The Malta Independent 24 October 2017, Tuesday

Fake statistics and fake news: why ovarian cancer global statistics differ from local ones

Helena Grech Thursday, 20 April 2017, 07:50 Last update: about 6 months ago

Mortality from ovarian cancer in Malta is the third highest in Europe for the year 2012 according to the European Cancer Observatory (ECO) at 10.3 people per a population of 100,000, and the sixth highest worldwide according to the Global Cancer Observatory. One particular source, World Life Expectancy says that Malta is globally the number one country for ovarian cancer mortality per 100,000.

Malta’s National Cancer Registry however, which is highly praised by Malta’s medical community, cites a mortality rate of 8.14 persons per a population of 100,000 according to the European Age Standardised Rate. It cites a mortality rate of 5.2 persons per 100,000 according to World Age Standardised Rates.

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Figures must be adjusted in accordance with age because in the case of ovarian cancer for example, which is more likely to hit women aged over 40, a population with a disproportionately high number of older people are far more likely to register higher instances of ovarian cancer and ovarian cancer mortality. With this in mind, the data is weighted in order to accurately reflect the instances of such a disease, and the mortality, as in the case when compiling national figures for any ailment.

This begs the question as to why Global figures register ovarian cancer rates to be much higher than what national statistics say. Firstly, Malta’s tiny population skew statistical figures. It is no secret that a smaller sample size, without proper adjustments, would erroneously show that a finding is much larger than it actually is.

For example, according to the National Cancer Registry, in 2012 a total of 29 people died because ovarian cancer, while a total of 40 new cases were registered in the same year. In the USA for example, with a population of 318 million, about 22,440 women are diagnosed with ovarian cancer each year. Without making proper adjustments for skewed data, figures can be misleading. This begs the question as to why certain global medical statistic sites are not bothering to ensure that the proper adjustments are being made. After speaking with a number of people in the medical community it became evident that due to Malta’s size, relatively small economy and obscurity, many do not take the time to ensure that the statistics being displayed are indeed accurate and proportionate.

A number of doctors have repeatedly stressed that the national cancer registry are extremely meticulous with following up and registering new cases as well as mortality, made all the more possible because of Malta’s low population size. Most other countries issue estimates by extrapolating the figures from a few cities.

In Malta in 2014, the number of new ovarian cancer cases amounted to 55 but the number varies quite markedly from year to year – 49 in 2010, 37 in 2011, 40 in 2012 and 36 in 2012 with an average of 43 per year. When dealing with such relatively small population figures, such changes can paint very different pictures when working out the rate of new cases per a population of 100,000. If an institution quotes the figures of a single year they may be misleading. A distinction must be made between ‘incidence’, meaning new cases and mortality rates. The figures quoted at the beginning of the story relate to the number of those who have unfortunately passed away due to ovarian cancer, but the rate of incidence shows the number of new cases per year.

What are the risk factors for Ovarian Cancer?

Multiple cancer research centres have listed a number of risk factors. As previously highlighted, women are more likely to contract ovarian cancer over the age of 40, while some cancer organisations say that half of all ovarian cancers are found in women 63 years of age or older.

Studies have also linked ovarian cancer with obesity, with one particular study claiming that a Body Mass Index of 30 and over increases the risk of ovarian cancer.

It was found that women who have been pregnant and carried the baby to term before the age of 26 have a lower risk of ovarian cancer than woman who have not. It was said that the risk goes down with each full-term pregnancy. It has also been claimed, by the American Cancer Society, among others, that women who have used oral contraceptives have a lower risk of ovarian cancer.

Links have also been found between ovarian cancer and the use of fertility drug, with the risk found to be highest in women who did not get pregnant while using the drug. Ovarian cancer is also known to run in the family.

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