Interpreting Radiation Treatment Planning Study Results: A Note of Caution

Email:[email protected] Prostate cancer is the most commonly diagnosed cancer among males in the United States.1 The treatment of prostate cancer has several options, including external beam radiation therapy. The primary goal of radiation therapy is to control the tumor by delivering a maximum dose to the tumor site, yet minimizing the radiation dose to normal tissues. The development of advanced delivery techniques such as intensity modulated radiation therapy (IMRT) and volumetric modulated arc therapy (VMAT) as well as more accurate treatment planning systems have improved tumor control in radiation therapy. Intensity modulated radiation therapy is a treatment technique that delivers the radiation beam in a static mode, whereas VMAT is considered to be a rotational IMRT that allows the beam to be delivered with the gantry of the machine rotating around the patient.2 Sophisticated treatment planning systems have also increased the accuracy of dose calculation and improved the work flow in the clinic. The results from different complex delivery techniques, however, may vary from one institution to another. The main purpose of this article is to provide a brief summary of the reasons that may have caused discrepancies among different treatment planning studies on prostate cancer. This study reviewed the most recent literature on prostate cancer treatment planning. The literature search was conducted using the terms “prostate cancer”, “IMRT”, and “VMAT” on Google Scholar. According to the review, the common agreement among different studies was the decreased treatment time and less number of monitor units (MUs) associated with VMAT when compared to IMRT.3-14 There were discrepancies in dosimetric results for organs at risk (OARs)among different authors.3-14 For example, Kjaer-Kristoffersen et al.3 reported that VMAT had the capability to produce better or equal sparing of OARs than IMRT. In contrast, Yoo et al.4 reported that IMRT was better in sparing OARs than VMAT. Zhang et al.5 showed that VMAT was better than IMRT in sparing the rectal wall. In a study by Tsai et al.,6 there