Journal of the National Cancer Institute Advance Access published online on July 24, 2007
JNCI Journal of the National Cancer Institute, doi:10.1093/jnci/djm050
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© The Author 2007. Published by Oxford University Press.
ARTICLES |
Additional Double Reading of Screening Mammograms by Radiologic Technologists: Impact on Screening Performance Parameters
Affiliations of authors: Department of Radiology, Catharina Hospital, Eindhoven, The Netherlands (LEMD); Expertise Centre Transitions of Care, Rotterdam University, University of Applied Sciences, Rotterdam, The Netherlands (JHG); Department of Public Health, Erasmus Medical Center, University Medical Center Rotterdam, Rotterdam, The Netherlands (JF, HJdK)
Correspondence to: Lucien E. M. Duijm, MD, PhD, Department of Radiology, Catharina Hospital, PO Box 1350, 5602 ZA, Eindhoven, The Netherlands (e-mail: lemduijm{at}hotmail.com).
Background: Studies have shown that having mammography technologists review screening mammograms in addition to radiologist review may increase the number of breast cancers that are detected at screening mammography. We prospectively examined the effects on screening performance of adding independent double reading of screening mammograms by technologists to standard double reading by radiologists.
Methods: Twenty-one screening mammography technologists and eight certified screening radiologists participated in this study. From January 1, 2003, to January 1, 2005, all 61251 screening mammograms obtained at two mammography screening units in The Netherlands were independently read (although the second reader was not blinded to the first reader’s interpretation) by two technologists and, in turn, by two radiologists. Radiologists were blinded to the referral opinion of the technologists. During a 2-year follow-up period, we collected clinical data, breast imaging reports, biopsy results, and breast surgery reports of all women with a positive screening result (i.e., those that required additional imaging) from any reader. The distributions of categorical variables between subgroups were compared using chi-square or Fisher's exact tests. Differences in referral and detection by radiologists and technologists were assessed using McNemar's test. All statistical tests were two-sided.
Results: The radiologists referred 905 women (referral rate = 1.48%, 95% confidence interval [CI] = 1.38% to 1.57%), of whom 323 had breast cancer, corresponding to a positive predictive value of referral (PPV) of 35.7% (95% CI = 32.6% to 38.8%). Review of 446 additional technologist-positive readings led to another 80 referrals, resulting in the detection of 22 additional cancers. These extra referrals increased the initial referral rate from 1.48% to 1.61% (difference = 0.13%; 95% CI = 0.10% to 0.16%) and the cancer detection rate (CDR) from 5.27 to 5.63 cancers per 1000 women screened (difference = 0.36 cancers per 1000 women screened; 95% CI = 0.24 to 0.55). With technologist double reading only, 829 women would have been referred (referral rate = 1.35%, 95% CI = 1.26% to 1.45%); among these women, 286 cancers were diagnosed (PPV = 34.5%, 95% CI = 31.3% to 37.7%; CDR = 4.67 cancers per 1000 women screened, 95% CI = 4.13 to 5.21). Referral of all 1351 radiologist- and/or technologist-positive readings would have led to 362 cancers found at screening. The cancer detection rate for radiologist double reading would have increased from 5.27 to 5.91 cancers per 1000 women screened (relative increase = 12.1%, 95% CI = 8.8% to 16.5%; difference = 0.64 cancers per 1000 women screened, 95% CI = 0.47 to 0.87).
Conclusion: A referral strategy that includes all technologist-positive readings, which would have increased the cancer detection rate while maintaining a low referral rate, should be considered.
| CONTEXT AND CAVEATS Prior knowledge Mammographic technologists who are taught to differentiate normal from abnormal mammograms have been shown to play a valuable role in the double reading of mammograms alongside radiologists, but this role has not been studied in a setting in which independent double reading of mammograms by screening radiologists is the standard of care. Study design Observational study conducted at two mammography screening units in The Netherlands where mammograms were independently read by two technologists and two radiologists. Contribution Adding independent double reading of mammograms by technologists to independent double reading by radiologists was effective in detecting additional cases of breast cancer while decreasing screening specificity only slightly. Implications All technologist-positive readings should be considered for referral. Limitations Reading conditions differed between technologists and radiologists. The technologists attended quality assurance sessions, which may have influenced their reading decisions. Assumptions were made concerning the screening outcomes of the technologist-positive readings that, in reality, had not been referred. The sensitivity of breast cancer screening at the 2-year follow-up was biased by new interval cancers that developed in the second year after screening.
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Manuscript received December 19, 2006; revised May 23, 2007; accepted June 7, 2007.
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