New to Forum - Q on Maintenance vs. Radiation - 1271757

Hi everyone. This is my first posting - just joined.
My wife (60yo, never smoker) was dx with Stage IV NSCLC adenocarcinoma in April, out of the blue, after appearance of persistent cough and what was thought to be non-responding pneumonia. No brain mets, mets in a couple of chest lymph nodes and two bone spots (one on sternum, one on vertebral). One main tumor was in lung - ca. 5cm in middle right lung.
No markers on immunohistology, guardant blood test suggests HER2 exon 20 mutation.

She has had 6 rounds of carbo/alimta - good response, by CT about 50-60% reduction in tumor volume (much of it after first 2 rounds), all lymph nodes back to normal size, and re-calcification spot in area of sternum cancer suggesting positive chemo response. Since there was a lot of dead tissue in early biopsies of vertebral cancer spot and lung via bronchoscopy, Dr. thinks much of remaining lung appearance on CT scan is dead/scar tissue. Side effects were manageable, and she had neulasta shot with every round after 2nd round of chemo to reduce WBC drop.

She is currently on Alimta maintenance - every 3-4 weeks. Her RBCs are coming up and she does not seem to need the neulasta for WBC either so far. She is still on xgeva every 4 weeks.

My question relates to radiation. In our first meeting with the oncologist he suggested that if the chemo went well he would likely do some radiation down the line to further reduce any remaining cells at chest tumor and bone spots. His current plan is to remain on alimta maintenance until any sign of recurrence, and then do radiation. My question is basically just wondering what the current thinking is as to when one does preemptive radiation for oligometastatic spots versus waiting on the radiation and using alimta maintenance.

Thanks - and I hope question isn't too general. Love the site. Video on HER2 in NSCLC was very useful!