Rifaximin for the Treatment of Gastrointestinal Toxicities Related to Pertuzumab-Based Therapy in Patients With Stage I-III HER2 Positive Breast Cancer

PRIMARY OBJECTIVE: I. To evaluate the reduction rate of grade \>= 2 abdominal toxicities, including abdominal distension, abdominal pain, diarrhea, dyspepsia, stomach pain, and typhlitis according to the National Cancer Institute Common Terminology for Adverse Events version 5.0 (NCI CTCAE v5.0) with the use of rifaximin in stage II-III HER-2 positive breast cancer patients with pertuzumab induced gastrointestinal toxicities. SECONDARY OBJECTIVES: I. Evaluate dose reductions, dose delays and discontinuation of treatment with pertuzumab due to gastrointestinal side effects. II. Evaluate and measure the change in the Bristol stool scale before and after rifaximin treatment. III. Evaluate and measure the change in the 4-point Likert scale patient questionnaire before and after rifaximin treatment. CORRELATIVE STUDY OBJECTIVES: I. Evaluate changes in the fecal microbiome, hydrogen breath test, and permeability test before and after rifaximin. II. Evaluate changes in the fecal microbiome, hydrogen breath test, and permeability test before and after pertuzumab-based chemotherapy. III. Evaluate the difference in the fecal microbiome, hydrogen breath test, and permeability test among patients with or without pertuzumab induced gastrointestinal toxicities (PIGT). OUTLINE: Patients are assigned to 1 of 2 arms. ARM I (GRADE \>= 2 PIGT): Patients that experience PIGT after receiving first standard of care cycle of pertuzumab-based chemotherapy receive rifaximin orally (PO) twice daily (BID) on days 1-5 and standard of care pertuzumab-based chemotherapy on day 1. Treatment repeats every 21 days for up to 5 cycles in the absence of disease progression or unacceptable toxicity. ARM II (GRADE =\< 1 PIGT): Patients that do not experience PIGT after receiving first standard of care cycle of pertuzumab-based chemotherapy continue receiving standard of care pertuzumab-based chemotherapy on day 1. Treatment repeats every 21 days for up to 5 cycles in the absence of disease progression or unacceptable toxicity.