No Difference in Toxicity Between Proton Therapy and IMRT for Prostate Cancer

No Difference in Toxicity Between Proton Therapy and IMRT for Prostate Cancer

Proton therapy does not reduce toxicity compared with intensity-modulated radiation therapy (IMRT) in men with prostate cancer, according to the results of a study published in the Journal of the National Cancer Institute.

Prostate cancer is the most commonly diagnosed cancer (other than skin cancer) in U.S. men. Each year, more than 240,000 men are diagnosed with the disease. When the cancer is diagnosed at an early stage, treatment options include surgery, radiation therapy, and active surveillance (close monitoring but no treatment unless the cancer shows signs of worsening).

Radiation therapy uses beams of radiation to slow or stop cancer cell growth, which shrinks or eliminates the tumor. Men with early stage prostate cancer have multiple radiation options, including conformal radiation therapy, IMRT, and proton therapy. In the past, conformal radiation therapy was the standard of care; however, the use of IMRT has become more commonplace in the past decade—with nearly 96% of men receiving IMRT in 2008. IMRT is a type of high-dose, targeted radiation meant to limit damage to surrounding organs. Proton therapy (PRT) is another type of targeted radiation therapy; it is a high-tech, costly method that requires specialized equipment and facilities—and there is insufficient evidence showing its effectiveness or ability to reduce toxicity.

To compare IMRT and PRT, researchers performed a retrospective study of all Medicare beneficiaries age 66 or older who received PRT or IMRT for prostate cancer during 2008 and/or 2009. The analysis included 27,647 men—553 (2%) received PRT and 27,094 (98%) received IMRT. In order to assess toxicity, each PRT patient was matched with two IMRT patients with similar clinical and sociodemographic characteristics.

The results indicated that PRT was associated with a statistically significant reduction in genitourinary toxicity at 6 months compared with IMRT (5.9% vs. 9.5%); however, there was no difference at 12 months (18.8% vs. 17.5%). In terms of cumulative rates of all toxicity—there was no significant difference between the two methods at 6 or 12 months.

The researchers concluded that PRT is substantially more costly than IMRT and does not produce a difference in toxicity 12 months after treatment.


Yu JB, Soulos PR, Herrin J, et al. Proton versus intensity-modulated radiotherapy for prostate cancer: Patterns of care and early toxicity. Journal of the National Cancer Institute. Published early online December 14, 2012. doi: 10.1093/jnci/djs463

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