Genetic tool evaluates treatment options

DEAR DOCTOR » A friend of mine was recently diagnosed with breast cancer and is terrified of the chemotherapy her doctor is recommending. I read that some women can skip it. Is this true?

DEAR READER » Your friend’s fear of chemotherapy is understandable. Its harsh side effects and its risk of toxicity to the body’s organs are well-known. However, survival rates significantly improve with chemotherapy. This too is well-known — and has been shown even in women with breast cancer that hasn’t spread to the lymph nodes.

A recent study in The New England Journal of Medicine, however, has called into question the need for chemotherapy in some women who have breast cancer without lymph node metastasis. The trial looked at 9,719 women, ages 18 to 75, with cancer that was hormone receptor-positive and HER2-negative. Such cancer is often treated with hormone therapy, although chemotherapy can be used as well. In this trial, the authors gauged the need for chemotherapy based on a genetic tool called the 21gene breast cancer assay, which evaluates the risk of recurrence based on 16 cancer-related genes and five other genes. Women who have higher scores in the screening have been shown to have a greater risk of recurrence of breast cancer compared to those with lower scores.

In this study, women with a 21gene score of 26 or greater received chemotherapy and endocrine therapy (medications that block the estrogen receptor in breast cancer). Those with scores of 11 to 25 received either chemotherapy with endocrine therapy (chemoendocrine therapy) or endocrine therapy alone. Those with a score of 10 or less received only endocrine therapy. The majority of women in the trial (6,711) had scores between 11 and 25. All patients were followed for eight years.

In the group with scores of 11 to 25, no statistically relevant difference was found between those who received chemoendocrine therapy and those who received endocrine therapy alone. Although there was a small non-significant increase in the rate of recurrence at a local or distant site with endocrine therapy, there was no difference in survival rates between those who received chemotherapy and those who didn’t. Extrapolating the data to nine years, the rate of invasive-free survival with chemoendocrine therapy would have been 84.7 percent, while it would have been 83.1 with endocrine therapy alone. The small difference suggests that chemotherapy might not be necessary in all patients with a midrange score.

For some, however, it might be. In women younger than 50, those with a 21-gene assay score of 16 to 25 showed a decrease in the rate of recurrence with chemotherapy. Still, no difference was seen in the survival rates.

I can’t say what your friend should or shouldn’t do. Perhaps — unlike in this study — her breast cancer involves lymph nodes and is hormone receptor-negative or HER-2 positive. Further, if she’s under 50 and has a gene score of 16 or greater, she would almost certainly benefit from chemotherapy.

But, overall, the study does show that for many women with localized breast cancer, and a 21-gene assay score of 25 or less, chemotherapy may not be necessary.