According to a landmark study, a large percentage of individuals with the most common form of early breast cancer could safely skip chemotherapy. The findings could impact thousands of people each year.

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A new study concludes that chemotherapy may be avoidable for many people with breast cancer.

While new therapies such as immunotherapies are becoming increasingly crucial in treating cancer, chemotherapy is still a mainstay.

In short, chemotherapy uses drugs to cure or control cancer throughout the body.

As opposed to surgery or radiation therapy — which concentrates on the tumor and the area surrounding it — chemotherapy will affect the whole body.

Though chemotherapy is effective, it carries with it a range of significant side effects, such as hair loss, increased risk of bleeding, susceptibility to infection, nausea, vomiting, and anemia.

Consequently, chemotherapy is only used when deemed entirely necessary. The challenge lies in determining exactly when it is entirely necessary.

Individuals with breast cancer sometimes have their tumors analyzed using a gene test called the Oncotype DX test. This examines how active 21 specific genes are and provides a “recurrence score” of 0–100.

A score nearer to 100 denotes a cancer that is most likely to recur and infiltrate other parts of the body.

When scores are high, chemotherapy will be used following surgery or radiation therapy to lower the risk of the cancer returning. For individuals with low scores, the tumors are considered less dangerous, and chemotherapy is not deemed essential.

This type of testing has proven useful but there is a substantial gray area. As it stands, those who score 0–10 do not receive chemotherapy and those who score above 25 do. The majority of women, however, fall in the intermediate range of 11–25.

People in the 11–25 category pose a problem for doctors. Chemotherapy is highly toxic, so it is only used when needed, but the consequences of not using chemotherapy could be a resurgence in cancer.

Chemotherapy has undoubtedly reduced breast cancer mortality. However, as the authors of the new study write, “[T]he majority of patients may receive chemotherapy unnecessarily.”

To get a better picture of who needs treatment, researchers from Loyola Medicine in Maywood, IL, and Montefiore Medical Center in the Bronx, NY, undertook a large-scale investigation. Their findings are now published in the New England Journal of Medicine.

They used data from more than 10,000 women with hormone-receptor-positive, HER-2 negative breast cancer — the most common form of breast cancer, accounting for about half of breast cancer cases in the United States.

Of particular interest to the team were the 69 percent of women who had scored 11–25 on the 21-gene test.

The participants were randomly assigned into two groups. Half of them received hormone therapy and chemotherapy, and the other half received hormone therapy alone.

The researchers followed the women and assessed them for certain outcomes: being cancer-free, cancer recurrence locally or in another part of the body, and overall survival.

When the study group was analyzed as a whole, there were no significant differences between the two groups.

In women under the age of 50, outcomes were similar when test scores were 15 or below. For younger women with scores of 16–25, chemotherapy slightly improved outcomes.

With [the] results of this groundbreaking study, we now can safely avoid chemotherapy in about 70 percent of patients who are diagnosed with the most common form of breast cancer.”

Study co-author Dr. Kathy Albain

“For countless women and their doctors,” she adds, “the days of uncertainty are over.” Indeed, the study will have positive implications for thousands of women across the U.S. and farther afield.

As Dr. Albain goes on to conclude, “Its findings will greatly expand the number of patients who can forgo chemotherapy without compromising their outcomes. We are de-escalating toxic therapy.”