Feature | Intensity Modulated Radiation Therapy (IMRT) | October 20, 2015

More targeted radiation therapy found to lessen reported moderate-to-severe toxicity compared to 3-D conformal RT

image-guided IMRT, IG-IMRT, bowel side effects, cervical cancer patients, ASTRO 2015

October 20, 2015 — For cervical cancer patients undergoing postsurgical radiation therapy, image-guided intensity-modulated radiation therapy (IG-IMRT) resulted in a 14 percent reduction in moderate-to-severe bowel side effects when compared to conventional three-dimensional conformal radiation therapy (3-D CRT). This conclusion was supported by research presented at the American Society for Radiation Oncology’s (ASTRO’s) 57th annual meeting.

Post-operative pelvic radiation therapy is the current standard of care for many patients with cervical cancer, yet may affect surrounding organs and tissue and be associated with long-term gastrointestinal side effects. IG-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.

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, ages 18 and over who were undergoing adjuvant chemoradiation therapy (combined chemotherapy and radiation therapy) and had no pre-existing bowel disease or injury.

This planned interim analysis of the study assessed 117 of the patients who had completed an average of 20-months follow-up (range: two to 46 months). Patients were categorized into two groups: Fifty-six patients received 3-D CRT and 61 patients received IG-IMRT. Patient groups were randomized and had similar treatment histories, with 41.3 percent (23 patients) of the 3-D CRT group having radical hysterectomies and 43.5 percent (27 patients) of the IG-IMRT group having radical hysterectomies. Additionally, 91.8 percent (51 patients) of the 3-D CRT group had chemoradiation therapy, with 85.5 percent (52 patients) of the IG-IMRT group undergoing chemoradiation therapy. RT included 50 Gy, administered over 25 treatments in a five-week timeframe. CRT patients received Cisplatin (40 mg/m2) congruently. This was followed by two fractions of brachytherapy (cylinder based intravaginal brachytherapy) of 6 Gy each.

Patients randomized to the 3-D CRT group received treatment on a linear accelerator, and the IG-IMRT patients received treatment using tomotherapy. Strict constraints were applied in the administration of the IG-IMRT to ensure that no more than 200 cc and 100 cc of small bowel received 15 and 40 Gy respectively.

At each follow-up visit, patients’ bowel side effects were recorded by clinicians using 11 symptom scales of Common Toxicity Criteria for Adverse Events (CTCAE version 3.0). In the 3-D CRT group, 58.9 percent (33 patients) experienced =2 acute bowel toxicity (indicating moderate to severe diarrhea, vomiting, nausea, lower abdominal distension or pain) compared to 54 percent (33 patients) in the IG-IMRT group (p=0.59). The reported late grade =2 bowel toxicity was 25 percent (14 patients) in the 3-D CRT group and 11.4 percent (7 patients) in the IG-IMRT group (p=0.13); and the 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 percent (10 patients) in the 3-D CRT group and 3.2 percent (2 patients) in the IG-IMRT group (p=0.02). Further, research indicated that 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 IG-IMRT, however at interim analysis the results are statistically nonsignificant,” said Supriya Chopra, M.D., lead study author and associate professor of radiation oncology at ACTREC, Tata Memorial Centre in Mumbai, India. “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.”

For more information: www.astro.org


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