Comorbidity and Symptom Measurement in Oncology Scale: Development and Pilot Results in Older Adult Cancer Survivors

Abstract

More than two thirds of all cancers are diagnosed in older adults and the diagnosis often co-occurs with normal and pathological changes of aging, which include chronic diseases and related symptoms. The purpose of this measurement study was to conduct initial psychometric testing of a newly developed self-report tool to assess comorbidity burden and symptoms, the Comorbidity and Symptom Measurement in Oncology Scale (COSMOS), and to examine the feasibility of utilizing it with older cancer survivors. Phase 1 of the two-phase design focused on determining content validity using a panel of six expert clinicians and researchers. Each subscale item was evaluated for interrater agreement of relevancy using the content validity index (CVI). The scale-CVI was .80 for the comorbidity burden subscale (CoB) and .98 for the symptom perception subscale (SxP). The intraclass correlation coefficient (ICC) for each subscale was .97 (CoB) and .84 (SxP), respectively. Subscale items with a CVI of ≥.83 and ICC ≥.60 were retained. Phase 2 included pilot testing the revised CoB and SxP subscales and symptom attribution descriptor scale in a convenience sample of 62 older adult cancer survivors (32 on active treatment and 30 off treatment for 1 or more years). Although CoB scores were equivalent between groups, off-treatment group participants had significantly more thyroid and other miscellaneous conditions. SxP scores were also similar between groups; however, the active-treatment group reported significantly more nausea (Chi Square = 4.03, p = .045), taste changes (Chi Square = 7.65, p = .006), and body image disturbances (Chi Square = 6.44, p = .011) than the off-treatment group. Three clinically relevant symptom-attribution descriptors discriminated between treatment status groups, indicating a shift from aging and cancer-related attributions in those on active treatment to aging and other causes in the off-treatment population. Test-retest reliability indicated strong stability for comorbidity burden (ICC = .917) and symptom attribution (ICC = .696). COSMOS was judged to be a feasible measure based on subsample interviews, completion time, and response patterns. The results of this study support initial validity, reliability, and usability of COSMOS.