The role of PET/CT in cervical cancer

Abstract

In locally advanced cervical cancer, (18)F-fluorodeoxyglucose (FDG) positron emission tomography - computed tomography (PET/CT) has become important in the initial evaluation of disease extent. It is superior to other imaging modalities for lymph node status and distant metastasis. PET-defined cervical tumor volume predicts progression-free and overall survival. Higher FDG uptake in both primary and regional lymph nodes is strongly predictive of worse outcome. FDG-PET is useful for assessing treatment response 3 months after completing concurrent chemo-radiotherapy (CRT) and predicting long-term survival, and in suspected disease recurrence. In the era of image-guided adaptive radiotherapy, accurately defining disease areas is critical to avoid irradiating normal tissue. Based on additional information provided by FDG-PET, radiation treatment volumes can be modified and higher doses to FDG-positive lymph nodes safely delivered. FDG-PET/CT has been used for image-guided brachytherapy of FDG-avid tumor volume, while respecting low doses to bladder and rectum. Despite survival improvements due to CRT in cervical cancer, disease recurrences continue to be a major problem. Biological rationale exists for combining novel non-cytotoxic agents with CRT, and drugs targeting specific molecular pathways are under clinical development. The integration of these targeted therapies in clinical trials, and the need for accurate predictors of radio-curability is essential. New molecular imaging tracers may help identifying more aggressive tumors. (64)Cu-labeled diacetyl-di(N(4)-methylthiosemicarbazone) is taken up by hypoxic tissues, which may be valuable for prognostication and radiation treatment planning. PET/CT imaging with novel radiopharmaceuticals could further impact cervical cancer treatment as surrogate markers of drug activity at the tumor microenvironment level. The present article reviews the current and emerging role of PET/CT in the management of cervical cancer.

Keywords: Fluorodeoxyglucose F18; Planning Treatment Volumes; cervical cancer; positron emission tomography; radiation therapy.

FIGURE 1

A 62-year-old woman with a FIGO IIB cervical cancer, treated with concomitant cisplatin based chemotherapy and radiotherapy. Image shows the radiotherapy contouring process on fused planning-CT and FDG-PET/CT images. Contouring is done on VelocityAI Software (Velocity, Atlanta, GA, USA), based on a method of automatic 3D volume segmentation of the functional image, that depends on the relationship between source to background ratio.

FIGURE 2

(A) A 48 year-old lady with a cervical cancer stage FIGO IIB, presenting with multiple positive lymph nodes in continuity located in the bilateral iliac and para-aortic regions on FDG PET/CT. She was treated with chemo-radiotherapy using helical TomoTherapy. (B) Three level of radiotherapy dose were design and treated simultaneously. Pelvis and para-aortic areas received 44.8 Gy/1.6 Gy in 28 fractions. The PAO and pelvis regions surrounding positive nodes but without metabolic uptake were treated with 50.4 Gy/1.8 Gy in 28 fractions. Positive FDG PET/CT lymph nodes were treated with a simultaneous integrated boost up to 59.36 Gy/2.12 Gy in 28 fractions. Scale dose banding shows the 95% of the dose.

FIGURE 3

A 43 year-old women with cervical cancer, FIGO IIB, without Kindly specify the same. evidence of macroscopic positive nodes at diagnosis. She was treated with chemotherapy and 3D conformal radiotherapy (45 Gy/1.8 Gy/fraction) followed by brachytherapy. (A) The initial radiotherapy field does not include the irradiation of common iliac nodes. (B) An FDG-PET/CT performed 2 years after primary treatment shows an isolated left iliac recurrence (arrow). This recurrence is observed near the border of the radiation field, which in the context of centrally controlled cervical cancer makes us suspect a component of marginal recurrence that typically arise immediately adjacent to the radiotherapy border. Surgical intervention was considered unfeasible and she underwent salvaged chemotherapy (carboplatin and taxane), followed by re-irradiation. (C) Re-irradiation was performed with helical tomotherapy using a hypofractionated schema of 15 daily fractions of 3.5 Gy. All tomotherapy plans were processed on VelocityAI to evaluate cumulative dose to normal tissue and organs at risk (OAR). Megavoltage computed tomography (MVCT) was performed every day before treatment to correct patient setup. The patient is alive without evidence of disease at the 3-year follow-up.

FIGURE 4

A 62-year-old lady with FIGO stage IIB cervix cancer and positive pelvic lymph nodes was treated with cisplatin based chemotherapy and radiotherapy. (A) Positive lymph nodes are delineated based on FDG-PET/CT uptake and treated with 60 Gy in 2.4 Gy per fraction in 25 fractions. (B) Radiotherapy was delivered with helical tomotherapy. Pelvis and para-aortic areas were treated with 45 Gy in 25 fractions of 1.8 Gy. (C) Scale dose banding shows the 95% of the dose. The tumor boost was delivered with MRI-guided brachytherapy in four fractions of 7 Gy.