Current controversies in radiotherapy for nasopharyngeal carcinoma (NPC).

Radiotherapy has a good track record in the treatment of NPC, yet the late toxicity profile and local failure rate for locally advanced disease remain a concern. Modern RT techniques incorporating IMRT and IGRT have widened our potential in treating NPC more effectively, and shall be regarded as the standard of care. Out of the various dose fractionation regimens in IMRT, 70 Gy in 35 fractions or the mini-SIB proves to be safe in combination with chemotherapy, but any further attempt of dose escalation must be tried out with extreme caution to avoid severe toxicities. CT-MRI image fusion improves the accuracy of GTV delineation, whereas the role of PET-CT has yet to be verified. RTOG definition of the CTV provides a reasonable template for the inclusion of sites at risk of microscopic involvement, and fine tuning has to be made in the future based on careful analysis of the pattern of local failure with long term follow-up. Toxicity reduction via radiation volume or dose reduction is tempting, but once again it has to be tested under scrutiny. Retrospective data have emerged that suggest a benefit of using adaptive IMRT replanning in NPC, however the optimal timing or frequency of replanning is still unclear. Future prospective studies are thus required to evaluate the cost-effectiveness of adaptive RT and streamline the workflow logistics before it can be widely accepted in routine practice.