Positron emission tomography/computed tomography evaluation of oncolytic virus therapy efficacy in melanoma

Talimogene laherparepvec monotherapy for head and neck melanoma patients

Talimogene laherparepvec (T-VEC) is a modified herpes simplex virus, type 1, intralesionally administered in patients with stage IIIB/C-IVM1a unresectable melanoma. When surgery is not a treatment option in the head and neck region, T-VEC can be an elegant alternative to systemic immunotherapy. Ten patients with metastatic melanoma in the head and neck region started treatment with T-VEC monotherapy at the Netherlands Cancer Institute. We collected data on response, adverse events (AEs), and baseline characteristics. For response evaluation, we used clinical evaluation with photography, 3-monthly PET/computed tomography (PET/CT) using 18F-fluoro-2-D-deoxyglucose, and histological biopsies. Median age at baseline was 78.2 (35-97) years with a median follow-up of 11.6months. Of these 10 patients, 5 had a complete response (CR), 3 had a partial response, 1 had stable disease and 1 showed progressive disease (PD) as their best response. Best overall response rate (ORR) was 80%. Median progression-free survival was 10.8 months (95% confidence interval, 2.2-19.4). Grade 1 AEs occurred in all patients. Mostly, these consisted of fatigue, influenza-like symptoms, and injection site pain. PET-CT and histological biopsies proved to be clinically useful tools to evaluate treatment response for T-VEC monotherapy, confirming pCR or PD to stage IV disease requiring systemic treatment. ORR for T-VEC monotherapy for melanoma in the head and neck region at our institute was 80% with 50% achieving a CR. This realworld data demonstrates promising results and suggests T-VEC can be an alternative to systemic therapy in this select, mostly elderly patient population.

False positive FDG uptake in melanoma patients treated with talimogene laherparepvec (T-VEC)

Talimogene laherparepvec (T-VEC) is a genetically modified herpes simplex virus-1-based oncolytic immunotherapy and has been approved for the local treatment of unresectable (stage IIIB/C and IVM1a) cutaneous melanoma. During T-VEC treatment, tumor response is often evaluated using [18F]2-fluoro-2-deoxy- d-glucose(FDG) positron emission tomography/computed tomography (PET/CT). In a Dutch cohort (n = 173), almost one-third of patients developed new-onset FDG uptake in uninjected locoregional lymph nodes during T-VEC. In 36 out of 53 (68%) patients with new nodal FDG uptake, nuclear medicine physicians classified this FDG uptake as "suspected metastases" without clinical or pathological confirmation in the majority of patients. These false positive results indicate that new-onset FDG uptake in locoregional lymph nodes during T-VEC treatment does not necessarily reflect progressive disease, but may be associated with immune infiltration. In current clinical practice, physicians should be aware of the high false positive rate of FDG uptake during treatment with T-VEC in patients with melanoma. Therefore, pathological examination of lymph node lesions with new FDG uptake is recommended to differentiate between progressive disease and immune infiltration after treatment with T-VEC.