Semiannual surveillance mammography after breast-conserving therapy (BCT) enables diagnosis at an earlier stage compared with annual exams, according to a study published in the August issue of Radiology. The findings provide evidence that contradicts existing expert opinion-based guidelines, which recommend annual mammographic surveillance for these women.

BCT is a standard treatment for women with small and early breast cancer; however, they remain at risk for recurrence with an incidence of 1 to 2 percent per year for 10 years. An optimal mammographic surveillance interval has not yet been defined for these women. The American Society for Clinical Oncology and the National Comprehensive Cancer Network have suggested annual surveillance, but the recommendations are based on expert opinion rather than data.  

Vignesh A. Arasu, MD, from the department of radiology and biomedical imaging at University of California, San Francisco, and colleagues sought to compare cancer recurrence outcomes among post-BCT women who complied with the institution’s semiannual ipsilateral surveillance protocol versus a noncompliant annual surveillance cohort.

The researchers devised a retrospective analysis and found 7,169 semiannual post-BCT exams and 1,065 annual post-BCT exams from 1997 through 2008. A total of 94 recurrences, defined as a diagnosis of ductal carcinoma in situ or invasive carcinoma within six months of a surveillance exam, were detected in the semiannual group and 15 were found in the annual group. The women were similar in age, family history and strong family history at the time of recurrence, according to Arasu and colleagues.

When the researchers analyzed the data by stage, they found 94 percent of recurrences in the semiannual group were stage 0 or stage 1. The corresponding rate among the noncompliant annual group was 73 percent. All remaining recurrences were stage 2. Invasive cancers in the semiannual group tended to be smaller and with more frequent node negativity than among the noncompliant annual group.

Arasu et al noted that 85 percent of women complied with the semiannual protocol. “On the basis of this high rate of compliance, we believe that a large percentage of patients who have undergone BCT, when offered ipsilateral semiannual surveillance, are likely to take advantage of its benefits.”

Although the study did not examine mortality, “early detection during surveillance may decrease mortality,” wrote Arasu et al. Earlier detection also might deliver improvements in survival, they added.    

Currently, University of California, San Francisco, recommends semiannual surveillance for five years after BCT. The researchers emphasized that semiannual approach is associated with detection of recurrences at a significantly earlier stage compared with noncompliant annual surveillance. The study also provides indirect evidence of a survival benefit with semiannual surveillance.

“[Our] results are the first evidence, to our knowledge, to support more frequent surveillance following BCT than is recommended by current expert-opinion-based guidelines,” wrote Arasu and colleagues.