Ph2 Study for Optimization of Adjunct Systemic Therapy in HER2+ Patients, MolecularPCR Trial

This phase II trial tests reduced post surgery (adjuvant) therapy for patients with early breast cancer who have confirmed that the disease has responded completely (pathologic complete response) after pre surgical treatment (neoadjuvant) therapy and do not have any tumor genetic material (molecular residual disease) circulating in their blood. Standard of care treatment after surgery consists of 1 year of pembrolizumab for patients with triple negative breast cancer or trastuzumab with or without pertuzumab to complete 1 year of treatment. Immunotherapy with monoclonal antibodies, such as pembrolizumab, may help the body's immune system attack the cancer, and may interfere with the ability of tumor cells to grow and spread. Pertuzumab and trastuzumab are monoclonal antibodies and forms of targeted therapy that attach to a receptor protein called HER2. HER2 is found on some cancer cells. When pertuzumab or trastuzumab attach to HER2, the signals that tell the cells to grow are blocked and the tumor cell may be marked for destruction by the body's immune system. Lowering the total amount of cancer therapy after breast surgery, may continue to keep the great tumor response to treatment, and may help lower the amount of side effects patients have.

PRIMARY OBJECTIVES: I. To determine the 3-year event free survival (EFS) after breast surgery in patients with early triple negative breast cancer (TNBC) that achieve a pathologic complete response (pCR) after neoadjuvant systemic therapy (NST) with a pembrolizumab plus chemotherapy-based regimen and are minimal residual disease (MRD)-negative (negative circulating tumor deoxyribonucleic acid \[ctDNA\] with the NeXT Personal™ assay) at 4-6 weeks after breast surgery and discontinue standard of care (SOC) adjuvant pembrolizumab. II. To determine the 3-year EFS after breast surgery in patients with early HER2+ breast cancer that achieve a pCR after NST with a trastuzumab and pertuzumab plus chemotherapy-based regimen and are MRD-negative (negative ctDNA with the NeXT Personal™ assay) at 4-6 weeks after breast surgery and discontinue SOC adjuvant trastuzumab and pertuzumab. SECONDARY OBJECTIVES: I. To estimate the rate of conversion from negative to positive ctDNA and time to conversion from negative to positive ctDNA among patients who undergo de-escalation of SOC adjuvant systemic therapy. II. To establish the prevalence of patients with early TNBC or early HER2+ breast cancer who achieve a pCR after receiving NST and have a positive ctDNA with the NeXT Personal™ assay at 4-6 weeks after breast surgery. III. To determine the 3-year EFS after breast surgery in patients with early HER2+ breast cancer or early TNBC that achieve a pCR after NST and have a positive ctDNA with the NeXT Personal™ assay at 4-6 weeks after breast surgery. OUTLINE: Patients with triple negative breast cancer are assigned to cohort 1, patients with HER2 positive breast cancer are assigned to cohort 2. COHORT 1: Patients may receive 1 to 3 cycles of standard of care treatment with pembrolizumab. Patients with a positive ctDNA test 4-6 weeks after surgery continue to receive standard of care treatment per their treating physician in the absence of disease progression or unacceptable toxicity. Patients with a negative ctDNA test will not receive further treatment with pembrolizumab and will undergo monitoring with ctDNA tests every 3 months for 3 years in the absence of disease progression. COHORT 2: Patients may receive 1 to 3 cycles of standard of care treatment with trastuzumab with or without pertuzumab. Patients with a positive ctDNA test 4-6 weeks after surgery continue to receive standard of care treatment per their treating physician in the absence of disease progression or unacceptable toxicity. Patients with a negative ctDNA test will not receive further treatment with pembrolizumab and will undergo monitoring with ctDNA tests every 3 months for 3 years in the absence of disease progression. Patients may receive standard of care endocrine therapy per their treating physician throughout the study.