A new study has found that clinical trials for breast cancer are not including enough younger women, which could be affecting treatment outcomes.

This is according to a Cancer Research UK study, published in the Journal of the National Cancer Institute, which shows a lack of clinical trials aimed specifically at younger breast cancer patients could be partly to blame for their poorer survival rates.

The study – funded by Cancer Research UK and The Wessex Cancer Trust – analysed almost 3,000 women diagnosed with breast cancer under the age of 40, treated at 127 UK hospitals.

Breast cancer is mostly diagnosed in post-menopausal women, and those diagnosed under 40 represent fewer than five per cent of all breast cancers treated in the UK.

The trials looked at survival for younger patients with oestrogen-receptor positive disease, whose cancers are fuelled by the female hormone oestrogen.

The findings revealed a rapid increase in disease relapse after five years in younger oestrogen-receptor positive patients who had received the usual treatment of chemotherapy followed by the chemotherapy drug tamoxifen for five years.

This finding was in contrast to observations from other studies in older women who do not show the same steep relapse rate after five years.

Tamoxifen blocks oestrogen receptors, preventing the hormone driving the cancer. The research suggests that taking tamoxifen for a longer period of time might help younger patients.

But the study also highlights the need for young breast cancer patients to be targeted to take part in treatment trials to explore different treatment approaches.

Chief investigator Professor Dianna Eccles, head of Cancer Research UK’s Southampton Clinical Trials Unit, said: “This study adds to the evidence that breast cancer can behave very differently when diagnosed in younger women. They may require a different approach to treatment – which isn’t necessarily understood from cancer trials in older patients.

“Research is the key to improving survival for these women and we urgently need trials to help us develop new treatments tailored specifically at this age group.”

Kate Law, Cancer Research UK’s director of clinical research, said: “Although in general breast cancer survival has improved dramatically in recent decades, with women now twice as likely to survive their disease for at least 10 years compared to those diagnosed in the 1970s, the same can’t be said for younger breast cancer patients.

She added that progress is being made, but added that there’s “still so much more we want to do to improve treatment for younger breast cancer patients and ultimately ensure that all women beat their disease”.