Growth in the Use of PET for Six Cancer Types After Coverage by Medicare: Additive or Replacement?

Background

In July 2001, PET became a covered service for Medicare beneficiaries when used for the diagnosis, staging, and restaging of non–small-cell lung, esophageal, colorectal, and head and neck cancers as well as lymphoma and melanoma. Whether physicians use PET as a replacement for or in addition to CT, MRI, or bone scintigraphy (BS) is uncertain.

Methods

A 20% sample of Medicare fee-for-service beneficiaries aged > 64 years from 2004 through 2008 was used. Annually for each cancer type, a cohort of patients was created defined as having at least one admission with a primary cancer diagnosis or two nonhospital claims with a cancer diagnosis ≥7 days apart per calendar year. Each year, imaging claims and claim-days were counted by modality and cancer type. The sequence of PET use was examined as before, after, or instead of other imaging.

Results

About 125,000 beneficiaries (2.5% of the cohort) met the cancer definition each year. In 2008, the combined annual imaging days per person-year were 2.3 for CT, 0.49 for MRI, 0.70 for PET, and 0.13 for BS. The annual rates of imaging from 2004 to 2008 increased by 0.5% for CT, 3.2% for MRI, and 18.0% for PET (range, 14.6%-19.9% by cancer type) and decreased by 12.7% for BS. The growth in PET use was not associated with meaningful changes in body CT. In 2007 and 2008, body CT preceded PET within 30 days in about half of patients, whereas PET preceded CT in only 22%.

Conclusions

Several years after its introduction, PET continued to grow rapidly, with evidence that it is replacing BS. Growth of PET occurred without evidence of a decline in body CT. About half of PET use occurred shortly after body CT, suggesting an additive or final arbiter role.

Introduction

Medical imaging serves an integral role at most decision points in cancer care, from diagnosis and initial staging to the termination of therapy for metastatic disease. Advanced imaging use evolved in a disorderly manner after the introduction of CT and, subsequently, MRI. In the absence of randomized trials, appropriateness criteria based on expert opinion using clinical vignettes have been the predominant source of practice guidelines [1, 2, 3].

Over the past decade, 4 trends arose related to cancer imaging. First, the costs of chemotherapies and targeted agents increased rapidly [4]. If cancer imaging could guide the effective use of these therapies, then increased imaging would be more easily defended. Second, the overall costs of medical imaging (not just for cancer) doubled between 2000 and 2006 [5, 6]. Third, CT and MRI scan volumes rose dramatically—by 9.5% per year for CT and 13.1% for MRI between 1998 and 2005—and shifted from predominantly hospital-based sites to freestanding outpatient sites [5, 7, 8]. Fourth, PET using ¹⁸F-fluorodeoxyglucose and integrated PET/CT (together referred to hereinafter as PET), a new technology based on a paradigm of characterizing metabolic processes rather than anatomy, was introduced for use in selected cancers. In July 2001 [9], CMS approved reimbursement for PET imaging for evaluating beneficiaries across the natural history—diagnosis, initial staging, and restaging—for 6 cancer types (non–small-cell lung, esophageal, colorectal, and head and neck cancers as well as lymphoma and melanoma).

It remains uncertain whether the growth in PET after the 2001 CMS coverage decision was associated with declines in other imaging. In this study, we assessed for 2004 through 2008 the temporal trends in PET use compared with the concurrent use of CT, MRI, and bone scintigraphy (BS) for these common cancer types. In addition, we assessed the temporal clustering and sequencing of PET use as “new” relative to “established” technologies (CT, MRI, and BS) to characterize its role as an additive or a replacement tool.