Randomized Trials and IMRT: Overkill or Overdue?
Abramson Cancer Center of the University of Pennsylvania
Last Modified: October 22, 2003
Moderator: Theodore L. Phillips, MD., University of California, San Francisco
Soeren M. Bentzen, PhD., DSc., Gray Laboratory Cancer Research Trust, Mount Vernon Hospital, Northwood, Middlesex, United Kingdom
- IMRT is an advanced technology for radiation therapy (RT), using non-uniform radiation beam intensities incident upon the patient.
- From a dosimetric and operational point of view, IMRT is superior to forward-planned treatment, including 3DCRT.
- Despite, the dosimetric advantages of IMRT, the question remains: Will IMRT improve clinical outcomes?
- Various schemes for levels of clinical evidence support of a treatment have been proposed; most define level I evidence as large, adequately powered randomized trials or a metaanalysis supporting the use of treatment. Level IV evidence can be defined as single-arm non-randomized trials comparing results to historical controls.
- Clinical outcome data for IMRT is almost solely level IV evidence.
- Level IV evidence does not equal Level I evidence.
- As a historical example, the use of continuous hyperfractionated accelerated radiation therapy (CHART) for head and neck (H&N) cancers was studied and compared to historical controls treated with conventionally fractionated RT matched for tumor site, T stage, and N stage. These comparisons showed improved outcome with CHART; however, a randomized trial of CHART showed no difference compared to conventional fractionation.
- The above example demonstrates the importance of randomized trials.
- In conclusion, evidence-based IMRT is not showing improved distribution but a therapeutic gain; it is not showing decreased toxicity, but doing so without compromising local control, it is not increasing local control, but doing so without increasing toxicity.