Loss of psoas muscle during neoadjuvant treatment for rectal cancer is associated with poor oncological and surgical outcomes.

Abstract

Sarcopenia has been associated with poor outcomes in rectal cancer patients. This study aims to assess the degree of muscle loss during neoadjuvant therapy in patients with rectal cancer, and its relationship with tumour response, post-operative complications and long-term disease recurrence. The change in the psoas muscle area was determined by measuring the psoas muscle area at L4 on initial staging PET CT scans and comparing this with the restaging scan 8-10 weeks after radiation treatment had been completed. The average change in the psoas muscle area was compared between patients who had residual disease versus complete clinical/pathological response, anastomotic leak vs. no leak, and distant recurrence vs. no recurrence on follow-up imaging. Ninety-two patients were included in the study. The mean loss of psoas muscle area was 5%. Patients who had a complete response to chemoradiotherapy showed a statistically significant difference in muscle mass loss (2.8%) compared to those with residual tumour present after therapy (6.2%), P = 0.02 on multivariable analysis. There was a statistically significant greater loss of muscle in patients who had an anastomotic leak versus those that did not (10.2% vs. 4.1%) and in those who developed metastatic disease versus those that did not (10.7% vs. 4.1%) (P < 0.05). Our study adds to the growing body of evidence that sarcopenia is a predictor of poor surgical and oncological outcomes in rectal cancer patients. We postulate that the loss of muscle is an indication of disease burden and worse tumour biology.