hybrid bone scintigraphy in gastrointestinal malignancies – institutional experience

Objective: Bone metastases in gastrointestinal (GI) malignancies are uncommon and known to be predominantly lytic thus rendering a limited role for conventional bone scintigraphy. The aim of the study is to review Tc99m MDP bone scans performed in patients with known GI malignancy and the utility of Single-photon emission computed tomography (SPECT)/CT in characterization of bone lesions. Methods: Retrospective review of bone scans was done from June 2014 to December 2016 in patients with known GI malignancy, using electronic Hospital Information System. Results: A total of 110 patients (60 males, 50 females; Age range: 22–84 years, Mean Age 51.4 years with SD of 14.8) had bone scan over a period of 30 months. The commonest indications for referral were suspected bone metastasis on other imaging modalities including [CT (n = 56), Magnetic resonance imaging (n = 10), Positron emission tomography/CT (n = 6)], musculoskeletal pain (n = 37), pathological fracture (n = 1), neurological symptoms (n = 1), hypercalcemia (n = 1) and others (n =14) including restaging workup etc. Metastatic lesions were identified in 32 (29%) patients whereas 78 (71%) patients had benign non-aggressive lesions leading to normal bone scans. Among 32 patients with osseous metastasis, 8 (25%) patients had unifocal lesion; axial skeleton (n = 2) appendicular skeleton (n = 6), 24 (75%) patients had multifocal lesions; axial skeleton (n = 6), appendicular skeleton (n = 6) and both axial + appendicular (n = 12). Four (12%) patients had concurrent visceral metastases. In our cohort, based on the location of primary tumour, the frequencies of osseous metastasis were; esophagus = 15 out of 43 (35%), gastric = 7 out of 18 (39 %), gastro-esophageal junction = 1 out of 8 (1.5%) and colorectal = 9 out of 40 (22.5). SPECT/CT was acquired in 29 out of 110 patients, which characterized metastatic lesions (n = 12) and benign looking non-aggressive entities (n =17). Overall, bone scan upstaged disease in 31% and down staged 15% patients. Conclusion: Bone metastases in GI malignancies, though uncommon, show an aggressive pattern, with axial and appendicular involvement, and can be readily identified with hybrid bone scintigraphy in symptomatic patients.   Key words: Hybrid imaging, Tc99m MDP, bone metastases, gastrointestinal malignancies