A review of the clinical evidence for intensity-modulated radiotherapy

Aims: Intensity-modulated radiotherapy (IMRT) is a development of three-dimensional conformal radiotherapy that offers improvements in dosimetry in many clinical scenarios. Here we review the clinical evidence for IMRT and present ongoing or unpublished randomised controlled trials (RCTs).

Methods: We identified randomised and non-randomised comparative studies of IMRT and conventional radiotherapy using MEDLINE, hand-searching Radiotherapy and Oncology and the International Journal of Radiation Oncology, Biology and Physics and the proceedings of the American Society for Therapeutic Radiology and Oncology and the European Society for Therapeutic Radiology and Oncology annual meetings. The metaRegister of Controlled Trials was searched to identify completed-unpublished, ongoing and planned RCTs.

Results: Sixty-one studies comparing IMRT and conventional radiotherapy were identified. These included three RCTs in head and neck cancer (205 patients) and three in breast cancer (664 patients) that had reported clinical outcomes; these were all powered for toxicity-related end points, which were significantly better with IMRT in each trial. There were 27 additional non-randomised studies in head and neck (1119 patients), 26 in prostate cancer (>5000 patients), four in breast cancer (875 patients) and nine in other tumour sites. The results of these studies supported those of the RCTs with benefits reported in acute and late toxicity, health-related quality of life and tumour control end points. Twenty-eight completed-unpublished, ongoing or planned RCTs incorporating IMRT were identified, including at least 12,310 patients, of which 15 compared conventional radiotherapy within IMRT as a randomisation or pre-planned stratification.

Discussion: Inverse-planned IMRT maintains parotid saliva production and reduces acute and late xerostomia during radiotherapy for locally advanced head and neck cancer, reduces late rectal toxicity in prostate cancer patients allowing safe dose escalation and seems to reduce toxicity in several other tumour sites. Forward-planned IMRT reduces acute toxicity and improves late clinician-assessed cosmesis compared with conventional tangential breast radiotherapy.