It is widely known that diagnosing cancer at its earliest stages often provides the best chance for a cure. Naturally, in line with this, new technologies in healthcare are improving the way we diagnose and treat cancer.

Alongside physical exams, laboratory tests, and biopsies, imaging tests offer a non-invasive look at the body's internal structure and function. One such technology is the PET-CT scan. It combines two types of scans (Computed Tomography (CT) and Positron Emission Tomography (PET)) to create a detailed picture of the cancer's presence and progression in the body.

Let’s take a closer look at why a PET-CT scan is so important for cancer care.

What is the Purpose of a PET-CT Scan?

PET stands for Positron Emission Tomography, while CT stands for Computed Tomography—both of which are imaging modalities used in medical settings. A PET-CT combines both of these modalities into one scan, which allows doctors to get a detailed picture of what is happening inside the body.

The CT component uses X-rays to create detailed images of your organs and tissues. The PET scan uses a small amount of radioactive sugar to identify areas of high activity, which suggests the presence of cancer cells. By combining these two scans, doctors can accurately locate and assess any tumours or abnormalities.

CT Scan vs PET Scan: What Does a CT Scan Show that a PET Scan Doesn’t?

While both CT and PET scans are important for diagnosis, they provide different types of information.

A CT scan helps with the visualisation of bones, organs, and other tissues, allowing doctors to identify structural abnormalities, injuries, or signs of disease.

A PET scan, on the other hand, focuses on cellular activity. As mentioned, it uses a special substance to highlight areas of high metabolic activity, which is often a characteristic of cancer cells. This allows doctors to detect cancer in its early stages, even before it causes any noticeable changes in the body's structure.

What is the Role of PET-CT Scan in Cancer?

As mentioned, the PET-CT scan merges two imaging techniques, which enhances the accuracy of cancer diagnoses compared to using PET or CT scans separately.

For instance, CT scans are particularly useful for screening and early detection of cancers such as colorectal and lung cancer. They can help identify polyps and tumours even before symptoms appear.

PET/CT scans are valuable for a wider range of cancers, including:

• Colorectal cancer: PET/CT helps determine the stage of colorectal cancer and guides treatment decisions.
• Lung cancer: PET/CT aids in diagnosing lung cancer, staging the disease, and evaluating treatment response.
• Lymphoma: PET/CT is highly effective in staging lymphoma and assessing treatment response.
• Melanoma: For melanoma, PET/CT accurately stages the disease and helps identify any recurrence.

Therefore, this combination aids oncologists in several key areas:

• Tumour Assessment and Staging: PET-CT scans help determine the size and extent of a tumour, including whether it has spread (metastasised). This information is vital for cancer staging, which guides treatment decisions.
• Treatment Planning: The detailed images from PET-CT scans assist oncologists in evaluating the feasibility of surgery and selecting the most effective treatment strategies, such as radiation therapy, chemotherapy, or targeted therapies.
• Treatment Response Monitoring: PET-CT scans are essential for monitoring how a patient is responding to their treatment. They can distinguish between active tumour tissue and residual scar tissue, allowing oncologists to adjust treatment plans as needed.
• Surveillance and Early Recurrence Detection: PET-CT scans play a crucial role in long-term cancer surveillance. By detecting any recurrence early on, they enable prompt intervention and improve the chances of successful treatment.

What Makes PET Important for Cancer Imaging?

PET scans are uniquely capable of showing how your cells are working, not just what they look like. This is really important because:

• Visualisation of Metabolic Processes: PET scans illustrate the metabolic activity of tissues and organs, providing valuable insights into cellular function.
• Early Cancer Detection: PET scans can detect tiny changes in cells that might be the very first signs of cancer, even before tumours form.
• Treatment Effectiveness Assessment: PET scans can help doctors see if a treatment is effectively targeting a tumour or if it needs to be adjusted.
• Location and Activity Monitoring: By showing both the location and activity of cancer cells, PET scans help doctors make the best decisions for diagnosis and treatment.

How Accurate is a PET-CT Scan for Cancer?

According to the study “Use of PET/CT scanning in cancer patients: technical and practical considerations”, published by the National Library of Medicine, PET-CT scans demonstrate a higher accuracy rate in detecting cancer compared to individual PET or CT scans.

Specifically, while CT scans alone have an accuracy between 63% and 64%, PET scans alone perform better, with accuracy rates ranging from 86% to 90%. When combined into PET-CT, the accuracy further increases to between 84% and 93%.

This slight enhancement over standalone PET scans significantly boosts diagnostic certainty, impacting both the clinical decision-making process and the cost-effectiveness of subsequent medical interventions.

Is PET-CT Used in Cancer Staging?

Besides imaging, PET-CT scans can also play a crucial role in the staging of cancer. According to insights from the University of Maryland Medical Centre, this technology stands out for its ability to identify both local and metastatic tumours.

Here’s why PET-CT is invaluable in oncology:

• Cancer Diagnosis: Determines whether a tumour is malignant, guiding further treatment.
• Staging Lymph Node Tumours: Provides detailed insights into lymph node involvement.
• Detecting Metastasis: Identifies spread to other tissues or organs with high accuracy.
• Evaluating Treatment: Assesses the effectiveness of ongoing therapy, allowing timely adjustments.
• Monitoring Recurrence: Checks for signs of cancer returning post-treatment.

Is a PET-CT Scan Just for Cancer?

And while it might seem like the utility of PET-CT scans is limited to just diagnosing cancer, that is not the case. Its versatility extends beyond cancer diagnosis.

