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Does occupation really affect ovarian cancer risk?

According to a recent study, accountants, hairdressers and beauticians are at an increased risk of developing ovarian cancer. But is the evidence strong enough to suggest they should be advised to consider changing jobs? Rod Tucker investigates.

The estimated lifetime risk of ovarian cancer among women born after 1960 in the UK is 2%. The causes of ovarian cancer are not well defined, though genetics is clearly important and, when present in a first-degree relative, the risk is nearly three times higher. In addition, a 2017 review of ovarian cancer identified exposure to several products – including the use of talc powder – as potential risk factors. In fact, daily use of talc for nearly 10 years, was found to be associated with a 42% higher risk of developing the cancer.

But is it possible that certain occupations also increase that risk? After all, an analysis from 2007 reported that workplace-related cancer killed over 200,000 people a year, so this is clearly something worth looking into.

A recent study by Canadian researchers set out to investigate the relationship between specific occupational exposure in relation to ovarian cancer risk.

Occupations and ovarian cancer

The researchers gathered information on 1,388 individuals, of whom 491 developed ovarian cancer. Researchers interviewed women roughly five months after their diagnosis and collected a draft of data including sociodemographic details, medical histories, medication use and their lifetime job history. Individuals were then categorised as working for either less than or more than 10 years in that role. Similarly, the team interviewed a group of matched control women who did not have ovarian cancer.

The risk of ovarian cancer was then expressed as an odds ratio (OR) between the occupation and the specific outcome of ovarian cancer. Equally important were the 95% confidence intervals (95% CI) associated with the OR.

In the study, the OR for accountants was 2.05 (95% CI 1.10 to 3.79). Thus, the researchers found that being an accountant for 10 years or more, roughly doubled the risk of developing ovarian cancer. The OR for hairdressers, beauticians and related workers was 3.22 (95% CI 1.25 to 8.27).

Before jumping to any conclusions, there are two important caveats attached to these findings.

First, the estimate of the OR was based on a sample of 44 accountants, which is really too small to derive any firm conclusions. Second, the 95% confidence intervals are very wide, ranging from 1.10 to 3.79. In practice, this means that while, on average, being an accountant for 10 or more years doubles the risk of developing ovarian cancer, the risk might only be 10% higher but could also be nearly four times greater.  A similar argument could be made for the hairdresser data, which was based on a sample of only 20 individuals.

One interesting finding, based on 31 women, was that the odds ratio for cosmetic talc use was 1.66 (95% CI 0.80 to 3.46). Again, this result suggests that the risk of developing ovarian cancer from using talc could be 20% lower or three times higher.

The main takeaway

So, should women change their jobs? The authors themselves provided the answer to this when they wrote: ‘We acknowledge the multiple comparisons in our study, and that the CIs of most OR estimates were wide.’ Translation: we can’t be sure about the risks from specific occupations.

They also accepted that as they carried out multiple statistical tests, it was inevitable that significant findings could arise merely by chance. But, to be fair, the study was exploratory rather than being a full oncology randomised clinical trial, and, in that sense, served only to highlight that there might be a greater risk of ovarian cancer in particular occupations.

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