Elimination of Axillary-Lymph-Node Metastases in a Patient With Invasive Lobular Breast Cancer Treated by First-line Neo-adjuvant Chemotherapy Combined With Methionine Restriction

Background/Aim: Invasive lobular carcinoma (ILC) of the breast has a low complete-response rate in the neoadjuvant-chemotherapy setting. The addiction to methionine is a fundamental and ubiquitous characteristic of cancer cells, termed the Hoffman effect. We have previously targeted methionine addiction of breast cancer with recombinant methioninase (rMETase) using patient-derived orthotopic xenograft (PDOX) models. The aim of the present study was to determine the efficacy of methionine restriction with rMETase and a low-methionine diet combined with first-line neo-adjuvant chemotherapy, in a patient with metastatic ILC of the breast. Case Report: A 62-year-old female was diagnosed with metastatic ipsilateral axillary-lymph-node recurrence of breast ILC 3 years after mastectomy. The patient underwent [11C]-methionine positron-emission tomography (METPET) which showed extensive methionine accumulation in the ipsilateral axillary lymph nodes, indicating the presence of cancer cells. The patient received standard neo-adjuvant chemotherapy, which consisted of 3 months of doxorubicin and cyclophosphamide followed by 3 months of docetaxel from March 2022. The patient also went on a low-methionine diet and daily oral rMETase as a supplement every 6 hours concurrently with six months chemotherapy. The patient’s blood carcinoembryonic antigen (CEA) level decreased gradually, and computed tomography findings showed loss of axillary lymph-node metastases in the first 3 months of neo-adjuvant chemotherapy with doxorubicin and cyclophosphamide combined with rMETase and a low-methionine diet. A complete response was demonstrated by METPET at 6 months, at conclusion of docetaxel chemotherapy. Conclusion: Combination therapy of doxorubicin and cyclophosphamide followed by docetaxel combined with methionine restriction led to a remarkable complete response that is expected in fewer than 10% of patients with ILC of the breast treated with neo-adjuvant chemotherapy alone. The present results suggest that methionine restriction in combination with doxorubicin and cyclophosphamide followed by docetaxel may be effective, after METPET has demonstrated the presence of methionine-addicted axillary-lymph-node metastases in ILC of the breast.