For breast cancer patients, determining the risk of developing distant metastasis continues to present as a challenge, as the precise mechanism leading to distant metastasis is not yet fully understood. There has been a recent effort to develop imaging markers that can help predict patient prognosis, and therefore assist in providing therapy that is tailored to a patient’s individual risk. It has been proposed that the apparent diffusion coefficient (ADC) in magnetic resonance imaging (MRI) with diffusion-weighted imaging (DWI) may provide useful information. In this cohort study, investigators used MRI images from 258 women with breast cancer who were preoperatively imaged in order to study any association between preoperative ADC values and later risk of metastasis. Investigators found that 9.7% of patients developed distant metastasis to bones, lung, liver, brain, and distant lymph nodes. In terms of ADC, the minimum preoperative ADC was significantly lower in patients with distant metastasis than in patients without distant metastasis (mean of 0.654 x 10-3 mm2/sec versus 0.753 x 10-3 mm2/sec, p=0.01). The ADC difference value was also significantly higher in patients with distant metastasis (p<0.001). The mean and maximum ADCs did not significantly differ. A univariable Cox regression analysis showed that a lower minimum ADC (<0.706 x 10-3 mm2/sec) was associated with poorer distant metastasis-free survival outcomes (HR 3.2, 95% CI 1.4 to 7.8, p=0.008). A higher ADC difference was also associated with poorer survival outcome (HR 4.7, 95% CI 2.1 to 10.5, p<0.001). The results from this study suggest that preoperative imaging and use of minimum ADC and higher ADC differences may play a role in identifying patients at higher risk for distant metastasis. This study is limited in that it was conducted at a single academic center and could not analyze subtypes of breast cancer due to limited sample size.
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