Here's how this imaging technique serves various medical fields:

• Cancer: Identifies malignant and benign tumours.
• Heart Disease: Assesses heart muscle function and detects abnormalities.
• Brain Disorders: Helps in evaluating neurological conditions and mapping brain activity.
• Fractures: Accurately locates breaks in bones.
• Blood Clots and Vascular Diseases: Detects blood flow issues and clots.
• Bowel Disorders: Provides images that support the diagnosis of gastrointestinal conditions.
• Kidney Stones: Identifies stones and other renal issues.
• Injuries: Critical in assessing brain and spinal injuries.
• Internal Bleeding: Detects areas of internal bleeding.

Benefits of Using PET-CT Scans For Cancer Staging & Treatment

So, why exactly is a PET scan beneficial in diagnosing cancer? A PET-CT scan has been proven to be extremely helpful in diagnosing cancer, staging it, monitoring its progress, and determining if a treatment is effective.

1. Early Detection for Cancer

Early detection is key when it comes to treating many types of cancers successfully. With early detection comes early intervention, which can significantly improve patient outcomes.

For instance, when prostate cancer is detected early, the 5-year survival rate is over 95%. Similarly, studies show that regular breast cancer screening can reduce mortality rates by up to 50%. These figures highlight the profound impact of early detection on increasing the chances of successful treatment and survival.

This is where PET-CT scans come into play.

The primary benefit of using PET-CT scans in diagnosing cancer is their accuracy. The combination of two imaging techniques means that cancer specialists can get a more detailed view than they would with either technique individually, helping them identify areas of disease that may not be visible on either scan alone.

They allow doctors to detect even very small changes in cellular activity, so cancer can be accurately diagnosed earlier than ever before. Together with other scans, scopes, and biopsies, it also helps doctors determine if tumour cells have spread to other parts of the body, which is known as staging the cancer. This increases the chances that treatments will be successful and reduce long-term side effects associated with more advanced stages of cancer.

2. Monitor Cancer Treatment Progress

In addition to helping with cancer diagnosis and staging, PET-CT scans can also be used to monitor the progress of treatment over time. They can be extremely helpful in treating cancer because they provide detailed information about where tumours are located and how large they are.

By tracking changes in tumour size and location over several scans and the decrease or increase of areas with high metabolic activity, doctors can determine whether or not a particular treatment is working or if it needs to be adjusted. This helps doctors adjust treatments quickly and effectively so that patients receive the best care possible.

Additionally, doctors also make use of the scans to decide on the most appropriate treatment plan for each individual patient. By monitoring changes over time, doctors can track how well they are working or if there is any progression or recurrence of disease.

3. Efficient and More Affordable

With its non-invasive nature, PET-CT scans have been proven to be both safe and effective for tracking the progression of cancer throughout many parts of the body. It also helps minimise costs by creating a single image that contains both information from a Positron Emission Tomography (PET) scan and Computed Tomography (CT) scan to give doctors greater insight, while avoiding redundant or unnecessary tests.

Preparing for Your PET-CT Scan: Steps and Expectations

If your doctor has recommended a PET-CT scan, preparing properly is crucial for accurate results.

To ensure a smooth and comfortable PET-CT scan experience:

• Fasting and Hydration: Most PET-CT scans require you to fast for about 4 to 6 hours before the scan.
• Physical Activity: It's advised to avoid strenuous exercise for 24 hours before your appointment.
• Diabetes Considerations: If you have diabetes, contact the radiology department in advance to discuss necessary adjustments to your diet or medication.
• Comfort and Anxiety: If prone to claustrophobia, communicate with your healthcare team beforehand—they can arrange measures to ease discomfort, including administering mild sedatives if necessary.

On the Day of the Scan:

• Dress Appropriately: Comfortable clothing without metal fasteners is recommended. A hospital gown may be provided.
• Radiotracer Injection: Approximately one hour before the scan, a radioactive tracer will be administered intravenously.

During the Scan:

• Scanning Process: The PET-CT scanner is typically shaped like a large doughnut. Patients will lie on a movable bed that slides in and out of the scanner. The radiographer should be notified if a change in position is needed.
• Communication: The radiographer will monitor the patient throughout the scan and can communicate with them via an intercom.

Post-Scan:

• Hydration: Drinking plenty of fluids is advised to help the body eliminate the radioactive tracer.
• Radiation Precautions: The tracer emits low levels of radiation, which dissipate quickly. As a precaution, patients should maintain a distance from pregnant women and young children for 6 hours after the scan.
• International Travel: If international travel is planned within a week of the scan, patients should carry their appointment letter with them to explain any radiation detection at airports.

Detect, Treat and Manage Your Cancer with PET-CT Scans

At OncoCare Cancer Centre, we offer a comprehensive diagnosis and treatment for various types of cancers.

Our team of specialists offer timely, expert services to detect, treat, and manage your cancer to give you the best possible chance of getting back to your usual quality of life as soon as possible.

Understanding the concerns about medical costs, we strive to maintain transparency regarding the expenses associated with your care. For specific details about the cost of a CT scan in Singapore or to discuss the financial aspects of your PET-CT scans and other treatments, please reach out to us. Our staff is here to guide you through the options and assist with any financial queries you might have.

“Expert knowledge means better care for cancer”

Written by:
Dr Angela Pang
MBBS (Singapore)
Grad Dip (GRM)
MRCP (UK)
M Med (Internal Med)