Study Evaluating Two Loading Regimens of Sunitinib or Bevacizumab Alternating With Cisplatin and Gemcitabine as Induction Therapy for Locally Advanced Nasopharyngeal Carcinoma (NPC)

\- Hypothesis We hypothesise that intermittent dosing of the anti-angiogenic RTKI sunitinib or bevacizumab prior to systemic cisplatin and gemcitabine chemotherapy to transiently "normalise" tumour vasculature in patients with locally advanced or metastatic NPC will allow greater efficiency in drug and oxygen delivery, thus potentiating sensitivity to chemotherapy. We hypothesise that a loading dose of sunitinib for 7 days is required to achieve this sensitization effect prior to the first cycle of chemotherapy, and that this effect can subsequently be maintained by a 7 day course of sunitinib prior to each subsequent cycle of chemotherapy. The other hypothesis tested is that bevacizumab 7 days prior to chemotherapy will achieve normalization of tumor vasculature as well, and may induce changes in the tumor microenvironment that is beneficial for antitumour effect.