Hi I Have A Question Regarding My Mom Who Is

hi I have a question regarding my mom who is 73 years old. she was diagnosed with breast cancer and had her mastectomy done. her tumor was then sent for biopsy. the report came out to be er positive pr positive and her negative. then we went for a test called onco type dx. the number came out to be 27 and the doctor said we could go for chemo only if we choose too. he is not making a strong suggestion either way and we are confused if chemo which would improve her survival condition by 5% or in other words reduce recurrence by 5%. Is 5%a significant number. I can send the oncotype test report.