A study followed 900,000 US adults from 1992 to 2008. At baseline, all participants were screened and determined to be cancer free and their body mass index (BMI) was calculated. Body mass index is a measure of obesity that is calculated using a person's height and weight. Subjects were separated into the following groups according to their BMI: a. normal weight
b. slightly overweight
c. moderately overweight
d. greatly overweight.

57,145 deaths from cancer occurred in the population during the follow-up period. The following results were seen for men and women when the heaviest members of the cohort (greatly overweight) were compared to those with normal weight:

Men: Risk ratio of cancer death = 1.5 95% confidence interval = 1.1 - 2.1
Women: Risk ratio of cancer death = 1.6 95% confidence interval = 1.4 - 1.9

To show the public health impact of obesity on cancer mortality in the total population, the authors stated that 90,000 cancer deaths could be prevented each year in the total US population if adults could maintain normal weight.

Required:
What additional information would need to be provided for you to be able to calculate the incidence rate of cancer deaths?