On 2015 Feb 15, William Grant commented:

More reasons why breast cancer rates are higher in the United States than in Malaysia

The paper by Horne and colleagues reported that breast cancer age-standardized incidence rates were much higher in the United States than in Malaysia for the period 2003-2011 [1]. From two SEER studies, the rates in the Unites States were 180.6 (SD, 0.31) cases/100,000/yr and 125.0 (SD, 0.68) cases/100,000/yr, while in Malaysia, the rate was 36.2 (SD, 20.3) cases/100,000/yr. Rates of ER+ breast cancer were six time higher in the United States while ER- breast cancer rates in the United States were about two times higher. Factors offered to explain the disparity in ER+ breast cancer rates were dietary fat intake, nulliparity, late age at first birth, and post-menopausal obesity, along with lower rates of mammography in Malaysia.

This comment addresses dietary and smoking as important factors that may explain the disparity. In a recent multi-country ecological study involving 157 countries, it was found that there were three important factors that explained about 70% of the variance in breast cancer incidence rates in 2008: energy derived from animal products, gross domestic product (GDP), and smoking, with normalized regression coefficients for all countries of 0.49, 0.26, and 0.22 [2]. Since diet affects risk of breast cancer 15-30 years later, it was found that dietary supply data for 1990 gave the highest correlation between diet and breast cancer in that study. Mechanisms whereby animal products and GDP contribute to cancer risk are discussed in Ref. 2.

Values for the two countries are as follows. In 1990, Malaysia obtained 484 kCal/d from animal products, while the United States obtained 968 kCal/d [3]. Fewer than 2% of women smoked in Malaysia in 2000 [4]. In 1990, 23% of women in the United States smoked [5]. In 2000, the GDP was $3380 per capita, while in the United States it was $35,040 per capita [6].

Thus, lower dietary consumption of animal products, lower GDP, and lower smoking rates may explain much of the disparities, along with some mentioned in Ref. 1. Unfortunately, it does not seem likely that the risk factors will change soon in the United States, and even if they did, it would be many years before there would be dramatic effects on breast cancer rates.

References 1. Horne HN, Beena Devi CR, Sung H, Tang TS, Rosenberg PS, Hewitt SM, Sherman ME, Anderson WF, Yang XR. Greater absolute risk for all subtypes of breast cancer in the US than Malaysia. Breast Cancer Res Treat. 2015;149(1):285-91. 2. Grant WB. A multicountry ecological study of cancer incidence rates in 2008 with respect to various risk-modifying factors, Nutrients. 2014;6(1):163-189. 3. http://faostat.fao.org/site/368/default.aspx#ancor (accessed Feb. 13, 2015) 4. http://www.tradingeconomics.com/malaysia/smoking-prevalence-females-percent-of-adults-wb-data.html 5. Centers for Disease Control (CDC). Cigarette smoking among adults--United States, 1990. MMWR Morb Mortal Wkly Rep. 1992;41(20):354-5, 361-2. 6. Encyclopedia Britannica Almanac 2004.

Disclosure I receive funding from Bio-Tech Pharmacal, Inc. (Fayetteville, AR), MediSun Technology (Highland Park, IL), and the Vitamin D Council (San Luis Obispo, CA).

On 2015 Feb 15, William Grant commented:

More reasons why breast cancer rates are higher in the United States than in Malaysia

The paper by Horne and colleagues reported that breast cancer age-standardized incidence rates were much higher in the United States than in Malaysia for the period 2003-2011 [1]. From two SEER studies, the rates in the Unites States were 180.6 (SD, 0.31) cases/100,000/yr and 125.0 (SD, 0.68) cases/100,000/yr, while in Malaysia, the rate was 36.2 (SD, 20.3) cases/100,000/yr. Rates of ER+ breast cancer were six time higher in the United States while ER- breast cancer rates in the United States were about two times higher. Factors offered to explain the disparity in ER+ breast cancer rates were dietary fat intake, nulliparity, late age at first birth, and post-menopausal obesity, along with lower rates of mammography in Malaysia.

This comment addresses dietary and smoking as important factors that may explain the disparity. In a recent multi-country ecological study involving 157 countries, it was found that there were three important factors that explained about 70% of the variance in breast cancer incidence rates in 2008: energy derived from animal products, gross domestic product (GDP), and smoking, with normalized regression coefficients for all countries of 0.49, 0.26, and 0.22 [2]. Since diet affects risk of breast cancer 15-30 years later, it was found that dietary supply data for 1990 gave the highest correlation between diet and breast cancer in that study. Mechanisms whereby animal products and GDP contribute to cancer risk are discussed in Ref. 2.

Values for the two countries are as follows. In 1990, Malaysia obtained 484 kCal/d from animal products, while the United States obtained 968 kCal/d [3]. Fewer than 2% of women smoked in Malaysia in 2000 [4]. In 1990, 23% of women in the United States smoked [5]. In 2000, the GDP was $3380 per capita, while in the United States it was $35,040 per capita [6].

Thus, lower dietary consumption of animal products, lower GDP, and lower smoking rates may explain much of the disparities, along with some mentioned in Ref. 1. Unfortunately, it does not seem likely that the risk factors will change soon in the United States, and even if they did, it would be many years before there would be dramatic effects on breast cancer rates.

References 1. Horne HN, Beena Devi CR, Sung H, Tang TS, Rosenberg PS, Hewitt SM, Sherman ME, Anderson WF, Yang XR. Greater absolute risk for all subtypes of breast cancer in the US than Malaysia. Breast Cancer Res Treat. 2015;149(1):285-91. 2. Grant WB. A multicountry ecological study of cancer incidence rates in 2008 with respect to various risk-modifying factors, Nutrients. 2014;6(1):163-189. 3. http://faostat.fao.org/site/368/default.aspx#ancor (accessed Feb. 13, 2015) 4. http://www.tradingeconomics.com/malaysia/smoking-prevalence-females-percent-of-adults-wb-data.html 5. Centers for Disease Control (CDC). Cigarette smoking among adults--United States, 1990. MMWR Morb Mortal Wkly Rep. 1992;41(20):354-5, 361-2. 6. Encyclopedia Britannica Almanac 2004.

Disclosure I receive funding from Bio-Tech Pharmacal, Inc. (Fayetteville, AR), MediSun Technology (Highland Park, IL), and the Vitamin D Council (San Luis Obispo, CA).