Thousands of women could avoid chemotherapy with this genetic test

“We've probably overtreated many patients,” says Hege Oma Ohnstad, a senior consultant at Oslo University Hospital.

If everything goes as she hopes, there will be less overtreatment of many breast cancer patients in the future.

A new study shows that an established genetic test can distinguish between those who need chemotherapy and those who do not – even when the cancer has spread to the lymph nodes in the armpit.

“This will have great significance for thousands of women,” says Ohnstad.

She led the Norwegian part of the study together with her colleague Bjørn Naume. The results were recently presented at the world's largest cancer conference in the United States.

Tests the tumour’s genes

Many patients who undergo surgery for breast cancer are subsequently treated using chemotherapy, antihormone therapy, and radiation therapy. The goal is to prevent the cancer from returning.

But chemotherapy can cause severe side effects such as hair loss, a weakened immune system, infertility, long-term fatigue, and reduced quality of life. Some patients struggle with lifelong problems after treatment, and many are unable to return to full-time work, Ohnstad explains.

The genetic test Prosigna, which was developed in part by Norwegian researchers, is already used for women whose breast cancer has not spread to the lymph nodes in the armpit.

This is hormone-sensitive breast cancer, which accounts for around 70 to 80 per cent of all cases.

The test analyses 50 genes in the tumour and calculates the risk of it coming back within the next ten years. A low score indicates a low risk of recurrence.

The researchers wanted to find out whether it could also help women who had undergone surgery for breast cancer that had spread to the lymph nodes in the armpit.

Two out of three women avoided chemotherapy

The Optima study is led by University College London. More than 4,000 patients are participating in the international study, with almost 500 of them from Norway.

Half of the women received standard treatment – chemotherapy, anti-hormone therapy, and radiotherapy.

The other half took the genetic test. A full two-thirds of them scored so low that they were able to skip chemotherapy.

After almost five years of follow-up, the survival rates in the two groups are approximately the same. 95 per cent of the women who received chemotherapy were alive and had not experienced a recurrence. The same was true for 94 per cent of the women who did not receive chemotherapy.

“If you have a low test score, then anti-hormone therapy and radiation therapy alone are just as effective,” says Ohnstad. “There are quite a few side effects that many women can now safely avoid without increasing their risk of recurrence.”

Can be implemented quickly in Norway

Ohnstad says that the Norwegian Breast Cancer Group, which operates under the Norwegian Medical Association, has already concluded that the study's results are strong enough to recommend that the test be introduced for this patient group.

Since the genetic test is already in use within the healthcare system, Ohnstad hopes that it can be implemented without requiring new, extensive evaluations.

“We believe this can be implemented relatively quickly,” she says.

The study is a good example of how cancer treatment is becoming increasingly personalised, according to the researchers.

“These findings represent a major step forward in delivering more personalised, precise care, ensuring that treatment decisions are driven by what will genuinely improve outcomes for patients,” Professor Iain MacPherson told The Guardian.

He is one of the main researchers behind the study.

Support for rapid implementation

Siver Andreas Moestue researches breast cancer at the Norwegian University of Science and Technology (NTNU). He believes the Optima study is a fantastic example of how medical science works in cancer research.

First, researchers find a patient group for whom the current treatment is not optimal.

For many patients, the risk of recurrence after breast cancer surgery is high enough that they are offered hormone therapy and chemotherapy. For some patients, that’s the correct choice; for some, that’s not enough; and for others, it’s too much, Moestue explains.

“Then we try to find new methods for assessing risk so that we can offer more personalised treatment. In this case, a genetic test of the tumour provides information indicating that one group of patients can receive somewhat less treatment than they do today while still having a very low risk of recurrence,” he says.

Moestue also believes it should be possible to introduce this new knowledge into clinical practice quickly.

“One advantage is that they used an established genetic test and not something that has been newly developed. That makes it easier to change current practice,” he says.

The reason behind the improved prognosis

The professor points out that even today, some groups of breast cancer patients are not offered chemotherapy.

“This is not a paradigm shift, but it's an improvement to the current treatment regimen that some patients will greatly appreciate. This is how we have worked for a long time, and it's the reason why the prognosis for breast cancer patients has gradually become better and better in recent years,” says Moestue.

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Translated by Nancy Bazilchuk

Read the Norwegian version of this article on forskning.no

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