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Extended-field IMRT does not increase duodenal toxicity in gynecologic cancers
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The use of extended-field intensity modulated radiation therapy to treat para-aortic lymph nodes resulted in a low duodenal toxicity profile and no high-grade late duodenal toxicity in women with cervical or endometrial cancer, according to the results of a retrospective analysis.
“This is one of the largest studies to examine duodenal toxicity rate for extended-field intensity modulated radiation therapy (EF-IMRT) treatment of gynecologic malignancies,” Sushil Beriwal, MD, medical director of radiation oncology at University of Pittsburgh Cancer Institute, said in a press release. “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 for adverse events and toxicity.”
Previous investigations have yielded conflicting results about the incidence of duodenal toxicity in patients receiving EF-IMRT covering the para-aortic lymph nodes for gynecologic cancers. However, a recent study of the use of EF-IMRT in gynecologic cancers found that receiving 55 Gy (V55) served as an important dosimetric predictor for duodenal toxicity.
Beriwal and colleagues reviewed experiences and rates of duodenal toxicity in patients treated with EF-IMRT to determine rates of duodenal toxicity.
The study included data from 76 women (median age at treatment, 54 years; range, 26-84) with cervical or endometrial cancer treated with EF-IMRT to the para-aortic nodes (n = 41) or prophylactically (n = 35) between 2005 and 2013.
Patients treated prophylactically received a radiation dose of 45 Gy in to the para-aortic nodes in 25 fractions. For involved lymph nodes, physicians delivered a boost to the gross disease with a 0.7 cm expansion to 55 Gy in 25 fractions.
For all patients, the researchers retrospectively contoured the entire duodenum from the gastric outlet to the jejunal transition.
Median follow-up for all patients was 18.5 months (range, 4.1-91.7).
For all patients, the duodenum had a median volume of 83.2 cm3 (range, 21.2-174.9).
Among patients treated with EF-IMRT to prophylactically treat the para-aortic region, the mean V55 for duodenum was 0 cm3, whereas patients treated with EF-IMRT for involved para-aortic lymph nodes, the mean V55 for duodenum was 0.8 cm3 (range, 0-10.6; P = .014). No patient had a V55 greater than 15 cm3. Patients treated prophylactically had a mean V40 of 28.3 cm3 (range, 0-77.3) and patients treated with for involved node had a mean V40 of 41.4 (range, 0-90; P = .016).
Three patients (3.9%) reported grade 3 acute gastrointestinal toxicity. One patient treated prophylactically and two patients treated with EF-IMRT experienced grade 2 gastrointestinal toxicity. No patients experienced grade 3 late gastrointestinal toxicity.
The researchers acknowledged limitations of their study, including its retrospective design and the difficulty associated with contouring the duodenum, which may lead to inter-institution variability in contouring. Further, the lack of late toxicity may have been due to the lower overall dose and decreased dose spread because of simultaneous integrated technique used for boosting involved nodes.
“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 adverse events and excellent regional control,” Beriwal said. “We hope to see larger, randomized trials to further define and refine EF-IMRT for these patients.” – by Cameron Kelsall
Disclosure: The researchers report no relevant financial disclosures.
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