Physical health and cancer-free survival in women diagnosed with breast cancer.

Abstract

Abstract Abstract #1114 Background: A protective effect of physical activity (PA) after breast cancer diagnosis is not a consistent finding across studies. It is possible that a beneficial effect from higher PA levels may be limited to a sub-group defined by level of physical health (PH). We investigated the role of PA and PH in predicting breast cancer free survival.
 Methods: The Women's Healthy Eating and Living (WHEL) Study enrolled 3088 women within 4 years of early stage breast cancer diagnosis from 1995 to 2000. At study entry, participants completed the RAND-36 Health Survey that includes a physical health summary score comprised of physical functioning, general health, pain, and role limitations due to PH subscales. PA was assessed with a questionnaire developed for the Women's Health Initiative and validated for the WHEL Study. Additional breast cancer events (recurrence or new breast primary; n = 518) were queried semi-annually through June 2006 and confirmed by oncologist review of medical records. Multivariate Cox modeling was used to associate PA and PH with additional breast cancer events, adjusting for demographic, lifestyle, tumor, and treatment-related covariates.
 Results: In the unadjusted analysis, quartiles of PA were not related to additional breast cancer events, whereas the PH summary score was [Hazard ratios (HR) for quintiles (Q), Q1 (reference): Q2= 0.90, Q3 =0.69, Q4=0.55, and Q5=0.74; p-values = 0.45, 0.01, <0.0001, and 0.03 respectively]. For further analysis, we grouped the bottom two quintiles (“poor” PH) and the upper three quintiles (“adequate” PH). In the adjusted Cox model, poor PH was associated with a 42% higher risk of additional breast cancer events (HR: 1.42, 95% CI: 1.15, 1.74).
 We compared participants in poor versus adequate PH group. Those in the poor PH group were much more likely to report role limitations (91% vs. 17%) and bodily pain (44% vs. 4%). They were much more likely to be minimally physically active (<90 MET-minutes/week) (23% vs. 12%, p>0.0001) and obese (37% vs. 19%; p <0.0001). We included an interaction term into the Cox model using the binary PH measure and a binary PA measure (540 ≥ vs. < 540 MET-minutes/week, equivalent to 30 minutes moderate walking 6 days/week). Compared to those with adequate PH and higher PA, only those with poor PH and lower PA were at increased risk (HR 1.46, 95% CI: 1.15, 1.74).
 Among those in this higher risk subgroup (poor PH, lower PA), the majority indicated that they would not be limited a lot in walking a mile (79%) or climbing several flights of stairs (73%) and a substantial proportion indicated that they could undertake vigorous activity (37%).
 Discussion: Breast cancer survivors categorized as in poor PH had a 42% worse prognosis than those in adequate PH. This was particularly the case for those in poor PH who did less PA. This suggests that a motivational intervention to increase physical activity in this subgroup may improve their prognosis following breast cancer. Citation Information: Cancer Res 2009;69(2 Suppl):Abstract nr 1114.