Diagnostic work-up of contralateral breast cancers has not improved over calendar period

Women who have been treated for breast cancer are typically followed up with regular mammography and palpation, with the aim of detecting recurrences and contralateral breast cancer (CBC). This study aims to investigate if the diagnostic work-up of breast cancer patients has improved over the last 25 years and resulted in earlier diagnoses of CBC. Two population-based cohorts were used; all CBCs in Sweden 1976–2004 (n: 2932), and all CBCs in Stockholm, Sweden, 1976–2005 (n: 626), both cohorts with a maximum of 3 years between the two cancers. Synchronous CBC was defined as two cancers <3 months apart, the remainder was defined as metachronous CBC. We calculated the odds ratio of being diagnosed synchronously, relative to metachronously, using logistic regression, adjusting for whether the second cancer was detected through clinical work-up or not. The odds of synchronous CBC were significantly increased: 1.27 (95% CI, 1.13–1.42) per 5-year period, compared to metachronous, and was not affected by detection mode, but seemed to be explained by adjuvant therapy. The proportion of CBCs detected by clinical work-up did not increase over the study period, and the mean size of the second tumor remained constant. We found an increase in the proportion of synchronous CBCs compared to metachronous, over calendar period, a change that was not associated with clinical work-up, but with adjuvant therapy. This study gives no indications that any improvement in diagnostic work-up of CBC have occurred over the last 25 years.