Appendix 1: Analysis of the risk of developing cancer other than breast cancer in women drinking 7-14 drinks per week in the Million Women Study
The following is an independent analysis of the data presented in the Million Women Study.
The Million Women Study1 by virtue of its large size, is helpful in evaluating the relationship of alcohol ingestion with multiple different types of cancer.1 For high levels of alcohol intake (≥15 drinks/week), there is an increase in the occurrence of cancer even when breast cancer is excluded.
However, for levels of alcohol intake of less than or equal to 14 drinks per week, the increase in the total cancer rate is entirely the result of the increase in breast cancer. Of note, the women drinking ≤14 drinks/week are a substantial portion of the study participants and comprise 93% of the study population that drank alcohol in the Million Women Study.
The details of the group drinking 7-14 drinks per week in the Million Women Study are as follows. There are 611 more diagnoses of all types of cancer in the group drinking 7-14 drinks per week than expected for the reference group. However, there are 653 more diagnoses of breast cancer for women drinking 7-14 drinks per week than expected when compared to the reference group. Hence, excluding breast cancer cases, there are 42 fewer cases of all cause cancer occurring in the drinking group than expected when compared to the reference group (though this is not statistically significant). Therefore, the net effect on the total number of cancer cases caused by alcohol ingestion at this level of intake is neutral except for breast cancer. (Findings are similar for women ingesting 3-6 drinks/week.)
DETAILS: Number of EXCESS ALL CAUSE cancer cases (611) occurring in women drinking 7-14 drinks/week in Million Women Study1 (Data derived from Table 2 in Reference 1)
| All Cancers | Excess cancer cases- all causes | Derivation |
| Relative Risk: 1.05 | 611 excess total cancer cases in women drinking 7-14 drinks/week | 1.05y=12,838 total cancer cases; y=12,227; Excess cancer cases= 611 (Excess cases= observed cases-y =12,838-12,227= 611 excess cases) |
DETAILS: Number of EXCESS BREAST cancer cases (653) occurring in women drinking 7-14 drinks/week in Million Women Study (derived from Table 2 in Ref 1)
| Breast Cancer | Excess cases of breast cancer | Derivation |
| Relative Risk: 1.13 | 653 excess breast cancer cases in women drinking 7-14 drinks/week | 1.13y=5,672 total breast cancer cases; y=5,019; Excess breast cancer cases= 653 (Excess cases= observed cases-y =5,672-5,019= 653 cases) |
For cancers other than breast cancer, there is no significant effect on total cancer incidence with alcohol ingestion at the level of 7-14 drinks per week compared to the reference group. This is also the case for women ingesting 3-6 drinks per week (derivations not detailed but similar to those shown).
The previously reported association of alcohol ingestion with a reduced incidence of renal cell carcinoma, thyroid cancer, and non-Hodgkin lymphoma2-5 are noted in the Million Women Study for women drinking 7-14 drinks/week. The previously described increased incidence in laryngeal, esophageal and stomach cancer is observed as well.
Even when the more easily treated thyroid cancer (which occurred less frequently than expected compared to the reference group in those drinking 7-14 drinks) is excluded, there still are a non significant fewer number of cases than expected of cancer, other than breast cancer, occurring in those drinking 7-14 drinks/week.
Thyroid cancer details: (Data derived from Table 2 in Reference 1)
|
Reduced number of thyroid cancer cases |
Derivation |
| 26 fewer cases than expected in group drinking 7-14 drinks/week | 0.7y=61; y= 87; 87-61=26 |
Alcohol at modest levels is a substance with multiple biologic effects and appears to increase some cancers and decrease others. The dominant net effect on cancer in women is overwhelmingly driven by the substantial effect of alcohol in promoting breast cancer. In the Million Women Study, in regards to cancers other than breast cancer, alcohol ingestion of less than or equal to 14 drinks/week increases some types of cancer which is counterbalanced by a decrease in other types of cancer.
References:
- Allen NE, Beral V, Casabonne D, Kan SW, Reeves GK, Brown A, Green J; Million Women Study Collaborators. Moderate alcohol intake and cancer incidence in women. J Natl Cancer Inst. 2009;101:296-305.
- Lee JE, Hunter DJ, Spiegelman D, et al. Alcohol intake and renal cell cancer in a pooled analysis of 12 prospective studies. J Natl Cancer Inst. 2007;99:801-10.
- Nagano J, Mabuchi K, Yoshimoto Y, et al. A case-control study in Hiroshima and Nagasaki examining non-radiation risk factors for thyroid cancer. J Epidemiol. 2007;17:76-85.
- Rossing MA, Cushing KL, Voigt LF, et al. Risk of papillary thyroid cancer in women in relation to smoking and alcohol consumption. Epidemiology. 2000;11:49-54.
- Morton, LM, Zheng T, Holford TR, et al. Alcohol consumption and risk of non-Hodgkin lymphoma: a pooled analysis. Lancet Oncol. 2005;6:469-76.
Eric Roehm, M.D. 2011
