Rational use of intensity-modulated radiation therapy: the importance of clinical outcome.

During the last 2 decades, intensity-modulated radiation therapy (IMRT) became a standard technique despite its drawbacks of volume delineation, planning, robustness of delivery, challenging quality assurance, and cost as compared with non-IMRT. The theoretic advantages of IMRT dose distributions are generally accepted, but the clinical advantages remain debatable because of the lack of clinical assessment of the effort that is required to overshadow the disadvantages. Rational IMRT use requires a positive advantage/drawback balance. Only 5 randomized clinical trials (RCTs), 3 in the breast and 2 in the head and neck, which compare IMRT with non-IMRT (2-dimensional technique in four fifths of the trials), have been published (as of March 2011), and all had toxicity as the primary endpoint. More than 50 clinical trials compared results of IMRT-treated patients with a non-IMRT group, mostly historical controls. RCTs systematically showed a lower toxicity in IMRT-treated patients, and the non-RCTs confirmed these findings. Toxicity reduction, counterbalancing the drawbacks of IMRT, was convincing for breast and head and neck IMRT. For other tumor sites, the arguments favoring IMRT are weaker because of the inability to control bias outside the randomized setting. For anticancer efficacy endpoints, like survival, disease-specific survival, or locoregional control, the balance between advantages and drawbacks is fraught with uncertainties because of the absence of robust clinical data.