Diagnosing Breast Cancer: Sonography in Addition to Mammography May Not Justify Time or Cost

A recent study was conducted to evaluate the diagnostic characteristics of sonographic surveillance for detection of metachronous contralateral breast cancer in patients with a history of breast cancer surgery, in order to determine whether sonography in addition to mammography might be justified in terms of time and cost.

The results, published in the American Journal of Roentgenology indicate that while annual screening sonography in addition to mammograhy may be useful for the discovery of metachronous contralateral cancers, the time and cost involved may not be justified.

The Study
Over a 1-year retrospective period, patients who had undergone surgery for biopsy-proven breast malignancy were identified.

Those who had sonographic evaluation in addition to mammographic evaluation were included in the study. Patients had undergone bilateral whole breast sonography in addition to mammography every 6 months for the first 2 years and then annually thereafter. Exclusion criteria included a history of bilateral breast cancer surgery.

Methodology
1256 Asian women (mean age, 50 years) were included in the study. Over the follow-up period, the contralateral breast was classified as a BI-RADS 1 or 2 93.6% of the time. A BI-RADS 3 category was assigned to 3.8%, category 4 to 2.3%, and category 5 to 0.3%.

One radiologist reviewed the reports of the imaging studies and documented the BI-RADS category. The images were not reread.

Those classified as BI-RADS 1 or 2 were considered negative. BI-RADS categorization of 3, 4, or 5 were only included if they were referring to the breast contralateral to the surgical breast.

In other words, the originally reported BI-RADS was re-categorized to assess only the contralateral breast. The final diagnosis of each patient was determined based on tissue diagnosis at a follow-up time of ≥1 year.

Results
Overall, 46 biopsies were performed. When tissue diagnosis was compared with BI-RADS category, the positive-predictive value (PPV) was 41.0%.

One cancer was missed, resulting in a false-negative rate of 0.06%.Of patients who continued sonographic adjuvant surveillance for >2 years, a 0.4% false-negative rate was revealed.

Two cases of biopsy-proven contralateral metachronous breast cancer were found on sonography and not detected on mammography.

Annual screening sonography may be useful for the discovery of metachronous contralateral cancers.

Reviewer’s Comments
The authors do not comment extensively on the finding that only 2 cancers discovered on sonography were also mammographically occult. For the remaining cases of metachronous cancer, the mammogram was judged to be positive as well.

Although a significant tool for those 2 cases, does it truly justify the time and cost of performing sonographic surveillance in addition to mammographic surveillance in a patient with otherwise no complaints?

On the other hand, those with a history of breast cancer, or any symptoms, might certainly consider having both sonography and mammography to rule out any chance of a false negative.

Author: Basil Hubbi, MD
Reference:
Kim MJ, Kim E-K, et al. Sonographic Surveillance for the Detection of Contralateral Metachronous Breast Cancer in an Asian Population. AJR; 2009; 192 (January): 221-228.