Sarcoid-like reaction mimicking disease progression in an ALK-positive lung cancer patient receiving lorlatinib

The administration of target inhibitors is paramount to grant the longest survival in patients with ALK-positive non-small cell lung cancer (NSCLC). The eventual resistance to tyrosine kinase inhibitors (TKI) is monitored clinically and radiologically for prompt molecule shift to further generation TKI, if available. However, the early radiological detection of progression pattern (e.g. nodule onset) should be regarded with caution because overlaps exist with non-tumor cell proliferation and/or accumulation. Here we report the case of a stage IV ALK-rearranged NSCLC patient exposed to serial crizotinib, brigatinib, ceritinib, and lorlatinib (this latter brought to complete brain and leptomeningeal disease response), in a period of more than five years. During lorlatinib, the appearance of solid pulmonary nodules was obviously interpreted as disease progression. However, surgical biopsies of the pulmonary nodules revealed features of sarcoid-like granulomatous lymphadenitis, namely without tumor cell. This invasive approach, besides documenting for the first time a sarcoid-like reaction to ALK inhibitors, allowed to revert the radiological diagnosis and maintain lorlatinib, for the best patient outcome. The pragmatic relevance of these findings suggests a careful attitude towards the interpretation of radiologic patterns of disease progression in patients under TKI.