Thursday, July 29, 2004

From The New York Times:Study Shows M.R.I. Scans Are Better Finding Tumors:
In women at high risk of breast cancer, new research suggests that M.R.I. scans find nearly twice as many tumors as mammograms do, but that they cost a lot and trigger more unneeded biopsies
So goes the lead paragraph about a study that was published in this week's New England Journal of Medicine:Efficacy of MRI and Mammography for Breast-Cancer Screening in Women with a Familial or Genetic Predisposition
Background:The value of regular surveillance for breast cancer in women with a genetic or familial predisposition to breast cancer is currently unproven. We compared the efficacy of magnetic resonance imaging (MRI) with that of mammography for screening in this group of high-risk women.

Methods: Women who had a cumulative lifetime risk of breast cancer of 15 percent or more were screened every six months with a clinical breast examination and once a year by mammography and MRI, with independent readings. The characteristics of the cancers that were detected were compared with the characteristics of those in two different age-matched control groups.

Results: We screened 1909 eligible women, including 358 carriers of germ-line mutations. Within a median follow-up period of 2.9 years, 51 tumors (44 invasive cancers, 6 ductal carcinomas in situ, and 1 lymphoma) and 1 lobular carcinoma in situ were detected. The sensitivity of clinical breast examination, mammography, and MRI for detecting invasive breast cancer was 17.9 percent, 33.3 percent, and 79.5 percent, respectively, and the specificity was 98.1 percent, 95.0 percent, and 89.8 percent, respectively. The overall discriminating capacity of MRI was significantly better than that of mammography (P<0.05). The proportion of invasive tumors that were 10 mm or less in diameter was significantly greater in our surveillance group (43.2 percent) than in either control group (14.0 percent [P<0.001] and 12.5 percent [P=0.04], respectively). The combined incidence of positive axillary nodes and micrometastases in invasive cancers in our study was 21.4 percent, as compared with 52.4 percent (P<0.001) and 56.4 percent (P=0.001) in the two control groups.

Conclusions: MRI appears to be more sensitive than mammography in detecting tumors in women with an inherited susceptibility to breast cancer.
The women in this study all had ,at minimum, a fifteen percent lifetime risk of breast cancer. The patients were stratified in groups according to risk, ranging from mutation carriers (BRCA) to medium (>15%) risk. As seen above MRI was twice as likely to detect a tumor as mammography and those found were smaller with fewer lymph node mets. The tumors in the mutation group were larger and more were ER/PR negative than in the other groups. In one area, the diagnosis of DCIS, mammography was superior:
Another important matter that we addressed was the best method for detecting carcinoma in situ. Our study showed that mammography had a higher sensitivity than MRI for detecting ductal carcinoma in situ: 83 percent (five out of six cancers detected), as compared with 17 percent (one out of six) for MRI (P=0.22).
This is likely to have a lot of women asking for MRIs.
Some issues I have with the study:
With a follow-up of only 2.9 years, the question remains open whether the early detection that is available with MRI leads to increased survival. In fact the "early detection = increased survival" debate still goes on about mammography.

Not every community MRI scanner can perform breast MRI. Specialized coils are needed. The few I have ordered in the past have had to be sent to an academic center.

There is a sacrifice of specificity:
A drawback of MRI screening is that it has a lower specificity than mammography, and as a result, MRI will generate more findings judged as uncertain, which require short-term follow-up or additional investigations In our study, screening by MRI led to twice as many unneeded additional examinations as did mammography (420 vs. 207) and three times as many unneeded biopsies (24 vs. 7).
All which leads to increased cost and anxiety on the part of the patient. Especially in a group that is unlikely to engage in a pattern of "watchful waiting'.

And finally, the cost of MRI:
An M.R.I. scan costs $700 to $1,000 - about 10 times the cost of a mammogram
Who will pay?

Overall a fairly good study. Hopefully this population will be followed long-term to evaluate for survival benefit.
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