Extended-Field IMRT Does Not Increase Risk of Duodenal Toxicity

A study of women with cervical or endometrial cancer who require treatment to the para-aortic (PA) lymph nodes can safely receive extended-field intensity modulated radiation therapy (EF-IMRT) without increased risk of duodenal toxicity. This study was published in Practical Radiation Oncology (2015; doi:10.1016/j.prro.2014.10.013).

IMRT is one of the radiation therapy (RT) treatment options for cervical and endometrial cancers. RT is employed to treat both known disease and to prophylactically treat lymph nodes that may harbor microscopic spread of cancer cells too small to be visualized by scans.

PET/CT scans are frequently used to assess the lymph node in locally advanced cervical cancer. Unfortunately, PET/CT scans have a false–negative rate of 20% to 25% for PA disease, which could result in undertreating patients if they receive pelvis-only RT.

EF-IMRT, including both the pelvic and PA region, is recommended for patients who present with PA nodal disease. In addition, some patients with cervical and endometrial cancers may be found to have pelvic nodal disease on a PET/CT scan and have a higher risk of microscopic disease in the PA region. For these patients, the IMRT treatment field may be extended to treat the PA region prophylactically.

This single-institution, retrospective analysis included 76 patients with cervical or endometrial cancers who were treated with EF-IMRT to the PA lymph nodes, either to treat known PA disease or for prophylactic intent. The study included patients cared for at the University of Pittsburgh Cancer Institute in Pittsburgh, Pennsylvania, between 2005 and 2013. The median age of patients at treatment was 54 years (range: 26 to 84 years).

Cervical cancer was the primary cancer type in 64 of the 76 patients (84.2%), and 12 patients (15.8%) had endometrial cancer. Forty-one patients were treated with EF-IMRT due to positive PA disease, and 35 patients were treated prophylactically. The median follow-up duration for all patients was 18.5 months (range: 4.1 to 91.7 months).

Among the 76 patients, three (3.9%) had grade 3 acute gastrointestinal toxicity, which is classified as "requiring hospitalization or elective operative intervention indicated; disabling." Only three of the remaining 73 patients experienced grade 2 gastrointestinal toxicity, which indicates a "likely duodenal obstruction creating symptomatic, altered gastrointestinal function."

"Our study confirms that when the duodenal dose was kept within the prescribed limits, V55 below 15 cm3, patients who received EF-IMRT had very low rates of side effects and excellent regional control," said Sushil Beriwal, MD, the study's lead author and an associate professor of Radiation Oncology at the University of Pittsburgh Cancer Institute, specializing in gynecologic, breast, and prostate cancers.

"This is one of the largest studies to examine duodenal toxicity rate for EF-IMRT treatment of gynecologic malignancies,” said Beriwal. “These findings are especially important for patients who have positive metastatic disease in the para-aortic lymph nodes; they are typically the patients with advanced cervical and endometrial cancer, many of whom will likely receive concurrent chemotherapy, which can increase the risk of side effects and toxicity. EF-IMRT is an excellent option for durable control of their disease. We hope to see larger randomized trials to further define and refine EF-IMRT for these patients."

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