pet imaging cancer



Early detection is one of the keys to curing cancer. But sometimes cancer spreads without being noticed by either the patient or physicians. When this happens, early detection of metastasized cancer – cancer that has spread beyond its initial location – is important in preserving the most treatment options and offering the best prognosis for the patient.

The presence of individual tumor cells in bone marrow and blood may not produce clinically evident symptoms, so doctors rely on certain immunologic or imaging methods to identify metastases as early as possible. The earlier metastases are found, the more likely patients are to benefit from treatments designed to eradicate them. Radiologists are constantly trying to find better methods for discovering metastases in bones, and one of the technologies they turn to most frequently is Positron Emission Tomography (PET).

With PET, the patient is injected with a radioactive tracer element. Then, a machine to detect emission of positrons is used in conjunction with another medical imaging technique (typically computed tomography) to find areas in the body where there is increased uptake of the radioactive tracer. Cancerous tumors are known for displaying increased uptake of these radioactive tracers, so an accumulation of tracer in a certain part of the body may indicate cancer metastasis, even if the patient has not yet experienced any clinical symptoms associated with metastases.

What Is NaF-18 PET?

NaF-18 has been an approved tracer for imaging bone metastases since the 1970s. But it was not widely used at first, because PET technology wasn’t used as often clinically until it was combined with CT imaging. Plus, conventional bone scintigraphy was in widespread use for years to detect bone metastases.

However, interest in NaF-18 PET for imaging bone metastases has re-emerged in recent years due to evidence that it has greater sensitivity and specificity when compared with conventional bone scintigraphy. Some of the reasons why NaF-18 PET is desirable as a bone imaging agent include:

• It is readily taken up by bones and cleared out much faster
• It offers superior bone-to-background ratios and can provide high-contrast images within one minute after injection
• It can demonstrate variation in bone metabolism, so it shows improved sensitivity compared to traditional bone imaging
• Little NaF-18 is retained residually in soft tissues after the procedure
• NaF-18 is deposited heavily in places where there is high bone turnover and remodeling
• Radiation doses with NaF-18 PET along with CT are comparable to those in traditional bone scans

In 2011, the Center for Medicare and Medicaid Studies (CMS) approved coverage of NaF-18 PET/CT scans through the National Oncologic PET Registry (NOPR). The NOPR was founded to ensure access to Medicare reimbursement for some types of PET scans for finding metastases with certain types of cancer. However, the CMS recently issued a new ruling that many radiologists consider a setback.

The New CMS Ruling on Sodium Fluoride PET

In September, the CMS released a memo saying that the agency will not offer lenience in its reimbursement conditions surrounding NaF-18 PET used in finding metastasized cancer in bones. However, the CMS will continue paying for NaF-18 PET scans under conditions known as “coverage with evidence development” (CED). Under these conditions, CMS reimburses new techniques gathered to further evidence about clinical effectiveness.

In March, CMS started reviewing NaF-PET reimbursement in response to requests that the procedure be fully reimbursed without CED limitations. Unfortunately, CMS declined to lift those limitations. The agency will continue with CED reimbursements for twelve months to allow collection of evidence and analysis leading to a more conclusive answer on whether NaF-18 PET leads to

• Changes in patient management to more appropriate curative or palliative care
• Better patient quality of life
• Improved patient survival

Coverage determinations will be revisited by the CMS when evidence about its clinical effectiveness has been published in a peer-reviewed journal.

Doctors’ Reactions to the CMS Ruling on NaF-18 PET

Radiologists and oncologists were disappointed in the CMS ruling because many of them strongly believed they were on the right track as far as demonstrating the clinical effectiveness and usefulness of NaF-18 PET imaging. The NOPR, for example, has been collecting data from medical imaging facilities for several years on how NaF-18 PET influenced patient management. But apparently the evidence the NOPR has is not considered definitive enough.

The CMS doesn’t necessarily disagree that NaF-18 PET does what it says it does, but are rather concerned about whether it leads to measurable improvement in patient outcomes. With all these factors in play, hospitals, patients, and private insurers are less likely to pay for NaF-PET scans. Private insurers typically follow what the CMS does, so if the CMS says it’s not lifting restrictions on the use of NaF-18 PET for detecting bone metastases, it’s unlikely that private insurers will either.

Plans to Move Forward with Advocacy for NaF-18 PET

None of this means that it’s the end of the road for NaF-18 PET. Doctors who use it are now evaluating their options. One option is to review claims data from the NOPR to determine exactly how the actual care a patient received changes compared to what the physician initially planned for that patient. Did the NaF-18 PET scan alter physicians’ thoughts on how to proceed, or alter patients’ treatment plans?

A 2014 study by the NOPR found that NaF-18 PET caused changes in treatment for more than half of male patients with prostate cancer. The scans changed management plans for more than three-quarters of initial staging patients, more than half of men with suspected bone metastases, and over 70% of those with suspected progression of bone metastases. What’s more, after NaF-18 PET, 70 to 80% of patients avoided additional imaging. Plans to gather additional biopsy or other information were necessary only in a small minority of patients.

PET Imaging for Cancer Patients

Radiologists like the Board-certified radiologists of SteleRAD understand the importance of nuclear medicine techniques like NaF-18 PET in detecting cancer metastases early and preserving the most treatment options for patients. If you’re interested in learning how the radiologist owner-operators of SteleRAD can assist your hospital, imaging center, or medical practice in South Florida, please call 954-358-5250 or contact us online at any time.