PURPOSE: Tumor hypoxia and low intrinsic radiosensitivity may counteract the 
efficacy of standard radiotherapy for locally advanced head and neck cancer 
(HNC). We investigated the involvement of hypoxia-regulated proteins (Hypoxia 
inducible factors HIF1alpha, HIF2alpha and carbonic anhydrase CA9) in HNC 
resistance to accelerated and hypofractionated radiotherapy.
MATERIALS AND METHODS: Thirty-nine patients with locally advanced HNC received 
15 daily fractions of 3.4 Gy amounting to a total tumor dose of 51 Gy 
(equivalent to 63 Gy in four weeks--one week split); this was combined with 
platinum chemotherapy and amifostine cytoprotection administered subcutaneously. 
Immunohistochemical analysis of hypoxia-regulated proteins, namely HIF1alpha, 
HIF2alpha and CA9, was performed in formalin-fixed paraffin-embedded tissues 
obtained prior to radio-chemotherapy.
RESULTS: HIF1alpha and HIF2alpha were expressed in the nuclei and cytoplasm of 
cancer cells, while CA9 had a membrane reactivity. A high expression of 
HIF1alpha, HIF2alpha and CA9 was noted in 21/39 (53.8%), 20/39 (51.3%) and 23/39 
(58.9%) cases, respectively. Complete response was obtained in 85.2% of patients 
and HIF1alpha was marginally related with persistent disease after RT (p = 
0.05). HIF1alpha was significantly associated with poor local relapse free 
survival (LRFS) (p = 0.006) and overall survival (p = 0.008), whilst HIF2alpha 
was not. A significant association of CA9 expression with poor LRFS was noted (p 
= 0.01).
CONCLUSION: In accord with previously reported studies, high levels of the 
hypoxia regulated proteins HIF1alpha and CA9 in HNC predict resistance to 
platinum based radio-chemotherapy. Whether HIF2alpha expressing tumors are more 
sensitive to larger radiotherapy fractions, compared to standard radiotherapy 
fractionation, is an issue that deserves further investigation.