Room: ePoster Forums
Purpose: To evaluate the impact of cancer free life lost by applying the organ specified lethality fraction with estimated excess relative risk (ERR) of radiation induced secondary malignancies for female lung cancer radiation therapy patients.
Methods: Research was based on the previous published results of the radiation induced cancer ERR estimation from 10 selected female lung cancer cases which received volumetric modulated radiation therapy (VMAT). The organ-at-risk (OAR) specified ERR modelling parameters for radiation induced cancer risk was provided by ICRP Publication 103. The dose distributions of all selected cases were re-calculated to the same dose level (50Gy) by Monte Carlo based dose calculation algorithm. Thyroid, esophagus, stomach, liver, female breast and normal lung were selected as OAR for the assessment. The risk assessment was based on the assuming attained age of radiation therapy at 30 and to the evaluation age of 70. The results of ERR estimation were further applied with the published lethality fraction data derived from representative national cancer survival data, to estimate the ERR based lethality-adjusted nominal risk (LANR).
Results: Based on the estimation of averaged secondary cancer ERR, among all 6 selected OARs, thyroid has the most significant averaged risk decrease, from 2.93 (ERR) to 0.21 (LANR). Female breast decreased from 4.09 to 1.19. Stomach decreased from 0.18 to 0.15. Normal lung decreased from 9.80 to 8.72. Esophagus decreased from 8.29 to 7.71. Liver decreased from 0.18 to 0.15. The LANR score also identified the case with highest potential of relative cancer free life lost.
Conclusion: Further estimation of the ERR based lethality-adjusted nominal risk based on the ERR estimation of radiation therapy induced secondary malignancies could be a useful information for the selection among multiple competitive treatment plans, by truly reflect the potential cancer-free life lost due to the radiation therapy induced cancers.