Getting expensive radioactive imaging tests to see if a cancer of the lung or esophagus has recurred is not linked to better survival, according to a new study.

The likelihood that people with those cancers would be alive two years after their diagnosis was the same whether they went to a hospital that frequently used so-called PET scans or one that used the imaging test less often.

"I think if you're doing well and you've been treated, there is no reason to seek out these scans," said lead author Dr. Mark Healy, of the University of Michigan Center for Healthcare Outcomes and Policy in Ann Arbor.

During positron emission tomography (PET) scans, radioactive liquid is injected into a vein to show how organs are functioning. Sometimes PET scans are partnered with computed tomography (CT) scans.

"PET is a great resource and can have benefits for people," Healy told Reuters Health. But some experts believe PET scans should not be used to check for cancer recurrence before other imaging tests have been done.

Using PET scans without good reason can lead to anxiety, wrong diagnoses, false alarms, unnecessary procedures and higher costs, according to the Choosing Wisely campaign from the ABIM Foundation, created by the American Board of Internal Medicine. Choosing Wisely aims to help doctors and patients choose treatments that are supported by evidence.

For the new study, reported in the Journal of the National Cancer Institute, the researchers used U.S. cancer data to see how often PET scans are used to monitor for cancer recurrence and whether those scans are tied to longer survival after a diagnosis of lung or esophageal cancer.

Overall, they had information on 97,152 lung cancer patients at 859 hospitals and 4,446 esophageal cancer patients at 215 hospitals. All were diagnosed between 2005 and 2009 and followed through 2011.

Overall, about 78 percent of lung cancer survivors and about 70 percent of esophageal cancer survivors never had a PET scan.

The researchers found wide variations in how often hospitals were using PET scans on these patients.

Yet, about 30 percent of cancer survivors were alive two years after their diagnosis regardless of whether their hospitals performed few or many PET scans.

"It does not seem there is any difference in survival for these patients at two years," said Healy.

The findings agree with recommendations the American Society of Clinical Oncology (ASCO) made to Choosing Wisely in 2013.

"PET and PET-CT are used to diagnose, stage and monitor how well treatment is working," ASCO said. "Available evidence from clinical studies suggests that using these tests to monitor for recurrence does not improve outcomes and therefore generally is not recommended for this purpose."

The researchers also note that the Centers for Medicare and Medicaid Services, which oversees U.S. public insurance programs, limited payments in 2013 to three PET scans following initial cancer treatment.

Healy cautioned that PET scans may be necessary if doctors need to investigate something they find on another imaging test.

"I think it's a great technology if their doctor is following up on an initial study," he said.

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