Successful treatment of in-transit metastatic melanoma with combination intralesional T-VEC and topical imiquimod immunotherapy

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Abstract
In-transit metastases of malignant melanoma pose a significant clinical challenge, particularly in patients with contraindications to systemic therapies. While surgical excision and systemic immunotherapies remain standard treatments, localized therapies such as intralesional talimogene laherparepvec (T-VEC) and topical imiquimod, which stimulate tumor-specific T-cell responses, have garnered increasing attention for their potential efficacy and tolerability. Although the individual efficacy of these therapies is well-documented, their combined use and their synergistic effects have not been well-documented. This case series reports on five patients with in-transit melanoma metastases treated with T-VEC and imiquimod at Northwestern Memorial Hospital from November 2018 to May 2023. Patients received a median of 13 (range 8–20) T-VEC injections over a median of 6 months (range 5–9), of which 4 of those months were with concurrent T-VEC and imiquimod cream. Four of the five patients achieved complete response (CR) by the end of the treatment course. One patient developed systemic progression during therapy, leading to early cessation of treatment. All patients with CR elected to continue topical imiquimod applications as maintenance following T-VEC for a median of 6 months (range 2–14 months). Only one of the four patients who achieved CR developed metastatic nodal disease 10 months after the last T-VEC injection. The three other patients are free of cutaneous and systemic disease 2–57 months after their last injection. All patients tolerated treatment well with zero patients discontinuing treatment due to side effects. These findings suggest that the combination of intralesional T-VEC and topical imiquimod can be an effective and safe treatment of in-transit metastases of malignant melanoma.

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