Abstract
Introduction:
25% of patients with an unknown primary tumour present to the orthopaedic surgeon with skeletal metastases. The onus is on the orthopaedic surgeon to establish the diagnosis, not only to decrease the patient's anxiety but also because the median survival increases from 6–9 months to 23 months when the primary is identified and allows for specific cancer treatment. The diagnostic work up of an unknown primary includes a multitude of special investigations.
Since PET/CT has high sensitivity and specificity for detecting the primary tumours, we asked the question: Can you diagnose the unknown primary in patients with skeletal metastases with a PET/CT?
Method:
We included all PET/CT scans done in our institution between 2010 and 2013 for patients with malignancies known to metastasize to bone (melanoma, breast, lung, head and neck, GIT, other) and all scans done in patients with unknown primaries. After reviewing 686 PET/CT scans, 492 showed metastatic disease, with 78 of these having either spinal or skeletal metastases.
Results:
Of these 78 patients, 68 primaries could be detected on the PET/CT scan. Thus the PET/CT detected the primary in 87% of cases. This number could possibly be higher as some were melanoma and breast cancer patients who had already undergone surgical resection. The most common primary detected was lung, followed by a group of other and unknown primaries which included cervical, kidney and thyroid carcinoma.
Conclusion:
PET/CT scan is a good modality to use when looking for a primary malignancy in patients who present to the orthopaedic surgeon with bone metastases. We postulate that this might be a possible first line investigation when looking for the primary.
