Clinical impact of follow‐up imaging on mortality in Korean breast cancer patients: A national cohort study

BACKGROUND: As the incidence of breast cancer has increased and the survival rate has improved, supporting the optimal follow‐up strategy has become an important issue. This study aimed to evaluate follow‐up imaging usage after breast cancer surgery and the implications on mortality in Korea. METHODS: This study included 96,575 breast cancer patients diagnosed during 2002–2010 and registered in the Korea Central Cancer Registry, Statistics Korea, and Korean National Health Insurance Service. We evaluated the frequency of breast imaging (mammography and breast MRI) and systemic imaging for evaluating the presence of distant metastasis (chest CT, bone scan, and PET‐CT), and performed analyses to determine if they had an effect on mortality. RESULTS: The median follow‐up period was 72.9 months (range: 12.0–133.3) and 7.5% of the patients died. Among all patients, 54.7%, 16.2%, 45.6%, and 8.5% received 3 or more mammograms, chest CTs, bone scans, and PET‐CTs within 3 years after surgery, respectively. Among patients who developed recurrence after 3 or more years, a comparison of overall mortality and breast‐cancer specific mortality according to the frequency of imaging by modality (<3 vs. ≥3) showed that only mammography had significantly reduced mortality (hazard ratio [HR]: 0.72, 95% CI: 0.61–0.84, p < 0.0001; HR: 0.72, 95% CI: 0.61–0.84; p < 0.0001). CONCLUSIONS: This study showed that only frequent mammography reduced mortality and frequent imaging follow‐up with other modalities did not when compared to less frequent imaging. This finding provides supportive evidence that clinicians need to adhere to the current guidelines for surveillance after breast cancer surgery.