Why do some patients need a PET CT scan for follow-up when others don't?

Posted in cancer diagnosis; Posted 11 months ago by Andreas Obermair

After treatment for gynaecological cancer, surgeons normally check on patients for a few years for fear the cancer might recur. Follow up and regular tests can assure patients that the cancer does not return. It can also detect recurring cancer when its small and can be dealt with easily.

However, it is important to consider the type and stage of the cancer (how aggressive and advanced it was), and outcomes of the surgery (how confident the surgeon was they removed all cancer traces); all of that will determine your follow-up frequency, and required tests or scans recommended.

During follow-up, I may order blood or medical imaging tests, known as PET scans, which can be combined with CT scans.

PET stands for a Positron Emission Tomography. A CT scan is similar to X-ray and shows images of the organs and tissues based on size and morphology inside your body. By contrast, a PET scan is a molecular scan because it detects small sugar-like molecules that are tiny. PET-CT scans are therefore more sensitive and can find abnormal activity more reliably.

However, not every cancer patient will not need these scans. In some cases, the risks may be greater than the benefits.

PET and PET-CT scans typically are not recommended for people who had treatment for low-risk cancers and who don’t have symptoms.

Instead, it’s better to:

• Be aware of symptoms of cancer recurrence.
• Attend regular follow-up appointments that include a physical exam.
• Ask your gynaecological oncologist which scans and tests (if any at all) is right for your circumstances.

PET and PET-CT scans include radiation exposure

PET-CT scans expose you to radiation. Each scan is only small and this low dose of radiation has not been shown to cause harm. Although, repeated scans can add up radiation exposure over your lifetime. Make sure all your doctors know how many imaging scans you have had in your lifetime.

It’s also possible for radiation to increase some types of cancer.

Multiple scans can lead to unnecessary worry

Scans after cancer treatment can lead to further worry or anxiety, false alarms, because sometimes tests produce unreliable results, and more costs. For example, some noncancerous, benign conditions can appear like cancer in a PET-CT scan scan. For example, uterine fibroids can produce (false) positive PET-CT findings. Further testing may be needed causing the patient more stress.

In some cases (I remember two ovarian cancer patients from last week) PET-CT scans can also be false negative and can falsely assure patients. My recent patients had ovarian cancer recurrence but the PET-CT did not pick it up because the volume of disease was very small. We identified the recurrent ovarian cancer only though a laparoscopy.

When are PET scans helpful after gynaecological cancer treatment?

A PET or PET-CT scan may be beneficial to determine the extent of the disease prior to treatment for treatment planning.

Or if your gynaecological oncologist suspects your tumour has come back. For example, because your tumour markers have risen after treatment has been successfully completed.

Or for whatever other reasons your gynaecological oncologist suspects that the cancer has recurred.

BRCA positive patients will benefit from yearly PET-CT scans because more often than not, the blood tumour markers will remain normal (even if the ovarian cancer recurs).  

Your gynaecological oncologist should be able to outline to you after your primary treatment is completed, how your follow-up program can be designed so that you have the investigations that you need -- but not more and no less.

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