Six-minute walk test (6MWT) as a measure of postoperative recovery after colorectal resection for cancer: further examination of its measurement properties.

Nicolo Pecorelli, MD1, Julio F Fiore Jr., MSc, PhD1, Benjamin Mappin-Kasirer1, Petru Niculiseanu, MD1, Chelsia Gillis, RD, MSc2, Rashami Aswathi, BSc2, Gerald M Fried, MD1, Franco Carli, MD, MPhil2, Liane S Feldman, MD1. 1Steinberg-Bernstein Centre for Minimally Invasive Surgery, McGill University Health Centre, Montreal, 2Department of Anesthesia, McGill University Health Centre, Montreal

Introduction: Patients, caregivers, employers and researchers seek an easy, reproducible, reliable, and valid measure of postoperative physical recovery, or the time it takes to return to “normal” after surgery. Walking is an important requirement for daily activities. The six-minute walk test(6MWT) is a low-cost measure of functional walking capacity measuring the distance walked on a flat surface in 6 minutes. A previous small study supported the validity and responsiveness of the 6MWT, but was likely underpowered to test some of the hypotheses examined. The aim of the present study is to contribute further evidence for the validity of the 6MWT as a measure of postoperative recovery after colorectal cancer surgery.

Methods and procedures: Patients from two previous clinical trials investigating interventions to enhance recovery after colorectal resection for cancer were included in the study. These patients performed the 6MWT and responded to a physical activity questionnaire(CHAMPS) within 4 weeks before surgery, and at 4 weeks postoperatively. Validity was assessed by testing the hypotheses that 6 minute walk distance(6MWD) at 4 weeks after surgery: (1)is greater in younger patients (<75 years old) vs. older patients (>75 years old); (2)is greater in patients with higher preoperative physical status (ASA < 2) vs. lower physical status (ASA ≥ 3); (3)is greater after laparoscopic vs. open surgery; (4)is greater in patients who did not have postoperative complications vs. those with any complication; (5)correlates cross-sectionally with self-reported physical activity. Statistical analysis was performed using linear regression. Missing data were addressed using multiple imputation.

Results: A total of 123 patients were included (63% male; mean age 66.7 (SD 11.2) years, 30% ASA≥ 3, 85% laparoscopic, 44% rectal cancer). All five hypotheses tested for validity were supported by the data shown in Table 1.

Table 1. Hypotheses tested to contribute evidence for validity of 6MWT as an outcome measure of postoperative recovery after colorectal resection.
ComparisonsCoefficient95% C.I.p-value
Younger (<75 years) vs. older patients (≥75 years)*52.61.45 – 103.840.044
Higher physical status (ASA < 2) vs. lower physical status (ASA ≥ 3)*47.37.57 – 87.030.020

Laparoscopic vs. open surgery*

76.425.91 – 126.950.004
No postoperative complications vs. any complication*38.91.42 – 76.370.042
Physical activity (kcal/kg/wk) at 4 weeks after surgery**0.7640.20 – 1.320.009

* mean differences (meters) between groups 4 weeks after surgery; regression analysis adjusted for preoperative 6MWD.

** effect of one meter change in 6MWD at 4 weeks

Conclusions: This study contributes further evidence for the validity of the 6MWT as a measure of recovery after colorectal surgery. Older age, poorer physical status, complications and open surgery are associated with lower walking capacity 4 weeks after surgery. Results from this study support the use of 6MWT as a measure of postoperative physical performance.

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