In the subgroup analysis based on ethnicity, SHMT1C1420T polymorphism has shown a protective effect on breast cancer in Asians (T vs. C, OR = 0.78, 95 % CI = 0.66-0.93) but not in Caucasian (T/T vs. C/C, OR = 0.98, 95 % CI = 0.86-1.12).
Conversely, for women over 50, the risk of breast cancer development was statistically associated with the MTHFR 677CT genotype, but especially significant was risk associated with the presence of the polymorphic allele of cSHMTC1420T (P = 0.0120) and the protective effect associated with the RFC1 G80A polymorphism allele (P = 0.0021), was restrict to this age group.