LETTERS TO THE EDITOR

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Letters to the Editor

Position, Position From David Ian Hammond, MD,* and Brian C. Lentle, MD† Department of Diagnostic Imaging, University of Ottawa and Ottawa Hospital, 501 Smyth Rd, Ottawa, ON, Canada K1H 8L6* e-mail: [email protected] Women’s Health Centre and Department of Radiology, University of British Columbia, Vancouver, BC, Canada†

Editor: We read with interest the article by Dr Kim and colleagues in the February 2014 issue of Radiology (1). We commend the authors for again demonstrating that some atypical femoral fractures are detectable on images of the proximal femur obtained to determine bone mineral density (BMD) with use of dualenergy x-ray absorptiometry (DXA) and for alerting radiologists to this important observation. We could not help but notice, however, that optimal positioning of the femur, with the long axis of the femoral shaft parallel to the long edge of the scanning table and only a small portion of the lesser trochanter visible (2), was not achieved in all of their patients (eg, figure 6c). As we are certain the authors are aware, insufficient internal rotation of the proximal femur, as assessed by the appearance of the lesser trochanter, causes an artifactual increase in BMD (3) that might lead to an underestimation of fracture risk and render follow-up studies inaccurate. Moreover, the authors imply in the title of their article that the isolated periosteal lesions they have observed, and analyzed so elegantly, always proceed to fracturing. The lesions may be endosteal, are often bilateral and sometimes multifocal, and do not always proceed to fracturing (4). Indeed, the lesions may persist after medication is 926

withdrawn and when the risk of fracturing decreases. Last, it might be helpful to note that the manufacturers of DXA machines have in recent years made provision for extended femoral scans, which might, for example, be used in patients with thigh pain or those on long-term medication. The details are manufacturer and machine specific, so interested practitioners should consult their supplier. Disclosures of Conflicts of Interest: D.I.H. No relevant conflicts of interest to disclose. B.C.L. No relevant conflicts of interest to disclose.

References 1. Kim S, Kyu HY, Lim H, et al. Detection of prefracture hip lesions in atypical subtrochanteric fracture with dual-energy x-ray absorptiometry images. Radiology 2014;270(2):487– 495. 2. Bonner SL, Lewis LA. Bone densitometry for technologists, 3rd edition. New York, NY: Springer, 2013; 102. 3. Cheng XG, Nicholson PHF, Boonen S, et al. Effects of anteversion on femoral bone mineral density and geometry measured by dual energy x-ray absorptiometry: a cadaver study. Bone 1997;21(1):113–117. 4. Mohan PC, Howe TS, Koh JSB, Png MA. Radiographic features of multifocal endosteal thickening of the femur in patients on longterm bisphosphonate therapy. Eur Radiol 2013;23(1):222–227.

Response From Sungjun Kim, MD, PhD,* and Kyu Hyun Yang, MD, PhD† Departments of Radiology* and Orthopedic Surgery,† Gangnam Severance Hospital, Yonsei University College of Medicine, 211 Eonjuro, Gangnam-Gu, Seoul, 135-720, South Korea e-mail: [email protected] We appreciate Drs Hammond and Lentle’s interest in and insightful comments about our article. The main

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LETTERS TO THE EDITOR

purpose of our article was to draw attention to physicians that a low-resolution DXA scan could depict tiny periosteal and/or endosteal callus on the lateral cortex in the subtrochanteric area (1). Needless to say, correct positioning of the patients and low precision error of the technicians are prerequisites for correct DXA examinations. We agree with Drs Hammond and Lentle’s comments that several DXA images in our article (eg, figure 6c) were not obtained with proper patient positioning. We believe that a small difference in rotation could affect not only the BMD values but also the detection rate of small callus because it can be hidden by being overlapped within the lateral cortex shadow. We hope the readers understand that this article is not saying that improperly taken images and their BMD data are acceptable for clinical practice. In addition, we did not intend to give a message with our title that every prefracture lesion proceeds to complete fracture. Some prefracture lesions do lead to complete fracture, but not all. Lee et al (2) recently reported that approximately half of incomplete atypical femur fractures required surgical intervention. As stated in our article and in the statement by Drs Hammond and Lentle, extended femoral scanning is now provided by vendors and is expected to be helpful in the detection of more prefracture lesions because atypical femoral fractures can occur distal to the subtrochanteric diaphysis (1). Disclosures of Conflicts of Interest: S.K. No relevant conflicts of interest to disclose. K.H.Y. No relevant conflicts of interest to disclose.

