The likelihood that a woman age 25 to 39 will be diagnosed with advanced breast cancer has steadily increased since the mid-1970s, researchers from Seattle Children’s and Oregon Health and Science University have found.
Analyzing data from hundreds of thousands of cases collected in three national cancer registries, the researchers, whose work is published in Wednesday’s issue of JAMA (Journal of the American Medical Association), found no other age group had such an increase.
Although breast cancer overall is relatively rare in younger women, it is the most common malignant tumor in young adult women, who tend to experience more aggressive disease and have lower survival rates, the study’s authors said.
The study looked at the extent of disease at the time of original diagnosis, comparing the change in incidence in each age group from 1976 to 2009.
The increase in incidence of metastatic disease in the 25-39 age group was small — an increase of 1.37 cases per year for every 100,000 women — but statistically significant and steady throughout the time period, said the study’s lead researcher, Dr. Rebecca Johnson, medical director of the Adolescent and Young Adult oncology program at Seattle Children’s.
Since 1992, when data on race and geographic location were added to the databases, the increase among women in that age group occurred in all races and ethnicities evaluated and in both metropolitan and nonmetropolitan areas, the researchers said.
Non-Hispanic white women and African-American women, as well as women with estrogen-receptor positive subtypes of cancer, appear to have been most affected.
186 percent increase
Over the time period analyzed in the study, the number of women ages 25-39 in the U.S. grew from about 22 million to approximately 28 to 30 million — a figure that’s been steady since the 1980s, Johnson noted. That’s an increase of about 36 percent.
But in the same period, the number of women in that age group with an original diagnosis of metastatic breast cancer increased from 293 in 1976 to 838 in 2009, an increase of 186 percent.
No other age group had a similar increase.
“We’re interested in these trends,” Johnson said, “with the hypothesis that cancers of adolescents and young adults may have unique biological features that more research may uncover.”
She hopes future studies may reveal why the rate of metastatic breast cancer in young women has increased.
“The rate of this change has been so rapid we think it’s likely there’s some sort of external factor,” she said — perhaps a “modifiable risk factor”such as obesity, alcohol use, the age when a woman first gives birth, an environmental toxin exposure, or a combination of factors.
“It could be complicated, it could be simple, or something we haven’t thought of yet,” Johnson said.
1) How could the Pill cause breast cancer?
Two of the most important types of hormones that control reproduction are estrogens and progestins. Birth control pills are made from synthetic estrogens and/or progestins. Experiments have shown that these hormones cause women’s breast cells to divide more rapidly.  Cells which divide more rapidly are more prone to develop into cancer cells.
2) What is the evidence that the Pill and breast cancer are connected?
In 2005, the World Health Organization classified oral contraceptives as a Group I carcinogen—the most dangerous classification known. Also, a comprehensive meta-analysis* published in the Mayo Clinic Proceedings in October, 2006 found that 21 out of 23 retrospective studies done since 1980 showed that women who took oral contraceptive prior to the birth of their first child sustained a 44% average increased risk of developing pre-menopausal breast cancer, [see Table A]. ] This risk rose to 52% for women who took the pill for at least four years prior to the birth of their first child.
3) How serious of a problem is breast cancer?
Breast cancer is the most common cause of cancer death in U. S. in women age 20-59. In the U.S. about 211,000 women are diagnosed annually and over 40,000 die from this disease. More than one in five women who are diagnosed with breast cancer (ie, 47,000 women annually) will develop it before menopause. About one in eight women will develop breast cancer at some time in her life and one fourth of such women will die from this disease. Using the birth control pill, especially at a young age, markedly increases a woman’s risk for developing breast cancer. This risk is increased even higher when combined with other breast cancer risk factors such as induced abortion, hormone treatment (such as estrogen supplementation), family history of breast cancer, and other factors.
4) Do some contraceptives cause more risk than others?
Yes. Research studies show that breast cancer risk is almost tripled for women who used Depo-Provera for 2 years or more before age 25. 
5) Are other types of cancer affected by oral contraceptive pills?
Oral contraceptives decrease the risk of ovarian and uterine cancer, while they increase the risk of cervical and breast cancer.  Since breast cancer is far more prevalent than the other three types of gynecological cancers, the pills overall effect is detrimental to women.
6) Are there other risks from contraceptives?
Yes. Well known side effects of the Pill include an increased frequency of blood clots, high blood pressure, and heart attacks, as well as migraines, depression, loss of libido, and a variety of other disorders. Less well known is that oral contraceptives and injectable progestins (such
as Depo-Provera) significantly increase the risk of contracting and transmitting HIV (the AIDS virus). [7,8] In addition, medical studies strongly suggest that oral contraceptives work at times by causing an early abortion. 
Next time you hear someone talk about the war on women being waged by Catholics, perhaps it'd be good to have them open their eyes to this.