Muscle mass estimation on breast magnetic resonance imaging in breast cancer patients: comparison between psoas muscle area on computer tomography and pectoralis muscle area on MRI.

OBJECTIVES: To evaluate the correlation between psoas muscle area (TPA) on CT images and pectoralis muscle area (PMA) on MRI in breast cancer patients.
METHODS: This retrospective study was institutional review board approved and women involved gave written informed consent. Twenty six patients with both body CT and breast MRI available were evaluated. Two radiologists calculated TPA on 1.25-mm and 5-mm body CT images. Two radiologists measured PMA on axial T1-weighted images. Statistical analysis included inter- and intra-reader agreement and correlation between TPA on CT and PMA on MRI.
RESULTS: The Pearson r correlation coefficient was 0.70 (95% CI 0.41-0.81) and the coefficient of determination was 0.49. The inter-reader agreement was k = 0.85 and k = 0.79 for axial 1.25-mm and 5-mm CT images, respectively. The intra-reader agreement of reader 1 was k = 0.98 and k = 0.94 for 1.25-mm and 5-mm CT images, respectively. The intra-reader agreement of reader 2 was k = 0.95 and k = 0.94 for 1.25-mm and 5-mm CT images, respectively. On axial T1-weighted images, the inter-reader agreement for radiologists evaluating the PMA was k = 0.61. Intra-observer agreement of reader 1 and reader 2 for PMA estimation was good (0.62 and 0.64), respectively.
CONCLUSION: The correlation between TPA on CT images and PMA on MRI was very good. Pectoralis muscle area on breast MRI could be useful to estimate muscle mass in women with breast cancer. KEY POINTS: • Pectoralis muscle area can be estimated on breast MRI • Total psoas area on CT and pectoralis muscle area on MRI are strongly correlated • Pectoralis muscle area on breast MRI could estimate the skeletal muscle mass.