Knee Extensor Weakness Potently Predicts Postoperative Outcomes in Older Gastrointestinal Cancer Patients.

Objectives: Muscle weakness, assessed by grip strength, has been shown to predict postoperative mortality in older patients with cancer. Because lower extremity muscle strength well reflects physical performance, we examined whether lower knee extension muscle strength predicts postoperative mortality better than grip strength in older patients with gastrointestinal cancer.

Design: Prospective, observational study in a single institution.

Setting And Participants: A total of 813 patients (79.0 ± 4.2 years, 66.5% male) aged 65 years or older with gastrointestinal cancer who underwent preoperative evaluation of grip strength and isometric knee extension muscle strength between April 2012 and April 2019 were included.

Methods: The study participants were prospectively followed up for postoperative mortality. Muscle weakness was defined as the lowest quartile of grip strength or knee extension strength (GS-muscle weakness and KS-muscle weakness, respectively).

Results: Among the study participants, 176 patients died during a median follow-up of 716 days. In the Kaplan-Meier analysis, we found that patients with both GS-muscle weakness and KS-muscle weakness had a lower survival rate than those without muscle weakness. As expected, higher clinical stages and abdominal and thoracic surgeries compared with endoscopic surgery were associated with increased all-cause mortality. In addition, we found that KS-muscle weakness, but not GS-muscle weakness, was an independent prognostic factor after adjusting for sex, body mass index, cancer stage, surgical technique, and surgical site in the Cox proportional hazard model.

Conclusions And Implications: In older patients with gastrointestinal cancer, muscle weakness based on knee extension muscle strength can be a better predictor of postoperative prognosis than muscle weakness based on grip strength.