They are newer treatments that use your immune system against the cancer. Not every type of breast cancer/cancer has them and not all are available with insurance, but it might not hurt to ask if there is anything at Stage 3.

Here's a little explanation from American Cancer Society https://www.cancer.org/cancer/managing-cancer/treatment-types/immunotherapy.html

Mine was specifically for Triple Negative Breast Cancer.

I was diagnosed July 2020 and did IV chemo Aug 2020--Dec 2020, started Keytruda (the immunotherapy) in Sept 2020-Sept 2021, followed by mastectomy Feb 2021, then radiation March-May 2021, and started Xeloda, the chemo pill May 2021 and that went to May 2022. I had reconstruction Sept 2021 and a touch up surgery Feb 2022.

Now I do 3 month bloodwork, yearly Pet/CT scans, and mammogram/MRI alternating every 6 months.