IMRT vs 2DRT for NPC Patients

Irradiation of the parotid gland with subsequent long-term xerostomia is a well-recognized complication after radiotherapy for head and neck (HAN) cancers. A number of studies have shown that IMRT could minimize the radiation dose to the parotid glands and hence the risk of developing xerostomia. The benefit of IMRT has also been demonstrated in prior dosimetric and non-randomized studies in NPC patients. In 2007, the investigators have published the prospective randomized study of IMRT versus 2DRT in early stage NPC patients. In the study, IMRT had lower incidence of observer-rated severe xerostomia, higher parotid and whole saliva flow rate, than patients in 2DRT arm at 1 year after treatment. However, there was no significant difference in patient-reported outcome, i.e. subjective xerostomia scoring, between the 2 arms. The underlying reason for the incoherent findings in terms of objective and subjective xerostomia outcome remains uncertain. One of the possible explanations for this observation could be the better parotidsparing with IMRT alone may not entirely sufficient to maintain oral cavity lubrication while the other mucin-secretory salivary gland protection is also essential. Another possible explanation for the insignificant improvement in patient-reported outcome with IMRT is the short follow-up time. Gradual recovery or improvement in various quality of life parameters was not uncommonly seen several years after definitive radiotherapy for HAN cancer patients. There is much interest in studying the long term clinical outcome, especially the treatment-related complications, for the patients who had randomized and treated in the prior presented prospective study.

In this study, the long term results, in particular the xerostomia rating will be assessed and compared in NPC patients who had participated in the prior reported prospective randomized study of IMRT vs 2DRT.