Construction of a proton therapy center typically requires debt financing, and servicing the debt requires a case mix with a high proportion of simple or prostate cancer patients, according to an analysis published in the August issue of the Journal of American College of Radiology. Pediatric or complex cases require more time and translate into reduced reimbursement per room.

Currently, nine proton centers operate in the U.S.; however, additional sites are under construction, and rely on a for-profit model. Actual profits hinge on an optimal patient mix, according to Peter A.S. Johnstone, MD, of the department of radiation oncology at Indiana University School of Medicine in Indianapolis, and colleagues.

Proton centers, like conventional radiation therapy practices, depend on a mix of simple and complex patients. Simple patients can be treated in 30 minutes or less and use easy immobilization or two or fewer treatment fields. Complex cases use difficult immobilization and three or more treatment fields; these cases and pediatric cases with anesthesia require one hour of treatment time. The researchers estimated that prostate cancer treatment requires 24 minutes of room time. In the time it takes to treat one complex patient, two to five simple or prostate cancer patients may be treated, according to the researchers’ calculations.

Johnstone et al sought to model the case distribution needed to handle the debt load associated with proton therapy center construction. They assumed 100 percent debt-financed construction with 15-year financing at 5 percent interest. The model included single, three and four-gantry facilities and assumed a 14-hour treatment day at full capacity with mix of payers and cases.

“Not surprisingly given the assumptions, the number of patients treated per day per room is maximized with an increasing percentage of simple and prostate cancer patients,” wrote Johnstone and colleagues.

In a single gantry facility, factoring in six or seven pediatric or complex patients drops the maximum number of daily patients from 35 to 16, which cuts daily billing per room by 61 percent. A site focused only on pediatric or complex patients would require 12 hours of operation to service debt, the researchers calculated. Additional costs of business including staff compensation further constrain single-gantry sites.

They calculated that a three-gantry site treating only complex and pediatric cases would not have enough treatment slots to cover debt and construction costs. A four-gantry site could not cover 60 percent of its debt service focusing on complex and pediatric cases. “Simple patients thus are critical to a proton facility of any size.”

Although treating simple cases enables treatment of pediatric and complex patients, simple cases drive maximum profits, according to Johnstone et al.

The researchers pointed to other troubling trends. Proton centers need to attract new patients to their facilities, many of whom are treated at other radiation therapy sites. In addition to “the cannibalization of existing patients,” proton centers will likely contend with decreased reimbursement in the future.

Johnstone and colleagues concluded with a dire prediction: Once operating costs and any profit are considered, centers without considerable workload devoted to simple and prostate cancer patients should not be expected to survive.