Are PET scans beneficial during cancer diagnosis, staging and monitoring?

Today positron emission tomography (PET) scanning is emerging as an increasingly helpful oncology tool for diagnosis, staging and monitoring. It is a computer-based, low-resolution imaging technology emitting a radioactive tracer to localise tumours. The radioactive positron tracer gathers in abnormal tissue. As a result, the malignant tissue stands out from normal tissue and appears as a "hot spot."

The use of multiple imaging technologies is growing in importance for the diagnosis, staging and monitoring treatment for many types of cancers. Once an oncologist diagnoses a patient with cancer, current standards of care require the doctor to decide which stage a cancer patient has reached. Before completing a treatment plan, the oncologist must decide whether the malignancy is localised, attacking nearby tissues or spreading to other parts of the body.

"After the staging step, oncologists often monitor a patient’s cancer treatment for effectiveness or reappearance of a tumour," said Dr. Skip Freedman, executive medical director at AllMed Healthcare Management, a leading Independent Review Organization (IRO).

According to Freedman, an oncologist usually combines a PET scan with computed tomography (CT) to capture higher resolution pictures of a patient’s tissue. Because the PET images are low-resolution, oncologists combine the two to increase the image resolution and clarity of any "hot spots" showing up in the PET scan.

However, scanning is expensive, about $1,800 for PET and $2,100 for a combined PET and CT scan. Both also emit high doses of radiation, about 150 chest x-ray equivalents (CXREs) for a PET scan and 350 to 550 CXREs for combined PET and CT scans. One CXRE equals the radiation a patient receives from one X-ray. So there are tradeoffs for both doctors and patients to consider.

"For many tumours, PET scans are only a slightly more effective diagnostic tool in terms of sensitivity and specificity than CT scans or MRIs," said Freedman. "So their use is being researched to discover if and how much they may improve patient outcomes."

(Source: Center for Medicare and Medicaid Services: August 2008)