Positron emission tomography-magnetic resonance imaging (PET-MRI) for response assessment after radiation therapy of cervical carcinoma: a pilot study.

BACKGROUND: Advanced stage cervical cancer is primarily treated by radiotherapy. Local tumor control is a prerequisite for cure. Imaging after treatment is controversial. Positron emission tomography (PET) combined with computer tomography (PET-CT) shows great promise for detecting metastases. On the other hand, magnetic resonance imaging (MRI) is superior in depicting anatomical details. The combination of PET-MRI could result in more accurate evaluation of cervical cancer treatment outcome. The aim of this pilot study is to share our initial experience with PET-MRI in the evaluation of treatment response in cervical cancer after radiation treatment.

METHODS: Ten patients with cervical carcinoma (FIGO ≥IB2) were prospectively evaluated. Eleven weeks (median; range 8-15 weeks) after radiation therapy, treatment response was evaluated by PET-MRI. The PET, MRI, and combined PET-MRI images were evaluated for the presence of local residual tumor and metastasis. Diagnostic performance was assessed by area under the receiver operator characteristic (ROC) curve for evaluation of local residual tumor. The readers were blinded for outcome data. Local residual disease, metastasis, diagnostic confidence, and change of opinion were scored on a 5-point Likert scale. The reference standard consisted of pathology and/or follow-up according to the clinical guidelines.

RESULTS: Three out of ten patients had local residual abnormalities suggestive for tumor residue after radiation treatment. The availability of both PET and MRI resulted in an increase in diagnostic confidence in 80-90% of all patients. Change of opinion was observed in 70% and change of policy in 50%, especially in the group with residual tumor. The diagnostic accuracy increased significantly for the radiologist if PET-MRI was combined (AUC .54 versus .83).

CONCLUSIONS: PET-MRI shows promise for evaluation of treatment response after radiation for cervical cancer, especially increasing diagnostic confidence, while potentially increasing diagnostic performance.