Complete tumour regression of in-transit melanoma following discontinuation of talimogene laherparepvec.

We report a case of complete tumour regression in a man in his 80s with in-transit melanoma following discontinuation of talimogene laherparepvec (T-VEC). The patient underwent a standard course of 1.0 mL of 1×10⁸ pfu/mL T-VEC every 2 weeks. After 10 T-VEC injections over approximately 5 months, the lesion still displayed fluorine-18 fluorodeoxyglucose activity on positron emission tomography/CT and biopsy-confirmed viable tumour. Due to side effects, including fatigue, headache and concern for a localised herpes simplex virus rash, the decision was made to discontinue T-VEC and perform surgical resection of the lesion. However, surgery was delayed by 8 weeks due to a minor stroke. After excision, the final pathology showed no residual melanoma, indicating a delayed, complete pathological response to T-VEC. This case may reflect the potential for continued or delayed anti-tumour immune activity after cessation of T-VEC and support further investigation into T-VEC's immune effects and timing of treatment in neoadjuvant settings.