On 2015 Jan 14, William Grant commented:

Differences in 25-hydroxyvitamin D concentrations may explain some of the racial disparities in noncardia gastric cancer incidence rates

The recent paper by Bautista and colleagues presented findings regarding risk modifying factors for noncardia gastric cancer related to racial disparities [1]. When averaged over the period 2000-2010, rates were highest for blacks, intermediate for Asians and Hispanics, and lowest for whites. However, median survival times were highest for Asians, followed by blacks, Hispanics, then whites. This letter proposes two factors to explain some of the findings.

First, it is noted that gastric cancer incidence and/or mortality rates have been found significantly inversely correlated with solar UVB doses in ecological studies in Australia, China, Japan, Nordic countries, Spain, and the United States [2]. The most likely explanation for these findings is that UVB raises 25-hydroxyvitamin D [25(OH)D] concentrations [2]. 25(OH)D concentrations are correlated with skin pigmentation in the United States, with whites having the highest mean concentrations, Hispanics intermediate concentrations, and blacks the lowest concentrations [3]. Based on this information as well as many black-white health disparities that cannot be explained by socioeconomic status, stage or condition at time of diagnosis, and treatment, it has been proposed that black-white health disparities and cancer survival rates in the United States are related to the disparities in 25(OH)D concentrations [4,5]. Thus, disparities in 25(OH)D concentrations may explain the disparities in noncardia gastric cancer incidence rates reported in Ref. 1. They may also explain the higher rate of diabetes mellitus in blacks and Hispanics compared to whites, and hypertension in blacks compared to whites [4]. They may also help explain why blacks are diagnosed at younger ages than whites. In addition, Asians, blacks, and Hispanics had higher Heliocobacter pylori infection rates than whites, which would also contribute to risk of developing noncardia gastric cancer at a younger age.

Second, age at time of diagnosis seems to affect survival rates. The data in Table 1 of Ref. 1 show that there are significant disparities in age at time of diagnosis, with whites having the highest fraction diagnosed after the age of 70 years and Asians and Hispanics the lowest fractions. A plot of median survival as a function of the percentage diagnosed after the age of 70 years yields a slope of -6.5 days/percent with r = 0.77, p = 0.23. While this regression is not significant at the 95% confidence level due to the large difference in survival times for Asians and Hispanics for similar fraction diagnosed over the age of 70 years, which could be due to differences in other factors such as diet, it does suggest that age is an important factor affecting survival rate.

Thus, if blood samples from near or before the time of diagnosis are available, 25(OH)D concentrations could be measured to evaluate the role of vitamin D in noncardia incidence and survival rates. The effect of age at time of diagnosis can be studied using the existing data.

References 1. Bautista MC, Jiang SF, Armstrong MA, Kakar S, Postlethwaite D, Li D. Significant racial disparities exist in noncardia gastric cancer outcomes among Kaiser Permanente's patient population. Dig Dis Sci. 2014 Oct 30. [Epub ahead of print] 2. Moukayed M, Grant WB. Molecular link between vitamin D and cancer prevention. Nutrients. 2013;5:3993-4023. 3. Ginde AA, Liu MC, Camargo CA Jr. Demographic differences and trends of vitamin D insufficiency in the US population, 1988-2004. Arch Intern Med. 2009;169:626-632. 4. Grant WB, Peiris AN. Possible role of serum 25-hydroxyvitamin D in Black–White health disparities in the United States. J Am Med Directors Assoc. 2010;11:617-628. 5. Grant WB, Peiris AN. Differences in vitamin D status may account for unexplained disparities in cancer survival rates between African and White Americans. Dermatoendocrinol. 2012;4:85-94.

Disclosure I receive funding from Bio Tech Pharmacal (Fayetteville, AR) and Medi-Sun Engineering, LLC (Highland Park, IL).

On 2015 Jan 14, William Grant commented:

Differences in 25-hydroxyvitamin D concentrations may explain some of the racial disparities in noncardia gastric cancer incidence rates

The recent paper by Bautista and colleagues presented findings regarding risk modifying factors for noncardia gastric cancer related to racial disparities [1]. When averaged over the period 2000-2010, rates were highest for blacks, intermediate for Asians and Hispanics, and lowest for whites. However, median survival times were highest for Asians, followed by blacks, Hispanics, then whites. This letter proposes two factors to explain some of the findings.

First, it is noted that gastric cancer incidence and/or mortality rates have been found significantly inversely correlated with solar UVB doses in ecological studies in Australia, China, Japan, Nordic countries, Spain, and the United States [2]. The most likely explanation for these findings is that UVB raises 25-hydroxyvitamin D [25(OH)D] concentrations [2]. 25(OH)D concentrations are correlated with skin pigmentation in the United States, with whites having the highest mean concentrations, Hispanics intermediate concentrations, and blacks the lowest concentrations [3]. Based on this information as well as many black-white health disparities that cannot be explained by socioeconomic status, stage or condition at time of diagnosis, and treatment, it has been proposed that black-white health disparities and cancer survival rates in the United States are related to the disparities in 25(OH)D concentrations [4,5]. Thus, disparities in 25(OH)D concentrations may explain the disparities in noncardia gastric cancer incidence rates reported in Ref. 1. They may also explain the higher rate of diabetes mellitus in blacks and Hispanics compared to whites, and hypertension in blacks compared to whites [4]. They may also help explain why blacks are diagnosed at younger ages than whites. In addition, Asians, blacks, and Hispanics had higher Heliocobacter pylori infection rates than whites, which would also contribute to risk of developing noncardia gastric cancer at a younger age.

Second, age at time of diagnosis seems to affect survival rates. The data in Table 1 of Ref. 1 show that there are significant disparities in age at time of diagnosis, with whites having the highest fraction diagnosed after the age of 70 years and Asians and Hispanics the lowest fractions. A plot of median survival as a function of the percentage diagnosed after the age of 70 years yields a slope of -6.5 days/percent with r = 0.77, p = 0.23. While this regression is not significant at the 95% confidence level due to the large difference in survival times for Asians and Hispanics for similar fraction diagnosed over the age of 70 years, which could be due to differences in other factors such as diet, it does suggest that age is an important factor affecting survival rate.

Thus, if blood samples from near or before the time of diagnosis are available, 25(OH)D concentrations could be measured to evaluate the role of vitamin D in noncardia incidence and survival rates. The effect of age at time of diagnosis can be studied using the existing data.

References 1. Bautista MC, Jiang SF, Armstrong MA, Kakar S, Postlethwaite D, Li D. Significant racial disparities exist in noncardia gastric cancer outcomes among Kaiser Permanente's patient population. Dig Dis Sci. 2014 Oct 30. [Epub ahead of print] 2. Moukayed M, Grant WB. Molecular link between vitamin D and cancer prevention. Nutrients. 2013;5:3993-4023. 3. Ginde AA, Liu MC, Camargo CA Jr. Demographic differences and trends of vitamin D insufficiency in the US population, 1988-2004. Arch Intern Med. 2009;169:626-632. 4. Grant WB, Peiris AN. Possible role of serum 25-hydroxyvitamin D in Black–White health disparities in the United States. J Am Med Directors Assoc. 2010;11:617-628. 5. Grant WB, Peiris AN. Differences in vitamin D status may account for unexplained disparities in cancer survival rates between African and White Americans. Dermatoendocrinol. 2012;4:85-94.

Disclosure I receive funding from Bio Tech Pharmacal (Fayetteville, AR) and Medi-Sun Engineering, LLC (Highland Park, IL).