Imaging for distant metastases in women with early-stage breast cancer: a population-based cohort study

Abstract

Background: Practice guidelines recommend that imaging to detect metastatic disease not be performed in the majority of patients with early-stage breast cancer who are asymptomatic. We aimed to determine whether practice patterns in Ontario conform with these recommendations.

Methods: We used provincial registry data to identify a population-based cohort of Ontario women in whom early-stage, operable breast cancer was diagnosed between 2007 and 2012. We then determined whether imaging of the skeleton, thorax, and abdomen or pelvis had been performed within 3 months of tissue diagnosis. We calculated rates of confirmatory imaging of the same body site.

Results: Of 26,547 patients with early-stage disease, 22,811 (85.9%) had at least one imaging test, and a total of 83,249 imaging tests were performed (mean of 3.7 imaging tests per patient imaged). Among patients with pathologic stage I and II disease, imaging was performed in 79.6% (10,921/13,724) and 92.7% (11,882/12,823) of cases, respectively. Of all imaging tests, 19,784 (23.8%) were classified as confirmatory investigations. Imaging was more likely for patients who were younger, had greater comorbidity, had tumours of higher grade or stage or had undergone preoperative breast ultrasonography, mastectomy or surgery in the community setting.

Interpretation: Despite recommendations from multiple international guidelines, most Ontario women with early-stage breast cancer underwent imaging to detect distant metastases. Inappropriate imaging in asymptomatic patients with early-stage disease is costly and may lead to harm. The use of population datasets will allow investigators to evaluate whether or not strategies to implement practice guidelines lead to meaningful and sustained change in physician practice.

Figure 1:

Creation of a population-based cohort to investigate the frequency of imaging for distant metastases among women with early-stage breast cancer.

Figure 2:

Yearly imaging trends for skeleton (A), thorax (B) and abdomen and/or pelvis (C) by conventional imaging (at left) and more advanced imaging (at right). CT = computed tomography, MRI = magnetic resonance imaging.