If breast cancer risk factors influenced levels of transcripts by modulation of the intracellular level of oxidative stress, selection of the exVARs PCOXY1 and GCLC might prevent selection of breast cancer risk factors into the previous multiple linear regression models (e.g., describing NQO, GSTT1, COMT, SULT1A2, GSTP1). The gene discussed is COMT; the disease is breast carcinoma.