CT halo sign as an imaging marker for response to adoptive cell therapy in metastatic melanoma with pulmonary metastases.

OBJECTIVES: The halo sign refers to a zone of ground-glass attenuation surrounding a pulmonary nodule. Pulmonary metastatic nodules exhibiting a halo sign are seen mainly in hypervascular tumours. We describe the appearance of a halo sign following treatment of adoptive transfer of autologous tumour-infiltrating lymphocytes (TIL) to melanoma patients with lung metastases.
METHODS: The study included 29 melanoma patients with pulmonary metastases who received TIL therapy. Pre- and post-treatment chest CTs were retrospectively reviewed for the presence of a halo sign and its correlation with therapeutic response.
RESULTS: A pulmonary halo sign was not seen in any pre-treatment CT. It was observed in four of 12 patients who responded to the therapy but not in those who failed to respond. Significant differences were found between response ratio in patients in whom post-TIL halo sign appeared compared with those without the halo sign (p = 0.02).
CONCLUSIONS: The appearance of a CT halo sign in melanoma with lung metastases following TIL therapy may indicate antitumoral effect and a good response to therapy. Our findings emphasize the importance of applying new assessment criteria for immunological anticancer therapies. KEY POINTS: Tumour-infiltrating lymphocytes (TIL) in melanoma patients is a promising novel immunotherapy. Post-therapy pulmonary halo sign appeared in one-third of TIL responders . Pulmonary halo sign may serve as an imaging marker for antitumoral activity.