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The role of PET/CT with pulmonary nodule workups: what you need to know

Posted on: 05.25.18

The two most common approaches after identifying a solitary pulmonary nodule are the wait-and-see approach, or to move straight to a biopsy. While medically sound, both of these paths present risks for the patient that could be solved with a PET/CT scan.

It’s a common misconception in nuclear medicine that a patient must have a cancer diagnosis before a PET/CT scan can be ordered. While this is generally true, many physicians are not aware that a solitary pulmonary nodule that measures less than 4cm qualifies for a PET scan without a prior cancer-confirming biopsy.

Avoiding Unnecessary Risks

Lung nodules are typically discovered via chest x-ray or CT and available guidelines for nodule management are generally based on nodule size or changes.

The wait-and-see approach is a standard recommendation for nodules under 4cm. The patient is given CT scan and then rescanned on a pre-determined schedule (every six or 12 months). This approach works well if the risk is in-fact low, but for patients who do have metabolically active nodules, this approach can have serious consequences. Properly identifying and diagnosing the cancer early can have a far-reaching impact on their long-term prognosis. Waiting to see if the nodule gets worse costs valuable time.

However, the reason most physicians chose the wait-and-see approach is that the alternative, a lung biopsy, also presents risks. For small nodules that may or may not be growing, many doctors decide that waiting is safer than subjecting the patient to a potentially unnecessary invasive medical procedure. Lung biopsies are a vital diagnostic tool, but they bring with them the risk of infection, collapsed lungs, bleeding in the lung, etc.

Gaining Clarity with PET/CT

The central issue physicians deal with in these situations is how to deal with the unknown and juggle the risks associated with both paths. With PET/CT imaging, you have a much clearer picture of what is actually happening within the nodules. Having this vital information makes the decision much easier and drastically reduces the risk for the patient.

For nodules that are not metabolically active during the PET/CT scan, it’s not recommended to follow up with a biopsy. So patients avoid the risks of an unnecessary procedure. However, if the nodule positively reacts to the radiotracer, further investigation and a biopsy are strongly recommended. Knowing this sooner, rather than later, saves the patient valuable time.

Additionally, in the new “value-based” culture we operate in, investing in a single PET/CT scan could save the healthcare system tens of thousands of dollars in unnecessary scans, biopsies, or advanced cancer treatments. It’s the right thing for the patient, and the system. That is precisely why Medicare covers it.

PET/CT vs. CT

In the wait-and-see approach, most physicians recommend having a series of follow-up CT scans. While CT scans are effective, PET/CT is more accurate than CT alone for characterizing pulmonary nodules, resulting in fewer equivocal findings and higher specificity. Low to intermediate risk nodules ≥ 8 mm should be evaluated by PET/CT, whereas high-risk nodules should be biopsied or excised.

In over 80% of indeterminate CT scans, PET/CT correctly characterizes lung nodules. Statistically speaking, PET/CT is far superior to CT in terms of diagnostic accuracy in solitary pulmonary nodule characterization. PET/CT is 97% sensitive, has an 85% specificity value, a 92% negative predictive value (NPV) and a 93% positive predictive value (PPV). Overall, PET/CT imaging provides 92% accuracy when diagnosing SPNs.

Industry Recommendations

The Society of Nuclear Medicine recommends that FDG PET/CT exams should be routinely obtained in the diagnostic work-up of solitary pulmonary nodules. Imaging will improve health care outcomes, mostly by avoiding futile surgeries in low-risk patients and enabling curative surgeries in high-risk patients.

PET/CT is approved by CMS for characterization of solitary pulmonary nodules not exceeding 4 cm to determine the likelihood of malignancy. Claims should include evidence of the initial detection of a primary lung nodule, usually by computed tomography. SPNs recommended with a PET/CT follow up using ICD 10 code R91.1

Although the Fleischner Society generally recommends a wait-and-see approach for nodules under 8cm, the under 4cm requirement for PET scan approval is causing many physicians to reevaluate their care strategy. PET/CT scans are a useful screening tool that clarifies where the patient actually stands.



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