Diagnostic accuracy of chest computed tomography in diagnosis of lung tumors among adults based on histopathology at Moi Teaching and Referral Hospital

Abstract

Background: Globally, lung cancer is the leading cause of cancer incidence and mortality, accounting for about 2 million diagnoses and 1.8 million deaths (18.4% of cancer deaths). In Kenya, lung cancer is ranked as the fourteenth cause of cancer morbidity and mortality. The burden of lung cancer in the adult population is largely unknown, as most patients are managed for pulmonary tuberculosis because of similar clinical manifestations. Most lung cancer patients in Kenya are diagnosed late when the disease is in its advanced stages, due to the long waiting time for definitive diagnosis from biopsy and histopathology studies. Chest Computed Tomography (CT) scan comprehensively evaluates lung tumors based on morphology and can stage the disease due to ability to reduce overlap from lung lesions, bones and mediastinal structures, and identify adenopathy. Image-guided biopsy and histopathology studies give definitive diagnosis when pre-biopsy evaluation and imaging highly suggests a lung tumor, but these services are limited mostly to referral hospitals. Objectives: To describe the chest CT and histopathologic findings of lung tumors, and to determine the diagnostic accuracy of chest CT in the diagnosis of lung tumors based on histopathology among adults at Moi Teaching and Referral Hospital (MTRH). Methods: This was a cross-sectional study conducted at the Radiology and Imaging Department between October 2021 and September 2022. A consecutive sampling method was used to enroll 86 participants. Chest CT images were acquired using the 128 slice Neo-soft 4000 Dual CT machine. Adults with suspected lung tumors from chest CT scan underwent image guided biopsy at the Interventional Radiology (IR) unit and histopathology results were obtained from histopathology laboratory. Data was collected using a data collection form, where demographics, chest CT findings and histopathological findings were recorded. Continuous variables were summarized using mean, median and standard deviation whereas categorical variables were summarized in frequency tables, percentages, charts and bar graphs. Analysis of data was done using STATA version 16 to determine correlation between chest CT and histopathology findings. The sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), positive likelihood ratio (PLR), and negative likelihood ratio (NLR) were determined from the 2X2 table. The diagnostic accuracy was determined by Cohen‟s kappa statistic. Results: The female to male ratio was 9:8 (52.3:47.7%). The mean age of the participants was 55 years (range 23-86 years, S.D. of 15.57). Malignant features were seen in 76.7% of chest CT scans and benign in 23.3%. Suspicious features of lung tumors on chest CT included: solid components, intense homogenous enhancement, irregular margins and lymphadenopathy. On histopathology, malignant tumors accounted for 86.0% while benign tumors were 14.0%. The commonest malignant lesion on histopathology was adenocarcinoma (51.2%). Chest CT had a diagnostic accuracy of 91.86%, sensitivity of 98.46%, specificity of 71.43 %, PPV of 91.43%, NPV of 93.75 %, with a PLR and NLR of 3.38 and of 0.17 respectively, in the detection of lung tumors. There was substantial agreement between CT and histopathology findings with Cohen‟s kappa, κ = 0.764, p < 0.0001. Conclusion: The common tumor on chest CT findings was the malignant type. The prominent tumor on histopathology findings was also the malignant type, with the major histopathologic sub-type being adenocarcinoma. Chest CT demonstrated a high diagnostic accuracy, sensitivity and specificity in detecting lung tumors based on the obtained histopathology results. Recommendation: There should be increased awareness among radiologists and clinicians on high index of suspicion for lung malignancy based on the salient chest CT features, especially where IR and histopathology services are limited. Chest CT can be used for pre-biopsy screening of lung tumors owing to its high sensitivity and specificity.