Dosimetric accuracy of three dose calculation algorithms for radiation therapy of in situ non-small cell lung carcinoma

BACKGROUND: Study determines differences in calculated dose distributions for non-small cell lung carcinoma (NSC LC) patients. NSC LC cases were investigated, being the most common lung cancer treated by radiotherapy in our clinical practice. MATERIALS AND METHODS: A retrospective study of 15 NSCLC patient dose distributions originally calculated using standard superposition (SS) and recalculated using collapsed cone (CC ) and Monte Carlo (MC) based algorithm expressed as dose to medium in medium (MCD(m)) and dose to water in medium (MCD(w,)) was performed so that prescribed dose covers at least 99% of the gross target volume (GTV). Statistical analysis was performed for differences of conformity index (CI), heterogeneity index (HI), gradient index (GI), dose delivered to 2% of the volume (D(2%)), mean dose (D(mean)) and percentage of volumes covered by prescribed dose (V(70Gy)). For organs at risk (OARs), D(mean) and percentage of volume receiving 20 Gy and 5Gy (V(20Gy), V(5Gy)) were analysed. RESULTS: Statistically significant difference for GTVs was observed between MCD(w) and SS algorithm in mean dose only. For planning target volumes (PTVs), statistically significant differences were observed in prescribed dose coverage for CC, MCD(m) and MCD(w). The differences in mean CI value for the CC algorithm and mean HI value for MCD(m) and MCD(w) were statistically significant. There is a statistically significant difference in the number of MUs for MCD(m) and MCD(w) compared to SS. CONCLUSION: All investigated algorithms succeed in managing the restrictive conditions of the clinical goals. This study shows the drawbacks of the CC algorithm compared to other algorithms used.