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Baseline PET Scans Becoming More Routine

Conquest - Summer 2010

By Scott Merville

Positron emission tomography can be a gift for patients. When PET images are taken early on in treatment, they not only help the patient and physician know if treatment is working, but now many of these tests are also being covered by Medicare.

This is due to changes in Centers for Medicare and Medicaid Services (CMS) coverage policies, which are allowing more cancers to be routinely assessed.

Homer Macapinlac, M.D.

“All cancers, with a few exceptions, can now be imaged up front with PET to determine the extent of disease and to help direct the next step for the patient,
which could be a biopsy, surgery or a combination of therapies,” says Homer Macapinlac, M.D., professor and chair of MD Anderson’s Department of Nuclear Medicine.

Having these baseline PET scans at initial staging also will help with future decisions about monitoring the disease or detecting its spread to other organs.

In addition to extending coverage of initial scans to new cancers, the CMS also approved coverage of second PET scans at the end of a course of treatment for ovarian cancer and multiple myeloma.

Breast cancer remains the only indication for which CMS allows routine monitoring during the course of treatment. Such coverage also is available for other patients on clinical trials.

“That’s good news for us because we are a protocol-driven institution, so patients have a good chance to be covered by Medicare and get monitoring of treatment that they otherwise would not get,” Macapinlac says. “We have encouraging data that if you have a course of six to eight cycles of chemotherapy for lymphoma, repeating a PET scan after cycle two or three can predict who will respond, even if tumor size has not changed. Those with abnormal PET scans are likely to become resistant to therapy.”

Outside of approved clinical trials, Medicare now permits early monitoring for patients entered in the National Oncologic PET Registry (NOPR), which allows evaluation of PET and its effect on treatment choices. The registry is part of the agency’s Coverage with Evidence Development (CED) program, which will use the data gathered to guide future recommendations about coverage for early monitoring. A CED assessment led to the new PET indications for additional types of cancer.

Nuclear medicine constantly evolving

PET is a nuclear medicine technique that relies on radioactive tracers to image an organ or tumor by capturing metabolic or chemical activity in action. The only radiotracer approved by CMS for cancer imaging is 18F-fluorodeoxyglucose (FDG). Most tumors crave glucose, so FDG is taken up by cancer cells. The extent of this uptake is a measure of the tumor’s health, with a decline indicating a therapy is working.

MD Anderson conducts research and clinical trials of other tracers that could give better or more specialized information. “We continue to work to provide the best imaging for the best care of our patients. That’s why they come here,” Macapinlac says.

Tracers in clinical trials at MD Anderson include:

  • The 18F-fluorothymidine (FLT) PET method could offer even earlier indications of response, because an effective cancer therapy quickly would shut down a cancer cell’s ability to divide in two. It correlates to DNA synthesis rather than glucose uptake.
  • Another new tracer permits monitoring of angiogenesis, the creation of new blood vessels. Anti-angiogenesis drugs block the development of a tumor’s blood supply. By imaging this process, researchers hope to select patients who would benefit from these drugs and to find biomarkers that assess response.
  • To assess bone metastases, 18F-sodium fluoride (NaF) PET imaging is being compared to the current technetium standard, a 99mTc-MDP gamma camera-based bone scan. It was approved for PET imaging decades ago and then was superseded by technetium-99 due to the infancy of PET scanners at the time. Improvements in PET technology could make 18NaF PET a less time-consuming, more sensitive and specific technique for patients.

© 2015 The University of Texas MD Anderson Cancer Center