Introduction
Most head and neck cancers arise from cells in the moist tissue that lines the internal organs and cavities of the mouth and nose, including the lips, gums, tongue, sinuses, pharynx, and larynx. Head and neck cancer treatment includes surgery, radiation therapy, and chemotherapy. New advances in molecular imaging are dramatically improving the way head and neck cancer is diagnosed and treated. Research in the field of molecular imaging has also contributed to our understanding of this disease, leading to more effective treatments for patients with head and neck cancer.
What Is Molecular Imaging?
Molecular imaging is a branch of the field of medical imaging that gives a detailed picture of what is happening inside a person’s body at the molecular and cellular levels. While other imaging modalities such as X-rays, computed tomography (CT), and ultrasound primarily provide anatomical images, molecular imaging allows doctors to see how the body functions and its chemical and biological processes can be measured.
What Are the Benefits of Molecular Imaging in Head and Neck Cancers?
Molecular imaging offers deep insights into the human body that enable doctors to personalize patient care. Molecular imaging techniques are non-invasive, safe, and painless. In terms of diagnosis, molecular imaging:
-
Provides information not available with other imaging techniques or requires more invasive procedures such as biopsy or surgery.
-
Detect disease at an early stage and pinpoint the exact location of tumors. Abnormalities can often be detected before symptoms appear or by other diagnostic tests.
-
Determining the extent or severity of the disease, including whether the disease has spread to other parts of the body.
-
Choose the most effective treatment based on patient-specific biological and molecular characteristics of the tumor or other disease.
-
Determining a patient's response to certain drugs.
-
Accurately assess the effectiveness of treatment plans.
-
Rapidly adjust treatment regimens in response to changes in cellular activity.
What Molecular Imaging Methods Are Used for Head and Neck Cancers?
The most commonly used molecular imaging modality for diagnosing or treating head and neck cancer is positron emission tomography (PET), often combined with CT.
-
Positron Emission Tomography (PET) - It includes an imaging device (PET scanner) and a radioactive tracer injected into the bloodstream of the patient. A commonly used PET radiotracer is 18F-fluorodeoxyglucose (FDG). This compound is made from simple sugars and a small amount of radioactive fluorine. When the FDG radiotracer accumulates in body tissues and organs, its natural decay involves the release of small particles called positrons that react with electrons in the body. This reaction is called annihilation. It produces energy in the form of photons. A PET scanner capable of detecting these photons makes a three-dimensional image showing how the FDG is distributed in the examined body region. Areas, where large amounts of FDG accumulate, are called 'hot spots' because they appear stronger than the surrounding tissue, indicating areas of high chemical activity and metabolism. Areas of low metabolic activity appear less intense and are sometimes known as cold spots. Using these images and the information they contain, doctors can assess how well organs and tissues are functioning and identify abnormalities.
- PET-CT: It combines PET with CT to provide highly detailed body images. Combining two techniques, called co-registration, fusion imaging, or hybrid imaging, allows the display of information from two different scans in one set of images. CT imaging uses advanced X-ray equipment and sometimes contrast medium to create three-dimensional images. A combined PET-CT examination can provide details about both anatomy and function of organs and tissues. This is achieved by superimposing the precise location of abnormal metabolic activity (from PET) and detailed anatomical images (from CT).
How Is a PET Scan Performed?
The procedure starts with injecting an intravenous (IV) radiotracer such as FDG. This usually takes 30 to 60 minutes to spread throughout the body. The patient is then placed inside the PET scanner, which includes a special detector to form a three-dimensional image of FDG distribution. The scans are reviewed and interpreted by qualified imaging professionals, such as nuclear medicine physicians and radiologists, who share the results with the patient's primary care physician.
How Is PET Scan Used for Head and Neck Cancers?
Doctors diagnose head and neck cancer and formulate a treatment plan using PET scans.
- Diagnosis and Staging - By determining the exact location of the tumor, the extent or stage of the disease, and whether cancer has spread through the body.
-
Treatment Plan - By choosing the most effective treatment based on the unique molecular characteristics of the disease and the patient's genetic makeup.
-
Assessment of Therapeutic Efficacy - By determining a patient's response to specific medications and ongoing therapy, one can quickly change treatment plans based on changes in cell activity observed on PET-CT images.
-
Manage Continuing Care - By detecting cancer recurrence.
What Are the Various Advantages of PET Scans for Patients With Head and Neck Cancers?
-
PET scanning has been a very important advance in the field of head and neck cancer staging in recent years.
-
A PET scan is an extremely powerful tool for diagnosing and staging many types of head and neck cancer.
-
The National Comprehensive Cancer Network (NCCN) includes the PET-CT in its practice guidelines for managing most malignancies.
-
With the detection of whether lesions are benign or malignant, PET scans can eliminate the need for surgical biopsies and, whenever biopsies are necessary, identify the best sites for conducting biopsies.
-
PET scans help doctors choose the most appropriate treatment plan for cancer and assess whether chemotherapy and other treatments are working as intended.
-
PET scans are now the most effective means of detecting cancer recurrence.
Conclusion
Molecular imaging advances the understanding of the underlying causes of disease and improves the detection and treatment of the disease. Molecular imaging technology also plays an important role in the development of a screening tool by providing a non-invasive and highly accurate method for assessing at-risk populations. It also helps develop new, increasingly effective drugs by enabling researchers to understand and evaluate new drug therapies quickly. It helps in personalized medicine, where treatment is based on a patient's unique genetic profile.
