If you have SPSS statistical software it will be most helpfull. You can use t-test, parametric and non parametric tests to find for statistical differences between your results, that depends on what is your research hypothesis.

I need to check whether there is carcinogenic effect on test article treated animals (rat). There is also concurrent control group animals which are given RO water orally for 104weeks.

In order to reject the null hypothesis ( that there is no difference between groups of animals ) you can use the t-test, , and if results are signifficant

Non parametric Mann whitney test