Positioning pelvic cancer patients on stomachs for radiation yields better results

Oregon Health & Science University Cancer Institute researchers have found that positioning pelvic cancer patients on their stomachs rather than their backs is a better method for delivering radiation therapy.

Because patients return for multiple therapies, being able to reproduce the positioning of the patient allowed more precision, which reduces toxicity.

“It was a surprising finding,” according to according to Martin Fuss, M.D., the director of the Program in Image-Guided Radiation Therapy, OHSU Radiation Medicine, and OHSU Cancer Institute member.

“This finding runs contrary to the common perception that the supine (on the back) position is more stable, convenient and therefore caused less variation in day-to-day setups. Variation in setups require the use of margins that extend beyond the tumor into normal tissues, exposing organs with limited tolerance to radiation to a higher risk for treatment-induced toxicity,” said Fuss, who is also a professor in the OHSU School of Medicine.

A poster presentation from this study will be presented Sunday, Oct. 28 at the 2007 American Society of Therapeutic Radiology and Oncology (ASTRO) meeting in Los Angeles.

Having a patient lay on his belly, or prone position, has been considered to be uncomfortable and can lead to more patient movement, which can cause more damage to healthy cells that need to be spared from high-dose radiation. But through this study it was found that lying on the stomach, using a belly board, with a hole cut out for the stomach area, may actually aid in sparing normal tissue. Lying on a belly board not only removes the bowel from the pelvis but also reduces pelvic setup variation. The type of radiation used in this study was helical TomoTherapy.

The TomoTherapy system used allows physicians to take a computed tomography or CT scan just before each treatment. With the scan, radiation specialists can verify the position of the tumor and, if necessary, adjust the patient's position to help make sure the radiation is directed right where it should be. This process is also referred to image-guided radiation therapy or IGRT. The treatment system in the study, TomoTherapy Hi•Art, delivers intensity-modulated radiation therapy (IMRT) with a helical, or spiral delivery pattern.

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