SAN ANTONIO – Interim results of an ongoing phase III trial show that women who have undergone surgical resection for cervical cancer may be less likely to experience late-onset bowel toxicity if they receive tomotherapy rather than conventionally delivered adjuvant radiotherapy.
In the PARCER trial, grade III or higher radiation-induced bowel toxicity occurred in just 3.2% of women who had adjuvant image-guided intensity-modulated radiation therapy (IG-IMRT) vs. 17.8% of those who received three-dimensional conformal radiation therapy (3D-CRT) at a median of 20 months. The 14.6% absolute difference was statistically significant (P = .02) but this was an exploratory endpoint.
The primary endpoint of late grade II or higher bowel toxicity was not statistically significant, but also showed around a 14% absolute difference between the arms, at 11.4% in the IG-IMRT- and 25% in the 3D-CRT–treated women (P = .13).
Nevertheless, the results are clinically relevant and the trial continues accrual to a target of 240 patients. The stopping rules were not met and there is the potential for the results to become statistically significant with longer follow-up, said Dr. Supriya Chopra of Tata Memorial Centre in Mumbai, India.
Speaking at a press briefing held during the annual meeting of the American Society for Radiation Oncology, she said: “Although this trial was done for cervical cancer, the trial results would impact practice for all endometrial cancer patients as well who would undergo postoperative radiation, and prostate cancer patients.”
“There was a substantial reduction in serious toxicities, something that justifies the added labor intensity and the added resource utilization of the more sophisticated approaches and still adds value to patients because there is a reduction in hospitalization and there is a reduction in the cost of downstream side effects,” said Dr. Brian Kavanagh of the University of Colorado at Denver, Aurora, and president-elect of the ASTRO Board of Directors, in an interview.
Data on 120 patients randomized to date were presented, of whom 58 had received conventional 3D-CRT, and 62 who had undergone IG-IMRT and received 50 Gy of radiation given in 24 fractions over 5 weeks. Patients also received weekly cisplatin (50 mg/m2) and two additional 6 Gy doses of pelvic radiation delivered via brachytherapy. In the IG-IMRT arm, investigators were careful to ensure that very little radiation reached the small bowel. Toxicity was assessed using the Common Toxicity Criteria for Adverse Events version 3.0.
Bowel toxicity can affect a substantial number of women after pelvic irradiation, and it tends to evolve over time, Dr. Chopra said.
“Most of the patients would be continually bothered about having chronic diarrhea or having abdominal bloating sensation which cannot be cured by anything, or just having some lower abdominal pain, which definitely affects their quality of life,” she explained.
The trial thus aimed to see if using the latest radiation technology could help to reduce these side effects.
“These early results are very encouraging but not robust enough to change practice at the moment,” Dr. Chopra said. If the trial is positive, however, she added that IMRT could become the new standard of care.
Final analyses will be undertaken after accrual has been completed and at a median follow-up of 3 years, so potentially by the end of 2018, she said.