A comparison of the radiation exposure to the left anterior descending artery (LAD) and left ventricle (LV) was performed for twenty-three left breast cancer patients. For each participant, two tangential fields 3D-CRT, two- and seven-field IMRT and two and four partial arcs VMAT plans were created. Dose constraints for CTV, ipsilateral lung and heart were followed. The V_40Gy, V_30Gy, D_av of LAD and V_23Gy, V_5Gy, D_av of LV were calculated and extracted from the plans. Parametric and non-parametric tests were applied to compare the parameters derived from the five treatment techniques. All generated plans fulfilled the dose constraints. The D_av ranges of the LAD and LV from all examined techniques were 11.77–14.73 Gy and 5.37–6.40 Gy, respectively. The V_40Gy and V_30Gy ranges of the LAD were 2.90–12.91% and 10.80–18.51%, respectively. The V_23Gy and V_5Gy of the LV were 4.29–7.43% and 18.24–30.05%, respectively. The VMAT plans and seven-field IMRT significantly reduced the V_40Gy, V_30Gy of LAD and V_23Gy of LV compared with the two-field treatments (p < 0.05). However, 3D-CRT plans provided statistically lower values for V_5Gy of LV over the other techniques (p < 0.05). The presented results provide a detailed dataset of the radiation burden of two critical cardiac structures from five radiotherapy techniques.

The objective of this study was to estimate the risk of developing second malignancies to partially in-field organs from volumetric modulated arc therapy (VMAT) of cervical cancer and to compare the above risks with those from the conventional three-dimensional conformal radiotherapy (3D-CRT). Seventeen consecutive patients with uterine cervix carcinoma were selected. VMAT and 3D-CRT plans were generated with 6 and 10 MV photons, respectively. The prescribed tumor dose was 45 Gy given in 25 fractions. Differential dose-volume histogram data from the treatment plans were obtained for the partially in-field organs such as bladder and rectum. These data were used to estimate the patient-specific lifetime attributable risk (LAR) for bladder and rectal cancer induction with a non-linear model based on a mixture of plateau and bell-shaped dose-response relationships. The estimated risks per 10000 people were compared with the baseline risks for unexposed population. The patient-specific rectal cancer risk estimates from VMAT were significantly lower than those from 3D-CRT (P = 0.0144). The LARs for developing bladder malignancies from VMAT were significantly high compared to those from conventional irradiation (P = 0.0003). The mean difference between the patient-specific LARs for radiation-induced bladder and rectal malignancies as derived from 3D-CRT and VMAT plans was 6.6% and 2.0%, respectively. The average LAR for developing bladder and rectal malignant diseases due to VMAT was 9.2 x 10(-4) and 43.7 x 10(-4), respectively. The corresponding risks following 3D-CRT were 8.6 x 10(-4) and 44.6 x 10(-4). These average risks showed that pelvic irradiation increases the baseline probability for cancer induction by 12.6-19.1%. The differences in the second cancer risks associated with the VMAT and 3D-CRT for cervical cancer were found to be small. Both treatment techniques resulted in considerable increased probabilities for developing bladder and rectal malignancies relative to those of unirradiated population.

The aim of the present study was to examine the effect of the photon beam energy on the volumetric modulated arc therapy (VMAT) plan quality for prostate cancer and on the risk of secondary carcinogenesis. Separate VMAT plans with 6‑MV and 10‑MV photons were created for 11 low‑risk patients with prostate cancer. The prescribed tumor dose was 70 Gy delivered in 28 fractions. The normal tissue integral dose and parameters associated with planning target volume and organs at risk were determined by the treatment planning data. A non‑linear mechanistic model considering the effects of tumor dose fractionation and cell proliferation was employed for estimating the patient‑specific lifetime attributable risk (LAR) for bladder and rectal cancer induction. Data from differential dose‑volume histograms were used for these risk assessments. The mean values of the planning parameters from 6‑MV treatment plans differed by 0.2‑3.4% from those associated with irradiation using 10‑MV photons. The LAR range for developing secondary bladder malignancies varied between 0.041 and 0.129% by the patient under investigation and the beam energy used. The corresponding range for the appearance of rectal malignant diseases was 0.047‑0.153%. The mean percentage difference between the bladder cancer risks from VMAT with 6‑MV and 10‑MV photons was 2.6±2.3%. The corresponding difference for secondary rectal malignancies was 0.7±0.6%. Therefore, VMAT for prostate cancer with both 6‑MV and 10‑MV photons leads to clinically equivalent treatment plans and to similar secondary bladder and rectal cancer risks.

(1) Aim: This study was conducted to radiobiologically compare radiotherapy plans for gastric cancer with a newly developed software tool. (2) Methods: Treatment planning was performed on two computational phantoms simulating adult male and female patients. Three-dimensional conformal radiotherapy (3D-CRT), intensity-modulated radiation therapy (IMRT) and volumetric modulated arc therapy (VMAT) plans for gastric cancer were generated with three-photon beam energies. The equivalent uniform dose (EUD), tumor control probability (TCP) of the target and normal tissue control probability (NTCP) of eight different critical organs were calculated. A new software was employed for these calculations using the EUD-based model and dose-volume-histogram data. (3) Results: The IMRT and VMAT plan led to TCPs of 51.3–51.5%, whereas 3D-CRT gave values up to 50.2%. The intensity-modulated techniques resulted in NTCPs of (5.3 × 10⁻⁶–3.3 × 10⁻¹)%. The corresponding NTCPs from 3D-CRT were (3.4 × 10⁻⁷–7.4 × 10⁻¹)%. The above biological indices were automatically calculated in less than 40 s with the software. (4) Conclusions: The direct and quick radiobiological evaluation of radiotherapy plans is feasible using the new software tool. The IMRT and VMAT reduced the probability of the appearance of late effects in most of the surrounding critical organs and slightly increased the TCP compared to 3D-CRT.