References 1. Kim S, Yang KH, Lim H, et al. Detection of prefracture hip lesions in atypical subtrochanteric fracture with dual-energy x-ray absorptiometry images. Radiology 2014;270(2):487– 495. 2. Lee YK, Ha YC, Kang BJ, Chang JS, Koo KH. Predicting need for fixation of atypical femoral fracture. J Clin Endocrinol Metab 2013;98(7):2742–2745.

Breast Density Categorization Creep From Ferris M. Hall, MD Department of Radiology, Beth Israel Deaconess Medical Center, 330 Brookline Ave, Boston, MA 02215 e-mail: [email protected]

Editor: I found the commentary by Dr Price and colleagues on behalf of the California Breast Density Information Group, which appeared in the December 2013 issue of Radiology (1), to be extremely comprehensive, balanced, and informative. I have sent it to my own state legislators, who are contemplating similar legislation. I congratulate the authors, who comprise many of the country’s leading breast imagers. I would like to add a comment regarding the statements in the article that “Breast density is currently classified by the subjective visual assessment of the interpreting physician into one of four categories…” and “…the frequency distribution of the BI-RADS [Breast Imaging Reporting and Data System] density categories is approximately as follows: almost entirely fatty, 10%; scattered areas of fibroglandular density, 40%; heterogeneously dense, 40%; and extremely dense, 10% (2).” Because classification is subjective, some might prefer a more “balanced” bell-shaped density curve with the fatty and extremely dense categories at 15%– 20% rather than 10%. More importantly, it is my distinct impression, and that of some colleagues, that a symmetric bell shape distribution is no longer the norm in the United States. I believe there has been a shift or creep toward the dense end of that curve. I suspect this change relates to medicolegal fears, often subconscious, and the slight sense of security that comes in the hedge statement that “dense parenchyma limits mammographic assessment.” In actuality, dense parenchyma primarily limits the assessment of masses rather than microcalcifications or distortions, and it would probably be more technically correct to state this in reports.

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The radiologist’s subjective and arbitrary assessment of breast density reminds me of the story of the three baseball umpires at the bar after a game discussing balls and strikes. The first umpire states that “when I’m behind the plate I calls them as I sees them.” The second umpire more authoritatively opines that “I calls them as they is.” Finally, the third umpire pronounces “well, when I’m behind the plate, there are no balls, and there are no strikes, until I calls them.” In any case, the mammographic density conundrum is impacted by any categorization creep because it means that even more than 50% of imaged women will fall into the two dense categories and will be become subject to current laws and associated anxiety. Disclosures of Conflicts of Interest: No relevant conflicts of interest to disclose.

References 1. Price ER, Hargreaves J, Lipson JA, et al. The California breast density information group: a collaborative response to the issues of breast density, breast cancer risk, and breast density notification legislation. Radiology 2013;269(3):887–892. 2. D’Orsi CJ, Sickles EA, Mendelson, EB, Morris EA. Breast imaging reporting and data system: ACR BI-RADS—breast imaging atlas. 5th ed. Reston, Va: American College of Radiology, 2013.

Response From Elissa R. Price, MD,* Jonathan Hargreaves, MD,† Jafi A. Lipson, MD,‡ Edward A. Sickles, MD,* R. James Brenner, MD, JD,*§ Karen K. Lindfors, MD, MPH,† Bonnie N. Joe, MD, PhD,* Jessica W. T. Leung, MD,|| Stephen A. Feig, MD,# Haydee Ojeda-Fournier, MD,** Allison W. Kurian, MD, MSc,†† Elyse Love, MS, CGC,‡‡ Lauren Ryan, MS, LCGC,§§ and Debra M. Ikeda, MD‡ Department of Radiology and Biomedical Imaging, University of California, San Francisco, 1600 Divisadero St, Room C-250, San Francisco, CA 94115* e-mail: [email protected] 927

