American Society of Clinical Oncology: 2012 Genitourinary Cancers Symposium
“Novel Mechanisms and Therapeutics in Multidisciplinary Management”
February 2-4, 2012 San Francisco, CA
Oral Abstract Session A
Senior Author: Ronald Chen, MD
Thursday, February 2, 2012 University of North Carolina
1:15 PM - 03:05 PM PT Chapel Hill, NC
Large Study Suggests IMRT Is Better Than Conventional Conformal Radiation Therapy for Reducing Prostate Cancer Recurrence and Side Effects, May Also Be Superior to Proton Beam Therapy
A large comparative effectiveness study shows that men with localized prostate cancer who are treated with intensity modulated radiation therapy (IMRT) are less likely to experience cancer recurrences or significant side effects from treatment than those who receive conventional conformal radiation therapy (CRT). The analysis also found that a more costly form of radiation treatment, called proton beam therapy, did not significantly improve outcomes compared to IMRT. This study is the first to comprehensively examine the comparative outcomes of patients with prostate cancer treated with these three types of radiation therapy.
“Patients and doctors are often drawn to new treatments, but there have not been many studies that directly compare new radiation therapy options to older ones,” said senior author Ronald Chen, MD, MPH, assistant professor of radiation oncology at the University of North Carolina (UNC) at Chapel Hill and Research Fellow at the Sheps Center for Health Services Research at UNC. “In the past 10 years, IMRT has largely replaced conventional conformal radiation therapy as the main radiation technique for prostate cancer, without much data to support it. This study validated our change in practice, showing that IMRT better controls prostate cancer and results in fewer side effects.”
Comparative effectiveness research is designed to help clinicians and patients make more informed treatment decisions and may also influence the future adoption of new therapies and technologies in medicine overall.
IMRT is a more advanced form of radiation that enables doctors to shape and vary the intensity of the radiation field, delivering an increased radiation dose to the tumor and sparing more nearby normal tissue than is possible with conventional conformal radiation therapy. In proton beam therapy, cancerous tumors are irradiated with high-energy particles called protons. The clinical effect of using protons compared to X-rays (which are used with CRT and IMRT) for prostate cancer is not completely understood, though proton beam radiation is often thought to be able to further spare normal tissue compared to X-rays
In the study, Chen and his team analyzed data from the Surveillance, Epidemiology, and End Results (SEER)-Medicare database of more than 12,000 patients with localized prostate cancer who were treated with conventional conformal radiation therapy, IMRT, or proton beam radiation from 2002 to 2007. They examined the proportion of patients who were diagnosed with radiation-related side effects after treatment, including gastrointestinal and urinary problems, erectile dysfunction and hip fractures. They also determined the proportion of patients in each group who required additional cancer treatments after radiation, using this as an indication of cancer recurrence.
The researchers found that after adjusting for demographic, disease and institutional characteristics, patients who received IMRT had fewer gastrointestinal problems diagnosed (rate ratio 0.91, meaning that IMRT reduced gastrointestinal problems by 9 percent) and fewer hip fractures (rate ratio 0.78, or a reduction of 22 percent) than those who received conventional conformal radiation therapy, suggesting that IMRT is a safer radiation technique. They also found that IMRT patients were less likely to require additional cancer treatments (rate ratio 0.81, or 19 percent fewer additional cancer treatments), suggesting that IMRT may offer better cancer control and reduce recurrence.
“Several trials have shown that higher doses of radiation therapy improve disease control, and it is likely that IMRT allowed a higher dose of radiation to be given to the prostate than conventional conformal radiation, resulting in improved cure rates while simultaneously reducing side effects due to less radiation being given to organs surrounding the prostate,” Chen said.
The investigators also found that patients who received proton therapy had a higher rate of gastrointestinal problems, and did not have significantly improved outcomes compared to IMRT.
“We’ve seen a rapid growth in the number of proton facilities in the U.S. in the past five years, despite its very high costs. Yet with the data we have to date in the published literature, there does not appear to be a clear benefit of proton bean therapy compared to IMRT,” said Chen. “The technology needs to be closely examined through comparative effectiveness research before we adopt it as the ‘next’ treatment for prostate cancer.”
Title: Comparative effectiveness of intensity modulated radiation therapy (IMRT), proton therapy (PT), and conformal radiation therapy (CRT) in the treatment of localized prostate cancer.
Authors: Nathan Christopher Sheets, Gregg Goldin, Anne-Marie Meyer, Yang Wu, YunKyung Chang, Til Sturmer, Jordan A Holmes, Bryce B. Reeve, Paul Alphonso Godley, William Ruffin Carpenter, Ronald C. Chen; University of North Carolina Hospitals, Chapel Hill, NC; University of North Carolina at Chapel Hill, Chapel Hill, NC; National Cancer Institute, Bethesda, MD
Background: Comparative effectiveness research is urgently needed in prostate cancer because of the rapid adoption of newer and costlier radiation treatments such as IMRT and PT despite limited demonstrated benefit compared to prior technologies. We compared the morbidity and disease control outcomes of IMRT, PT and the older CRT for primary prostate cancer treatment. Methods: Population-based study using Surveillance, Epidemiology, and End Results (SEER)-Medicare linked data from 2000 through 2009 for patients with non-metastatic prostate cancer. Propensity score adjustment was used to balance demographic, disease and institutional characteristics. Rates of morbidity (gastrointestinal, urinary, erectile dysfunction, hip fractures) and additional cancer therapy (surrogate for recurrence) were calculated. Results: IMRT use increased from 0.15% in 2000 to 95.9% in 2008. In propensity score-adjusted analyses, men who received IMRT vs. CRT were less likely to be diagnosed with GI morbidity (13.4 vs. 14.7 per 100 person-years, p<0.001) and hip fractures (0.8 vs. 1.0, p=0.006), but more likely to be diagnosed with erectile dysfunction (5.9 vs. 5.3, p=0.006). IMRT patients were less likely to receive additional cancer therapy (2.5 vs. 3.1, p<0.001). In a propensity-score matched comparison between PT and IMRT, PT patients had a higher rate of GI morbidity (17.8 vs. 12.2 per 100 person-years, p<.001). No significant differences in rates of other morbidities or additional therapies between PT and IMRT. Conclusions: IMRT vs. CRT was associated with less GI morbidity and hip fractures, more erectile dysfunction, and less need for additional cancer therapy. This large-scale population-based study is the first to suggest a simultaneous reduction in disease recurrence and morbidity in patients treated with IMRT vs. CRT for localized prostate cancer. Proton therapy did not significantly improve outcomes compared to IMRT, but had increased GI morbidity. These results provide new and long-needed information to decision-makers regarding the currently available evidence on the comparative effectiveness of different RT techniques. Disclosures: Nothing to disclose.
Funding for this study was provided by the Agency for Healthcare Research and Quality.