Background and Clinical Significance: Breast cancer is the most frequent malignancy in women. Advanced metastatic breast cancer is considered a treatable but incurable condition, with a median overall survival of only 2-3 years. Among its subtypes, triple-negative breast cancer (TNBC) accounts for a high proportion of breast cancer–related deaths. It is characterized by an aggressive clinical course, early recurrence, and a strong propensity for visceral and brain metastases. Case Presentation :We report the case of a Caucasian woman who, two years after being initially diagnosed and treated for TNBC, developed disease relapse with lung and mediastinal lymph node metastases. The patient received three months of chemotherapy combined with an adjuvant integrative protocol consisting of melatonin, cannabidiol, and oxygen–ozone therapy. This combined approach led to the complete disappearance of the lung nodules. Subsequently, stereotactic radiotherapy was performed and, in association with the ongoing integrative treatment, resulted in a significant reduction of mediastinal adenopathy. Introduction of immunotherapy, supported continuously by the same adjuvant strategy, achieved a complete and durable remission. Strikingly, the patient remained disease-free five years after the diagnosis of lung and mediastinal metastases. Conclusions: This clinical case highlights the potential benefit of using melatonin, cannabidiol, and oxygen–ozone therapy as part of an integrative approach in patients with aggressive metastatic TNBC. While it is not possible to establish causality from a single case, the sustained remission observed suggests that such unconventional adjuvant strategies could play a supportive role in enhancing the efficacy of standard oncologic therapies.