Importance of PET scan In Cancer Diagnosis

Positron emission tomography (PET) is now a vital cancer imaging instrument, both for detecting and staging, as well as providing prognostic data based on the response. This report aims to analyze the value of PET in the locoregional comprehensively and distant staging of non-small cell lung cancer (NSCLC), illustrates the potential effects of patient management and give a short overview of new applications. PET sets the golden standard for the evaluation of an unknown solitary pulmonary nodule, where PET has proven to be significantly more approximate than computed tomography (CT) in the distinction between benign and malignant lesions. In the testing of metastatic reach to locoregional lymph nodes, PET is significantly more correct than CT, so that invasive surgical staging technique may be omitted in several patients with negative mediastinal PET images. Patients with positive mediastinal PET images experience invasive surgical staging technique, as it remains mandatory because of the chances of false-positive findings due to granulomatous disorders or inflammatory nodes. In the search for metastatic reach, PET is a useful adjunct to conventional imaging. It is due to the finding of unexpected metastatic lesions or due to the removal of malignancy in lesions that are equivocal on traditional imagery. Anyhow, at this time, PET does not restore conventional imaging. Large-scale randomized studies are presently examining whether PET staging will enhance the appearance of lung cancer outcome.

PET Benefits

PET is more beneficial in analyzing pleural effusions. Pleural involvement is relatively common in patients with lung cancer. Differentiation between benign and malignant effusion is vital in determining the resection and use of radiotherapy. Pleural thickening or nodularity on CT scan is suggestive of the metastatic pleural disease. CT is not conclusive of the benign or malignant nature of the pleural diseases. Similarly, MRI scan has failed to show high precision in differentiating benign from malignant pleural effusions. Thoracocentesis may not prove malignancy in 30–40% of patients with truly malignant pleural effusion. In one study, 35 patients with lung cancer and surprising pleural findings on CT underwent PET. Sensitivity, specificity, and exactness of FDG-PET were 89%, 94%, and 91%, respectively. In another study, the sensitivity, specificity, and accuracy were 95%, 67%, and 92%, respectively. The highly negative predictive value of PET in pleural effusions may be of help in lowering the number of repeat thoracoscopic or thoracocenteses biopsies in patients with negative PET findings and benign effusion.

Impact on Staging and Management

PET is an attractive staging instrument because of its ability to define the main tumor as well as distant and local metastases in a single non-invasive test, and because of its overall greater accuracy than standard imaging procedures, hence, the potential impact of PET on therapeutic management and stage designation. The use of PET scan for clinical staging resulted in various stages from the one determined by conventional methods in 27–62% of the patients with NSCLC.

Whether the use of PET enhances the management, NSCLC remains unsettled. There is evidence that PET reduces the requirement for the invasive process by more approximate staging. Whether it seemingly enhances the survival due to stage migration, or whether it truly can improve survival because of some better therapeutic strategies, remains to be determined.

Recommendations for PET in Staging of NSCLC

PET is useful in the evaluation of SPN’s and in the staging of NSCLC patients who are considered to be the candidates for radical treatment and also for cancer treatment in India. As a complementary instrument to CT, PET has become more universal and reimbursed in several countries. The additional primary interest of PET is its ability to assess the locoregional lymph node reach more precisely than CT, to diagnose metastatic lesions that would have been missed on conventional imaging or are located in clinically hidden or hard areas, and to support in the differentiation of lesions that are equivocal following conventional imaging.

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