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A small retrospective study finds measurement of serum progesterone concentrations can aid in scheduling breast MRI in premenopausal women who do not have regular menses.

A report in the December issue of the American Journal of Roentgenology says that of 11 women who had breast MRI when progesterone concentrations corresponded with the follicular phase of the menstrual cycle, none needed a repeat MRI.

The use of breast MRI has increased considerably during the past decade and is likely to increase further, evolving from an adjunct imaging modality to a primary screening tool for greater numbers of women, Ellis said.

But hormone fluctuations can affect gadolinium uptake in normal breast tissue, making interpretation of MRI findings difficult.

Previous research has shown that performing the scan during the follicular phase of the menstrual cycle -- days three to 14 in a normal cycle -- minimizes the tissue enhancement that results from these fluctuations.

Such timing works for women with regular 28-day cycles, but if women with irregular cycles or those who've had a hysterectomy but have normally functioning ovaries are scanned mistakenly during the luteal phase, false-positives could result because of gadolinium uptake in normal tissue or false-negatives because of masking of small enhancing cancers.

Many clinicians simply scan these women without regard to timing, and if the results suggest a false-positive result they rescan the patient two weeks later to determine whether the abnormal enhancement reflects hormonal fluctuation in normal tissue.

A serum progesterone concentration ≤1.5 ng/mL was considered to correlate with the follicular phase, and if the level was too high it was checked again three to five days later, and the test repeated until the concentration fell below the cutoff point.

Of the 11 patients, eight needed only one blood draw, two required two, and one required three to identify the follicular phase.

None of the MRI scans showed disproportionate enhancement of glandular tissue that would have required a repeat scan.

Repeat MRI scanning consumes time and resources, and can add considerably to the cost of care: Medicare reimbursement for bilateral breast MRI with contrast is $981.50, and reimbursement for serum progesterone is $29.15.

Therefore, it would require only one repeat MRI scan in 33 patients to be cost neutral, the author said.

Source: American Journal of Roentgenology

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