Breast Cancer Tumors Grow Faster in Younger Women

A new study shows that tumor growth rates vary considerably among patients, with generally slower growth rates with increasing age at diagnosis.

Researchers at the Cancer Registry of Norway (Oslo) developed a likelihood based estimating procedure, where both tumor growth and screen test sensitivity (STS) were modeled as continuously increasing functions of tumor size. The estimating procedure to follow tumor growth was based on breast screening results from 395,188 women aged between 50 and 69 years old included in the Norwegian breast cancer screening program.

The researchers found that tumor growth varied considerably between subjects, with 5% of tumors needing less than 1.2 months to grow from 10 to 20 mm in diameter, and another 5% using more than 6.3 years. The mean time a tumor needed to grow from 10 to 20 mm in diameter was estimated at1.7 years, increasing with age. STS was estimated to increase sharply with tumor size, going from 26 % at 5 mm to 91 % at 10 mm. Compared to previously used Markov models for tumor progression, the applied model gave considerably higher model fit (85 % increased predictive power) and provided estimates directly linked to tumor size. The study was published online on May 8, 2008, in Breast Cancer Research, a publication of BioMed Central (www.biomedcentral.com).

"There are enormous implications for the sensitivity of breast cancer screening programs,” said Harald Weedon-Fekjær, a statistician the department of etiological research. "We found that mammography screen test sensitivity (STS) increases sharply with increased tumor size, as one might expect. Detection rates are just 26% for a 5 mm tumor but increase to 91% once a tumor is 10 mm in size.”

The study also describes a new model for estimating the proportion of breast cancers, which are detected at screening, and the ability of mammography screening to detect tumors.


Related Links:
Cancer Registry of Norway
BioMed Central