Low levels of serum vitamins A and E in blood and subsequent risk for cervical cancer: Interaction with HPV seropositivity

Nutritional factors have been associated with risk of cervical cancer, but it is unclear whether the associations are of etiological significance or secondary to human papillomavirus (HPV) exposure. A delineation of this question requires a prospective study with invasive cancer as the end point. We conducted a nested case-control study in Finland and Sweden within a joint cohort of 405,000 women followed up for, on average, 4 years. Blood samples from 38 prospective cases of invasive cervical cancer diagnosed between 1985 and 1994 and 116 controls matched for age, country, and sample storage time were available for the study. Levels of retinol or unoxidized alpha-tocopherol in the blood were not risk factors for cervical cancer. However, joint-effect analysis of low levels of retinol disclosed statistically significant (p = 0.023) synergistic (more than multiplicative) interaction with HPV (HPV16, HPV18, or HPV33) seropositivity (observed relative risk = 2.6, 95% confidence interval = 0.7-8.8, expected relative risk = 0.3). Retinol might act as an effect modifier of the HPV-associated risk for cervical cancer; exposed women may require adequate levels for immunologic surveillance of HPV.