The importance of being screened for breast cancer was once again highlighted by Norwegian researchers who reported that breast cancer tumors appear to grow more rapidly in younger women.

Harald Weedon-Fekjaer, PhD, of the Cancer Registry of Norway of Oslo and colleagues used a computer model fed with national screening and cancer data on 395,188 women (ages 50 to 69) to calculate how rapidly the tumors grow and estimate the proportion of breast cancers detected at screening.

The researchers found that tumor growth varies considerably between subjects. About one in 20 tumors doubles 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.

They also said the estimated time for a tumor to double in diameter from 10 to 20 mm was 1.4 years in women ages 50 to 59 compared with 2.1 years from women 60 to 69.

Debbie Saslow, director of breast and gynecologic cancer at the American Cancer Society, says the study confirms the necessity of having a mammogram every year once women hit age 40. Being screened properly allows doctors to keep the size of tumor in control and also take better decisions regarding its treatment. Moreover, it is already known that early detection of breast cancer tumors means good chances to escape dying from it.

According to the American Cancer Society, breast cancer is the leading cause of cancer deaths among women worldwide. About 465,000 women died from it last year and 1.3 million new cases were diagnosed.

The study findings appeared in the online journal Breast Cancer Research.