Breast Cancer Research manuscript: 1107122775268527
Mammogram image quality as a potential contributor to disparities in breast cancer stage at
diagnosis: an observational study
Reviewer #1
This is an interesting study that reports the following:1. Technologist-associated indicators of image
quality (positioning, compression, sharpness) generally scored lower than mammography machineassociated indicators, suggesting that mammography quality in these Health Care facilities could gain
from more technologist training 2. Higher-technologist-associated image quality was associated with
early stage at diagnosis 3. Income is associated with higher image quality Conclusion: Considerable gains
could be made in terms of increasing image quality through better positioning, compression and
sharpness.
Comments:
1. This is certainly a novel approach to studying the impact of mammography, mammography quality,
and impact on health disparity.
2. The associations reported feel tenuous and raise several questions.
#1: Higher-technologist-associated image quality was associated with early stage at diagnosis. I find this
statement problematic for the following reasons: Did the authors consider frequency of attendance for
earlier stage of diagnosis in the multivariate model? High income, high frequency of attendance of
screening, and image quality may all lead to early stage. Was frequency of screening a confounding
variable?
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The reviewer raises an important point. We redid these analyses with the following
modifications. First, we analyzed the association between image quality and stage at diagnosis
after excluding the index films (that detected the breast cancer), using only the “prior” films that
were performed on these women approximately one or two years prior to the index film.
Second we adjusted for income, education, health insurance status, age at diagnosis, recency of
prior mammogram, race/ethnicity, film type (digital vs. analog) and facility type (hospital-based
academic vs. all other). Despite the smaller sample size (N=210 prior films) and adjustment for
multiple potential confounders, we found that lower technologist-associated image quality
remained associated with later stage at diagnosis, whereas lower machine-associated image
quality was not.
Description of the revised methods begins on the bottom of Page 9, and results are presented
on the bottom of Page 11.
What about impact of tumor size and skin condition (ulceration) on image quality? It is known that large
fungating or ulcerating tumors are associated with poor image quality due to pain, tenderness, and
technical difficulty. In such cases, the truth is that technologists perform “poor quality imaging” out of
compassion and consideration for the patient (imaging likely adds little value to the management
algorithm), rather than are in need for increasing imaging quality. How did the authors adjust for such
factors? Was this information available? An asymptomatic breast allows better positioning,
compression, sharpness. Most patients reported symptomatic discovery. In this case, it is the tumor size
and tumor biology that leads to poor ratings for technologist-associated image quality and not vice
versa.
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Patients reporting either initial awareness of their breast cancer through screening
mammography or initial awareness through symptoms despite a prior mammogram within 2
years of detection were eligible for this substudy (bottom of Page 15). The sample of breast
cancer patients included in this analysis was restricted to patients who were either screendetected or had at least one prior mammogram, prior to any symptomatic awareness of their
breast cancer. As such, the influence of symptoms and clinical signs of breast cancer on image
quality should be non-existent in this sample.
3. A single radiologist reviewed all films. What about intra-observer and inter-observer variability?4. A
subjective rating of 1-5 was utilized. Was this purely subjective, or that poor, moderate, good, very good
and excellent had guiding definitions that would permit reproducibility of ratings?

Our breast imaging specialist is a nationally recognized expert at reviewing films for image
quality, using measures and methods according to American College of radiology Guidelines.
Had we been able to employ multiple readers and perhaps taken average of their quality
assessments, we might have had a more generalizeable assessment of image quality, but the
average assessment may or may not have been a better reflection of the truth.
5. The majority of the films evaluated were analog: 345 vs. 144 digital. Did this have any bias on the
results?
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The distribution of analog vs. digital mammograms was fairly representative of the experience in
this sample at the time (2005-2008), and many institutions still use analog mammography. Prior
studies have found that digital mammogram images are more likely to be judged as being higher
quality compared to analog images. In the present study, our expert consistently scored digital
images as being of higher quality across all seven image quality indicators. Nonetheless, after
controlling for type of mammogram in our analyses, lower income remained associated with
lower quality imaging, and lower technologist-associated image quality remained associated
with later stage diagnosis. Therefore, our results do not appear to be due to variation in the use
of digital versus analog mammography across the study sample. Please see the top of Page 15
for this description.
6. There were 494 images from 268 patients, which is 1.8 images per patient. A routine mammogram
comprises 4 images per patient with two breasts, or 2 images per breast. Was there a range and median
number of images for each patient? How were these images selected? In order to avoid bias? Why were
not all 4 images for each patient interpreted?
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We apologize for the confusion in our language. There were 494 mammograms from 268
patients. Image quality was assigned at the level of the mammogram not at the level of the
image. Approximately 90% of mammograms were bilateral, standard four view mammograms,
while the remainder were unilateral mammograms (bottom of Page 5).
7. Did every facility participating in this study have MQSA certification? This is not stated.
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Yes, now stated on page 6
Reviewer number: 2
The authors found that patients with higher socioeconomic status (annual income greater than $30,000)
had higher quality images, which was associated with earlier breast cancer stage at diagnosis. Factors
that were associated with higher image quality were images obtained at an academic medical center,
technologist-associated factors including positioning, compression and sharpness, and digital
mammograms. Overall the paper is well written and adds important information to the literature
regarding racial/ethnic disparity in health care. The authors’ results suggest that improving image quality
through better positioning, compression, and sharpness may translate into diagnosis of breast cancer at
earlier stage.
Specific comments follow:
1. Page 7, last line: The authors report that they dichotomized the practice type variable “to indicate
whether a facility was located within an academic hospital or medical center.” Please clarify---was this
group including only private university-based hospital or medical center (d) only or private with an
academic-affiliation (c) and (d)?
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Yes, defined as private university-based hospital or medical center (Page 8, line 5)
2. In the discussion, another paragraph with more detail discussing the results of income disparity
associated with later breast cancer stage at diagnosis would strengthen the paper.
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We have dropped the mediation analyses exploring why lower income patients experienced
lower quality imaging in order to streamline the text.
3. The authors report that digital mammograms were associated with higher image quality. 345 analog
mammograms compared with 144 digital mammograms (table 4, page 22) were included in the study,
which is a high proportion of analog to digital, likely because the study included mammograms from
2005-2008. Since 2008, there has been transition to digital equipment at many facilities. Updating the
study to include more recent mammograms would strengthen the study.
Would having digital equipment alone translate into earlier stage of breast cancer diagnosis?
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Digital mammography was associated with better image quality and better image quality was
associated with earlier stage at diagnosis, yet we did not find any overall association between
digital mammography and earlier stage at diagnosis in the sample of 210 patients with prior
mammograms. Results suggest that the influence of image quality on stage at diagnosis is not
simply due to higher quality digital images.
How much more important is it for lower socioeconomic status patients to have digital equipment vs.
improved technologist factors?
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We cannot answer such a broad question with our somewhat limited sample size.