DOI: 10.1148/radiol.2431060486
(Radiology 2007;243:299-300.)
© RSNA, 2007
Does the Marginal Benefit Exceed the Marginal Cost?
John D. Keen, MD, MBA* and
James E. Keen, DVM, PhD
* Department of Radiology, John H. Stroger Hospital of Cook County, 1912 West Harrison Street, Chicago, IL 60612
e-mail: jkeen{at}ccbhs.org
Hastings, Neb
Editor:
In the March 2006 issue of Radiology, Dr Ganott and colleagues (1) have shown that women have an excessive fear of breast cancer diagnosis, as shown previously (2). Women also overestimate cancer lethality, death risk, and screening benefit (3,4). These beliefs interfere with rational marginal cost-benefit decision making.
Dr Ganott and colleagues essentially asked women if radiologists should increase sensitivity from 78% to 85% on the typical receiver operating characteristic (ROC) curve (5). The baseline cancer detection rate (CDR) of 3.5 per 1000, or one in 285, implies an average prevalence of cancer of 3.5 ÷ .78 = 4.5 per 1000 (5). Reaching a new CDR of one in 200 (five per 1000) is impossible unless Dr McCoy is beamed down with his medical tricorder. On the 20th century ROC curve, the new CDR would be 3.8 per 1000 (one in 260), a gain of 0.3 per 1000.
Regarding cancer screening benefit, 74% of adults believe that early detection saves lives most or all of the time (6), and 94% of women equate mammographic cancer detection with a benefit (7). However, assuming a 20% relative mortality risk reduction, on average only about three out of every 10 000 women 50 years of age would have their lives extended by a single screening examination (4,8,9). This means no marginal benefit for more than 90% of women. Dr Ganott and colleagues also did not quantify the financial, opportunity, and psychological marginal costs of the recall examination. A recent production cost estimate for obtaining a diagnostic mammogram is $228 (10), and our decision analysis negative-recall price estimate (with consults and biopsy) is over $700. Decreasing the specificity by 5% will increase the expected price of a single mammogram by $35 (11).
Question 6 of the authors' study should have asked: Would you pay an extra $35 now if the radiologist would detect an extra three cancers in over 10 000 women screened once, understanding that less than three in 100 000 women would have their lives extended by finding the extra cancers 1 year earlier and that some women will have needless treatment from overdiagnosis (7,12,13)?
We applaud their effort, but hope Dr Ganott and colleagues will promote informed medical decision making in the future.
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References
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- Ganott Marie A., Gumkin JH, King JL, et al. Screening mammography: do women prefer a higher recall rate given the possibility of earlier detection of cancer? Radiology 2006;238:793–800.
- Dolan NC, Lee AM, McDermott MM. Age-related differences in breast carcinoma knowledge, beliefs, and perceived risk among women visiting an academic general medicine practice. Cancer 1997;80:413–420.[CrossRef][Medline]
- Silverman E, Woloshin S, Schwartz LM, Byram SJ, Welch HG, Fischhoff B. Women's views on breast cancer risk and screening mammography: a qualitative interview study. Med Decis Making 2001;21:231–240.[Abstract]
- Black WC, Nease RF, Tosteson AN. Perceptions of breast cancer risk and screening effectiveness in women younger than 50 years of age. J Natl Cancer Inst 1995;87:720–731.[Abstract/Free Full Text]
- Yankaskas BC, Taplin SH, Ichikawa L, et al. Association between mammography timing and measures of screening performance in the United States. Radiology 2005;234:363–373.[Abstract/Free Full Text]
- Schwartz LM, Woloshin S, Fowler FJ, Welch HG. Enthusiasm for cancer screening in the United States. JAMA 2004;291:71–78.[Abstract/Free Full Text]
- Schwartz LM, Woloshin S, Sox HC, Fischhoff B, Welch HG. US women's attitudes to false positive mammography results and detection of ductal carcinoma in situ: cross sectional survey. BMJ 2000;320:1635–1640.[Abstract/Free Full Text]
- Fletcher SW, Elmore JG. Mammographic screening for breast cancer. N Engl J Med 2003;348:1672–1680.[Free Full Text]
- Sirovich BE, Sox HC. Breast cancer screening. Surg Clin North Am 1999;79:961–990.[CrossRef][Medline]
- Chen SL, Clark S, Pierce LJ, et al. An academic health center cost analysis of screening mammography: creating a financially viable service. Cancer 2004;101:1043–1050.[CrossRef][Medline]
- Keen JD. Should I request computer-aided diagnosis (CAD) with my baseline or subsequent screening mammogram? [abstr]. In: Radiological Society of North America scientific assembly and annual meeting program. Oak Brook, Ill: Radiological Society of North America, 2006; 565.
- Gotzsche PC. On the benefits and harms of screening for breast cancer. Int J Epidemiol 2004;33:56–64.[Free Full Text]
- Gur D. Lung cancer screening: radiology's opportunity here and now [editorial]. Radiology 2006;238:395–397.[Free Full Text]
Response
Marie A. Ganott, MD,
Jules H. Sumkin, DO and
David Gur, ScD
Department of Radiology, University of Pittsburgh and Magee-Womens Hospital of the University of Pittsburgh Medical Center, 300 Halket Street, Pittsburgh, PA 15213-3180
e-mail: gurd{at}upmc.edu
We disagree with the assessment by Drs Keen and Keen that, in our article (1), we have shown that women have excessive fear of breast cancer diagnosis. That may be, but this was not the focus of the study. What we have shown is that those who responded were largely misinformed of the actual probability of having a cancer detected during a single screening examination. More important, given a choice, women who responded would prefer a conservative interpretation of their mammogram even if it means being recalled more often. Clearly the expected detection rates that these authors have presented are related to averages and do not assume population-related variances nor the fact that mixed populations of first and repeat screening examinations can yield significantly different detection rates than they quote. Regardless, the use of a specific number as a simple example in a survey (even if high) was not the primary reason for the responses we received. Cost was not an issue in this study of women's preferences. One can easily use the cost listed in the letter to question the cost-benefit ratio of screening as a whole, yet it is a well-regarded standard of practice. We appreciate the short lesson in epidemiology and cost-benefit analysis and in how we should or should not conduct our own work. We hope the authors do better in this regard in their own environment.
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REFERENCE
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- Ganott Marie A., Gumkin JH, King JL, et al. Screening mammography: do women prefer a higher recall rate given the possibility of earlier detection of cancer? Radiology 2006;238:793–800.[Abstract/Free Full Text]
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