Over eight years of follow-up on nearly 8,000 women, during which time 1,432 patients saw their cancer come back, the disease-free survival rate was 18% higher in the women already on statins at the start of the study, compared with those who were not. A University of Aston study of more than 600,000 British women found that the risk of breast cancer was nearly double in those that had unusually high blood fat levels.
Jennifer Litton, an oncologist at MD Anderson Cancer Center in Houston, who wasn't involved in the study, called the latest data "very reassuring" but added that young women who have had breast cancer still face several hard issues.
Among the 1,207 patients, 333 became pregnant and 874 did not.
Ahern said such a trial would be "daunting" because of the number of women who would need to be initially enrolled, the possibility that a control group could need statins for cardiovascular treatment during the trial, and because a drug with so many generic options offers little hope of "cost recovery".
This was true even for women treated for estrogen receptor (ER)-positive disease, news that may assuage a common concern that pregnancy hormones could stimulate the growth of any estrogen-fueled cancer cells left in the body after treatment.
The new study, presented at the American Society of Clinical Oncology (Asco) meeting in Chicago, looked at seven existing pieces of research covering 197,048 women.
Rachel Rawson from Breast Cancer Care in the United Kingdom told The Guardian that many woman feared their breast cancer returning, so anything that reduced this risk was worth considering as a treatment option in the future.
Among survivors of ER-positive cancer, there was also no difference in overall survival between women who became pregnant and those who did not.
Dr Binliang Liu, from the department of medical oncology at the centre in Beijing, said: "We did a meta-analysis which showed statins truly can change the prognosis of breast cancer but it is constrained by the type of statin and user-time".
He said he believes statins may prove a useful treatment in the future for breast cancer.
The study had limited information on the use of assisted reproductive technologies and did not address the effect of pregnancy outcomes in women with BRCA mutations.
A 2013 study by Azim and colleagues showed no detrimental effect of pregnancy on breast cancer outcomes within the first 5 years following conception. No data from that study will be available for some years, Litton said.
DFS in patients with ER-positive breast cancer served as the primary endpoint. The study authors explain that aspirin may help reduce cancer risk and the spread of the disease by blocking this mechanism.
The Conquer Fear psychology intervention is based on a novel theoretical framework developed by the authors (the intervention was developed for research and is not yet used in clinical practice).
The researchers also explored other patient outcomes, including cancer-specific distress (how much someone is plagued with thoughts about cancer), general distress (anxiety, depression, and stress), and quality of life (covers independent living, physical pain, mental health, happiness, coping, relationships, and self-worth).