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This report is from AHRQ's Data Points Publication Series.
Overview
Geographic and demographic variation is seen in the adoption of intensity-modulated radiotherapy (IMRT) as a replacement of conformal radiotherapy (CRT) for treatment of prostate cancer.
The increase in IMRT is associated with an increase in patients using external beam radiotherapy (EBRT) alone instead of in combination with brachytherapy.
IMRT has almost completely replaced CRT as the form of EBRT used in prostate cancer treatment.
Prostate cancer is the most common nondermatologic cancer among adult males in the United States. The American Cancer Society estimated that 192,280 men would be diagnosed with and 27,360 men would die from prostate cancer in 2009. Approximately 90 percent of prostate cancer cases are diagnosed while the cancer is confined to the prostate (i.e., clinically localized disease).
The risk of dying from prostate cancer is low, approximately 3 percent. The disease course may be very slow even if left untreated. The goal of clinical evaluation is to identify men who would benefit most from treatment to prevent prostate cancer deaths or disability while minimizing side effects. Available treatments include watchful waiting, removal of the prostate (prostatectomy), radiation therapy from external beams or radioactive seeds placed within the tissue, cryotherapy (freezing the prostate), and androgen deprivation therapy (ADT). Use of external beam radiotherapy and brachytherapy has increased over the last two decades. Proton beam radiotherapy (PBRT) is another form of external beam radiotherapy that has applications in prostate cancer, which was examined in the Data Points report Proton Beam Radiotherapy.
The two most common types of external beam radiotherapy in use during the last decade are three-dimensional conformal radiotherapy (3D CRT or CRT) and intensity-modulated radiotherapy (IMRT). IMRT allows more precise control of the radiation dose than CRT and is associated with fewer rectal complications than CRT, although neither randomized nor contemporaneous comparisons exist. IMRT also allows higher radiation dose delivery to the prostate (>80 Gy) than CRT, which may improve cancer-free outcomes, especially in higher risk tumors, although evidence is lacking.
In 2000, Medicare began reimbursing for hospital-based IMRT of the prostate at a rate approximately four times that of the previous generation of external beam CRT.
In 2002, this payment change was expanded to include freestanding facilities.7 IMRT is increasingly used in the treatment of several tumors and has been identified as a major factor in the rising cost of cancer care. In 2008, Medicare spent an estimated $1 billion minimum on IMRT, mostly driven by treatment of prostate cancer.
In a study using the linked Surveillance, Epidemiology, and End Results (SEER)Medicare claims database, Nguyen, et al., recently reported a significant increase in the use of IMRT for prostate cancer. In 2002, 29 percent of those undergoing external beam radiation received IMRT. By 2005, that proportion had increased to 82 percent. Prior examinations of the same database have shown tumor characteristics such as size or stage to be unrelated to use of CRT or IMRT. Therefore, national trends can be studied using Medicare claims alone with minimal worry about confounding due to indication. We sought to expand the scope of study to include the entire U.S. Medicare population and update the findings of Nguyen, et al., to the 2006–2008 period
Conclusion
IMRT allows the delivery of highly targeted radiotherapy, minimizing the likelihood of rectal toxicity and thus permitting higher doses to be delivered to the prostate. Higher doses of CRT are associated with lower tumor recurrence rates. Therefore, the combination of higher doses permitted with IMRT and lower rectal toxicity are potential reasons providers and patients find IMRT preferable to CRT in prostate cancer treatment. Yet we have no randomized comparisons or even contemporaneous nonrandomized comparisons of CRT and IMRT. Higher Medicare reimbursements have provided incentive for IMRT use.
IMRT has almost completely replaced CRT as the form of EBRT used in prostate cancer treatment. As of 2008, IMRT is used more often than CRT whether patients are receiving EBRT alone or in combination with other therapies. In fact, the shift toward IMRT has been associated with a move toward more EBRT as monotherapy--IMRT alone or CRT alone was used in 63.6 percent of patients in 2006 but 68.2 percent in 2008. Over the same time period, the use of brachytherapy decreased, both in men receiving CRT + brachytherapy and brachytherapy alone. The only brachytherapy use that increased was IMRT + brachytherapy.
The shift toward IMRT has not occurred as rapidly in some groups. Older patients, blacks, American Indians, and men receiving State assistance continue to receive CRT more frequently than their peers. This may reflect poorer access to care, including new technologies, among disadvantaged groups.
The Midwest has also been slower to adopt IMRT than other regions. However, a comparison of IMRT use across the United States between 2006 and 2008 points to greatly expanding use through the central Midwest, including Kansas, Iowa, and Indiana.
Given the large-scale conversion to IMRT, it seems unlikely that physician groups are using both CRT and IMRT in their treatment of prostate cancer. If CRT becomes less accessible, we may expect IMRT use to increase in other tumors, perhaps even in tumors where the indications for IMRT are not very strong (i.e., where the risk of adjacent organ toxicity is not as critical as in prostate cancer). Monitoring IMRT use should be a priority for these other cancers as well as for groups of prostate cancer patients and patients in areas of the country that have been slower to adopt this new technology.
