Tuesday June 29 2010
The study looked at men who received radical prostatectomy
“Cholesterol-lowering statins taken by millions might help prevent prostate cancer returning,” according to The Daily Telegraph. The newspaper said a study has found that men taking statins before their prostate removal surgery were less likely to show signs of the cancer returning.
The study looked at data on 1,319 men who had their prostate removed as a result of prostate cancer, following them up for approximately two to three years on average. The researchers made statistical adjustments to account for differences between statin users and non-users. After this, they found that men who had been taking statins were at 30% reduced risk of having an increase in levels of prostate-specific antigen (PSA), a protein that can indicate the cancer is coming back. The study did not look at whether statin use was associated with differences in length of survival, or the risk of the cancer spreading to other parts of the body.
Although this study took into account a range of factors that could have affected the results, other differences between statin users and non-users could still have contributed to the differences seen. As the researchers suggest, if other studies support their findings, it would need a randomised controlled trial of statins to confirm any potential effect on recurrence rates.
Where did the story come from?
The study was carried out by researchers from Duke University School of Medicine and other research centres in the US. It was funded by the US Department of Defence, Department of Veterans Affairs, National Institutes of Health, the Georgia Cancer Coalition, and the American Urological Association. The study was published in the peer-reviewed medical journal, Cancer.
The Daily Telegraph has reported on this research in a balanced way.
What kind of research was this?
This was a cohort study looking at whether statin use was related to risk of prostate cancer recurrence in men whose prostates had been removed (radical prostatectomy).
This type of study is good for identifying associations between a treatment and an outcome that may not have been expected. However, the design of the study makes it difficult to determine whether the treatment is truly responsible for any differences in outcome seen. This is because potential differences between those taking the treatment and those who did not could have led to the differences seen.
In this case, the best way to confirm the hypothesis that statins may reduce the risk of prostate cancer recurrence would be to test the hypothesis using a randomised controlled trial.
What did the research involve?
The researchers looked at data collected on 1,319 men who received radical prostatectomy for prostate cancer. They identified those men who had been taking statins, and looked at whether the time taken for these men to have a recurrence of prostate cancer was different to those not taking statins.
The researchers obtained the data from the Shared Equal Access Regional Cancer Hospital (SEARCH) database. Men who received radical prostatectomy between 1996 and 2008 at five Veterans Association medical centres across the US were eligible. For inclusion, the men also had to have data available on their statin use, the characteristics of their cancer, their length of follow up and their race.
Recurrence of prostate cancer was defined based on raised PSA levels in the blood. Recurrence was defined as PSA levels higher than 0.2ng/mL on one occasion, two measurements of 0.2ng/mL, or receiving further treatment as a result of detectable PSA levels. Statin use before and after the surgery was assessed, with men taking statins for one or more days before surgery being classed as users. Statin use starting after surgery was not assessed.
The methods the researchers used for their analyses were standard ways of looking at the time for an event to occur in a population. In their analysis they took into account factors that could affect results (confounding factors), such as age at surgery, year of surgery, medical centre, race, body mass index (BMI), clinical stage, and tumour characteristics (Gleason score, preoperative PSA, percentage of biopsy cores containing cancer, extent of cancer spread).
What were the basic results?
Among the 1,319 men assessed, 236 (18%) had been taking statins. Statin users had been followed up for a shorter period on average (median 24 months) than non-users (median 38 months). Statin users were also older, were more often white, had higher BMIs, had radical prostatectomy more recently, had presented at earlier clinical stages of their cancer, but had more aggressive tumours according to their biopsy. There was no difference between statin users and non-users in extent of spread of the disease, or in the treatments received after surgery (radiotherapy or hormone therapy).
During follow up, 16% of statin users and 25% of non-users developed a biochemically-detected recurrence of prostate cancer. After taking into account potential confounding factors, statin use was associated with a 30% decrease in risk of biochemically-detected recurrence of prostate cancer (hazard ratio [HR] 0.70, 95% confidence interval [CI] 0.50 to 0.97). There was a tendency for this risk reduction to be greater for the higher doses of statins.
How did the researchers interpret the results?
The researchers conclude that, ‘statin use was associated with a dose-dependent reduction in the risk of biochemical recurrence’ of prostate cancer after radical prostatectomy. They say that if their findings are confirmed in other studies, a randomised-controlled trial of statins in men undergoing prostatectomy ‘may be warranted’.
Some number of points to note about this study:
- As with all studies of this kind there is a possibility that factors other than the factor of interest (i.e. statin use) may be affecting results. For example, the researchers found differences between statin users and non-users, including age, race, BMI, clinical stage and biopsy findings. The researchers took these and other factors into account in their analyses, but unknown or unmeasured factors, such as smoking, diet, physical activity, how often the men were screened and other diseases associated with prostate cancer such as diabetes, may still be having an effect.
- The researchers had to rely on retrospectively analysing data already collected, which can mean that the data is not as reliable as any the study would have collected itself. There may have been some inaccuracies on this recorded information, or differences in how it was recorded across centres.
- This research defined recurrence based on the levels of PSA in the blood. The researchers say that their previous research has found that statins reduce PSA levels in men without prostate cancer. Future studies will need to focus on whether statins are merely suppressing PSA levels or whether they also reduce other measures of prostate cancer recurrence, including the risk the cancer spreading elsewhere in the body.
- It is not possible to say from this study whether statins are associated with an increase in overall survival.
Overall, these findings suggest that statins may affect risk of biochemically-assessed prostate cancer recurrence in men who have had radical prostatectomy. However, four randomised-controlled trials of statins have been conducted already in an attempt to see if they reduce the onset of prostate cancer, and a meta-analysis of the results in 2006 showed no increase in risk of developing prostate cancer.
If other observational studies confirm an association between statin use and a reduced risk of recurrence after prostatectomy, this would support the need for randomised controlled trials to give a definitive answer about the effects of statins on this outcome.