PROGNOSTIC SIGNIFICANCE OF THE SKELETAL MUSCLE INDEX IN PATIENTS WITH RECTAL CANCER TREATED WITH NEOADJUVANT RADIATION-CHEMOTHERAPY

Abstract

Objective 

Sarcopenia (low skeletal muscle mass) is an emerging syndrome associated with poor outcome in cancer patients treatment. We investigated the relationship between skeletal muscle index (SMI) and neoadjuvant rectal score (NAR score) in a group of patients with locally advanced rectal adenocarcinoma treated with neoadjuvant concurrent chemoradiotherapy (nCCRT) with capecitabine and subsequent surgery. 

Methods  

In this multicenter study, we retrospectively analyzed patients with locally advanced lower and middle rectal adenocarcinoma (n = 91) in Stage II and III disease between 2016 and 2022. All patients were treated with nCCRT with Capecitabine and after 6-8 weeks, surgical treatment and subsequent adjuvant chemotherapy. SMI was calculated at the third lumbar vertebra L3 position on computed tomography before start with nCCRT. NAR score was developed as a composite short-term endpoint for clinical trials involving neoadjuvant therapy for rectal cancer and can predict a response of the treatment. NAR score was defined as [5pN - 3 (cT - pT) + 12]2/9.61. 

Results 

The study included 61 men (67%) and 30 women (33%), with a total mean age of 63.4 (±8.4) years. The Kruskal-Wallis one-way analysis of variance showed that there were significant differences in NAR score only between high and intermediate (18.8 ± 4.4 vs 25.7 ± 4.8; p = 0.044) and high and low SMI (18.8 ± 4.4 vs 28.5 ± 5.2 ; p = 0.007). Moreover using ordinal logistic regression analysis after adjustment for age and sex, having low or intermediate SMI were associated with an increased likelihood of having higher NAR score (estimate = 1.59, 95% CI = 0.48–2.71, p = 0.005;  estimate  =  1.18, 95% CI = 0.12–2.24, p = 0.03). 

Conclusions 
Low muscle mass is a potential new predictive marker of non-response to nCCRT.