Abstract
BackgroundHigh background parenchymal uptake (BPU) on molecular breast imaging (MBI) has been identified as a breast cancer risk factor. We explored the feasibility of offering a short-term intervention of low-dose oral tamoxifen to women with high BPU and examined whether this intervention would reduce BPU.MethodsWomen with a history of high BPU and no breast cancer history were invited to the study. Participants had an MBI exam, followed by 30 days of low-dose oral tamoxifen at either 5 mg or 10 mg/day, and a post-tamoxifen MBI exam. BPU on pre- and post-tamoxifen MBI exams was quantitatively assessed as the ratio of average counts in breast fibroglandular tissue vs. average counts in subcutaneous fat. Pre-tamoxifen and post-tamoxifen BPU were compared with paired t tests.ResultsOf 47 women invited, 22 enrolled and 21 completed the study (10 taking 5 mg tamoxifen, 11 taking 10 mg tamoxifen). Mean age was 47.7 years (range 41–56 years). After 30 days low-dose tamoxifen, 8 of 21 women (38%) showed a decline in BPU, defined as a decrease from the pre-tamoxifen MBI of at least 15%; 11 of 21 (52%) had no change in BPU (within ± 15%); 2 of 21 (10%) had an increase in BPU of greater than 15%. Overall, the average post-tamoxifen BPU was not significantly different from pre-tamoxifen BPU (1.34 post vs. 1.43 pre, p = 0.11). However, among women taking 10 mg tamoxifen, 5 of 11 (45%) showed a decline in BPU; average BPU was 1.19 post-tamoxifen vs. 1.34 pre-tamoxifen (p = 0.005). In women taking 5 mg tamoxifen, 2 of 10 (20%) showed a decline in BPU; average BPU was 1.51 post-tamoxifen vs.1.53 pre-tamoxifen (p = 0.99).ConclusionsShort-term intervention with low-dose tamoxifen may reduce high BPU on MBI for some patients. Our preliminary findings suggest that 10 mg tamoxifen per day may be more effective than 5 mg for inducing declines in BPU within 30 days. Given the variability in BPU response to tamoxifen observed among study participants, future study is warranted to determine if BPU response could predict the effectiveness of tamoxifen for breast cancer risk reduction within an individual.Trial registrationClinicalTrials.gov NCT02979301. Registered 01 December 2016.
Highlights
High background parenchymal uptake (BPU) on molecular breast imaging (MBI) has been identified as a breast cancer risk factor
As a first step toward characterizing the impact of tamoxifen on MBI, we aimed to explore the feasibility of offering a short-term intervention of low-dose oral tamoxifen to women with high BPU and to examine whether this intervention would reduce BPU
The 1 participant who did not complete the study had initiated 5 mg tamoxifen but withdrew from the study after a lesion was detected on her pre-tamoxifen MBI exam; biopsy of this lesion demonstrated benign pseudoangiomatous stromal hyperplasia
Summary
High background parenchymal uptake (BPU) on molecular breast imaging (MBI) has been identified as a breast cancer risk factor. Molecular breast imaging (MBI), a nuclear medicine test performed with the radiotracer Tc-99m sestamibi and a dedicated gamma camera, has shown utility for supplemental screening in women with dense breasts on mammography. Because mammography relies on the differences in X-ray attenuation among breast structures to detect cancer, tumors can be masked by surrounding fibroglandular tissue. Fibroglandular tissue of the breast, called breast density when imaged by mammography, has similar X-ray attenuation properties to tumors. Background parenchymal uptake (BPU) is the term used to describe the relative uptake in breast fibroglandular tissue to that in subcutaneous fat. An analysis of women presenting for screening MBI showed that most (63%) have minimal to mild BPU, which describes a similar or slightly higher level of uptake in fibroglandular tissue and fat; 15% of women have moderate or marked BPU, in which higher uptake is seen in fibroglandular tissue compared to fat, and 22% of women have photopenic BPU, in which fibroglandular tissue shows less uptake than in fat [5]
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