Childhood Factors Increase Breast Cancer Risk
Search for Breast Cancer Risks Uncovers Early-Life Clues
Oct. 13, 2004 -- Early-life growth patterns -- from before birth until after puberty -- have much to do with whether a woman gets breast cancer.
The finding comes from researchers who looked in an unlikely place for clues to the cause of breast cancer: the school records of 117,415 Danish girls dating back to the 1930s.
Mads Melbye, MD, PhD, head of epidemiology research at Statens Serum Institute, Copenhagen, Denmark, led a team that painstakingly matched these girlhood records to the health records of the girls once they became women. They report their findings in the Oct. 14 issue of The New England Journal of Medicine.
"We have put so much emphasis on breast cancer risk factors in the adult woman," Melbye tells WebMD. "But this study clearly indicates that maybe some of the more important risk factors for later-life breast cancer occur very early in life -- much earlier than we thought."
Fast Growth Boosts Breast Cancer Risk
The Danish researchers identified four factors independently linked to breast cancer:
- The more a girl weighs at birth, the higher her breast cancer risk. Each 2.2 pounds over 5.5 pounds at birth ups a woman's risk of breast cancer by 10%.
- The younger a girl is when she hits her peak growth rate, the higher her breast cancer risk. Every year's delay in peak growth dropped a woman's risk of breast cancer by 3%.
- The taller a girl is at age 14, the higher her breast cancer risk. Every 2 inches over 59.5 inches of height at age 14 ups a woman's risk of breast cancer by 11%.
- The girls who were thinnest at age 14 had the highest risk of breast cancer as adults.
This makes for a complex picture of lifetime breast cancer risk, notes Harvard breast cancer researcher Karin Michels, ScD. Michels' editorial accompanies the Danish study.
To minimize risk of breast cancer, Michels writes, "one would want to be born light, to grow slowly but steadily into a chubby, short child, and to maintain one's fat mass until one reached menopause, at which point one would want to shed the excess pounds immediately."
That's neither possible nor truly a good idea, Michels says. Just because we have new pieces for the puzzle of breast cancer doesn't mean all the pieces fit together -- yet. But a rough picture is beginning to emerge.
"There is growing evidence that breast cancer can originate early in life," Michels tells WebMD. "Understanding that breast cancer can originate in early childhood -- maybe even in the womb -- means women are susceptible to environmental factors."
Growth, Nutrition, and Breast Cancer Risk
The central clue here, Michels says, is that early, fast growth during childhood increases breast cancer risk.
To interpret this finding, Michels turns to data from Japan. The current generation of Japanese women grew much faster than their parents did. They have a much higher rate of breast cancer than their parents do, too. The difference between the generations isn't genetic. It's dietary. Younger Japanese women grew up on diets with much more meat and dairy products than previous generations of Japanese women.