Published online Nov 10, 2018. doi: 10.5306/wjco.v9.i7.140
Peer-review started: April 30, 2018
First decision: June 6, 2018
Revised: August 6, 2018
Accepted: October 8, 2018
Article in press: October 8, 2018
Published online: November 10, 2018
Performance status (PS) is an estimate of a subject’s ability to perform activities of daily living. Several tools are available to estimate the PS. Among them, the Karnofsky performance status (KPS) scale and the Eastern Cooperative Oncology Group (ECOG) scale are the most commonly used PS scales worldwide for patients with cancer. The KPS scale is an 11-point numerical scale, with scores ranging from 100 (normal functional status) to 0 (death), in decremental steps of 10. The ECOG PS scale is a 6-point numerical scale, with scores ranging from 0 (normal functional status) to 5 (death), in incremental steps of 1. Since the number of scoring points in each scale is different, these scales are not readily interconvertible.
PS is an important clinical factor which affects prognosis and influences treatment decisions in subjects with lung cancer. Hence, researchers who attempt to compare clinical characteristics or outcomes across different patient populations should ensure that their PS levels are matched. Failure to do so may result in erroneous conclusions. Most clinical studies employ only one of these two scales (either KPS or ECOG PS) in their study population for assessment of PS. When the PS scale used in the studies are different (either KPS or ECOG PS) this may lead to difficulty. Several investigators have tried to overcome this hindrance by suggesting KPS categories for interconversion to the ECOG PS scale. However, the performance of these suggested KPS categories has been variable.
We attempted to establish the KPS categories which would facilitate the interconversion of the KPS scale to the ECOG PS scale.
We retrospectively analyzed the data of 1501 patients from a lung cancer clinic. In these patients, at every visit, paired assessments of PS had been made using both the KPS and ECOG PS scales by physicians. We also studied the performance of other KPS categories suggested in the literature, on our patient cohort. We used statistical methods called hit rate and weighted kappa to test the agreement between the KPS categories and the actual observations.
We found that the KPS categories 10-40, 50-60, 70, 80-90, and 100 were equivalent to ECOG PS categories of 4, 3, 2, 1, and 0 respectively. We also found that the agreement between the KPS categories suggested in the past literature (for interconversion to ECOG PS) and the paired KPS-ECOG PS assessments made in our cohort was variable.
The current study is the largest set of paired KPS-ECOG assessments published in the literature in patients with lung cancer to date. The suggested KPS categories will facilitate interconversion of the KPS to the ECOG PS scale and will enhance communication between researchers utilizing either of the two scales.
The KPS categories suggested in our study may be prospectively evaluated to test their validity. The applicability of the suggested categories may be evaluated in other populations to study the effect of cultural and regional variations.