I have written this before, but in your case, I think it's worth repeating. At age 70 in 2020 my breast cancer diagnosis was very similar to yours. I had IDC. The tumor was also 6mm, 95% ER+ and 95% PR+, Grade 1 with no lymph nodes involved. They did not do an oncotype because they said the tumor had been entirely removed during the biopsy. I'm not sure that I buy that, but that's another story. After a lumpectomy, I had clean margins.
The radiation oncologist recommended that I have 16 rounds of radiation. He informed me that there are studies that indicate that radiation after the age of 70 may not be necessary or beneficial. However, he knew of patients who were older than I, had decided against radiation, and had a recurrence. I decided to have the radiation. I was fortunate because I did not have any known side effects from it. It was the easiest part of my treatment. I was then prescribed anastrozole. I had no family history of breast cancer, nor had I been through it with any friends, so I was very unfamiliar with the treatment options. I thought that the little white pill couldn't be too bad. After all, women stay on it for 5 to 10 years. At the only cancer center in my area, patients are required to attend a session with a nurse who explains the possible side effects of the medicine. I was also required to sign a contract which stated that I understood the possible side effects. That should have given me a clue.
I had MANY side effects from anastrozole which severely diminished my quality of life. After 3 months, I stopped taking it. I am definitely not saying that you shouldn't try it. Many patients take it with minor or no side effects. The reason I am repeating my thoughts is to caution anyone deciding whether or not to have radiation. That decision is made before we know, if our bodies will be able to tolerate an aromatase inhibitor. I was glad that I had decided to have the radiation to give myself the protection that it might provide. None of the treatments give us a 0% chance of recurrence. We each must decide for ourselves what treatments we choose based on our pathology, age, quality of life while on medication and many other individual factors. I am soon to be 74, feeling well and enjoying a good quality of life.
I wish you and all who read this blog the best of luck with your decisions and many healthy years ahead.