Autologous Tumor Vaccination in Melanoma and Colon Cancer Patients With Recurrent Liver Metastases: A Case Series

Background: Patients with colorectal cancer (CRC) and malignant melanoma (MM) are at a significant risk of developing liver metastases. Despite surgical resection and systemic therapies, disease recurrence is common and long-term survival after relapse remains limited. Autologous tumor vaccines represent a promising immunotherapeutic approach by harnessing the immune system’s capacity to elicit durable antitumor responses. Case Report: A previously established melanoma immunotherapy protocol was used, combining low-dose cyclophosphamide with repeated intradermal injections of dinitrophenyl-modified autologous tumor cells admixed with Bacillus Calmette-Guérin as an immune adjuvant. Vaccine-induced delayed-type hypersensitivity (DTH) responses were prospectively monitored as a clinical marker of antitumor immune activation and treatment efficacy. This approach was adapted for use in non-melanoma solid tumors. Two patients with advanced disease – one with metastatic melanoma and one with metastatic CRC – experienced recurrent liver metastases following standard treatments and underwent vaccination using tumor cells derived from resected liver lesions. Initial vaccination failed to prevent disease recurrence in both patients. Treatment was subsequently individualized: a modified vaccine was generated for the patient with melanoma, whereas the patient with CRC was successfully treated with vaccine rechallenge. In both cases, the emergence of a positive DTH response was associated with complete clinical remission and durable disease control, with follow-up exceeding 20 years. Conclusion: Autologous tumor cell vaccines derived from liver metastases may represent a feasible therapeutic strategy capable of achieving durable remission and improved long-term outcomes in selected high-risk patients with metastatic disease.