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Secondary Malignancy Risks in Lung Cancer Radiotherapy with Helical Tomotherapy, Intensity Modulated Radiotherapy, and Conformal Radiotherapy

N Papanikolaou

N Papanikolaou1*, G Komisopoulos2, S Rodriguez1, S Stathakis1, C Esquivel1, G Nikiforidis2, G Sakellaropoulos2, P Mavroidis1,3, (1) University of Texas Health Science Center, UTHSCSA, San Antonio, TX, (2) University of Patras, Patras, Greece, (3) Karolinska Institutet and Stockholm University, Stockholm, Sweden

SU-E-T-488 Sunday 3:00PM - 6:00PM Room: Exhibit Hall

Purpose: The aim of the study is to examine the risk of inducing secondary malignancies in association with the clinical effectiveness of treatment plans in terms of tumor control and normal tissue complication probabilities.

Methods: Four patients having been treated for lung cancer were examined. For each of them, three treatment plans were developed based on the Helical Tomotherapy (HT), MLC-based Intensity Modulated Radiation Therapy (IMRT), and 3D-Conformal Radiation Therapy (CRT) radiation modalities. The different plans were evaluated using the complication-free tumor control probability (P+), the overall probability of injury (PI), the overall probability of control/benefit (PB), and the biologically effective uniform dose (BEUD). The risks for secondary malignancies in the spinal cord, heart and contra-lateral lung were calculated for the three radiation modalities.

Results: Regarding the overall evaluation of the different radiation modalities based on the P+ index, the average values of the HT, IMRT and CRT are 67.3%, 61.2% and 68.2%, respectively. The corresponding average values of PB are 75.6%, 70.5% and 71.0%, whereas the average values of PI are 8.3%, 9.3% and 2.8%, respectively. Regarding the risk for secondary cancer, for spinal cord the CRT modality produces the lowest average risk (1.4%) compared with the HT (2.1%) and IMRT (1.6%) radiation modalities. In heart, the lowest average risk is produced by IMRT (3.8%) compared with the HT (5.1%) and CRT (4.7%), whereas the three radiation modalities show almost equivalent results regarding the contra-lateral lung (0.8% for HT, 0.9% for IMRT and 0.9% for CRT, respectively).

Conclusion: The plans that appear to be more effective for the treatment are prone to show the highest risk of secondary malignancy. Radiobiologically-based treatment planning taking into account the risk of secondary cancer can be established as an effective clinical tool for treatment optimization.

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