteins they need to aggressively spread to organs beyond the breast. The new treatment, being tested now for the first time in humans, strikes at the process that allows breast cancer to go from a localized problem to a potentially fatal disease. This first-in-human study is administering this novel treatment to metastatic breast cancer patients for whom the standard of care has not been effective, in the hope that it will halt or slow the metastatic process and open a new approach to the treatment of metastatic breast cancer.
This focus on metastatic breast cancer research is important and needed because finding and treating breast cancer in its earlier stages, before it spreads, does not mean the person will never have breast cancer again. Unfortunately, early-stage breast cancers can recur five, ten, or 15 plus years after a person’s original diagnosis and treatment. An estimated 20-30% of women who are initially diagnosed with an early-stage cancer will go on to be diagnosed with metastatic breast cancer. Additionally, 3 to 6% of women in high income countries are diagnosed with de novo metastatic breast cancer, meaning that their initial diagnosis is that of metastatic breast cancer.
Research into metastatic breast cancer and its treatments are important to every one of us.