LETTERS TO THE EDITOR

Department of Radiology, University of California, Davis, Sacramento, Calif† Department of Radiology, Stanford University School of Medicine, Advanced Medicine Center, Stanford, Calif‡ Bay Imaging Consultants, Sutter Health, Alta Bates Summitt Medical Center, Carol Ann Read Breast Health Center, Oakland, Calif§ Department of Radiology, Sutter Health, California Pacific Medical Center, San Francisco, Calif|| Department of Radiology, University of California, Irvine Medical Center, Fong and Jean Tsai Professor of Women’s Imaging, University of California Irvine School of Medicine, UCI Medical Center, Orange, Calif# Department of Clinical Radiology, Moores Cancer Center, UC San Diego Health System, La Jolla, Calif** Divisions of Oncology and Epidemiology, Stanford University School of Medicine, Stanford, Calif†† Department of Obstetrics and Gynecology, UC Davis Health System, University of California Davis Cancer Center, Sacramento, Calif‡‡ Athena Breast Health Network and UCSF Cancer Risk Program, San Francisco, Calif§§ We thank Dr Hall for his interest in our work and his thought-provoking insights. Density creep is a phenomenon that takes on new import in the era of breast density notification legislation. Many believe a trend exists toward overstating density (as Dr Hall discusses), whereas others believe that,

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in fact, there is a trend toward underestimating breast density. There are no current data supporting drift in either direction. Pre-legislation data from the Breast Cancer Surveillance Consortium, which included millions of mammograms from across the United States, demonstrated no change in the 10%– 40% to 40%–10% density distribution from before to after BI-RADS provided guidance on assessing breast density by quartile volume of dense breast tissue, as reported in both our article (1) and in the newly published 5th edition of the BI-RADS atlas (2). Notably, the California Breast Density Information Group concluded that the masking effect of density is more important than the relatively small associated increase in breast cancer risk (1). This conclusion is also echoed in the new BI-RADS atlas (2), which now advises radiologists to subjectively categorize density on the basis of whether there is substantial masking. The recommendation to classify density based on quartile volume of dense breast tissue has been eliminated. This new approach to clinical density classification may or may not alter the existing frequency distribution. In addition, the paradigm of notification legislation itself could cause the proverbial pendulum to swing either way. Radiologists may continue to (falsely) perceive medicolegal protection by overstating density. Alternatively, radiologists may infer an increase in medicolegal exposure by classifying a woman’s breast tissue as dense, resulting in the receipt of a density notification letter and, hence, the possibility of

additional downstream imaging. Other motivating factors (financial gain, desire to minimize patient anxiety, workforce shortages, etc) may also drive creep in either direction. Both the new BI-RADS recommendations and breast density notification legislation may have an impact on the distribution of breast density classifica­ tion. We await future data to elucidate the multifactorial concept of density creep. Disclosures of Conflicts of Interest: E.R.P. No relevant conflicts of interest to disclose. J.H. No relevant conflicts of interest to disclose. J.A.L. No relevant conflicts of interest to disclose. E.A.S. No relevant conflicts of interest to disclose. R.J.B. Financial activities related to the present article: none to disclose. Financial activities not related to the present article: none to disclose. Other relationships: is a consultant for Hologic. K.K.L. No relevant conflicts of interest to disclose. B.N.J. No relevant conflicts of interest to disclose. J.W.T.L. No relevant conflicts of interest to disclose. S.A.F. No relevant conflicts of interest to disclose. H.O. No relevant conflicts of interest to disclose. A.W.K. No relevant conflicts of interest to disclose. E.L. No relevant conflicts of interest to disclose. L.R. No relevant conflicts of interest to disclose. D.M.I. No relevant conflicts of interest to disclose.

References 1. Price ER, Hargreaves J, Lipson JA, et al. The California Breast Density Information Group: a collaborative response to the issues of breast density, breast cancer risk, and breast density notification legislation. Radiology 2013;269(3):887–892. 2. D’Orsi CJ, Sickles EA, Mendelson EB, Morris EA. Breast imaging reporting and data system: ACR BI-RADS—breast imaging atlas. 5th ed. Reston, Va: American College of Radiology, 2013.

radiology.rsna.org  n  Radiology: Volume 271: Number 3—June 2014

Breast density categorization creep.

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