Proton/heavy ion therapy in salvage of locally recurrent nasopharyngeal carcinoma

Abstract

: Radiotherapy is the major modality for treating advanced local recurrence of nasopharyngeal carcinoma (NPC). However, as the nearby critical neurological structures have already absorbed a dose close to their maximum tolerance in the primary treatment, even state-of-the-art intensity modulated radiotherapy (IMRT) cannot achieve a satisfactory dose distribution, and re-irradiation is often associated with serious, or even fatal, late complication, as well as substantial local failure. Proton/heavy-ion therapy, with their superior energy deposition characteristics and biological effectiveness, have the potential to overcome these obstacles. The use of proton/heavy-ion therapy to treat re-current NPC dates back to the last millennium when such facilities were extremely rare and dose delivery technique was in its infancy (mainly passive-scattered beams from very limited directions were available). Over the last two decades there have been substantial technological development in proton/heavy-ion therapy, the facilities have become much more widely available, with proton therapy being accepted as a suitable mean for re-irradiation setting in general. The advancement in diagnostic technology and systemic treatment have also contributed significantly to the effectiveness of such highly conformal radiotherapy modalities. Many have applied proton/heavy-ion therapy in the extremely challenging recurrent NPC situation, with various degrees of success. This article provides a brief review of the basic principle of proton/heavy-ion therapy, the issues unique to their usage, studies on their application in treating recurrent NPC and their possible future development.