Introduction: Skeletal muscle abnormalities, such as low skeletal muscle mass, measured by skeletal muscle index (SMI), and low skeletal muscle quality, measured by skeletal muscle density (SMD), are associated with poor prognosis in cancer. There has been little investigation of their impact on tolerance to radiation therapy and overall outcome in gynaecologic cancers. We examined the effect of low SMI and SMD on treatment tolerance and survival outcomes in patients with endometrial cancer receiving pelvic radiation.
Methods: Stage IB-IVA patients with endometrial cancer treated at one institution between 2007 and 2017 were reviewed. All patients received hysterectomy and pelvic radiation. SMI was based on the cross-sectional area of skeletal muscle at the L3 vertebral body. SMD was expressed as the mean radiation attenuation in Hounsfield units (HUs) at the same vertebral level.
Results: Sixty-four patients met criteria for analysis. Forty-four per cent had low SMI (<41 cm2 /m2 ), 80% had low SMD (mean < 33 HU if BMI> 25 and mean < 41 HU if BMI < 25), and 33% had both. Patients with both features were less likely to complete planned chemotherapy (p = 0.01); this was consistent on multivariate analysis. Radiation treatments were well-tolerated regardless of SMI or SMD. On survival analysis, having both low SMI and low SMD was associated with poorer outcomes compared with having either individual factor (p = 0.04).
Conclusion: Large percentages of patients with endometrial cancer have low skeletal muscle mass and density. Low skeletal muscle measures predict for poor tolerance to chemotherapy in this patient population. Compliance with adjuvant radiation is high, regardless of SMI and SMD.
Keywords: endometrial cancer; radiation therapy; sarcopenia; skeletal muscle density; skeletal muscle index.
© 2019 The Royal Australian and New Zealand College of Radiologists.