Recent Breakthroughs in Breast Cancer Treatment
The second most common form of cancer in women (after skin cancers), breast cancer affects 1 in 8 American women in their lifetimes. Over 280,000 will be diagnosed with invasive breast cancer this year alone. (Men can contract it as well, though they represent less than 1 percent of cases.)
Survival rates are high, though—99 percent for localized cancers and 86 percent for regional ones. However, in cases of metastasis (when cancer spreads to other parts of the body), survival rates plummet to 28 percent. Fortunately, advancements in effective treatments, combined with early diagnosis, are improving outcomes.
Overview of breast cancer
Breast cancer occurs when breast cells begin to grow and divide abnormally. Breast cancers can be subdivided into hormone receptor (HR) positive—including estrogen receptor (ER) positive and progesterone receptor (PR) positive—human epidermal growth factor receptor 2 (HER2) positive and triple-negative breast cancer (TNBC), with no ER, PR or HER2.
There are multiple risk factors for developing the disease, and symptoms can vary widely. Diagnosis is usually made via a combination of exams. Untreated, breast cancer can spread throughout the breast and to nearby lymph nodes, subsequently gaining access to other areas of the body for metastasis. Treatments typically include surgery, radiation, chemotherapy, hormone and targeted therapies, immunotherapy and palliative care.
Breast surgery is the most common form of treatment for breast cancer. Procedures include lumpectomy, or removal of only cancerous breast tissue, and mastectomy or double mastectomy (removal of an entire breast or both breasts, and possibly lymph nodes).
Many women who undergo surgery are additionally recommended for chemotherapy or radiation, both of which have challenging side effects. Hormone therapies are commonly implemented after these treatments to keep estrogen levels low and minimize recurrence risk. Targeted therapies may be used to target specific elements of cancerous cells without harming healthy ones. Immunotherapies use the body's defense system to kill cancer.
An array of targeted therapies are being studied and approved for the treatment of different forms of breast cancer. Targeted therapies can be used in combination with hormone therapies to extend survival in cases of advanced and metastatic HR-positive cancers.
In March 2017, based on findings from the PALOMA-2 study, the FDA approved a targeted therapy called palbociclib for postmenopausal women also taking an aromatase inhibitor. That same month, another targeted therapy called ribociclib was approved for HR-positive/HER-2 negative breast cancer. A year later, in April 2018, everolimus was approved for the same cohort of women if they had not improved with letrozole or anastrozole. In May 2019, alpelisib was approved for these women if they had a PIK3CA gene mutation.
HER-2 positive breast cancer treatments have similarly advanced. A targeted therapy called pertuzumab was approved by the FDA in December 2017 in combination with chemotherapy and trastuzumab for women with a high risk of recurrence. Ado-trastuzumab emtansine got FDA approval in May 2019 for early breast cancer that is HER-2 positive.
In February 2020, the FDA approved neratinib to be taken with capecitabine for women, and just two months later, in April 2020, tucatinib was approved for use with trastuzumab and capecitabine for women with unresectable or metastatic advanced HER-2 positive breast cancer.
There's good news for breast cancer patients and their loved ones.
Finally, treatment of triple-negative breast cancers—notoriously difficult to treat due to a lack of receptors to target—has also progressed. In 2018, two PARP inhibitors (which block key proteins in DNA damage repair) were approved for TNBCs with certain gene mutations. Atezolizumab became FDA approved in March 2019 in combination with carboplatin (a chemotherapy medication) for TNBC cases with the PD-L1 protein. Another targeted therapy called sacituzumab govitecan was approved in April 2020 for metastatic triple-negative breast cancer patients who have failed two other therapies.
In June 2018, the TAILORx clinical trial found promising results indicating a test can determine which ER-positive, lymph node-negative women can safely avoid chemotherapy, and the RxPONDER trial applied the same test to more advanced cancer to conclude that HR-positive/HER2 negative breast cancer patients with lymph node involvement don't benefit from chemotherapy. This can significantly change the course of treatment for these women, allowing them to avoid the challenging side effects of chemo.
While not a treatment, 3-D mammography (also called breast tomosynthesis) is being studied in the National Cancer Institute (NCI) Tomosynthesis Mammographic Imaging Screening Trial (TMIST) as a potentially more accurate form of screening for the disease, enabling earlier detection and preventing false positives (when the test says you have cancer, but you don't).
In short—there's good news for breast cancer patients and their loved ones. While breast cancer risk remains high for the average woman at 13 percent, survival rates and treatment options continue to improve. If you're diagnosed, ask your doctor about new medications and trials. The future is bright, and there is every reason to be optimistic.