Dosimetric and radiobiological comparison of TomoTherapy and IMRT plans for prostate cancer

The purpose of this study was to investigate the dosimetric and radiobiological parameters of IMRT and TomoTherapy techniques to determine the best technique for the treatment of prostate cancer. Dynamic IMRT and Helical TomoTherapy (HT) radiotherapy techniques were used for the treatment planning of 10 patients with prostate cancer. Tumor Control Probability (TCP) and Normal Tissue Complication Probability (NTCP) based on Lyman-Kutcher-Burman (LKB) and Relative Seriality (RS) models as radiobiological parameters in addition to the multiple dosimetrics including Equivalent Uniform Dose (EUD), Heterogeneity Index (HI), and Conformity Index (CI) were evaluated. The mean NTCP value based on the LKB model for the IMRT method was higher than that for the HT method by approximately 4.62% for the bladder and 4.89% for the rectum, respectively. Similarly, in the RS model, the average NTCP values for IMRT were approximately 4.14% and 12.78% for the bladder and rectum, higher than the HT. The mean values of the HI and CI indices in IMRT were obtained as 0.06 ± 0.01 and 1.13 ± 0.08, respectively. With the HT technique, the index values were equal to 0.04 ± 0.01 and 1.09 ± 0.05, respectively. The mean doses to the rectum and right/left femoral heads were 13.19%, 11.32%, and 10.90% higher in IMRT than in HT, respectively. However, the mean dose to the bladder tissue was 17.13% higher in HT than in IMRT. Our study demonstrated that HT plans were superior to IMRT plans in terms of estimated NTCP using radiobiological models (LKB and RS) for healthily tissues. Except for the higher treatment duration, while having a desired and uniform dose distribution to the tumor, the TomoTherapy technique leads to preservation of healthy organs.