AbstractID: 9562 Title: Intensity Modulated Arc Therapy for Treatment of High-Risk
Endometrial Malignancies
We present an Intensity Modulated Arc Therapy (IMAT) technique for treatment of high- risk endometrial cancer in the context of
multimodality therapy with full surgical staging and high-dose chemotherapy. We wish to treat the tumor bed and nodes but with less
toxicities than that from conventional radiotherapy. To accomplish that, we aimed to reduce bone marrow and small bowel doses.
Published fixed beam Intensity Modulated Radiation Therapy (IMRT) techniques for gynecological treatments are complex due to the
leaf travel limit of 14.5cm on Varian dynamic multileaf collimators. Typically, 5-9 fields are used in the IMRT planning and when
field splitting is required, the number of fields could double. Furthermore, feathering techniques are introduced to avoid junction
problems. The proposed IMAT technique offered a simpler method of treatment planning and delivery. For five patients, two of
whom involved the para-aortic nodes, we found that using two anterior intensity modulated arcs (300o-30o, 330o-60o) adequately treat
the intended target volumes. While this technique does not intentionally spare the bladder and rectum, it does not irradiate them with
more dose than the tumor bed. Comparative conventional and 5-field IMRT plans were generated for each patient. The IMAT
technique spares the small bowel quantitatively similar to IMRT plans and spares the bone marrow by having beams exiting through
the iliac crests and femoral heads. We developed and successfully piloted an optimal IMAT technique that significantly reduced the
dose to critical organs compared with conventional techniques and is simpler to deliver than multi-field IMRT.