A low cost test could identify breast cancer patients who have an increased risk of relapse, according to the findings of a major clinical trial reported today.
The results of the POETIC trial, published in The Lancet Oncology, found that measuring the growth rate of cancer cells two weeks after starting treatment with a hormone therapy strongly indicated if the cancer was likely to return.
The researchers from The Institute of Cancer Research, London, and The Royal Marsden NHS Foundation Trust, say their results provide definitive evidence of the benefit of testing response to aromatase inhibitors to guide treatment after women have had surgery.
The trial involved 4,480 women with early-stage, hormone-positive breast cancer, two thirds of whom were given one of the aromatase inhibitors, letrozole or anastrozole, for two weeks before and after their surgery.
The remaining women were treated with surgery and received the aromatase inhibitors only after surgery. All women were asked to continue their hormone treatment for at least five years as part of their standard care.
The researchers compared the levels of the Ki67 protein in tumour samples taken when women were first diagnosed and two weeks after they had started treatment with an aromatase inhibitor.
They analysed how changes in Ki67 affected the risk of their cancer coming back in women who received aromatase inhibitors before surgery and found that 4% of women in this group, whose levels of Ki67 were low to start with and remained low after starting treatment, saw their breast cancer come back five years after surgery.
Among the women whose Ki67 started out high, 22% whose Ki67 remained high after starting treatment saw their cancer return within five years, compared with 8% whose tumour samples showed low Ki67 levels after the two weeks’ treatment.
The researchers say their results provide the strongest evidence yet for giving women a short-term course of aromatase inhibitors around the time of their surgery combined with the relatively cheap test needed to measure Ki67 levels in tumour samples.
Study co-leader Professor Judith Bliss, director of the Cancer Research UK-funded Clinical Trials and Statistics Unit at The Institute of Cancer Research, London, said: “Our study suggests that many more women with early-stage, hormone-positive breast cancer should be offered treatment with aromatase inhibitors around the time of their operation, as it has the important benefit of also helping us pick out those patients at higher risk of their cancer coming back.”
Chief investigator Professor Ian Smith, consultant medical oncologist at The Royal Marsden NHS Foundation Trust and Honorary Professor of Cancer Medicine at The Institute of Cancer Research, London, said: “We have shown that giving patients with early breast cancer two weeks of simple endocrine therapy using aromatase inhibitor tablets before surgery allows us to determine what is the most appropriate medical treatment after surgery for each individual patient.
“In particular, it helps us identify which patients could avoid chemotherapy with all its unpleasant toxicities. The test is much cheaper and easier than current genomic tests, and we believe it should become part of the standard treatment for early breast cancer.”
Lancet Oncology 3 November 2020
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