Regional Variation in Cancer Imaging Not Related to Overuse

Roxanne Nelson

December 01, 2014

The utilization of medical care varies considerably across the United State, and is seemingly unrelated to health outcomes. This variation has often been interpreted to imply that areas of high spending are overusing or misusing services, especially when the differences are not associated with better outcomes and cannot be explained by patient characteristics.

But at least when it comes to the use of cancer-related imaging, geographic differences in the allocation of care do not necessarily indicate overuse, according to a new analysis.

In fact, say the authors, comparing utilization of cancer-related imaging across regions is not a reliable way of measuring the overuse of these services.

The article was published online December 1 in the Annals of Internal Medicine.

To investigate the question of whether or not geographic variation is a reliable correlate of the amount of overuse in a healthcare system, J. Michael McWilliams, MD, PhD, associate professor of health care policy at Harvard Medical School, Boston, and colleagues examined cancer-related imaging in two patient populations.

They compared the average use and geographic variation in cancer-related imaging between fee-for-service Medicare patients (n = 34,475) and those who received care in the Department of Veterans Affairs (VA) healthcare system (n = 6835). The two cohorts were composed of older men with lung, colorectal, or prostate cancer.

Specifically, the authors evaluated whether the use of cancer-related imaging was lower for the VA patients than for the Medicare beneficiaries, and if that was the case, whether lower average use was associated with less geographic variation.

Lower for VA, Same Geographic Variation

Overall, they found that care was less expensive for VA patients than for Medicare beneficiaries, but the cost in different locations varied as much for VA patients as it did for those on Medicare. Lower use was not associated with less geographic variation.

The adjusted annual use of cancer-related imaging was nearly 50% lower in the VA cohort than in the Medicare group within the same geographic areas (mean price-weighted utilization count, $197 per patient vs $379 per patient; difference, -$182; P < .001).

CT, positron emission tomography, and nuclear studies were used less in the VA group, and that accounted for 90% of the cost difference in the two arms. A lower use of MRI and ultrasonography contributed as well to lower costs, whereas the use of radiography was higher in the VA cohort.

However, cost varied by region in similar fashion for both VA patients and Medicare patients.

The variation in the adjusted per-patient use of cancer-related imaging across hospital referral regions in the VA cohort (standard deviation [SD] in hospital referral regions mean price- weighted utilization count, $78 [confidence interval (CI), $60 - $101]) was similar in magnitude to that observed among Medicare patients ($60; CI, $45 - $79).

Among Medicare patients, the adjusted annual use of cancer-related imaging was $141 (47%) higher per patient in the highest user hospital referral regions than in the lowest. Looking at the same comparison among the VA patients, the adjusted annual use of cancer-related imaging was $237 (240%) greater between highest and lowest users.

The authors noted that geographic variation was moderately correlated between the two cohorts, but the "correlations were imprecise and not consistently positive and significant across cancer types."

Previous research has suggested that the VA system delivers a quality of cancer care that is equal to or better than that in traditional fee-for-service Medicare, say the authors. The current findings suggest that the VA system utilizes cancer-related imaging in a more efficient manner, but that lower levels of cancer-related imaging were not associated with less geographic variation.

The authors add that their results have important implications for assessing health system performance. In line with other research, the findings "suggest that achievement of lower average spending and better average quality for a clinical condition in a system may not be associated with less geographic variation in care intensity for that condition."

"Because the extent of variation may not signal the level of system efficiency, research documenting geographic variation in risk-adjusted use of medical services may not be useful for reliably characterizing the amount of wasteful care in a system," they conclude.

The study was funded by the Doris Duke Charitable Foundation and the Department of Veterans Affairs Office of Policy and Planning.

Ann Intern Med. Published online December 1, 2014.

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