A114
Comparative analysis of TCP, NTCP, Conformity Index and risk of second malignancies when radical radiotherapy is delivered using three different techniques for the treatment of Head and Neck Squamous Cell Carcinomas
Sanjoy Chatterjee1, Nick Willis1, Vivien H W Loo1, Judith Mott2, Gregory Smyth2, Werner Dobrowsky1, Charles Kelly1, Steve M Locks2
1Northern Centre for Cancer Care, Newcastle, UK, 2Regional Medical Physics Department, Newcastle, UK
Background
Many UK centres use a photon-electron matched two-phase technique for treatment of Head and Neck Squamous Cell Carcinomas (HNSCC). In Newcastle all radical HNSCC are treated using a complex one-phase technique or with image guided IMRT using Tomotherapy. The conformity index (CI), tumour control probability (TCP), normal tissue complication probability (NTCP) and risk of second malignancies using 3 different planning methods were compared.
Method
Four head and neck cancer patients who have been treated with Tomotherapy were re-planned using a forward planned complex field in field forward planned single phase technique and the 2 phase photon-electron junction technique. Using Bioplan software we predicted the TCP and NTCP (Parotids, Larynx, Mandible and Spinal Cord) for each of the plans. Given the larger penumbra with more complex plans we compared the risk of second malignancies. The study also compares the conformity index of the high and low risk planning target volumes (PTV) for each technique.
Results
TCP was highest using Tomotherapy followed by single-phase plans whilst the 2 phase plans had a lower TCP. Parotid NTCP was not likely to be clinically different for the forward planned techniques although Tomotherapy plans had significantly less parotid NTCP. Complex plans had higher point doses to the mandible but spared the larynx better than the 2-phase plans. The risk of cord damage was least using Tomotherapy.
Conclusion
Comparative data on TCP/NTCP for the 3 plans would be discussed. The single-phase plan is a good alternative for centres looking to treat HNSCC without the uncertainties of matched photon-electron 2-phase plans. Risk of radiation induced second malignancy will also be discussed.
