High prevalence of osteoblastic bone reaction in computed tomography scans of an European Organisation for Research and Treatment of Cancer prospective randomised phase II trial in extensive stage small cell lung cancer

Background: Osteoblastic bone reaction is an important phenomenon defined by an increase in apparent bone density of previously known bone metastasis or development of new osteoblastic lesions in the presence of response in other tumour sites. Osteoblastic bone reaction in lung cancer has only been described in a few reports and mostly in patients with pre-existing bone metastasis. Methods: In this report we present the data of an independent, blinded and preplanned radiological review of the occurrence of osteoblastic lesions in patients with extensive stage small cell lung cancer (SCLC). The computed tomography (CT) scans of the chest and upper abdomen of 71/88 patients who had an investigator reported complete response (CR), partial response (PR) or stable disease (SD) were retrospectively analysed for the development of osteoblastic lesions. Furthermore, baseline exams were reviewed for the presence and location of bone metastasis and local radiological reports were reviewed for any knowledge of bone metastasis. Results: There were 14 patients with osteoblastic bone lesions in the reviewed follow-up CT scans. Three patients had known bone metastases at baseline, and 11 patients had no history or findings of bone metastases on the baseline scan. During the course of the disease, 13 out of 14 patients developed new osteoblastic lesions, while all responded in other sites. The prevalence of osteoblastic bone reaction in our study was 19.7%. Conclusion: In this study osteoblastic bone reaction was observed in a larger number of patients without previously documented bone metastases, indicating a high prevalence of occult bone metastases in SCLC. If bone metastases are not documented at diagnosis, then osteoblastic bone reaction may cause confusion in a responding patient. (C) 2012 Elsevier Ltd. All rights reserved.