Head and Neck Cancer: Studies on microvessel density, radiation response and FDG PET

Sammanfattning: Treatment options of head and neck squamous cell carcinoma (HNSCC) usually include combinations of radiotherapy and surgery, and in some cases addition of chemotherapy. In locally advanced cases cure rates are low. Current prognostic factors cannot foresee the outcome for the individual patient. There is consequently a need for reliable prognostic and predictive factors. Through identification of such factors therapeutic interventions can be made early during therapy to increase tumour control and survival. In the present studies the association between microvessel density (MVD) in tumours and response to radiation has been explored. We have also studied the association between response to radiation and tumour metabolism, both prior to and during therapy (radical radiotherapy and in 10 cases also neoadjuvant chemotherapy). Metabolism was studied with a glucose analogue, FDG, and positron emission tomography, PET.The metabolic rate of FDG was compared to treatment outcome and survival and also to established tumour properties, as cell proliferation, tumourgrade and DNAcontent. Microvessel density showed a complex relation to radiation treatment response and outcome. Among patients with tumours manifesting complete response to radiotherapy MVD was above the lowest quartile of the MVDcounts according to computerised image analysis. In the subsequent study the relationship between higher MVD and response to radiotherapy could not be reproduced, when performed manually. High MVD within the epithelial tumour tissue, not in the tumour stroma, was then found to be an adverse prognostic factor, with a lower probability of local control and a higher rate of distant metastases.Tumour response evaluated histopathologically, after a preoperative radiation dose of 50 Gy was strongly correlated to outcome, regardless of the subsequent radical surgery.This implies that radiosensitivity per se is a strong prognostic marker. Tumour metabolism (FDG PET) was associated to therapy outcome. The pre treatment value was of limited prognostic value whereas the second PET, early during therapy, was associated to therapy outcome, in terms of complete response, local control and survival. When comparing the value of the metabolic rate (MR) to a simpler quantification, the standar-dised uptake value (SUV) of FDG, we found that MR was more strongly correlated to therapy outcome. Furthermore associations were found to be significant only for the primary tumours and not for node metastases. This implies a different pattern of response in node metastases compared to that of the corresponding primary tumour. There was no strong association between tumour metabolism and proliferation, DNA content or histologic grade. MR FDG reflects tumour aggressiveness. Repeated FDG studies during therapy are feasible and might justify therapeutic interventions in non-responders.