The Significant Contribution of Pain in Determining the Health Status of Patients with Multiple Myeloma (MM)

BACKGROUND: Most cancer patients with bone metastases report significant pain and substantial impairment in their ability to function. In particular, patients with MM are susceptible to bone pain because of bone damage. Patient-reported outcomes such as a general health outcome measure and a legacy pain instrument may provide valuable information in determining the impact of this condition. The goal of this study was to provide a descriptive profile of health status for cancer patients using the EQ-5D-3L (EQ-5D), a commonly used tool to measure health utility scores. Another goal is to evaluate the predictive information provided by the Brief Pain Inventory (BPI), a self-report pain assessment tool designed to capture pain severity and interference in patients. These information may be useful in estimating the health status of patients where the EQ-5D was not administered.

METHODS: Data was pooled across three denosumab registrational trials '20050136', '20050103', and '20050244'. Patients completed the EQ-5D and the BPI at baseline. Eligible patients had histologically confirmed advanced cancers, radiographic evidence of at least one bone metastasis (or lytic bone lesion from multiple myeloma), ECOG of 2 or better and adequate organ function. Using data from patients with MM (N=168), descriptive statistics were used to present summary information on health-related quality of life states and utility scores. Linear regressions were used to examine how BPI severity and interference subscale scores relate with EQ-5D utility scores. Ordinal regressions were used to evaluate how well BPI items predict EQ-5D individual items. Bonferroni adjustments were made when evaluating the relationships of BPI items to individual EQ-5D items. These analyses were repeated using data across several groups of cancer patients to determine if similar results can be obtained (breast cancer, N=2,044, prostate cancer, N=1,819 and others, N=1,509).

RESULTS: About 9% of MM patients reported perfect health compared with 11% of all cancer patients. Of the 5 dimensions measured by the EQ-5D, the MM cohort rated pain (80%) the highest with moderate to extreme problems. This was followed by usual activities (68%), mobility (63%), anxiety/depression (49%), and self-care (36%). Similar order was observed across all cancer groups, but with slightly lower percentages for most items: pain (78%), usual activities (58%), mobility (55%), anxiety/depression (57%), and self-care (26%). Although pain interference subscale score explained more of the variability in the EQ-5D utility scores compared with pain severity items in the MM cohort (39% vs 31%) and for all patients (41% vs 34%), model fit was less than ideal (mean squared error=0.23 - 0.25). Hence, BPI items were fitted into individual EQ-5D items. Ordinal regression models fitting BPI items into individual EQ-5D items for the MM cohort showed good predictive power as measured by the concordance index c for mobility (86%), self-care (80%), usual activities (83%), pain (90%) and anxiety/depression (78%). For all patients, similar model fit were obtained for mobility (83%), self-care (78%), usual activities (81%), pain (90%) and anxiety/depression (72%). Further examination of the ordinal regression models across all groups showed that three BPI pain severity items, 'pain at its worst', 'average pain' and 'pain now' in addition to interference with activity and interference with work significantly predicted the EQ-5D pain item. Five interference items, activity, walking ability, work, sleep and enjoyment of life significantly predicted the EQ-5D usual activities item. Finally, 'pain now' and four interference items, relationship with others, enjoyment of life, mood, and activity significantly predicted the EQ-5D anxiety/depression item.

CONCLUSIONS: Patients with MM reported several functional limitations on the EQ-5D. Majority of the patients reported moderate to extreme problems in all EQ-5D dimensions except self-care. Model fit of ordinal regression models relating BPI items with EQ-5D items are reasonable underscoring the benefit of using the BPI for planning patient care and health status evaluation. This consistency was also found across cancer groups that primarily include breast and prostate. The resultant model demonstrates the significant contribution of pain severity and interference in determining health status in this patient population.