Not a doctor, but gut microbiome modulation (e.g. fecal microbiota transplantation) is one of the most talked-about adjuncts for (metastatic breast) cancer right now.

https://scholar.google.com/scholar?as_ylo=2022&q=fecal+micro...

--- example:

"Understanding the relationship between breast cancer, immune checkpoint inhibitors, and gut microbiota: a narrative review"

https://pmc.ncbi.nlm.nih.gov/articles/PMC11557166/ ( Transl Breast Cancer Res. 2024 Oct 21)

  """
  Conclusions
  The composition of gut microbiota could help predict 
  the chance of response to immunotherapy, 
  and modulating gut microbiota has the potential 
  to enhance the  efficacy of chemo-immunotherapy 
  in breast cancer. 
  However, the available data relating to breast cancer 
  are limited. 
  Larger prospective studies are required 
  to further elucidate their role 
  as a biomarker and treatment.
  """

Look into companies doing trials with a credible track record. For example, Immunocore has good T cell receptor designs to bind common antigens in breast cancer tumors. For solid tumors, including breast cancer, the protein ID is IMC-F106C. For advanced cases, this is usually combined with a checkpoint inhibitor.

Depends on a lot of things. Subtype, ER, PR, HER2? For triple negative breast cancers some patients may avoid chemo if they have highly active immune system (TILs)

Here is a possibly different (or supplemental) point of view, with repurposed drugs and metabolic interventions. I believed it would be applicable to the breast cancers: https://imahealth.org/research/cancer-care/

Step 1: See Oncologist and take their advice.

Step 2: Definitely don't take internet advice. Disregard the following.

Step 3: Hit the gym

Step 4: Intermittent fasting + 50% fat, 50% protein diet.

Step 5: Ask doctor for a standard run of Fenbendazole or Mebendazole

Step 6: Play with them as much as possible.