Nov. 4, 2010 (San Diego) -- A study of nearly 600 younger women with a very early stage of breast cancer suggests that women under age 45 are at higher risk of recurrence.
Canadian researchers studied women with ductal carcinoma in situ (DCIS) who were given the standard treatment of breast-conserving surgery followed by radiation, says study head Iwa Kong, MD, a clinical research fellow in radiation oncology at Sunnybrook Health Sciences Center in Toronto.
By an average of nearly eight years after treatment, cancer had come back in the affected breast of 18% of women under 45, compared with 11% of women aged 45 to 50.
"Based on previous large randomized trials [of women of all ages], we expected a recurrence rate of about 10%, so it's almost double in younger women," Kong tells WebMD.
Most of the returning tumors represented invasive cancers, which are further along and more worrisome than DCIS, she says.
A total of 12% of women under 45 suffered a recurrent invasive cancer vs. 7% of women aged 45 to 50.
"That corresponds to a 70% increased risk of getting a recurrent invasive cancer if you're under 45," Kong says. Although this finding could have been due to chance, Kong says she expects the increased risk in the younger women to become more prominent over time.
"This was a very strong trend, with the difference [in recurrence rates] between the two groups becoming bigger and bigger over time," Kong explains.
The findings were presented at the annual meeting of the American Society for Radiation Oncology.
Previous Studies Include Few Younger Women With DCIS
DCIS accounts for about one in four newly diagnosed breast cancers in North America, Kong says.
Some previous studies have shown increased rates of recurrence in younger women with DCIS, who tend to have either a genetic predisposition to breast cancer or a family history of breast cancer, she says.
"But other studies did not [show increased rates of recurrence in younger women], and all the studies included few women under age 50," Kong says.
Additionally, there is no standard definition of "younger," she says. "Is it under 39? 45? 50?" Kong says.
Age 45 Appears to Be Cutoff
To find out, she and colleagues combed Canadian databases and identified all 574 women diagnosed with DCIS in Ontario from 1994 to 2003 who were 50 or younger at diagnosis and treated with breast-conserving surgery and radiation.
The outcomes of the 66 women under age 40 and the 176 women aged 40 to 44 were similar, so they were combined into one group. Then their recurrence rates were compared to those of the 332 women aged 45 to 50.
"Based on our findings, it appears under 45 is perhaps the definition of young age. These appear to be the women at highest risk of recurrence," Kong says.