Thousands more women with the most common form of breast cancer will no longer need chemotherapy. That’s thanks to a landmark study using an established genetic test of tumor DNA to show that more women than previously thought do not benefit from chemotherapy.
Patients with hormone receptor-positive, axillary node-negative breast cancer — about half of all cases — have long used a genetic test of their tumor to predict the risk of it coming back or recurring.
Doctors already know patients with a low risk don’t need chemotherapy and people with a high risk do. But what about people in the middle?
This study, published recently in the New England Journal of Medicine, “was designed to address these gaps in our knowledge by determining whether chemotherapy is beneficial for women with a mid-range recurrence score,” according to its authors.
They followed more than 10,000 women for nine years and found that it didn’t matter whether women with a mid-range score in this genetic test had chemotherapy or not. Both survived at the same rate, suggesting the chemotherapy had no benefit and does not need to be used for this group.
Florida Hospital has long offered breast cancer patients genetic testing.
“Until now, the intermediate risk category was a gray zone. The results of this study supports the omission of select cases,” said Martin Dietrich, MD, a medical oncologist with the Cancer Institute of Florida. “However, this result has to be interpreted in the context of other clinical factors, and a comprehensive discussion about the impact and side effects of chemotherapy should come before the final decision. Regardless, I am confident that fewer women will have to be exposed to the side effects of chemotherapy.”
Medicine, with precision
Unfortunately, most major drugs do not work on most cancer patients. That simple fact means that, without a solid understanding of which patients are likely to see a benefit from a given drug, doctors must often try several medicines before one works.
In addition to lost time, many of these drugs have serious side effects.
“Whenever I have a chance to create a genetic profile for a patient to choose their most effective treatment, I jump at it,” Dr. Dietrich says. “This has been a field of great interest for over a decade now since the introduction of the first ‘targeted’ therapies and has only been accelerating since the introduction of immunotherapy.”
The promise of precision medicine — also called personalized or individualized medicine — is that each patient receives the therapies targeted to his or her particular subgroup. In other words, while it’s not as if each person will receive a different treatment, DNA analysis can put patients into subgroups that will benefit from a particular therapy.
One example of these subgroups in breast cancer concerns patients whose cancer makes too much of a protein called HER2, which makes cancer cells grow faster. This subgroup is a double-edged sword: Yes, it grows more quickly, but there are effective medicines that target HER2-positive breast cancers.
“It was this understanding that turned a previously unfavorable diagnosis upside-down,” Dr. Dietrich says. “What was once bad news for a patient is now a vulnerability of the cancer that we can target with very minimal side effects for most patients”.
Another well-known use of targeted therapy in breast cancer is all about hormones.
Hormone therapy and chemo
Breast cancer is classified by “biomarkers” that allow therapy to be tailored individually to the patient’s situation. The most common receptors we target for cancer treatment are those for the hormones of.estrogen and progesterone. About 70 percent of breast cancers express these hormone receptors.
This opens up a potential line of attack, and some hormone therapies like tamoxifen block estrogen from binding to the cancer cell. Other therapies lower the overall levels of estrogen in the body.
The study only covered women with receptor-positive tumors. Many of these women take so-called “adjuvant” chemotherapy, which refers to chemo that is given alongside other treatments to reduce the risk of cancer recurrence.
Even after the new study, women with a receptor-positive tumor and a high recurrence score may still need chemotherapy to lower their risk of a recurrence.
Questions remain for young women
The one exception for chemotherapy being unnecessary in medium-risk recurrence scores concerns women who are younger than 50.
Chemotherapy was associated with “some benefit” for these women, the study found.
“Reducing the risk of breast cancer coming back is a key goal of my patients, and if chemotherapy is effective in achieving that goal I won’t hesitate to recommend it,” Dr. Dietrich says.
Talk to your doctor
If you think you or a loved one might benefit from a genetic profile, don’t hesitate to ask. At Florida Hospital, a pathology report of a tumor’s genetic profile is a key step in determining the most effective treatment for each patient and cancer type.
“Newly diagnosed breast cancer is a scary time for patients, though medical advancements like this can guide us to create an effective and less toxic treatment plan,” Dr. Dietrich said.
Here are some potential questions to ask your doctor:
- What is my cancer’s genetic profile?
- What are likely to be the most effective therapies for me?
- What does my pathology report say about whether I will benefit from chemotherapy?
- What is the likelihood for my cancer to come back, and what can we do to prevent that from happening?
Women who would like to learn more about how a genetic profile can help them obtain the most effective treatments for breast cancer can schedule a one-on-one consultation at the Cancer Institute of Florida by calling 855-303-3627.