Evaluating repetitive 18F-fluoroazomycin-arabinoside (18FAZA) PET in the setting of MRI guided adaptive radiotherapy in cervical cancer

Abstract

Background. The aim of this pilot study was to assess tumour hypoxia in patients with cervical cancer before, during and after combined radio-chemotherapy and Magnetic Resonance Imaging (MRI) guided brachytherapy (BT) by use of the hypoxia Positron Emission Tomography (PET) tracer ¹⁸F-fluoroazomycin-arabinoside (¹⁸FAZA ). Material and methods. Fifteen consecutive patients with locally advanced cervical cancer referred for definitive radiotherapy (RT) were included in an approved clinical protocol. Stage distribution was 3 IB1, 1 IB2, 10 IIB, 1 IIIB, tumour volume was 55 cm³ (+/− 67, SD). Dynamic and static ¹⁸FAZA -PET scans were performed before, during and after external beam therapy (EBRT) and image guided BT +/− concomitant cisplatin. Dose was prescribed to the individual High Risk Clinical Target Volume (HR CTV) taking into account the dose volume constraints for adjacent organs at risk. Results. Five patients had visually identifiable tumours on ¹⁸FAZA -PET scans performed prior to radio-chemotherapy and four patients before brachytherapy. One of five ¹⁸FAZA PET positive patients had incomplete remission three months after RT, one had regional recurrence. Four of ten ¹⁸FAZA-PET negative patients developed distant metastases. The one patient with incomplete remission received 69 Gy (D90) in the HR CTV, whereas all other patients received mean 99 Gy (+/−12, SD). Conclusion. PET imaging with ¹⁸FAZA is feasible in patients with cancer of the uterine cervix. However, its predictive and prognostic value remains to be clarified. This applies in particular for the additional value of ¹⁸FAZA-PET compared to morphologic repetitive MRI within the setting of image guided high dose radiotherapy which may contribute to overcome hypoxia related radioresistance.