Evaluation of asymptomatic skeletal metastasis by 99mTc MDP bone scans in NSCLC patients attending INMAS, Rajshahi

Background: Lung cancer is the leading cause of cancer deaths worldwide. Lung cancer is often insidious, producing no symptoms until the disease is well advanced. In approximately 7-10% of cases, lung cancer is diagnosed in asymptomatic patients. Some patients are asymptomatic for skeletal metastasis and a recent prospective study showed that in staging of non-small cell lung cancer (NSCLC), failure to perform a bone scan could miss asymptomatic bone metastasis in 14–22% of patients. Radionuclide bone scintigraphy with 99m Tc MDP (Technetium-99mmethylene diphosphonate) is very useful nuclear imaging tool to detect skeletal metastasis with a sensitivity of 98.2% and a specificity of 95.2%. The aim of this study was to detect the asymptomatic skeletal metastasis of non-small cell lung cancer patients by 99mTc MDP bone scan. Patients and methods: It is a retrospective study, carried out from January 2015 to December 2016 in Institute of Nuclear Medicine and Allied Sciences, Rajshahi. Bone scan was performed by an intravenous bolus injection of 20 m Ci 99mTc MDP. Bone phase images were taken at three hours after injection of the radiotracer. Results: A total of 52 patients were enrolled in the study. The mean age of the patients was 57.6 ± 14.5 years (mean ± SD) with range from 36 to 75 years and 42 (80.77%) were male and 10 (19.23%) were female. Out of 52 patients, only 06 (11.54%) patients were diagnosed as positive and 46 (88.46%) were negative for bone metastasis. Out of 06 patients with positive skeletal metastasis 04 (66.67%) patients had multiple sites (two or more) and 02 (33.33%) patients had solitary site of bone involvement. Common sites of metastasis were in thoracic (83.33%) and lumbar spine (83.33%), ribs (50%), pelvic bones (33.33%), long bones (16.66%), skull (16.66%) and other bony sites including clavicle, sternum, scapula, sacrum (16.66%). Regarding staging prior to bone scan, out of 06 bone scan positive patients 03 (50%) patients were in stage III, 02 (33.33%) patients were in stage IV and 01(16.67%) patient was in stage II. On the basis of histopathology, out of 06 skeletal metastatic patients 04 (66.67%) patients had adenocarcinoma, 01 (16.67%) patient had squamous cell carcinoma and 01 (16.67%) had large cell carcinoma. The exclusion of bone metastasis is important in the initial staging of non-small cell lung cancer. Conclusion: There is debate about whether bone scans should be performed routinely or restricted to patients who present with clinical or laboratory indicators suggesting skeletal metastasis. The present study indicates