Return to Website

Number Watch Web Forum

This forum is about wrong numbers in science, politics and the media. It respects good science and good English.

Number Watch Web Forum
Start a New Topic 
Statins halve cancer mortality

You might have seen this story appearing in all the media the past couple of days. If not here is a small flavour of what you have missed, taken pretty randomly from the Daily Mail coverage.

Typical of the tone of the coverage is this:-

Taking statins can cut your risk of dying from cancer by up to 50 per cent, two major studies have shown.
While the drugs do not seem to prevent cancer in the first place, it is believed they boost survival rates by slowing the rate at which tumours grow.
Experts say the evidence is overwhelming that, as well preventing heart attacks and strokes, statins can be as effective at fighting cancer as conventional treatments such as chemotherapy.
A study involving almost 150,000 women found those taking statins, whether initially healthy or not, were 22 per cent less likely to die from any form of cancer than those not on the drugs.
But this effect varied between the different types of the disease. For breast cancer, statins reduced death rates by 40 per cent, for ovarian by 42 per cent and bowel by 43 per cent.
For bone cancer, which is rarer, death rates were cut by more than half – 55 per cent.

After a bit of sleuthing I managed to track more details of the study down to here

Here is the abstract from the study:-

Background: Statin medications are widely used for lipid lowering and heart disease prevention. Retrospective studies and basic scientific evidence have suggested that statins may also reduce cancer mortality. Data fromthe Women’s Health Initiative Observational Study (WHI-OS) and Clinical Trial (WHI-CT) were used to investigate the association between statin use and all-cancer mortality in a prospective cohort of postmenopausal women. Methods: The WHI study enrolled women aged 50-79 from 1993-1998 at 40 U.S. clinical centers. Among 146,326 participants with median 14.6 follow-up years, 23,067 incident cancers and 3,152 cancer deaths were observed. Cox proportional hazards models were used to investigate the relationship between statin use (as a time-dependent exposure) and cancer mortality. Analyses were adjusted for age, race/ethnicity, education, smoking, body mass index, physical activity, family history of cancer, current health care provider, hormone use, age at menarche, solar irradiance, and history of heart disease/diabetes. Results: Compared with never users, current statin use was associated with significantly decreased cancer mortality (HR 0.78; 95% CI 0.71-0.86). Use of other lipid lowering medications was associated with a similar reduction in cancer deaths compared to monotherapy statin use (p-het = 0.57). The reduction in cancer death associated with statin use was not dependent on statin potency (p-het = 0.22), lipophilicity/hydrophilicity (p-het = 0.43), type (p-het = 0.34) or duration (p-het = 0.33). Current statin use was associated with significantly decreased mortality of multiple cancer types, including breast, colorectal, ovarian, digestive, and bone/connective tissue cancer deaths, but not lung cancer. However, past statin users were not at lower risk of cancer death compared to never users (HR 1.06; 95% CI, 0.85-1.33); additionally, statin use was not associated with a reduction in cancer incidence despite its effect on mortality (HR, 0.96; 95% CI: 0.92-1.001). Conclusions: In a cohort of postmenopausal women, regular use of statins or other lipid-lowering medications may decrease cancer mortality, regardless of the type, duration, or potency of statin medications used. Clinical trial information: NCT00000611

Any thoughts on this? My first thought is that although the article does mention this is a study in women, and post menopausal women at that, you wouldn't know that from the headlines. Does the same effect occur in men? The trojan number is large but the actual number of women who had cancer and therefore counted in the study is about 23,000 or roughly a sixth of the trojan number. They list ten adjustments that they make, including the inevitable smoking, but also solar irradiance. What does decreased mortality mean? OK not so many might have died, but did they live one year longer, two years longer after their diagnosis.

I could go on but I have to get back to work.

Re: Statins halve cancer mortality

My first thought was: "I wish I understood Cox proportional hazards better. I should know this stuff."

My second thought was to spend far too much time looking at the risk adjustments, and comparing their (off the top of my head) positive and negative associations with both statin use and cancer mortality. In particular spent far too much effort thinking about diabetes/heart disease, which is the last mentioned, but which drives statin use through the roof and cancer mortality down (since there is a rather important competing cause of death there).

My third thought was the devil is in the detail that current statin users are at reduced cancer mortality risk compared to past or never users. And why would you bother treating a terminal cancer patient with statins? You'd take them off ASAP.t

Re: Statins halve cancer mortality

In other words, this is a pretty special example of volunteer bias. We came across something similar some years ago, in a study which showed people prescribed sleep aids were more likely to die within 3? (6? dunno but it doesn't really matter) months of the prescription than people on the rolls at the same docs who didn't get prescriptions.

Of course there the control group is wrong, since 100% of people bothering a doctor for sleep aids have something wrong with them (at a minimum they can't sleep, but many of them will have something quite seriously wrong with them). In the control group, chances are 90% of them go one year to the next without ever bothering a doctor about anything at all.

In this case, current statin users are basically healthy, other than having (assuming the statins are prescribe correctly), an elevated risk of (often sudden) death from a non-cancer cause. Cancer takes longer to kill and you know about it, and if you have it stuff like statins will be stopped for futility.

Bias is legion.

Re: Statins halve cancer mortality

OK. Strap yourselves in. This is a roller-coaster of confounding factors.

Michael D. Shaw on writes on statins… over-prescribed and over-hyped.

In this case the substantial confounding factor is that high cholesterol is protective against cancer. Those most likely to be prescribed statins are, if the statins have little effect (as they often do/don't) then the patients are already more resistant to cancer.