PET/CT shows strength for staging cervical cancer

Correctly staging cervical cancer is imperative to establish both treatment protocols and prognostic factors for the patient, particularly with regard to para-aortical spreading and localizing distant metastases. Now Danish researchers have found that the fusion imaging capabilities of PET/CT provide a powerful tool for cervical cancer staging.

"According to the International Federation of Gynecology and Obstetrics (FIGO), patients with cervical cancer are staged by a clinical examination, which includes a cystoscopy, urography, and an x-ray of thorax," said Dr. Annika Loft. "No imaging techniques except the imaging of the thorax are included and no investigation of lymph node metastases is included. This is quite surprising, because from surgical staging procedures it is known that for patients with locally advanced disease, stage 2B to 4A, 24% of the patients have para-aortic nodal disease; and it is also known from other studies that the para-aortic nodal status is the most significant prognostic factor for these patients."

Loft, chief physician in the Centre of Diagnostic Investigations' PET and Cyclotron Unit at Rigshospitalet in the Copenhagen University Hospital in Denmark, presented the results of a prospective study for staging cervical cancer with PET/CT at the 2006 Academy of Molecular Imaging (AMI) scientific meeting in Orlando, FL, earlier this year.

"Identification of the para-aortic nodal status allows modification of radiation therapy fields to include this nodal disease, which is not routinely included in the treatment field because of intestinal morbidity by many radiation oncologists," she said.

The research team set out to evaluate the usefulness of PET/CT as a noninvasive supplement to the clinical staging procedure of cervical cancer. Over a three-year period, the group examined 120 consecutive patients ranging in age from 19 to 81, with a mean age of 48 years, who had newly diagnosed cervical cancer with a FIGO stage of 1B or higher.

All patients in the study were scanned in a Discovery LS PET/CT system (GE Healthcare, Chalfont St. Giles, U.K.) after the injection of 400 MBq of F-18 FDG. The patients fasted for a minimum of six hours, Loft said. Emission scans were conducted at three to five minutes per bed position, depending on the size and weight of the patient, she said.

The CT portion of the examination was performed as a diagnostic whole-body CT scan with the modality's four-slice CT capabilities. Intravenous contrast media was used with a 40-second scan delay to delineate the vessels. The team also administered oral contrast media 30 minutes prior to the start of the CT scans, Loft said. The scans were conducted at 140 kVp and 80-120 mAs and, if possible, were acquired while the patients were positioned with their arms above the head.

The resulting images were interpreted by a nuclear medicine physician and a radiologist working in tandem, she said. In addition, the whole-body CT scans were independently reviewed by another radiologist.

According to Loft, 28 of the patients underwent surgery. In this surgical cohort, PET/CT staging showed a sensitivity of 80%, a specificity of 87%, a positive predictive value of 57%, a negative predictive value of 95%, and an accuracy of 86%. In 78 of the patients who did not have surgery, excluding the remaining 14 who only had pelvic metastases, the researchers determined that PET/CT staging demonstrated a sensitivity of 100%, a specificity of 88%, a positive predictive value of 76%, a negative predictive value of 100%, and an accuracy of 91%.

In the 14 patients who had pelvic nodes only, PET/CT produced a sensitivity of 96%, a specificity of 88%, a positive predictive value of 71%, a negative predictive value of 99%, and an accuracy of 79%.

The results of the three-year study have led to a change in how staging is conducted for cervical cancer at the hospital. PET/CT is now implemented as a routine staging method at the facility, Loft said.

The PET/CT scans also proved helpful for those patients who went on to radiation therapy treatment.

"An extra bonus for these patients was that we could use the PET/CT scans for planning the radiotherapy; and it was very useful in planning the IMRT (intensity-modulated radiation therapy) for these patients," she said.

By Jonathan S. Batchelor staff writer
May 31, 2006

Related Reading

MRI ready for prime time in cervical cancer diagnosis, November 27, 2005

Host factor role confirmed in etiology of squamous cell cervical cancer, September 6, 2005

Triple-modality approach effective against cervical cancer, August 31, 2005

Optical coherence tomography seen feasible for cervical screening, August 16, 2005

Cervical tumor volumes on FDG-PET predict treatment outcome, July 14, 2005

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