CORR Insights®: What Is the Prevalence of Clinically Important Findings Among Incidentally Found Osseous Lesions?

Where Are We Now?

The frequency of discovering an incidental bone lesion on an imaging diagnostic test ranges from 2% to 10% [4-7]. This topic is relevant to clinicians of all disciplines, patients, and healthcare systems because of the high cost it carries. All too often, a diagnostic imaging study—such as an MRI of an intraosseous lipoma or enchondroma or an x-ray of a nonossifying fibroma—lists benign and malignant tumors in the differential, prompting referral to an orthopaedic oncologist or further imaging. In the vast majority of such instances, the imaging is diagnostic, and subsequent imaging and referral to an orthopaedic oncologist is not necessary or worthwhile [1]. More concerning is when a clinically important finding is ignored because the clinician thinks the word “incidental” implies unimportant.

Against that background, the current study in Clinical Orthopaedics and Related Research® by Blackburn et al. [2] found that about 7% of incidental bone lesions referred to two experienced orthopaedic oncologists at two academic institutions were concerning enough to get a biopsy, and of those, about 2% were malignant. Although surveillance rarely resulted in a change of management, the authors found that the median cost of following these lesions was also low. While the incidence of clinically significant findings was minimal, surgeons must acknowledge that the implications are profound for the 2% of patients with malignant bone lesions. We must avoid “playing the odds” by simply ignoring an incidental finding. When confronted with an incidental finding, the surgeon must determine the extent to which they can be certain that the finding is not significant. The surgeon should avail themselves to available experts, such as a musculoskeletal radiologist and orthopaedic oncologist, who may be more well versed in the management of skeletal lesions.

Where Do We Need To Go?

While the current paper sheds light on incidental bone lesions, it did not provide information on the type of imaging study that prompted the referral to an orthopaedic oncologist. Additionally, the quality of the interpretation of the imaging study (which is largely subjective and difficult to quantify), or the experience of the radiologist and/or referring physician, was not reported. It is important for future studies to ascertain whether these factors make a difference, since this could inform educational efforts oriented at helping referring physicians.

The practice of defensive medicine because of real or perceived risk of litigation may be important, but its impact on this topic is not known. In an effort to address this issue, the Society of Skeletal Radiology proposed an algorithm [3] for reporting incidental bone lesions found on MRIs and CTs. The algorithm makes recommendations from “leave alone” to “surveillance” to “biopsy and/or re-referral to orthopaedic oncology.” This is a step in the right direction, and the algorithm is a thoughtful one: It takes into consideration important clinical information, such as a prior history of cancer. The importance of clinical history is emphasized in the current study [2] as well, as evidenced by the increased odds of clinically important findings being observed in patients with a prior cancer diagnosis.

The current study includes only patients referred to and seen by an orthopaedic oncologist, which is a specific patient demographic that already has access to an orthopaedic oncologist. This access is influenced by geographic, economic, and insurance status; it would be interesting if future studies could assess the impact of access to specialists for underserved populations, such as those who are under- or uninsured and/or who live in remote settings. Remote consultation with an orthopaedic oncologist could increase access while reducing cost and other barriers. Finally, many patients benefit from the common practice of informal consultation that takes place between orthopaedic surgeons, orthopaedic oncologists, and radiologists and are never referred for imaging or consultation.

How Do We Get There?

Just like the evaluation of a patient with an incidental bone lesion requires the collaboration of clinicians and radiologists, so too will future studies to identify the prevalence of clinically important findings among incidentally found osseous lesions. This would ideally involve a multicenter prospective data collection study that includes longitudinal clinical follow-up. All patients with incidental bone lesions should be included. A relatively small group of participating institutions (five centers or more) could enroll the sufficient number of patients with a follow-up period of two years or more without incurring substantial additional costs or time. The prospective nature would allow further investigation of a diverse patient population, including those who did not get referred to an orthopaedic oncologist. As such, it would include those who had an informal consultation with a specialist without a documented patient visit to an orthopaedic oncologist, which would likely increase the reported rate of incidental findings. More importantly, this study would include those patients who may have been referred to an orthopaedic oncologist but were never seen, as may be the case with individuals who need to travel a longer distance for specialty care and do not have the financial resources to do so.

Such a study would validate the unvalidated guidelines proposed by the Society of Skeletal Radiology [3] for the incidental solitary lesion identified on CT and MRI in adults. It could also inform the creation of guidelines for further management of incidentally found lesions in children and adults, both on radiographs and other treatment modalities. While such studies can be time consuming and expensive, they could be accomplished through efforts of the Musculoskeletal Tumor Society (MSTS), whose members include community and academic fellowship-trained orthopaedic oncologists and many musculoskeletal radiologists.