Abstract P2-08-30: The role of skeletal muscle volume on prognosis of breast cancer survivors using with cross-sectional image
Authors: Song EJ , Park SJ , Lee MH , Kwon Y , Ko KL , Lee KS , Ro J , Jung SY , Lee SY , Kang HS , Lee ES 
Published: May 2016

Background: Obesity is one of the well-known cause and prognostic factor of breast cancer. Body mass index (BMI) is often used to estimate the magnitude of obesity. Currently, muscle weight itself, instead of higher BMI, is more closely related to poor outcomes in chronic metabolic disease. However, this question was not thoroughly questioned in breast cancer survivors. We aim to find out whether the prognosis of breast cancer survivors is affected by muscle mass and fat volume. We also present that the higher muscle mass and muscle fat ratio do have a good influence on the prognosis.

Methods and Materials: Between January, 2001, and December, 2009, all consecutive patients diagnosed the breast cancer in National cancer center, Republic of Korea were 3909. Of all populations, the patients who had available chest Computed Tomography (CT) images within two years after the time of diagnosis were extracted. CT images were analyzed for total skeletal muscle and adipose tissue in cross-sectional area of 10mm thickness at level 3 of the lumbar vertebrae.

Results: Of all consecutive 3909 patients, final eligible cases were 1493. The median age was 46.0 (range 25∼77). Median follow up period was 96.8 months and the 5 year survival rate was 96.5%. Recurrence free survival rate was 92.1%, and local recurrence free survival was 98.6% in 5 years. Median skeletal muscle volume of all patients was 93.3cc (range 39.6∼236.9). Median fat volume of the same sections was 419.7cc (range 19.5∼1392.3) and the median muscle-fat ratio was 0.22 (0.08∼3.18). There is no known standard value of muscle mass in Korean women, the median volume was used as an indicator for comparison of two groups in terms of overall survival and recurrence free survival. The group with muscle volume greater than median value appeared better outcomes in overall survival and recurrence free survival than those of the other group (p=0.007, p=0.019). There were several factors related to overall survival and recurrence free survival such as age, operation types, clinical stage, pathologic stage, and tumor size in univariate cox regression analysis. In multivariate analysis by adjusting those factors, the muscle volume showed a remarkable correlation with survival, especially in recurrence free survival (Hazard ratio 0.61, p=0.029). As the indicator using with median muscle-fat ratio, the analysis revealed that overall survival had no significant difference (p=0.177) between two groups. However, the group with higher muscle-fat ratio showed better recurrence free survival and local recurrence free survival (p-value &lt;0.0001, 0.038 respectively).

Conclusions: Our study showed that the actual amount of skeletal muscle rather than fat volume has higher effect on the prognosis of breast cancer survivors. In our knowledge, this is the largest study to analyze the prognosis of breast cancer with skeletal muscle volume. In view of the different magnitude of obesity among multiple ethnics, the actual muscle mass could be the most important parameter to assess the amount of exercise and patient's health status.

Citation Format: Song EJ, Park SJ, Lee MH, Kwon Y, Ko KL, Lee KS, Ro J, Jung SY, Lee SY, Kang HS, Lee ES. The role of skeletal muscle volume on prognosis of breast cancer survivors using with cross-sectional image. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P2-08-30.