In new data presented at last week's AAPM Annual Meeting, researchers from Spain have demonstrated that treatment of endometrial cancer using the Axxent eBx delivered a lower dose of radiation to surrounding organs-at-risk (OARs) than commonly used radionuclide-based high-dose-rate brachytherapy.

The study, headed up by Sergio Lozares from Miguel Servet University Hospital, studied 36 patients with endometrial cancer previously treated with the Axxent. The researchers compared the eBx plan with equivalent plans created for iridium-192 (Ir-192) and cobalt-60 (Co-60) brachytherapy, using a prescription of 5 Gy per fraction applied in three or five fractions. Each eBx treatment fraction took about 3–6 minutes, similar to that for Ir-192.

Patients receiving the electronic brachytherapy experienced a reduction in V35% and V50% (the percentage of volume receiving 35% and 50% of the prescription dose) to all OARs, as well as a reduction in D2cm3 (the highest dose to a 2 cm3 OAR volume, as a percentage of prescription dose).

For example, dosimetric analysis showed that V35%, V50% and D2cm3 for the bladder were 14.8%, 7.2% and 66.4% for eBx, compared with 26.6%, 11.9% and 71.6% for Ir-192, and 23.2%, 10.6% and 70.2% for Co-60. The researchers saw similar dosimetric trends for the rectum and sigmoid.

"Ir-192 provides a similar dose to eBx, but the X-rays are higher in energy, so after treatment they travel further into the body," explained Rob Neimeyer, director of X-ray Technologies at Xoft.

As observed previously, the dose delivered to the target volume was considerably higher for eBx, with a V150 (the volume receiving 150% of the prescribed dose) of 20.5%, compared with 8.6% and 7.8% for Ir-192 and Co-60, respectively. Despite this, no rectal or urinal toxicity above Grade 1 was observed in any of the 36 cases, and only one instance of Grade 2 vaginal mucositis occurred.

"By precisely targeting cancer cells and sparing surrounding healthy tissue and organs, the Xoft system can successfully treat endometrial cancer while reducing the risk of exposure to surrounding tissue," said Lozares. "We are encouraged by these early results demonstrating that the Xoft system can be a clinically valuable treatment option for appropriate patients."

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