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Dose-painted intensity-modulated radiation therapy reduced toxicity for anal canal cancer
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Dose-painted intensity-modulated radiation therapy — which allows delivery of escalated radiation doses to gross tumor and lower doses to normal surrounding tissue — plus 5-FU and mitomycin-C demonstrated significant sparing of grade-3 or higher gastrointestinal and dermatologic acute toxicity for patients with anal canal cancer.
Lisa Kachnic, MD, chief of the department of radiation oncology at Boston University School of Medicine, presented findings from this phase-2 study.
Researchers from the Radiation Therapy Oncology Group conducted a multi-institutional study (RTOG 0529) to examine whether the combined rate of grade-2 or higher gastrointestinal (GI) and genitourinary (GU) acute adverse events with dose-painted intensity-modulated radiation therapy (DP-IMRT) was reduced by 15% as compared with the mitomycin-C arm of the recently published RTOG 9811 trial.
An important secondary endpoint was to assess the ability of investigators to perform DP-IMRT within the guidelines delineated.
Fifty-two patients were analyzed. Seventy-seven percent of patients had grade-2 or higher GI and GU acute adverse events, which was equivalent to the rate from RTOG 9811.
Therefore, the primary endpoint was not met. However, compared with RTOG 9811, there was a statistically significant reduction in grade-3 or higher GI and GU acute adverse events (P < .008), grade-3 or higher GI adverse events (P=.012) and grade-3 or higher dermatologic adverse events (P <.0001).
Concerning the secondary endpoint, required initial IMRT planning revisions, 69% required volume recontouring before treatment, and the No. 1 offender was incorrect mesorectal contouring, according to data presented by Kachnic.
No major deviations concerning tumor and nodal planning target volume were noted; there were three cases with major deviations for exceeding small bowel and femoral head tolerance.
The median radiation duration was 43 days vs. 49 days in RTOG 9811. Sixty-three percent of patients showed complete clinical response, 15% had persistent but not progressive disease, one patient had clinically suspicious progression and there was no evaluation performed in 10%.
“The early clinical complete response is encouraging, but we need to look at our two-year endpoints to validate this approach,” Kachnic said.
For more information:
- Kachnic LA. #10.