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Extended-Field Intensity-Modulated Radiation Therapy for Cervical and Endometrial Cancers Does Not Increase Risk of Duodenal Toxicity

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Key Points

  • When the duodenal dose was kept within prescribed limits, patients who received extended-field intensity-modulated radiation therapy had very low rates of side effects and excellent regional control.
  • Only about 5% of study participants experienced grade 2 or higher gastrointestinal toxicity.

Women with cervical or endometrial cancer who require treatment to the para-aortic lymph nodes can safely receive extended-field intensity-modulated radiation therapy without increased risk of duodenal toxicity, according to a study by Xu et al in Practical Radiation Oncology.

Extended-Field Intensity-Modulated Radiation Therapy

Positron-emission tomography/computerized tomography (PET/CT) scans are frequently used to assess the lymph nodes in locally advanced cervical cancer. Unfortunately, PET/CT scans have a false-negative rate of 20% to 25% for para-aortic disease, which could result in undertreating patients if they receive pelvis-only radiation therapy.

Extended-field intensity-modulated radiation therapy that includes both the pelvic and para-aortic region is recommended for patients who present with para-aortic 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, as such, have a higher risk of microscopic disease in the para-aortic region. For these patients, the intensity-modulated radiation therapy treatment field may be extended to treat the para-aortic region prophylactically.

Study Findings

This single-institution, retrospective analysis included 76 patients with cervical or endometrial cancers who were treated with extended-field intensity-modulated radiation therapy to the para-aortic lymph nodes to treat known para-aortic disease or for prophylactic intent. The study included patients treated at the University of Pittsburgh Cancer Institute between 2005 and 2013.

The median age of patients at treatment was 54 years. Of the 76 patients, 64 (84.2 %) had cervical cancer as their primary cancer type, and 12 (15.8%) had endometrial cancer. A total of 41 patients were treated with extended-field radiation due to positive para-aortic disease, and 35 patients were treated prophylactically. The median follow-up duration for all patients was 18.5 months (range = 4.1–91.7 months).

Two recent gynecologic studies have examined the safety of extended-field intensity-modulated radiation therapy, and in one, the volume of the duodenum receiving 55 Gy (V55) was found to be an important dosimetric predictor of duodenal toxicity. None of the patients in this study had V55 above 15 cm3, the previously published criterion for an increased risk of duodenal toxicity.

Utilizing the National Cancer Institute’s Common Terminology Criteria for Adverse Events (CTCAE) scale, 3 of the 76 patients (3.9%) in this study were found to have 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 [extended-field intensity-modulated radiation therapy] 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. “This is one of the largest studies to examine duodenal toxicity rate for [extended-field intensity-modulated radiation therapy] treatment of gynecologic malignancies.”

He continued, “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. [Extended-field intensity-modulated radiation therapy] is an excellent option for durable control of their disease. We hope to see larger, randomized trials to further define and refine [extended-field intensity-modulated radiation therapy] for these patients.”

Dr. Beriwal is the corresponding author for the Practial Radiation Oncology article.

The content in this post has not been reviewed by the American Society of Clinical Oncology, Inc. (ASCO®) and does not necessarily reflect the ideas and opinions of ASCO®.


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