WASHINGTON – Younger women may suffer under new national mammography screening guidelines that recommend that the procedure become biennial and begin at age 50 years, according to investigators who conducted a retrospective study of breast cancer patients in the 40- to 49-year age group.
Breast tumors that arise in this group may not be discovered until they present clinically, at which time treatment will be more expensive and curative therapy perhaps impossible, lead author Dr. Paul Dale said at the annual meeting of the American Society of Breast Surgeons.
"Our study found that tumors identified through mammography generally had better outcomes after treatment [than did] those found through clinical exam," Dr. Dale said at a press briefing. "Breast cancer has a better prognosis when treated before tumors become palpable and identifiable" through a physician- or self-exam of the breast.
The 10-year retrospective study found that women aged 40-49 years who presented with a breast cancer through clinical symptoms or palpation had significantly larger tumor size, more nodal involvement, and lower 5-year survival rates than did a similarly aged group whose cancers were detected through mammography.
The study comprised 311 women aged 40-49 years who were treated for breast cancer at a single center in 2004-2008. Of these, 145 (47%) had undergone a screening mammography that detected the tumor, whereas 166 (53%) had a tumor that presented clinically, either by symptoms or by physician- or self-exam of the breast.
Tumors in the mammography group were significantly smaller than those among the clinically presenting group (median, 2 cm vs. 3 cm; P less than or equal to .001). Sentinel lymph node involvement occurred in significantly fewer of those in the mammography group (28 vs. 115; P less than or equal to .001)
The 5-year disease-free survival rate was significantly better in the mammographically detected group (94% vs. 71%); their 5-year overall survival was also significantly greater (97% vs. 78%).
These advantages occurred despite the fact that significantly more women in the mammographically detected group had a family history of breast cancer (25% vs. 15%; P = .034).
A multivariate analysis found that mammographic cancer detection, node negativity, and smaller tumor size were all significantly associated with an increase overall survival.
"In our institution, we find that 20% of the women diagnosed with breast cancer are younger than age 50," said Dr. Dale, chief of surgical oncology at the University of Missouri–Columbia. Both the findings of this study and his own clinical experience have convinced him that annual mammographic screening has "great value" to this younger set of women, despite the 2010 U.S. Preventive Services Task Force (USPSTF) recommendation that biennial screening mammograms begin at age 50.
The agency recommended this screening regimen for women aged 50-75 years, but said that for women aged 40-49 years the benefit of screening is small and is balanced by "moderate harms," including false positives that lead to unnecessary invasive interventions, anxiety, and the small impact of pain from biopsy and radiation exposure.
The statement was largely informed by a 2009 review of the SEER (Surveillance Epidemiology and End Results) database. That review concluded that among women aged 40-49, the number needed to treat to prevent one breast cancer death was 1,904, compared with 1,339 for women aged 50-59.
"Although the relative risk reduction is nearly identical (15% and 14%) for these two age groups, the risk for breast cancer increases steeply with age starting at age 40 years," the document stated. "Thus, the absolute risk reduction from screening ... is greater for women aged 50-59 years than for those aged 40-49 years."
However, the USPSTF document did not recommend against earlier screening, saying that the decision should be based on a woman’s family history of the disease and her individual desires, and only after a discussion about the relative risks and benefits.
In an interview, Dr. Dale debated this approach, saying that "when it’s your cancer, it matters a lot.
"I have been doing this for 20 years, and of all the women I have put through a breast biopsy because of something suspicious identified on a screening mammogram, I can tell you that 100% of those with a negative result were glad they did it. The woman’s level of comfort in hearing that is huge," he added.
A 2011 study supports the idea that screening more women will save more lives, Dr. Dale said, referring to another analysis of the same SEER data. Dr. Edward Hendrick of the University of Colorado at Denver and colleagues, concluded that annual screening for women aged 40-84 years would result in a 71% greater mortality reduction than the USPSTF recommendation of biennial screening in those aged 50-74 years. An annual screening for women aged 40-84 years would save almost 100,000 more lives, the authors argued (AJR 2011;196:W112-6).