Frequency of superscan on bone scintigraphy: A systematic review

Bone scintigraphy (BS) is an important tool for detecting bone metastasis. BS with diffuse increased skeletal radioisotope uptake with absent or faint urinary tract and soft tissue activity is defined as a superscan. In this review, we investigate the different etiologies causing superscan and the reported frequency of superscan among different disease entities.

The search terms were 'bone' AND 'superscan' OR 'superscan' in the PubMed database from 1980 to November 2020. Eligibility criteria included the following: Peer-reviewed studies containing original data using 99mTc-phosphate-analogue BS reporting a superscan pattern. Unretrievable papers, imaging modalities other than BS or with insufficient information to assess the aetiology were excluded. The abstracts of every paper and full texts of potentially eligible papers were assessed independently by three observers.

Sixty-seven papers were included (48 case reports and 19 cohort studies). Studies conducted in patients with osteomalacia or skeletal fluorosis revealed superscan in all patients. Other benign causes of superscan were hyperparathyroidism and kidney disease. Among papers with malignant cause, prostate cancer was the most common cause, followed by gastric cancer. The frequency of superscans ranged from 1.3% in a cohort of mixed cancer types up to 2.6% in patients with gastric cancer and up to 23% in a cohort of prostate cancer patients.

Superscan is most frequently seen in prostate cancer, but numerous other cancers and metabolic bone diseases can cause superscan, which should be kept in mind when encountering an unexpected superscan on BS.