Osteoblastic Changes During Non-Small Cell Lung Cancer (NSCLC) Treatment:How to Distinguish between Objective Response and Progressive Disease

Bone metastases are common in disseminated NSCLC, occurring in approximately 30% to 40% of patients [2]. In the majority of cases, they present an osteolytic imaging pattern, even though osteoblastic or mixed-type patterns have also been reported in nearly 8% of cases [3,4]. Generally, in the assessment of objective response to anticancer agents, bone metastases are classified as non-target lesions and therefore “not evaluable” for response. However, according to the revised Response Evaluation Criteria in Solid Tumors guideline (RECIST version 1.1) [5], the appearance of new non-target lesions, including lytic or osteoblastic bone metastases, is a criterion for defining progressive disease. Sometimes, the evaluation of bone lesion response may be challenging and misinterpreted.