Thoughts from The Mayor of Worldwide Breast Cancer

Mapping the Journey of The Worldwide Breast Cancer Project

Archive for September, 2007

In 2010, 1.5 million people will be told they have breast cancer?

This week I am focusing on worldwide breast cancer statistics to help me assess the size of the current situation as a foundation for my PhD research. The most common statistic used is “1 in 8 women will get breast cancer” This statistic is taken from the US population, and is a little misleading. The folks at Dr Susan Love have given a great explanation of this term:

The one-in-eight statistic [for Americans] doesn’t accurately reflect the average woman’s breast cancer risk. Age is the most important risk factor for breast cancer. That means the older a woman is, the greater her risk of developing the disease. Statistics from the US National Cancer Institute (those are the US Government Cancer Guys) show that a woman’s chance of being diagnosed with breast cancer by age is:

 

  • From age 20 to age 30 . . . 1 in 2,000
  • From age 30 to age 39 . . . 1 in 229
  • From age 40 to age 49 . . . 1 in 68
  • From age 50 to age 59 . . . 1 in 37
  • From age 60 to age 69 . . . 1 in 26
  • Ever . . . . . . . . . . . . . . . . . . . .1 in 8

“Ever” is lifetime risk. This means a woman has a one-in-eight chance of getting breast cancer after the age of 70.

So, in pursuit of statistics that are globally minded I’m analyzing charts and graphs and reading a lot of articles. As I come to find new information, I’ll share.

The article I’ve found the most informative today is one called:

Global Cancer Statistics, 2002
D. Max Parkin, MD, Freddie Bray, J. Ferlay and Paola Pisani, PhD

Max, Freddie, J. and Paola are a quartet of French cancer researchers and epidemiologists that sum up the world cancer incidence, mortality and prevalence pretty well using statistics available in 2002 and then using them to predict the future. The most interesting part to me of course is the comments about breast cancer. So I’ll share the juicy parts:

“The most prevalent cancer in the world is breast cancer (4.4 million survivors up to 5 years following diagnosis).”

“Prevalent” means that more people are alive in the world with this cancer, than other cancers which have higher death rates. Of all cancers registered worldwide, 17.9% of them were breast cancer.

“Breast cancer, the second most common cancer overall (1.15 million new cases [in 2002]), ranks less highly (fifth) as a cause of death [worldwide] because of the relatively favorable prognosis (mortality to incidence ratio, 0.35).”

This and other information contained in the article about their statistics means that 35% of people who have been diagnosed with breast cancer worldwide, in 2002, died within 5 years of their diagnosis, if they were younger than age 64. The reason why there is an age limit, is that the older a person is the more likely they are to die from something not directly related to their cancer so that would distort the statistics of cancer mortality.

Of course also keeping in mind, that these statistics are only comparing cancers to cancers. So to say that breast cancer was more prevalent than say heart disease, which is not a cancer, would be an inaccurate interpretation. But you already knew that.

“…the majority of cancers in developed countries are those associated with affluence—the so-called Western lifestyle—such as cancers of the colon and rectum, breast, and prostate, with a rather good prognosis. In developing countries, cancers of the liver, stomach, and esophagus are relatively more common; these all have a poor prognosis. Furthermore, as cancer survival data become increasingly available, it is clear that prognosis is much poorer in developing countries, so that the ratio of deaths to cases is much less favorable. The estimated survival rates in Table 2 show that, for cancers with a poor prognosis (liver, lung), there is little difference in outcome between world regions; however, for those cancers where early diagnosis and treatment can materially influence prognosis (colon-rectum, breast, leukemia), survival is generally considerably better in developed countries.”

Basically some cancers are more destructive than others no matter where you live, but some cancers that are more susceptible to treatment have a better survival rate in a more developed country. This Maria’s story illustrates one of the reasons why that is, and why education is so important:

“It took Maria more than three years to discover the words to describe her pain – breast cancer – and to receive the treatment she desperately needs. “It all started with a swollen armpit and a bad fever,” she recalls.”

Here is a chart that I’ve adapted based on the worldwide statistics of breast cancer and a chart by these guys in this article.

age-standardised rates (world population).

“One in ten of all new cancers diagnosed worldwide each year is a cancer of the female breast, and it is the most common cancer in women in both developing and developed areas. It is also the principal cause of death from cancer among women globally.”

A large part of Lemonland will be dedicated to providing visuals that show the signs and simply educate doctors and patients the signs of breast cancer and steps of diagnosis. Especially when we learn that:

“Breast cancer is by far the most frequent cancer of women (23% of all cancers), with an estimated 1.15 million new cases in 2002, ranking second overall when both sexes are considered together.”

This study only had the statistics of women diagnosed with breast cancer and didn’t include men (which is very small, making up less than 1% of breast cancer cases in the US alone and was perhaps not available on a cancer registry.) However it is remarkable that with just women alone, it still ranks second overall to other cancers that include both sexes. Nearly 1 in 4 women globally with cancer, have breast cancer, and half of them live in highly developed countries.

“In part, the high incidence in the more affluent world areas is likely because of the presence of screening programs that detect early invasive cancers, some of which would otherwise have been diagnosed later or not at all.”

“The prognosis from breast cancer is generally rather good […] the average in developed countries is 73% and in developing countries 57%. As a result, breast cancer ranks as the fifth cause of death from cancer overall, although still the leading cause of cancer mortality in women (the 411,000 annual deaths represent 14% of female cancer deaths). The very favorable survival of breast cancer cases in Western countries (89% at five years, in cases registered by the US SEER Program in 1995–2000)10 is also a consequence of the presence of screening programs.”

So, in Western countries, 89% of women diagnosed with breast cancer are still alive 5 years after their diagnosis, those are great odds.

“It has been estimated that 1.5% of the US female population are survivors of breast cancer.”

This is based on an analysis in 1999 on the 1992 National Health Interview Survey.

“There has been an overall increase in incidence rates of about 0.5% annually [since 1990]. At this rate of growth […] the world total in 2010 would be 1.5 million.”

Because this is an incidence rate, that means in the year 2010, 1.5 million people will be told they have breast cancer. That isn’t very far away!