Which field walking test should be used to assess functional exercise capacity in lung cancer? an observational study

There is emerging evidence regarding the efficacy of exercise training to improve exercise capacity for individuals with non-small cell lung cancer (NSCLC). Cardiopulmonary exercise testing (CPET) is the gold standard measure of exercise capacity; however this laboratory test has limitations for use in research and clinical practice. Alternative field walking tests are the six-minute walk test (6MWT), incremental-shuttle walk test (ISWT) and endurance-shuttle walk test (ESWT); however there is limited information about their clinimetric properties in NSCLC. Aims: In NSCLC to determine the 1) criterion validity of the 6MWT, ISWT and ESWT against CPET; 2) construct validity of the 6MWT, ISWT and ESWT against measures of function, strength, respiratory function and health-related quality of life (HRQoL); and 3) clinical applicability of the tests.

Twenty participants (40 % male, mean ± SD age 66.1 ± 6.5 years) with stage I-IIIb NSCLC completed the 6MWT, ISWT, ESWT and CPET within six months of treatment. Testing order was randomised. Additional measures included Eastern Cooperative Oncology Group Performance-Status (ECOG-PS, function), respiratory function, hand-grip dynamometry and HRQoL. Correlations and regression analyses were used to assess relationships.

The ISWT demonstrated criterion validity with a moderate relationship between ISWT distance and CPET peak oxygen consumption (r = 0.61, p = 0.007). Relationships between CPET and six minute walk distance (6MWD) (r = 0.24, p = 0.329) or ESWT time (r = 0.02, p = 0.942) were poor. Moderate construct validity existed for the 6MWD and respiratory function (forced vital capacity % predicted r = 0.53, p = 0.019; forced expiratory volume in the first second % predicted r = 0.55, p = 0.015). There were no relationships between the walking tests and measures of function, strength or HRQoL. The ESWT had a ceiling effect with 18 % reaching maximum time. No floor effects were seen in the tests. The mean ± SD time required to perform the individual 6MWT, ISWT and ESWT was 12.8 ± 2.5, 14.7 ± 3.7 and 16.3 ± 5.0 min respectively; in comparison to CPET which was 51.2 ± 12.7 min. Only one assessor was required to perform all field walking tests and no adverse events occurred.

The ISWT is a promising measure of functional exercise capacity in lung cancer. Findings need to be confirmed in a larger sample prior to translation into practice.