In this large cohort of breast cancer survivors, moderate alcohol intake compared to non/minimal drinking was associated with reduced all-cause mortality. However, alcohol consumption among WHEL Study breast cancer survivors was low, with only 21% consuming more than 300g/month (about one alcoholic drink a day). This level is comparable to that reported for other US samples (2
) and less than half that reported in the Italian sample (11
). Some of this difference may be associated with the more heterogeneous population in the United States which has significant numbers of African-Americans and Asian-Americans. Both of these racial/ethnic groups have traditionally reported lower levels of alcohol consumption (31
) than non-Hispanic white women. Another reason for the difference could be that the WHEL sample represents women with more serious breast disease (83% of deaths were from breast cancer) and that U.S. oncologists may be more assertive in recommending reduced alcohol intake for these patients. Previously, we have noted that 41% of the WHEL sample reported reducing their alcohol consumption following breast cancer diagnosis (33
). One year alcohol intake, which changed little after baseline in the WHEL Study, suggests that these post-diagnosis decreases in alcohol intake were maintained after study enrollment.
Our finding that light to moderate alcohol intake did not increase mortality after breast cancer was in line with that reported in two recent studies in breast cancer patients (9
) as well as a study in the general population (32
). The protective hazard ratio in the WHEL Study for daily drinkers was comparable to that reported in the United Kingdom study (10
). However, our data did not show a protective association between alcohol consumption and cancer recurrence. Of note, 92% of the WHEL population consumed fewer than 2 small drinks daily, and most “moderate drinkers” appeared to drink approximately 1 drink per day. Alcohol intake in a primarily white, educated population of breast cancer survivors who elected to participate in a dietary intervention trial may be associated with other healthy behaviors, as contrasted with alcohol intake in studies focusing on primary prevention, in which alcohol intake may be associated with less desirable health behaviors.
One of the mechanisms by which alcohol intake may influence risk for primary breast cancer is via effects on estrogen metabolism (34
). Alcohol intake has been observed to be directly associated with circulating sex hormones in several studies (36
). However, the hormonal milieu is considerably altered following the diagnosis and treatment of breast cancer, and the majority of women are treated with chemotherapy and/or anti-estrogenic agents which further modify reproductive hormonal status. Li et al demonstrated a positive association between retrospectively self-reported alcohol consumption and second primary contralateral breast cancer (2
), results which are difficult to compare given differences in sample characteristics including tumor ER status, frequency of chemotherapy use, different rates of new primaries, and greater frequency of metastatic disease in WHEL
Bioactive constituents in beer and wine, such as flavonoids and polyphenols, have been hypothesized to reduce mortality risk after cancer (38
). This effect was not observed in the WHEL sample, where higher consumption of spirits was predictive of lower mortality. Indeed, the effect observed in this study may not be related to alcohol consumption per se but rather to correlates of alcohol intake. Further examination demonstrated that the lower risk of death among alcohol consumers was confined to women who were not obese at enrollment in the study. In this subsample of the WHEL population, women with higher education and physical activity levels were more likely to be in the upper two categories of alcohol consumption. Both socioeconomic status/education (32
) and physical activity (39
) have been associated with improved survival. Additionally, African American women, who have higher mortality following breast cancer diagnosis (41
), were three times more likely to be non/minimal drinkers and this association could also partially explain the observed effect.
The association of alcohol consumption with decreased all-cause mortality may be attributed to other potential confounders. In the WHEL Study, women with more serious disease (node positive, higher grade, ER− tumors, or a history of chemotherapy) were more likely to be minimal drinkers. Further, women who were more highly educated (and presumably had higher socioeconomic status) were less likely to be minimal drinkers. The association between socioeconomic status and improved health outcomes has been well established (32
A number of strengths as well as limitations of this analysis should be considered. Many of the measures in the WHEL Study were validated, although alcohol consumption was self-reported. The alcohol data in this study were collected shortly after the publication of observational studies that suggested that alcohol increased breast cancer risk. Thus, social desirability may have led some participants to underreport their alcohol intake. However, strengths of our study are our use of two separate instruments to measure alcohol intake and our application of a conservative algorithm for assigning participants to a category of consumption. Further, the WHEL Study assessed alcohol intake five times over the duration of the study and intake demonstrated considerable stability in measurement (data not shown). A major strength in the WHEL Study is the oncologist verification of initial diagnosis and reported outcomes. Nevertheless, the WHEL Study results cannot be generalized to all breast cancer survivors. The WHEL population was comprised of women who elected to participate in a dietary intervention trial, excluded breast cancer survivors with low level disease (e.g. less than 1 cm tumors or carcinoma in situ) and it was limited to early stage disease (through Stage IIIA using the AJCC classification IV edition). Further, the WHEL Study allowed enrollment up to 4 years post-diagnosis and therefore may under-represent women diagnosed with ER− tumors (43
In summary, light alcohol consumption reported by breast cancer survivors in the United States was not associated with adverse outcomes (either additional breast cancer events or death). A moderate level of alcohol consumption, approximately one alcoholic drink per day, was associated with reduced all-cause mortality in the study, particularly among women who were not obese. However, this study cannot rule out that women at lower risk for death were more likely to be moderate drinkers.