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What Is the Clinical Importance of Incidental Findings on Staging CT Scans in Patients With Sarcoma?

Mayo, Zachary, BS; Kennedy, Sean, BS; Gao, Yubo, PhD; Miller, Benjamin J., MD, MS

Clinical Orthopaedics and Related Research®: April 2019 - Volume 477 - Issue 4 - p 730–737
doi: 10.1007/s11999.0000000000000149
2017 MUSCULOSKELETAL TUMOR SOCIETY PROCEEDINGS
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Background Baseline staging CT scans are performed on nearly every patient after the diagnosis of a sarcoma to evaluate for the presence of metastatic disease. These scans often identify abnormalities that may or may not be related to the known malignancy. Despite the high frequency of incidental findings, there is little guidance for clinicians faced with assessing these radiographic abnormalities. The interpretation of incidental findings is important because it may influence decisions regarding surveillance frequency, prognostic estimation, and surgical and medical intervention.

Questions/purposes The purpose of this study was to determine (1) the frequency of abnormal findings and indeterminate nodules on staging CT scans; (2) the natural history of indeterminate nodules identified at the time of sarcoma diagnosis; and (3) the factors associated with indeterminate nodules representing true metastatic disease.

Methods Between September 2010 and February 2016 we treated 233 patients with bone and soft tissue sarcomas. Of those, 227 (97%) had a staging CT scan of the chest or chest/abdomen/pelvis performed within 2 months of diagnosis. To be eligible for this retrospective study, a patient had to have a minimum of 6 months of radiographic followup after that initial CT scan. A total of 36 (16%) were lost to followup or did not have radiographic surveillance at least 6 months later, and 48 (21%) were excluded for other prespecified reasons, leaving 149 patients for evaluation. We recorded all abnormal findings listed in the official radiology CT report of the lung, bone, liver, and lymph nodes. We assessed progression of indeterminate nodules by reviewing radiology reports, which listed both size and number of findings, and clinical notes outlining the current assessment of disease status and treatment plan. If indeterminate nodules grew in size or number consistent with metastatic disease or were confirmed histologically, they were considered to represent true metastasis. Bivariate methods were used to investigate an association between various clinical factors, which were obtained from chart review, and progression of indeterminate nodules to clear metastatic disease.

Results One hundred thirty-five of 149 patients (91%) had at least one abnormal finding on a staging CT scan. Forty-nine patients (33%) presented with indeterminate lung nodules, 15 (10%) with indeterminate liver lesions, four (3%) with indeterminate bone lesions, and 57 (38%) with enlarged lymph nodes. Fifteen of the 49 patients with indeterminate lung nodules (31%), one of 15 liver nodules, zero of four bone lesions, four of 13 lymph nodes 1 to 2 cm in size, and two of 44 subcentimeter lymph nodes (4.5%) were clearly metastatic on followup. A primary tumor size ≥ 14 cm in greatest dimension was more suggestive of indeterminate nodules representing true metastatic disease compared with smaller primary tumors in both lung (eight of 10 compared with seven of 36 [19%]; odds ratio, 16.6; 95% confidence interval, 2.9-95.9; p < 0.001) and lymph nodes (six of 18 compared with zero of 36 [0%], p < 0.001).

Conclusions It is extremely common for abnormal findings and incidental nodules to be present at the time of a staging CT scan in patients with sarcoma. Although patients with indeterminate nodules should have continued surveillance, it appears from this study that the majority of these findings do not represent true metastatic disease. Given a minimum followup of 6 months, it is possible the actual proportion of indeterminate lesions representing true metastatic disease may increase over time.

Level of Evidence Level III, prognostic study.

Department of Orthopaedics and Rehabilitation, University of Iowa, Iowa City, IA, USA

B. J. Miller, University of Iowa Department of Orthopaedics and Rehabilitation 200 Hawkins Drive 01015 JPP Iowa City, IA 52242, USA email: benjamin-j-miller@uiowa.edu

Each author certifies that neither he, nor any member of his immediate family, has funding or commercial associations (consultancies, stock ownership, equity interest, patent/licensing arrangements, etc) that might pose a conflict of interest in connection with the submitted article.

All ICMJE Conflict of Interest Forms for authors and Clinical Orthopaedics and Related Research® editors and board members are on file with the publication and can be viewed on request.

Each author certifies that his institution approved the human protocol for this investigation and that all investigations were conducted in conformity with ethical principles of research.

Received August 15, 2017

Accepted December 7, 2017

© 2019 Lippincott Williams & Wilkins LWW
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