Reference no: EM133375004

As part of the baseline exam, the researchers assessed x-ray exposure in the ACLS cohort. A total of 11,017 members of the cohort had been exposed to 0 chest x-rays, 3,001 members of the cohort had been exposed to 1 or 2 chest x-rays, and 1,991 members of the cohort had been exposed to 3 or more chest x-rays. The number of breast cancer deaths in the 10 year follow-up within the three chest x-ray exposure groups was as follows: 18 women from the group with 0 chest x-rays died of breast cancer, 12 women from the group with 1 or 2 chest-x-rays died to breast cancer, and 9 of the women from the group with 3 or more chest x-rays died of breast cancer.

Based on this information, what was the relative risk for breast cancer death in the group with 1 or 2 chest x-rays by comparison to the group with 0 chest x-rays (referent group)?