(Wednesday, 8/1/2018) 9:30 AM - 10:00 AM
Room: Exhibit Hall | Forum 4
Purpose: To predict a preferable fractionation regimen (FR) for the radiation therapy of early-stage nasopharyngeal cancer.
Methods: Each of twenty-four patients was designed with volumetric modulated arc therapy (VMAT) plans with same parameters using three different FRs of 70Gy/30fractions (F30), 70Gy/33fractions (F33) and 70Gy/35fractions (F35), respectively. The Webb-Nahum model which accounts for tumor repopulation and hypoxia was employed to compute tumor control probability (TCP) for gross tumor volume (GTV), and the Lyman-Kutcher-Burman (LKB) model was used to calculate normal tissue complication probability (NTCP) for organs at risk. Then the TCP and NTCP values were combined to calculate uncomplicated TCP (UTCP) for each FR. The UTCP, TCP, NTCP and dosimetric parameters were compared and analyzed.
Results: The F30 scheme was predicted to be more beneficial compared with the other two FRs. The F30 scheme yielded the highest UTCP value of 80.6% while the F35 produced the lowest UTCP of 78.0% (P<0.05). The F30 provided higher TCP by up to 7.3% and lower NTCP by up to 2.2% (left parotid). All NTCP values were within tolerance. No significant dosimetric difference was found among the three FRs.
Conclusion: Based on the radiobiological modeling analysis, the 70Gy/30fractions scheme is recommended for the VMAT for early-stage nasopharyngeal cancer cases, as it may improve the local control rate of tumor while not significantly increase the toxicities of normal tissues. These predictions should be validated in future clinical trials.
Funding Support, Disclosures, and Conflict of Interest: This work was sponsored by Medical Scientific Research Foundation of Guangdong Province (B2016048) and National Natural Science Foundation of China (81602667).
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