Statins could reduce breast cancer death risk

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Statins may reduce the risk of death from women diagnosed with breast cancer by as much as 38%, an analysis of seven observational studies has found, prompting fresh calls for clinical trials.

The new analysis of seven previous observational studies was presented at the American Society of Clinical Oncology in Chicago, by Dr Binliang Liu, of the National Cancer Centre/Cancer Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing. It examined the protective factors linked to the cholesterol-lowering lipophilic statins, and comes after research in April found breast cancer patients who took them were less likely to see their cancer come back.

The analysis found that taking statins after a breast cancer diagnosis was associated with an overall reduction in mortality, especially in patients who took the drugs for less than four years. In the group of women who had breast cancer, the risk of death from cancer and all other causes was reduced by 38%. Overall statin use was associated with a 27% reduction in both cancer-specific and overall mortality.

However, those who took the same drugs for more than four years did not appear to show the same protective association, with only a 16% reduction in cancer-specific death, or death from all others causes.

The analysis acknowledged that statins’ effect on breast cancer prognosis has “long been controversial”, and experts emphasised that the evidence is still not definitive.

“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,” Liu is quoted as saying. “I think lipophilic statins penetrate cell membrane more easily and lipophilic statins have been confirmed have some good effect on the immune system, which may help to kill cancer cells.”

Experts and charities said the evidence presented a “high promise avenue of investigation” for a clinical trial.

“It’s kind of do or die time – do the trial, get the answer, or we have to move on,” said Thomas Ahern, an observational cancer epidemiologist at the University of Vermont’s Larner College of Medicine, not involved in the new analysis.

“We hear every day that for many women, fear of their breast cancer coming back or spreading never goes away,” said Rachel Rawson, senior clinical nurse specialist at the UK group Breast Cancer Care. “Anything that could stop the cancer in its tracks and help to reduce this risk, including taking statins, is worth considering as a potential future treatment option.

“However, we must approach this news with caution, as further trials are needed to truly determine whether statins have a part to play. This research alone will not change clinical practice in the short term.”

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”.

“To get at this question further, to answer the question definitively, we need to have a clinical trial,” said Ahern. “It would be a long trial because you’re looking at breast cancer recurrence outcomes over at least five years, perhaps 10 years, so you have to enroll a significant number.”

However, he said it was the only way to definitively answer whether statins protect women from cancer recurrence and death.

Abstract
Background: Breast cancer is the most common cancer in females. The effects of statins on breast cancer prognosis have long been controversial, so it is important to investigate the relationship between statin type, exposure time, and breast cancer prognosis. This study sought to explore the effect of statins on breast cancer prognosis.
Methods: We searched the MEDLINE, EMBASE, Cochrane Library between October 15, 2016 and January 20, 2017. Searches combined the terms “breast neoplasms[MeSH]”, “statins”, “prognosis” or “survival” or “mortality” with no limit on publication date. Data were analyzed using Stata/SE 11.0.
Results: 7 studies finally met the selection criteria and 197,048 included women. Overall statin use was associated with lower cancer-specific mortality and all-cause mortality (HR 0.73, 95% CI 0.59-0.92, P = 0.000 and HR 0.72, 95% CI 0.58-0.89, P = 0.000). Lipophilic statins were associated with decreased breast cancer-specific and all-cause mortality (HR 0.57, 95% CI 0.46-0.70, P = 0.000 and HR 0.57, 95% CI 0.48-0.69, P = 0.000); however, hydrophilic statins were weakly protective against only all-cause mortality (HR 0.79, 95% CI 0.65-0.97, P = 0.132) and not breast cancer-specific mortality (HR 0.94, 95% CI 0.76-1.17, P = 0.174). Of note, more than four years of follow-up did not show a significant correlation between statin use and cancer-specific mortality or all-cause mortality (HR 0.84, 95% CI 0.71-1.00, P = 0.616 and HR 0.95, 95% CI 0.75-1.19, P = 0.181), while groups with less than four years of follow-up still showed the protective effect of statins against cancer-specific mortality and all-cause mortality (HR 0.62, 95% CI 0.44-0.87, P = 0.000 and HR 0.61, 95% CI 0.45-0.80, P = 0.000).
Conclusions: Although statins can reduce breast cancer patient mortality, the benefit appears to be constrained by statin type and follow-up time. Lipophilic statins showed a strong protective function in breast cancer patients, while hydrophilic statins only slightly improved all-cause mortality. Finally, the protective effect of statins could only be observed in groups with less than four years of follow-up.

Authors
Binliang Liu, Zongbi Yi, Xiuwen Guan, Fei Ma, Yi-Xin Zeng

The Guardian report
2017 ASCO abstract


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