Lori McDonald MD, Abstract Co-Author: Nothing to Disclose

Judy Sharon Caines MD, Presenter: Nothing to Disclose

Gerald Schaller MD, Abstract Co-Author: Nothing to Disclose

Jennifer Payne PhD, Abstract Co-Author: Nothing to Disclose

Theresa Foley RT, Abstract Co-Author: Nothing to Disclose

Julie Gallant, Abstract Co-Author: Nothing to Disclose

To conduct a review by three independent radiologists of all interval breast cancer cases aged 40 to 69 at diagnosis who were participants of the Nova Scotia Breast Screening Program (NSBSP) at any point in the period 1991 to 2004.

Pathology reports for all breast cancer cases diagnosed in the province of Nova Scotia (population 950,000) are sent to the Nova Scotia Breast Screening Program for tracking of outcomes among program participants. Interval breast cancer cases for the period 1991 (program inception) through 2004 were defined as a cancer arising after a negative screening mammogram, but before the next screening mammogram was due. Interval breast cancer cases were identified within the NSBSP database and the most recent (negative) screening mammogram for each of these cases was reviewed independently by 3 from a pool of experienced mammographers (i.e., each reads a minimum 2500 screens/yr). Mammograms were reviewed as either normal or abnormal. Each cancer was classified as either a true interval (i.e., >= 2 radiologists indicated normal) or a missed cancer (i.e., >= 2 radiologists indicated abnormal).

A total of 332 interval breast cancer cases aged 40-69 at diagnosis were identified among participants who were ever screened during the period 1991 to 2004. Further review led to the exclusion of cases which were lymphomas or breast as the metastatic site (N=10) leaving a final total of 322 interval cancers. The review yielded the following results: among women 40-49 screened annually (0.93 true intervals/1000 women or 3.99 true intervals/10000 screens; 0.45 missed/1000 women or 1.95 missed/10000 screens); among women 50-69 who are screened annually (2.22 true intervals/1000 women; 1.08 missed/1000 women); among women aged 50-69 who are screened biennially (3.15 true intervals/1000 women; 0.90 missed/1000 women); and among women aged 50-69 as a whole (10.44 true intervals/10000 screens; 3.34 missed/10000 screens).  

The NSBSP results meet Canadian guidelines for interval breast cancer rates and the NSBSP has implemented this review process as standard procedure.

On-going review of interval breast cancer rates can be used by screening programs as a quality check for screening and for informing screening intervals for women at high risk.

McDonald, L, Caines, J, Schaller, G, Payne, J, Foley, T, Gallant, J, Radiological Review of Interval Breast Cancer Cases in the Context of Organized Screening.  Radiological Society of North America 2008 Scientific Assembly and Annual Meeting, February 18 - February 20, 2008 ,Chicago IL. http://archive.rsna.org/2008/6022401.html