The final sample for this analysis was composed of women with physical health scores at baseline and year 1 (n=2343). Of the total WHEL sample (n=3088), 113 participants either had a cancer recurrence or died between baseline and year 1 and therefore are not included here. In addition, 632 participants had missing physical health scores at baseline and/or year 1. We conducted a sensitivity analysis including 581 participants who had either their baseline or 1 year scores missing (51 had missing physical health score at both time points), under the conservative assumption that their physical health scores did not change between these two time points. This analysis did not change the results or conclusions presented below.
In this sample of 2343 women, the mean (SD) baseline age of participants was 53.8 (8.8) years and BMI was 27.1 (5.9) kg/m2; 55.2% were college graduates and 86.6% were non-Hispanic white. The original tumors were Stage I (40.5%) or Stage IIA (32.8%) and poorly (33.7%) or moderately (41.4%) differentiated. Most women received some form of adjuvant therapy as part of their post-surgical treatment (68.4% tamoxifen; 68.3% chemotherapy, and 61.5% radiation therapy). Finally, 75.4% of tumors were ER-positive. At the end of the trial (June 01, 2006), there were 294 (12.5%) additional invasive breast cancer events and 162 (6.9%) deaths from all causes. Among the deaths, 125 (77.1%) were caused by breast cancer.
Overall, the physical health mean score statistically significantly increased from baseline (mean score 76.3) to Year 1 (mean score 77.2). Among the subscales of the physical health summary score, the largest increases were seen for role limitation and general health ().
Mean physical health summary score and four sub-scales at baseline and at year 1 of follow-up in a cohort of breast cancer survivors from the Women’s Healthy Eating and Living (WHEL) Study (N=2343).
As shown in , improvements in physical health were associated with the following baseline characteristics: younger age, lower BMI, being employed, not receiving tamoxifen, lower physical activity, lower baseline physical and mental health, and fewer years from diagnosis to study enrollment.
Baseline characteristics associated with change in physical health (baseline to year 1) in a cohort of breast cancer survivors from the Women’s Healthy Eating and Living Study (N=2343).
Investigation revealed that there was an interaction of change in physical health with years since the original cancer diagnosis and study enrollment. Specifically, in a model predicting mortality, the effect of change in physical health (adjusted for baseline physical health) was statistically significantly different among women diagnosed ≤2 years before study enrollment and women diagnosed >2 years before enrollment (p-value 0.01 for interaction). Therefore, the model of change in physical health and cancer outcomes was stratified by years between cancer diagnosis and study enrollment.
As shown in , there was no association of change in physical health with additional breast cancer events or mortality among women diagnosed relatively soon before study enrollment (i.e., ≤ 2 years). However, among women who entered the WHEL study >2 years post diagnosis, there was an approximate 60% reduction in risk of mortality for women who reported an increase compared to a decrease in physical health.
Adjusted associationsa of change in physical health (baseline to year 1) with breast cancer outcomes in a cohort of breast cancer survivors from the Women’s Healthy Eating and Living Study (N=2343).