Imaging Technology News 9/08

Solutions Applied A CASE STUDY Using Image-Guided IMR Radiation Treatment Image-guided radiation therapy (IGRT) treatments are rapidly becoming standard practice everywhere. In small community cancer centers, as well as large research hospitals, daily imaging at the time of treatment is catching on because it fills in a key piece of the radiation therapy picture. With advances in imaging technology, clinicians are able to visualize the location, extent and motion of tumors with a high degree of accuracy and to plan very precisely targeted treatments. Now imagers on the treatment machine itself give clinicians confidence that the treatments they plan are the treatments they deliver. Varian's IGRT, which integrates simulation, planning and delivery, enables clinicians to deliver dose more accurately to the target while accounting for various factors such as tumor or critical structure motion or daily differences in patient set up. The following case study is one example of the growing trend toward image-guided treatment. The case shows how image-guidance is reducing the risk of toxic effects in the extended-field treatment of cervical cancer. by Dwight E. Heron, MD, FACRO Department of Radiation Oncology, University of Pittsbur Introduction Cancer that arises in the cervix typically spreads in an orderly progression through the lymphatic system from the pelvic lymph nodes to the external iliac nodes up the para-aortic chain toward the chest and neck. Treating cervical cancer patients with evidence of pelvic lymph-node involvement prophylactically with an extended field of radiation to the abdomen from the T12 vertebral body through the ischial tuberosities has been shown to improve cure rates.1 However, extended-field radiotherapy has also been associated with significant gastrointestinal toxicity, especially when it is combined with chemotherapy.2 For this reason, the technique has not been widely adopted. At UPMC, we have demonstrated that image-guided, intensity-modulated radiation therapy (IG-IMRT) reduces the radiation dose to normal tissues of the abdomen, making extended-field radiotherapy, in combination with chemotherapy, a feasible treatment option for appropriately selected cervical cancer patients.3, 4 This case study details the successful treatment of one such patient. In 2005, this patient received extended-field IG-IMRT with a simultaneous integrated boost to the involved lymph nodes. Her comprehensive treatment plan also included concurrent tandem and ring brachytherapy to the cervix and cisplatin chemotherapy. Figure 2. Axial (left upper), coronal (left lower) and sagittal (right lower) views show the contours of the cervical cancer and regional lymph nodes. The lymph nodes are outlined in green and the regional nodal and cervical cancer is outlined in orange. The modeled view (right upper) shows the extended field, including the cervix and lymph nodes. The abnormal lymph nodes are outlined in green. Image courtesy of the University of Pittsburgh Cancer Institute. cervix and a 4-centimeter expansile mass with bilateral parametrial extensions. A Pap smear and endometrial biopsy confirmed a diagnosis of squamous cell cervical cancer. An MRI revealed a tumor measuring 4.6 x 3.6 x 4.5 centimeters. (Figure 1.) In addition, an FDG PET/CT scan showed spread to the left obturator and external iliac lymph node. Based on these findings, she was staged at IIB cervical cancer. Treatment The large size of the cervical mass and the evidence of pelvic lymphadenopathy made this patient an ideal candidate for extended-field radiation treatment. We devised a treatment plan for her that (1) was extendedfield IMRT, (2) integrated a simultaneous boost, (3) was PET/CT based, (4) involved 4D CT evaluation of abdominal organ motion and (5) used all the elements of onboard imaging to localize and verify her positioning each day. We delivered a radiation dose of 45 Gy (1.8 Gy per fraction) over five weeks to an extended field that included the pelvis and the para-aortic chain. Simultaneously, we delivered an in-field radiation boost of 55 Gy (2.2 Gy per fraction) to the FDG-avid abnormal lymph nodes. PET/CT simulation images were utilized by the Varian Eclipse™ treatment planning system to create the highly conformal plan with the integrated boost. We used 4D CT imaging to contour the gross tumor volume (both primary and lymph node), as well as the lymph node regions, small bowel, rectum, bladder, bone marrow, and femoral heads. In addition, we delineated the treatment margin based on 4D imaging taken during the entire respiratory cycle. (Figure 2.) The PET/CT-based IMRT treatment plan was delivered with the Varian Trilogy® system, using a sliding-window technique to shape the beam. (Figure 3.) Patient setup was verified daily by kV-kV and gated kV-kV image matching and twice a week by cone-beam CT, using the Trilogy’s On-Board Case report A 67-year-old AfricanAmerican female presented with intermittent postmenopausal bleeding. Physical examination showed a barrel-shaped Figure 1. The pretreatment sagittal MRI demonstrates expansile cervical mass and intrauterine fluid collection. Image courtesy of the University of Pittsburgh Cancer Institute.

Table of Contents Feed for the Digital Edition of Imaging Technology News 9/08

Imaging Technology News 9/08 Contents IGRT How IGRT Targets the Prostate ASTRO Oncology Information Management Systems (OIMS) Imaging Leading the Intense Race Against Cancer SBRT - The New Treatment of Choice Top IMRT/IGRT Centers to Watch Molecular Imaging: Ready for the Limelight CR or DR in the ER? Have You Hit the Glass Ceiling?

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