The effect of the different calculation algorithms in non small cell lung cancer 3-dimensional conformal radiotherapy planning on lung dose-volume parameters

Objective: In this study, it was aimed to compare the two different treatment planning algorithms named PB (?pencil beam?) and CS (?convolution superposition?) with regard to lung dose-volume parameters (V5, V13, V20, V30 and MLD) obtained from the created 3-D conformal radiotherapy plans of the lung cancer patients who had lobectomy/bilobectomy surgery.Method: The treatment plans were found retrospectively concerning 10 lung cancer patients who had lobectomy/bilobectomy surgery and adjuvant 3-D conformal radiotherapy. Using PB and CS algorithms, calculations were performed for 6 and 18 MV-X photon beams, respectively. The differences on the relevant lung dose-volume parameters were analyzed retrospectively using Wilcoxon signed rank test in SPSS 15.0 statistical analysis program.Results: For 6 MV-X photon beam, mean V5, V13 and V20 were higher for CS algorithm compared to PB algorithm. On the other hand, mean V30 and MLD were higher for PB algorithm. For 18 MV-X photon beam, mean V5, V13, V20 and MLD were higher for CS algorithm compared to PB algorithm. However only mean V30 was higher for PB algorithm. In terms of lung dose-volume parameters, the difference between PB and CS algorithms was statistically significant in V5, V13 and V30 obtained from plans for 6 MV-X photon beam energy (p= 0.005; p=0.005; p=0.008, respectively).Conclusion: In this study, higher values were found especially in parameters expressing ?low doses to large volumes of lungs? (V5, V13, V20 ) for CS algorithm compared to PB algorithm in3-D conformal radiotherapy planning. In terms of accuracy in dose calculation, CS algorithm is close to MC (?Monte Carlo?) algorithm which is the ?gold standard? in radiotherapy planning but cannot be used routinely in photon beam dose calculations. In conclusion, CS algorithm should be preferred to PB algorithm due to its increased accuracy in dose calculation especially in lung cancer radiotherapy.