The impact of PET with 18FDG in radiotherapy treatment planning and in the prediction in patients with cervix carcinoma: results of pilot study.

Positron emission tomography (PET) is used to distinguish between benign and malign tumors, to diagnose relapse or post-therapeutic changes. Lately, PET is used to predict the treatment response. and also a complementary method to determine target volumes in radiotherapy. Daily using of PET in the oncology praxis can change treatment strategy and improve its outcome. Results of this pilot study show the role of PET with 8-F-fluorodeoxyglucose ((18)FDG) for staging of cervical carcinoma and in the radiotherapeutic planning. Between March 2005 and May 2007, 51 patients with cervical carcinoma were treated with combination of external beam radiotherapy and HDR brachytherapy, with or without concomitant cisplatin. The lymphatic nodes treatment field size was determined by PET/CT fusion. Treatment results were evaluated by PET 3 and 9 months after treatment. The differences in the results of PET and CT were evaluated in this study. In 32 cases (62.75%) the results of PET and CT were identical, in 14 cases (27.45%) the nodal involvement was more extensive according to PET, in 5 cases (9.8%) the nodal involvement was more extensive according to CT. PET results 3 months after treatment were as follows: in 3 cases (5.88%) stable disease, in 35 cases (68.63 %) negative, in 4 cases (7.84%), progression of disease, in 3 cases (5.88 %) partial regression. There were no false positive results caused by inflammatory reaction persisting 3 months after radiotherapy, as was confirmed by repeating PET 9 months after treatment. The results of this study confirmed the important role of PET in diagnosis and treatment of cervical carcinoma and in determination of target volumes in radiotherapy. PET was found to be a standard staging examination of cervical carcinoma in Masaryk Memorial Cancer Institute. The predictive value of PET has not yet been validated.