Giving chemotherapy in higher average doses reduces the risk of early stage breast cancer coming back, according to new unpublished results
Dose intensity can be increased by shortening the intervals between chemotherapy treatments, or by giving higher doses of drugs individually rather than lower doses at the same time.
Professor Richard Gray, from the University of Oxford who led the Cancer Research UK-funded study, said the number of deaths from breast cancer has halved in many countries over the last 30 years because of a series of step-by-step improvements in treatment.
“It is important to continue to find out whether or not there are worthwhile benefits from one treatment compared to another,” he said.
The unpublished study, presented at the 2017 San Antonio Breast Cancer Symposium in the US, analysed the results from 16 trials that included more than 21,500 women.
Seven trials that included a total of 10,004 women tested giving chemotherapy every 2 weeks instead of every three weeks. Combining treatment with molecules called growth factors allows the bone marrow to recover faster so chemotherapy can be given every two weeks. The same total chemotherapy dose was given to all patients, but those treated every two weeks received a higher average weekly dose.
Patients who were treated every two weeks were 17% less likely to see their breast cancer come back than those who were treated every three weeks. They were also less likely to die because of their breast cancer within 10 years of treatment:
• 16.7% of patients treated every 2 weeks died due to their disease;
• 19.7% of patients treated every 3 weeks died due to their disease.
Nine trials with 11,533 women tested giving two chemotherapies individually or together. Giving the drugs separately allows higher doses of the individual drugs to be used in each cycle, while keeping side effects manageable.
Patients who received individual chemotherapy were 14% less likely to see their disease return than those who received combined drugs. And they were also less likely to die within 10 years of treatment:
• 19.2% of patients receiving individual chemotherapy individually died due to their disease;
• 21.5% of patients receiving combined chemotherapy individually died due to their disease.
Gray said the results could apply to most women receiving chemotherapy for early-stage breast cancer, as similar benefits were seen in women of different ages, and who had different genetic faults driving their disease. He added that some hospitals prefer less intense dosing because of concerns about side effects and uncertainty about the additional benefit.
“Looking at the data from large numbers of women receiving dose-intense chemotherapy, we have found no evidence to justify these concerns, and the results show consistent benefit from the more intense treatments,” he said.
Professor Daniel Rea, a Cancer Research UK-funded breast cancer expert, said: “In the UK many women are already treated with sequential drugs but a small change in treatment frequency, made possible with growth factor injections, would further improve treatment.
“For women with early breast cancer, individual circumstances need to be considered in determining treatment and women should always discuss their chemotherapy treatment options with their oncologist.”