A new study of almost 400,000 women finds that 5 percent of breast tumors are capable of doubling in size within a one-month period.

The research, published in the journal Breast Cancer Research, makes a case for the importance of early detection in breast cancer.

The study found that breast tumors are more aggressive in young women and that the rate of growth in tumors decreases as the age of diagnosis increases.

Harald Weedon-Fekjaer of the Department of Etiological Research at the Cancer Registry of Norway and colleagues studied 395,188 women between the ages of 50- and 69-years-old. They found that tumor growth varies considerably between subjects.

About one in 20 tumors double in size in just over a month from 10 to 20 millimeters, while similar tumors took more than six years to grow to this size. Researchers estimated the mean time for a tumor to double in size from 10 to 20 millimeters in diameter is 1.7 years.

Researchers hope the research provides a new approach to estimating the growth rate of breast cancer and the ability of mammography screening to detect tumors.

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