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.

METHODS

We used the Chronic Condition Warehouse (CCW) claims-based algorithm to identify men newly diagnosed with prostate cancer. We identified men newly diagnosed between January 2006 and December 2008 by using the date the beneficiary first met the clinical criteria of the algorithm. We limited our study to men over age 65 who were alive and enrolled in Medicare fee-for-service (FFS) Parts A and B for at least 12 months after this date.

Radiation therapy: We identified men using radiation therapy treatments in the Part B (outpatient and carrier) claims using Healthcare Common Procedure Coding System (HCPCS) codes (Table 2).

Table 2

Codes used to identify receipt of radiation therapy and surgery in outpatient and carrier claims.

Patients with codes suggesting both IMRT and CRT were coded as IMRT.

Radical prostatectomy: We classified type of radical prostatectomy as minimally invasive or open if they had claims with select HCPCS codes, and NOS if the only indication of radical prostatectomy was an ICD-9 procedure code.

Race/ethnicity: Race and ethnicity were defined using the Research Triangle Institute Race Code, which uses a surname algorithm to assign Hispanic ethnicity.

Hospital referral region (HRR): We grouped beneficiaries into HRRs based on residential ZIP Code using a categorization obtained from the Dartmouth Atlas Web site.¹¹ We do not report percentages for HRRs with fewer than 30 resident prostate cancer patients in one year.

Region: We assigned region according to the four United States Census Bureau regions (Northeast, Midwest, South, and West) based on State of residence.

State assistance: We designated patients as receiving State assistance if the beneficiary Medicare Entitlement Buy-in indicator was between 01 and 09 in the month they were newly diagnosed.

The analysis is restricted to men who received radiation therapy within 12 months of the first date suggestive of prostate cancer in the claims. In addition to CRT and IMRT, we examined rates of proton beam therapy (a new form of external beam radiotherapy rarely used by prostate cancer patients) and brachytherapy (“internal” radiotherapy).

We exclude men who had radical prostatectomy within the 12 months of the first date suggestive of prostate cancer in the claims.

We investigated trends in use of radiation therapy services over time in two ways. First, we created mutually exclusive categories (IMRT alone, CRT alone, PBRT alone, brachytherapy alone, and any combination of external beam radiation [IMRT or CRT] and brachytherapy).

We also measured any use of these therapies (CRT alone or in combination with other treatments, IMRT alone or in combination with other treatments, etc.). We mapped “Any IMRT” use during each year by HRR.

RESULTS

We identified 121,728 men newly diagnosed with prostate cancer between 2006 and 2008 who received radiation therapy within 12 months of diagnosis.

Use of IMRT alone or in combination with other therapies increased from 62.2 percent of all radiation users in 2006 to 73.6 percent in 2008. Meanwhile, use of CRT decreased from 24.1 percent to 12.7 percent. Use of brachytherapy decreased overall (35.5 percent in 2006 to 30.3 percent in 2008), despite a small increase in the proportion of radiation users using HDR brachytherapy (2.8 percent in 2006 to 3.3 percent in 2008; Table 3).

Table 3

Older males newly diagnosed with prostate cancer by radiation therapy type and year, 2006–2008.

Use of IMRT alone was the most common form of radiotherapy in 2006 (52.5%) and the proportion of users increased in 2008 (63.4%). The proportion of radiation users who used IMRT plus brachytherapy increased slightly over the same period from 9.7 percent to 10.1 percent. The share of radiation users who used HDR alone or any PBRT also increased slightly over the period (0.5% to 0.7% and 0.8% to 1.4%, respectively), while the share of people using CRT alone or CRT plus brachytherapy and LDR brachytherapy decreased (Table 4).

Table 4

Percent distribution of older males newly diagnosed with prostate cancer by combinations of radiation therapy and year, 2006–2008.

Overall, 7.9 percent of radiation users used CRT alone. This rate was higher in men ages 80–84 (12.6%) and men over 85 (29.0%), blacks (9.2%), American Indians (14.4%), men living in the Midwest (9.4%) and men receiving State assistance (11.7%; Table 5).

Table 5

Percent distribution of older males newly diagnosed with prostate cancer by demography and combinations of radiation therapy and year, 2006–2008.

Brachytherapy alone made up 20.8 percent of radiation use. Rates were higher in younger men (66–69: 26.5%, 70–74: 23.4%), non-Hispanic white men (21.5%), and men living in the Midwest (23.7%).

Rates were much lower among men older than 85 (6.5%), Hispanic men (14.0%), and men receiving State assistance (13.8%) (Table 5).

The maps display the proportion of radiotherapy users in each HRR who used IMRT alone or in combination with another therapy. The proportion of HRRs with rates over 75 percent grew from 2006 to 2008 from 18.6 percent of HRRs to 40.7 percent (Figure 1).

Figure 1

Proportion of men receiving radiation therapy for prostate cancer who received IMRT alone or in combination with other radiation therapies, 2006–2008.

CONCLUSIONS

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.⁵ Higher Medicare reimbursements have provided incentive for IMRT use.⁹

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 (Figure 1) 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.

Acknowledgments

The authors wish to thank Jessica Zeglin and Mary A. Leonard for their graphic design expertise.

This project was funded under Contract No. HHSA29020100013I from the Agency for Healthcare Research and Quality, U.S. Department of Health and Human Services as part of the Developing Evidence to Inform Decisions about Effectiveness (DEcIDE) program. The authors of this report are responsible for its content. Statements in the report should not be construed as endorsement by the Agency for Healthcare Research and Quality or the U.S. Department of Health and Human Services. This study was approved by the University of Minnesota Institutional Review Board. The data were provided by the Centers for Medicare & Medicaid Services, and we followed all procedures in accordance with data use agreement number 21399.

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Suggested Citation: Elliott SP, Jarosek SL, Virnig BA. Changes across time and geography in the use of prostate radiation technologies for newly diagnosed older cancer patients. Types of prostate radiation. Data Points # 16 (prepared by the University of Minnesota DEcIDE Center, under Contract No. HHSA29020100013I ). Rockville, MD: Agency for Healthcare Research and Quality; November 2012. AHRQ Publication No. 12-EHC095-EF. [PubMed: 23285489]