A Prospective Study on Stage Distribution of Lung Cancer at Clinical Suspicion, Histological Diagnosis and Pet-Ct Confirmation

Abstract

Background: Lung cancer is the most common cause of death from cancer worldwide and is still a major public health problem. Accurate staging is required for selection of the appropriate treatment modality and for prediction of prognosis. Traditional imaging modalities may underestimate or overestimate the extent of disease. The diagnosis is confirmed histopathologically but this does not define the full anatomic extent of disease. Positron Emission Tomography-Computed Tomography (PET-CT) combines metabolic and anatomic imaging and can improve the accuracy of staging by detection of occult nodal and distant metastases.

Objectives: To compare lung cancer stage distribution at clinical suspicion, histological diagnosis and PET-CT confirmation to evaluate the impact of PET-CT on stage migration.

Methods: An observational prospective study was carried out in Department of Respiratory Medicine, Coimbatore Medical College Hospital. We included fifty consecutive patients with a clinical suspicion of lung cancer who underwent histopathological confirmation and PET-CT staging after providing informed consent. Demographic details, smoking history, clinical findings, radiological investigations, histopathological diagnosis and PET-CT findings were noted. Patients with non-small cell lung carcinoma (NSCLC) were staged according to the 8th edition of the TNM classification. Patients with small cell lung carcinoma (SCLC) were classified as limited-stage or extensive-stage disease. Statistical analysis was performed using software SPSS. Continuous variables were expressed as mean ± standard deviation and categorical variables as frequency and percentage. Appropriate tests were performed using chi-square test, Fisher's exact test, and McNemar test. A p-value of <0.05 was considered statistically significant.

Results: Fifty patients were included in the study with a mean age of 62 ± 10 years. Forty-two patients (84%) were males and thirty-four patients (68%) had a history of smoking. Histopathological examination showed adenocarcinoma in 34 patients (68%), squamous cell carcinoma in 2 patients (4%) and small cell lung carcinoma in 14 patients (28%). In 36 patients with NSCLC PET-CT upstaged 26 patients (72.2%), down staged 8 patients (22.2%) and there was no stage change in 2 patients (5.6%). A highly significant difference was found between the clinical TNM stage and the PET-CT TNM stage (McNemar test, p<0.001).14 patients had SCLC, of whom eight had limited stage disease and six extensive stage disease at clinical assessment. PET-CT changed the classification of six of the eight limited-stage patients to extensive-stage disease, while the other two limited-stage patients and all six extensive-stage patients were unchanged. PET-CT resulted in upstaging in 32 patients (64%), downstaging in 8 patients (16%) and no stage change in 10 patients (20%).

Conclusion: PET-CT is a very useful tool to increase the accuracy of staging in lung cancer, by detecting occult nodal and distant metastases. Stage migration was significant after PET-CT, particularly in patients with NSCLC. PET-CT also identified occult extensive-stage disease in patients with SCLC, thereby impacting treatment planning. The routine inclusion of PET-CT in the staging work-up of lung cancer may improve therapeutic decision-making and optimize patient outcome.