DO WE LIVE IN A “CHEMICAL SOUP”?
A television story last week reported a new analysis that had identified an increase in advanced breast cancer in young women age 25 to 39 [click here for the news story].
Why is this happening? Are doctors missing the signs of cancer when it is small? [see next post] Or are young women doing things that cause them to show up with advanced breast cancer?
Some persons opine that the increase in breast cancer – not only in young women, but in all women – is the result of choices women have made. They blame birth control pills, alcohol, delayed childbirth, not breastfeeding when they do have children, hormone replacement in older women, etc.
These “usual suspects” are cited because they influence how hormones have acted on a woman’s body through her life, and breast cancer is influenced by hormones. For example, most of the increase in younger women is an increase in lobular cancers, and most lobular cancers have estrogen receptors, meaning that they are driven by estrogens. Likewise, most of the excess of breast cancer in Marin County is of estrogen receptor positive tumors – again the kind that are driven by estrogens.
These observations fit with the idea that breast cancer is increasing because of choices women have made that influence the hormones in their bodies.
But we shouldn’t jump to conclusions too quickly. There’s a big catch to that interpretation.
Men are getting more breast cancer, too!
Breast cancer has gone up in men just like in women, and over 90 percent of male breast cancers have estrogen receptors. This means not only that most male breast cancers are driven by estrogens, but you can’t assert this is because of decisions that men made that raised their estrogens or changed their reproductive history. Men don’t take birth control pills, delay having a full term pregnancy, not breastfeed their babies, take hormones at menopause, etc.
The parallel between men and women gets even more puzzling when you see that the rate of breast cancer in men [click here] has the same proportional increase, and the curve has the same shape, as for women [click here]. [Note that the line graph for men is more irregular, but the overall shape of the curves is the same. Men have experienced the same increase as women. Click here for a longer article about the increase in men.]
Some argue that breast cancer has gone up in women because of more detection with mammograms, and that the increase in women is not important because many of these cancers found by mammograms would never have caused any problems.
However, men don’t get mammograms. Cancers in men are usually found when the man notices a growing mass that is a real, life-threatenting cancer. So why would we detect more cancers unless there really was more breast cancer?
And, for both men and women, there is a peak in the incidence on breast cancer just before 2000, a little drop by 2005, and then the number stabilizes at a level about 20 percent higher than in the early 1970s. Whatever the reason, when the pattern is the same, it seems likely that the causes are related.
We need to look for a factor that would affect both men and women the same.
The lesson from DDT.
It wasn’t initially obvious that some of the amazing chemicals we’ve allowed into our lives might be harmful. DDT, for example, kills lice and stopped spread of disease especially during and after World War II. A recent book published by the NATIONAL GEOGRAPHIC pictures a truck spraying DDT at Jones Beach in New York in 1945. Kids play in the fog of insecticide, and the sign on the side of the truck reads, “D.D.T. Powerful Insecticide. Harmless to Humans.”
Or so everyone thought.
An early warning about DDT came from a Florida swamp where DDT had been spilled. Researchers began to find fewer and fewer male alligators. Someone wondered if it might be the DDT and exposed alligator eggs to DDT. The number of males dropped, but it wasn’t because there were fewer male eggs. There was the same number of male eggs, but a lot of the male eggs exposed to DDT developed as females. DDT acted like an estrogen.
Could DDT act like an estrogen in women?
In a serendipitous study, researchers at Kaiser Hospitals in Oakland found some stored blood samples drawn from pregnant women in the 1950s and 1960s. They analyzed these samples for DDT and compared the levels of DDT to the incidence of breast cancer in the same women over the next 30 years. If a woman had been exposed to DDT when she was very young – which was literally everyone who grew up in the 1940s and 1950s – and she was in the group with the highest levels of DDT in 1960 – she was five times more likely to develop breast cancer as she grew older.
Chemicals acting like estrogens isn’t a new idea.
DDT causing breast cancer would not have surprised Rachel Carson, but the chemical industry certainly acts incredulous. Yet the idea that a chemical that is not estrogen can act like estrogen has been around for a long time. Eighty years ago, Dr. Edward Charles Dodds, the researcher who led the development of DES (diethylstilbestrol, as in DES babies) wrote an article, “A Synthetic Oestrus-Exciting Compound” [That funny English habit of spelling estrogen with an “o” as in oestrogen]. He’d guessed that a chemical with a structure that looked like natural estrogen on paper might act like an estrogen in real life, and he was right.
Before his laboratory invented DES, Professor Dodds had already demonstrated that bisphenol-A (BPA) looked a lot like estrogen, and acted like estrogen. More importantly, Professor Dodds studied more than 20 chemicals that he thought looked enough like estrogen on paper to act like estrogen in his laboratory animals. And they did, too.
The key feature of many of the chemicals Dodds studied was what chemists call a “ring” structure. These rings all around us in various commonly used chemicals. Many of them have the potential to act like estrogens.
So is there a “chemical soup”? I don’t think anyone can deny that. The need is to put the effort into figuring out what part of the “soup” is affecting the rate of breast cancer in both men and women.
But why is there more advanced breast cancer in young women?
The “chemical soup” helps us understand why there is more breast cancer, but the “soup” does not explain why there are more cancers that are advanced. How do they become advanced? Why are they missed when they are smaller? What’s happening with young women?
Coming next [click here].