Younger Age, Faster Breast Cancer Growth

May 9, 2008 -- Breast cancers tend to grow faster in younger women, Norwegian researchers report.

They estimated breast cancer tumor growth rates among more than 395,000 Norwegian women aged 50-69 who got screened for breast cancer from 1995 to 2002.

On average, breast cancer tumors took 1.7 years to double in diameter from 10 millimeters (mm) to 20 mm.

Breast cancer growth rate varied widely. The fastest-growing tumors, which made up 5% of the tumors studied, doubled in diameter from 10-20 mm in about a month. The slowest-growing tumors, which accounted for another 5% of the tumors, took roughly six years to reach that size.

Age mattered, "with faster growth among younger women," write the researchers, who included Harald Weedon-Fekjaer of the Cancer Registry of Norway.

Their report, published online in Breast Cancer Research, doesn't show why younger women had faster-growing breast tumors or what traits, besides age, may also be important.