What are indications to add WPRT +/- PA field to chemotherapy for uterine serous carcinoma?

There is variation in practice.

After adequate surgical staging, our approach:

Stage 1A brachytherapy alone.

Stage IB and above, EBRT.

If node negative, treat pelvic including entire common iliac.

If pelvis node positive and PA node dissected same as above, up to common iliac.

If pelvis is positive and PA node is not dissected, then pelvic and PA nodal region.

If PA positive, then pelvic and pa nodal region.

I would typically use chemo (plus herceptin if HER2 overexpression) in this situation based on GOG258 and multiple retrospective studies showing a benefit to chemo in uterine serous. The patient’s highest risk is going to be distant recurrence. I would not want to add the morbidity of pelvic radiation with a chimney when they’re highly likely to recur outside of the field. Additionally, your next systemic option may be pembro/lenvima (if MS stable), which also has a high risk of fistula, so the risk is even higher when someone has had surgery, pelvic radiation, and then lenvima.