Prostate cancer patients treated with intensity-modulated radiation therapy (IMRT) do not have an increased risk of secondary cancers such as leukemia or myelodysplasia, compared to the standard 3D conformal radiotherapy.

The study, “Second Primary Cancers After Intensity-Modulated vs 3-Dimensional Conformal Radiation Therapy for Prostate Cancer,” was published in the online version of JAMA Oncology.

IMRT is used often in clinical practice for the treatment of prostate cancer and has been shown to reduce radiation exposure to the healthy tissue, allowing focused radiation dose escalation to the specific tumor site. Although questions have been raised over whether this exposure could increase a patient’s risk of developing secondary cancers due to increased radiation exposure to the bone marrow, no concrete observational studies have been conducted to validate this hypothesis.

Amy Berrington de González, DPhil, senior investigator of the National Cancer Institute’s Radiation Epidemiology Branch, was the lead author of this study. González’s research focuses on quantifying potential cancer risks from therapeutic radiology to provide information for public health and clinical purposes.

González and her colleagues compared the health risks associated with IMRT compared to 3D-CRT in terms of the patient’s risk of developing secondary cancers after treatment of their primary prostate tumor. This was an important clinical question because, according to the authors, the radiation dosing for the treatment of prostate cancer is of “particular concern given the potentially higher bone marrow dose.”

Using SEER (Surveillance, Epidemiology, and End Results) Medicare data, the research team analyzed secondary cancer rates in 39,028 men with nonmetastatic prostate cancer treated with intensity-modulated versus 3D-conformal radiotherapy.

The findings showed that:

• 2,901 men developed second cancers; 1,691 were treated using IMRT, and 1,210 were treated using 3D-CRT
• There was no difference in the risk of leukemia or myelodysplasia after IMRT compared to 3D-CRT
• Risks of colon cancer and rectal cancer were significantly lower after IMRT

When discussing the findings, González and her team found that “IMRT was not associated with an early elevated risk of leukemia or myelodysplasia. There was some preliminary evidence of reduced risks of colon and rectal cancers compared with 3D-CRT, which is potentially consistent with lower radiation doses from IMRT to these organs.”

The authors also point out that further confirmatory as well as follow-up studies to monitor the potential impact of IMRT on secondary cancer risks are needed.