Six hundred and ninety-one patients enrolled in the study, of which 671 provided evaluable data with an average age of 53 (range 25–90). The majority of these patients were female (94%), white (88%), and had received some college education (59%). Ninety percent had breast cancer, 9% had lymphoma, and the remaining 1% was a mix of myeloma, endometrial, sarcoma, and bladder cancer patients.
Overview of Nausea and Quality of Life
Five hundred and sixty-two (84%) patients reported at least some nausea in the four days following treatment and 165 (25%) reported severe nausea (rating of 6 or 7 on the 7-point scale). Overall, mean nausea on the four days following chemotherapy was 2.2 (SD=1.2) and the mean peak nausea was 4.0 (SD=2.1). Before their first chemotherapy treatment patients had a mean quality of life of 86.3 (SD=13.0), which decreased to 76.3 (SD=15.8) after the treatment.
Expectancy and Nausea
For average nausea, the overall model with age, gender, diagnosis, susceptibility to motion sickness, baseline quality of life, and expectancy included was significant and accounted for 16% of the variance (R2=0.16, F8,659=15.3, p<0.001). Expectancy had a significant impact on average nausea. Specifically, an increase of one standard deviation on the expectancy measure was associated with a 0.27 increase in average nausea after controlling for all other variables in the model (R2 change=0.02, b=−0.27, t659=4.18, p<0.001). Age and baseline quality of life were the only other significant predictors in the model. An increase in age of 10yrs was corresponded to a decrease of 0.3 points on average nausea (b=−0.03, t659=7.12, p<0.001), and a 10 point increase in baseline quality of life corresponded to a 0.1 decrease in average nausea (b=−0.008, t659=2.26, p=0.02).
For peak nausea, the overall model was also significant and accounted for 15% of the variance (R2=0.15, F8,659=14.3, p<0.001). Expectancy was again significant after controlling for all other variables. Here, an increase of 1 standard deviation on the expectancy measure corresponded to a 0.43 increase in peak nausea (b=−0.43, t659=3.86, p<0.001). As with average nausea, age and baseline quality of life were also significant predictors. A 10yr increase in age was associated with a 0.51 decrease in peak nausea (b=−0.05, t659=6.97, p<0.001). A 10 point increase in baseline quality of life corresponded to a 0.1 decrease in peak nausea (b=−0.01, t659=1.98, p<0.048). In addition, lymphoma patients reported less 0.84 points less peak nausea than breast cancer patients (b=−0.84, t659=2.28, p<0.02). Overall, expectancy accounted for 2% of the variance in both average nausea and peak nausea after controlling for all other variables.
Level of Expectancy and Nausea
shows average nausea across the different levels of expectancy. The ANCOVA, with age, gender, susceptibility to motion sickness, diagnosis, baseline quality of life, and study group as covariates, revealed that average nausea differed significantly as a function of level of expectancy (F3,658=8.9, p<0.001). Using pairwise comparisons, highly expectant patients reported significantly higher levels of average nausea than all other levels of expectancy. Specifically, highly expectant patients reported average nausea as 0.62 points higher than not expectant patients (t658=4.49, p<0.001), 0.56 points higher than slightly expectant patients (t658=4.12, p<0.001), and 0.47 points higher than somewhat expectant patients (t658=3.61, p=0.002). There were no significant differences in average nausea between somewhat expectant, slightly expectant, and not expectant patients (highest t659=1.18, p=1).
Figure 1 Covariate adjusted mean (+SEM) average (A) and peak (B) nausea by level of expectancy. Highly expectant individuals reported both more average nausea and higher peak nausea than all other expectancy levels, *p<0.05, **p<0.01, ***p<0.001. (more ...)
shows peak nausea for each level of expectancy. As with average nausea, the ANCOVA revealed significant differences in peak nausea as a function of level of expectancy (F3,658=6.5, p<0.001). Highly expectant patients reported peak nausea 0.94 points higher than not expectant patients (t658=3.88, p=0.001), 0.91 points higher than slightly expectant patients (t658=3.76, p=0.001), and 0.63 higher than somewhat expectant patients (t658=2.81, p=0.03). Again there were no differences between somewhat expectant, slightly expectant, and not expectant patients in terms of peak nausea (highest t658=1.41, p=0.96)
Expectancy and Pre-treatment Quality of Life
The partial correlation between expectancy and pre-treatment quality of life was significant (r=−0.29, t660=7.79, p<0.001). This means that stronger expectancy for post-chemotherapy nausea was associated with lower quality of life before treatment.
Impact of Nausea on Post-treatment Quality of Life
The overall model, with age, gender, baseline quality of life, average nausea, and peak nausea included was significant and accounted for 55% of the variability in post-chemotherapy quality of life (R2=0.55, F8,657=100, p<0.001). The only two significant predictors in the final model () were baseline quality of life (b=0.58, t657=17.6, p<0.001) and average nausea (b=−5.1, t657=8.80, p<0.001). This means that even after controlling for age, gender, diagnosis, baseline quality of life, study group, and peak nausea, a 1 point increase in average nausea corresponded to a 5 point decrease in post-chemotherapy quality of life. Peak nausea was marginally non-significant (b=−0.65, t657=1.92, p=0.056). Together, average and peak nausea accounted for 20% of the variability in post chemotherapy quality of life (R2 change=0.20, F2,657=143, p<0.001).
Final step in the hierarchical regression of predictors of quality of life after chemotherapy treatment.