ASTRO 2015: Image-Guided Intensity-Modulated Radiation Therapy Reduces Bowel Side Effects in Cervical Cancer Patients
For cervical cancer patients undergoing postsurgical radiation therapy, image-guided intensity-modulated radiation therapy (IMRT) resulted in a 14% reduction in moderate-to-severe bowel side effects when compared to conventional three-dimensional conformal radiation therapy (3D CRT), according to research presented by Chopra et al on October 19 at the American Society for Radiation Oncology’s (ASTRO’s) 57th Annual Meeting.
Postoperative pelvic radiation therapy is the current standard of care for many patients with cervical cancer, yet it may affect surrounding organs and tissue and is sometimes associated with long-term gastrointestinal side effects. Image-guided IMRT uses technology to manipulate beams of radiation to conform to the shape of a tumor, thus allowing clinicians to limit exposure to surrounding tissue.
Trial Details
The phase III randomized clinical trial, conducted at Advanced Centre for Treatment Research and Education in Cancer (ACTREC), Tata Memorial Centre in Mumbai, India, included 240 patients aged 18 years and over who were undergoing adjuvant chemoradiation therapy and had no preexisting bowel disease or injury. This planned interim analysis of the study assessed 117 of the patients who had completed an average of 20-month follow-up (range = 2–46 months).
Patients were categorized into two groups: 56 patients received 3D CRT, and 61 patients received image-guided IMRT. Patient groups were randomized, and had similar treatment histories, with 41.3% (23 patients) of the 3D CRT group having radical hysterectomies and 43.5% (27 patients) of the IMRT group having radical hysterectomies. Additionally, 91.8% (51 patients) of the 3D CRT group had chemoradiation therapy, with 85.5% (52 patients) of the IMRT group undergoing chemoradiation therapy.
Radiotherapy included 50 Gy, administered over 25 treatments in a 5-week time frame. CRT patients received cisplatin (40 mg/m2) congruently. This was followed by two fractions of cylinder-based intravaginal brachytherapy at 6 Gy each.
Patients randomly assigned to the 3D CRT group received treatment on a linear accelerator, and the IMRT patients received treatment via TomoTherapy. Strict constraints were applied in the administration of the IMRT to ensure that no more than 200 cc and 100 cc of small bowel received 15 and 40 Gy, respectively.
Findings
At each follow-up visit, patients’ bowel side effects were recorded using 11 symptom scales of Common Toxicity Criteria for Adverse Events (CTCAE version 3.0). In the 3D CRT group, 58.9% (33 patients) experienced grade ≥ 2 acute bowel toxicity (indicating moderate to severe diarrhea, vomiting, nausea, lower abdominal distension, or pain) compared to 54% (33 patients) in the IMRT group (P = .59).
The reported late grade ≥ 2 bowel toxicity rate was 25% (14 patients) in the 3D CRT group and 11.4% (7 patients) in the IMRT group (P = .13); and the rate of late grade ≥ 3 bowel toxicity (indicating severe diarrhea, lower abdominal pain, subacute intestinal obstruction requiring medical or surgical intervention, bowel perforation, or death) was 17.6% (10 patients) in the 3D CRT group and 3.2% (2 patients) in the IMRT group (P = .02). Neither the surgery type nor the administration of CRT had an impact on bowel side effects.
“These initial results of this interim analysis are encouraging and trend toward possibly a clinically important reduction in moderate-to-severe bowel side effects with the use of [image-guided] IMRT; however, at interim analysis the results are statistically nonsignificant,” said Supriya Chopra, MD, Associate Professor of Radiation Oncology at ACTREC, Tata Memorial Centre.
“While we evaluated patients with cervical cancer in this trial, a significant proportion of patients with other cancers undergo postoperative pelvic radiation worldwide. Therefore, the results of this trial could impact the choice of future radiation delivery technique for various pelvic malignancies,” he added.
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