SAN FRANCISCO – Two new U.S. studies involving more than 150,000 older men with prostate cancer are likely to add to the intense debate about the optimal treatment for early disease, especially the various radiation therapy options.
One study suggests that the newer intensity-modulated radiation therapy (IMRT) is more effective and less toxic than the older conformal radiation therapy. But it found that proton therapy, which is even newer, not only wasn’t more effective than IMRT but also had higher bowel toxicity.
The second study suggests that external beam radiation therapy (EBRT) is more toxic than both prostatectomy and brachytherapy. Also, EBRT was at least twice as expensive.
Dr. Paul L. Nguyen
Both studies used linked SEER (Surveillance, Epidemiology, and End Results) and Medicare data.
"We all love new technology, regardless of how much it costs," said Dr. Paul L. Nguyen in a discussion of both presentations at the Genitourinary Cancers Symposium. But third-party payers are increasingly seeking comparative effectiveness data to show that the benefits of newer therapies justify their higher expense.
"Whether you agree with the findings or not, these two provocative studies provide data that are going to shape the public’s thinking about the relative value of our treatments," added Dr. Nguyen of the Dana-Farber Cancer Institute in Boston.
"More work is needed from us as a field to generate the data [to prove] that our treatments are cost effective. And if we do not generate [these data], then third parties are going to increasingly dictate the treatments that we can and cannot offer."
IMRT Tops External RT Options
In the first study, Dr. Nathan C. Sheets and colleagues at the University of North Carolina at Chapel Hill analyzed data for 12,976 men who had localized prostate cancer and were diagnosed in 2002-2006. "We observed a rapid and nearly complete adoption of IMRT as the radiation treatment of choice for localized prostate cancer between 2002 and 2008," he noted.
Dr. Nathan C. Sheets
Results using propensity adjustment (to try to compensate for factors that might have influenced treatment choice) showed that with a median follow-up of 4.5 years, IMRT was superior to conformal radiation therapy in terms of a lower rate of additional cancer treatment, which is a proxy for effectiveness (2.5 vs. 3.1 events per 100 person-years; P less than .001), and which he proposed might be related to the ability to increase the radiation dose given with IMRT.
Billing claims data indicated that IMRT also had lower rates of bowel toxicity (13.4 vs. 14.7 events; P less than .001) and hip fracture (0.8 vs. 1.0 events; P = .006), but a higher rate of erectile dysfunction (5.9 vs. 5.3 events; P = .006).
Proton Therapy Adds Cost, Toxicity
In an additional analysis of 1,638 men that compared proton therapy vs. IMRT – the largest series of proton therapy to date – the former was no more effective, as assessed from receipt of additional cancer treatments. Furthermore, it had a higher rate of bowel toxicity (17.8 vs. 12.2 events per 100 person-years; P less than .001), Dr. Sheets reported.
"This study supports the use of IMRT as the current standard radiation technique for prostate cancer. ... There is currently no clear evidence that proton therapy is better than IMRT," he concluded, adding that because of limitations of the data, the result for proton therapy is "hypothesis generating, but it is not in any way definitive."
The favorable findings for IMRT vs. conformal radiation therapy add to results of other studies to "support the use of IMRT despite its higher cost," according to Dr. Nguyen, the discussant. However, "this study raises doubts that protons are better than IMRT for prostate cancer."
"If you are a proponent of proton therapy, you should consider participating in the randomized trial of protons vs. IMRT that’s going to hopefully be opening later this year, ... or otherwise, commit to enrolling patients on the national prospective registry so that we can try to collect prospectively some of the data and make some of the adjustments, so we can see a little bit better what’s causing these differences," he recommended.
"In 2012, absent any data which has ever shown any clinical benefit for proton beam therapy over photon therapy, while the randomized trials are going on, how can we continue to pay what we pay for proton therapy?" Dr. Matthew R. Cooperberg of the University of California, San Francisco, asked during the comments period.
"Protons have a lot of promise, and there is a model now, maybe, of paying for this kind of therapy while we investigate it. So we want to pay for protons, but we want to learn something from every patient that is going to get proton therapy," Dr. Nguyen replied. "So I think that if we have that model where we try to enroll patients on trials, it’s worth it."