Impact of low muscle mass and myosteatosis on treatment toxicity and survival outcomes in non-resectable pancreatic cancer patients treated with chemoradiotherapy.

Background: Low skeletal muscle mass and impaired muscle quality (myosteatosis) have been associated with poor outcomes in cancer patients. This study aimed to evaluate the impact of pre-therapeutic low muscle mass and myosteatosis on chemoradiotherapy (CRT)-induced toxicity and survival outcomes in patients with non-resectable pancreatic cancer (PC).

Methods: In this retrospective study, pre-therapeutic CT scans were used to measure muscle mass/density. Low muscle mass was defined as a skeletal muscle index <38.5 cm²/m² (women) and <52.4 cm²/m² (men), and myosteatosis as a mean psoas density <41 HU if BMI < 25 kg/m² or <33 HU if BMI > 25 kg/m². Adverse effects were collected per week (W) of treatment. Dose-limiting toxicity (DLT) was defined as any toxicity leading to dose reduction, treatment delays or permanent discontinuation.

Results: Among the 85 included patients, 75 (88.2%) and 18 (22.2%) had pre-therapeutic low muscle mass and myosteatosis, respectively. Only 12 patients (14.1%) experienced DLT. Patients with low muscle mass developed significantly more toxicities at W2 (p = 0.013) and W5 (p = 0.026), notably more nausea (p = 0.037) and anemia (p = 0.004). Low muscle mass was associated with poorer overall survival (HR 4.41 [1.50-12.94], p = 0.007) in multivariate Cox analysis, while myosteatosis was not associated with CRT toxicities, DLT and overall survival (p = 0.408).

Conclusion: Patients with low muscle mass experienced more toxicities and poorer outcomes during CRT for non-resectable PC.