I basically had the same diagnosis as you. Stage 1 IDC, onco score of 20 and after much research I did go through chemo. For ME this was the right decision, and you must do what you feel is right for you and only you.
I based my decision on the following things:
1. if breast cancer metasizes it comes back in the bones, brain, liver or lungs, and I didn't want to deal with cancer in those organs,
2. I would always regret not doing chemo if my cancer did recur, and my personality is such that I could not live with always second guessing my decision,
3. and finally I would try the chemo and if I did experience terrible side effects I could always stop.
I had 6 rounds of taxotere and cytoxan for chemo and made sure to rest and to carefully eat lean protein and many fruits and vegetables - no fatty or greasy food and the only side effect I had was fatigue. I am 67 years old and retired so I did not have to go to work every day while doing chemo. For me all worked out well.
I am now having whole breast radition in the prone position and have completed 16 of the 33 sessions and so far have only fatigue and just got a mild rash which is getting better with the prescription cortisone cream. I then face 5 years of an aromatase inhibitor.
Please remember that MY decision works for ME and whatever decision you make must work for you. When you make your decision, you must feel that it is right for you in your gut and your heart. Do NOT make the decision that is popular wih your family and friends or the one that gets the most votes on this website! In fact I purposely did not discuss my chemo or no chemo quandry with anybody in my family until I arrived at my decision. I did not want them to feel guilty if they said yes to chemo for me and I got horribly sick, or they said no to chemo and the cancer came back. SO ONCE AGAIN, I DID WHAT WAS RIGHT FOR ME, and you must do the same thing.
I wish you much good luck and hope you reach the inner peace of mind that I had when I finally made my decision. It was a powerful, empowering, positive feeling.
You will make the best decision for you and I wish you well. Please let us know what your decision is and how you arrived at your decision so you can help others who come to this website.
Love and hugs to you,
Judy