LONDON (Reuters) - Five percent of breast cancer tumors appear to double in size in just over a month, Norwegian researchers said on Thursday in a study underscoring the potential benefits of more frequent screening.
The study published in the journal Breast Cancer Research also suggested detection rates of just 26 percent for a 5 mm tumor, and 91 percent for a 10 mm tumor.
The researchers used a computer model fed with national screening and cancer data to calculate how quickly tumors grow and estimate the proportion of breast cancers detected at screening.
This data on nearly 400,000 women aged 50 to 69 helped them estimate that about 5 percent of tumors may double in just over a month, growing from 10 mm to 20 mm. This was mainly among younger women in the study's age group.
Another 5 percent of tumors took more than six years to grow to the same size, according to the data collected before and after Norway began national breast cancer screening in 1995. This was mostly among older woman in the study.
"The variation was larger than what I was expecting," said Harald Weedon-Fekjaer, a statistician at the Cancer Registry of Norway, who led the study.
"Now we can be more certain about estimates."
The researchers used a complex formula that took into account what size tumors were when detected, measurements of surgically removed tumors and other data.
They said their findings could help in the debate over how often women should get mammograms. Some countries offer mammograms only once every three years and studies have provided conflicting evidence over whether mammograms save lives.
There is no question, experts say, that breast cancer detected earlier is far easier to treat, however.
Breast cancer is the leading cause of cancer deaths among women worldwide, according to the American Cancer Society. The group estimates about 465,000 women died from it globally in 2007, with 1.3 million new cases diagnosed.
Declining death rates from breast cancer in developed countries have been attributed to early detection through mammography screening and to improved treatment, it said.
The large study reviewed here looked at information on tumor size and growth from more than 400,000 women age 50 to 69 in Norway who were diagnosed with breast cancer. The scientists used a mathematical formula to estimate the growth of each breast cancer.
The researchers found that about 5% of the breast cancers grew very rapidly, doubling in size in just 1 month. Rapidly growing breast cancers were more likely to be found in younger women.
Slower growing breast cancers were more likely to be found in older women.
Mammograms, along with regular breast self-exams (BSE) and examinations by a medical professional, are the best ways to diagnose breast cancer early, when it's most treatable. Other research has shown that regular mammograms mean more women survive breast cancer. Still, some researchers and public health officials have suggested that annual mammograms should start later -- at age 50 instead of the current recommended age of 40 -- or that mammograms don't need to be done every year.
The results of this study show that a breast cancer can double in size in just 1 month in some women, especially younger women. These results are an important reason why current mammogram recommendations shouldn't change. These results also show how important it is for every woman age 40 and older to get a mammogram every year.
Visit the breastcancer.org Screening and Testing section to learn more about breast self-exam, mammograms, and other techniques used in breast cancer screening and diagnosis.
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