PET CT in Lung Cancer: A Life-saving Investigation

BY: Dr Ganesh Kumar - 20 Nov-2021

Lung cancer has not only been the leading type of cancer to affect humanity, but it has also been a malignancy associated with significant morbidity and early mortality among all cancers. However, extensive clinical research in recent times has gone into understanding, diagnosing and managing this pathology. This in turn has significantly reduced the possibility of adverse outcomes in the course of treatment of lung cancer.

Cancer in any organ of the body poses a variety of challenges to the treating specialist as much as it affects the patient. These challenges may range from achieving an early diagnosis to other major factors such as staging, response monitoring, confirmation of remission and surveillance following remission. 

PET CT AND CANCER

The utility of PET CT lies at the heart of cancer imaging, as it is used rather commonly in patients diagnosed with cancer. In short, for PET CT imaging (or ‘PET Scan’ in colloquial terms), specialized molecules tagged with radioactive elements are injected into the patient and subsequently images are acquired which yield information about the extent, nature as well as behaviour of a disease. In the context of lung cancer, radio tagged modified glucose molecule called F-18 FDG (FDG in short) is used extensively. It is drawn from circulation by cells and tissues and utilized in a manner similar to its parent molecule, glucose. Thus, cancer cells which are often aggressive in nature with high metabolic demands accumulate FDG at a higher rate than normal cells. On PET Scan, this mechanism is utilized to understand and interpret disease behaviour in a patient suspected/diagnosed with cancer.

PET CT AND LUNG CANCER

PET CT is a robust investigation, employed in almost every aspect of lung cancer imaging. It provides a plethora of advantages; to name a few, these include whole body imaging, extraction of structural and functional information with a single investigation, and identifying/monitoring metabolic signature of the disease.

When a patient suspected with lung cancer undergoes his/her PET CT, the information provided can help reduce/remove any ambiguities, define extent of the disease and guide the referring specialist towards the most optimal site for tissue sampling. In many patients it also provides other pieces of information such as involvement of critical structures and any coexistent pathologies (within and outside lungs).

Once the diagnosis is confirmed, due to its inherent advantage as a whole-body imaging modality, PET Scan is often used to define the extent of the disease. Based on the disease extent, the modality helps in choosing the next best step in management (viz. surgery, radiotherapy, chemotherapy or targeted therapies).

Also, once any form of treatment is initiated, it is imperative to monitor its effect on the patient such that decisions can be taken by the treating clinician at critical junctures. Since the metabolic response has been proven to be a better prognosticator in cancerous tissues rather than shrinkage in their size, PET CT helps in monitoring response to therapy in patients with lung cancer. Also, once the treatment is completed, PET CT is used to confirm cure/disease remission in these patients. Once in remission, a surveillance PET CT is routinely advised time-to-time in order to confirm remission or look for any disease recurrence.

PET CT IN LUNG CANCER IN THE ERA OF PANDEMIC

The onset of global pandemic has brought its own set of challenges in cancer imaging. In our personal institutional experiences, PET CT has sometimes helped identify incidental active COVID-19 pneumonia in patients with lung cancer and vice versa. Identifying such findings helps the patient as well as the treating doctor in taking necessary measures in treating both pathologies.

CONCLUSION

To conclude, PET CT plays a major role in the management of lung cancer in every step of its management. Due to its many inherent advantages, this modality helps in having a holistic and individualized approach in the diagnosis and treatment of this pathology. The crucial role of PET CT is highlighted by its inclusion in multiple international lung cancer diagnostic and treatment monitoring guidelines.

By - Dr Ganesh Kumar M, Consultant, Nuclear Medicine,
        HCG EKO Cancer Centre, Newtown, Kolkata

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