IMRT produced less toxicity, similar outcomes as conventional radiation in anal cancer

Issue: February 10, 2011

2011 Gastrointestinal Cancers Symposium

SAN FRANCISCO — Chemotherapy with dose-painted intensity-modulated radiation therapy for anal cancer produced similar OS and DFS as 2 years of treatment with chemotherapy and conventionally delivered radiation therapy, but with fewer significant adverse events, results from the phase 2 Radiation Therapy Oncology Group study 0529 showed.

Lisa Kachnic, MD, chair of radiation oncology at Boston University and one of the study’s researchers, said the Radiation Therapy Oncology Group (RTOG) will now use dose-painted IMRT as the standard radiation technique in future trials assessing novel agents combined with radiation to treat anal cancer.

“Dose-painted IMRT with 5-fluorouracil and mitomycin-C chemotherapy for anal canal cancer is associated with significant sparing of grade-3+ dermatologic and gastrointestinal toxicity without compromising 2-year outcomes,” Kachnic said.

She presented the results during a press conference in advance of the 2011 Gastrointestinal Cancers Symposium.

Kachnic and colleagues analyzed OS and DFS for 52 patients with stage II/stage III disease treated with IMRT and 5-FU/mitomycin-C chemotherapy. The primary endpoint for the study was a 15% reduction in acute grade 2 or higher gastrointestinal/genitourinary toxicities compared with results from the 325-patient, 5-FU/mitomycin-C arm of RTOG 9811. That trial used conventionally delivered radiation.

At a median follow-up of 26.7 months, 2-year DFS was 77% and OS was 86%. Kachnic said those outcomes were similar to results from RTOG 9811. At 2 years, DFS in that trial was 75% and OS was 91%. Other outcomes proved to be similar (see graph).

Patients underwent a median of 43 days of dose-painted IMRT compared with 49 days for conventional radiation therapy in RTOG 9811. Kachnic said fewer days of radiation are important because earlier studies have shown that a longer duration of radiation increases the risk for local recurrence.

Clinical response was 64% at 8 weeks and 81% at 12 weeks after dose-painted IMRT.

Patients in RTOG 0529 experienced fewer incidents of grade-3/grade-4 dermatologic and gastrointestinal acute toxicity compared with patients in RTOG 9811. The study did not the meet primary endpoint, but Kachnic said dose-painted IMPRT was associated with a significant sparing of grade-3+ gastrointestinal toxicities.

She said dose-painted IMRT was also associated with an unexpected reduction of more than 50% for grade-3+ dermatologic toxicities. – by Jason Harris

For more information:

Kachnic L. #368. Presented at: the 2011 Gastrointestinal Cancers Symposium; Jan. 20-22, 2011; San Francisco.

Disclosure: Dr. Kachnic has no relevant financial disclosures.

The majority of patients with anal cancer, almost 85%, are cured with chemotherapy and radiation alone. Because of this high success rate, researchers are now focused on ways to improve the side effect profile of this already very effective therapy. After short-term follow-up, IMRT appears to be as effective as conventional radiation in the treatment of anal cancer, but with decreased side effects. While larger studies will need to be performed and longer follow-up is required, IMRT may emerge as a key treatment modality for anal cancers.

- Jennifer C. Obel, MD,
Assistant Clinical Professor of Medicine, University of Chicago

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