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Adding PET to CT Scan for Cervical Carcinoma Staging Leads to Change in Treatment

 A study recently published in JAMA Network Open has found that for patients with newly diagnosed stage IB to stage IVA cervical carcinoma, using positron emission tomography (PET) in combination with computed tomography (CT) results in increased detection of paraaortic or common iliac adenopathy compared with CT alone.

According to the study authors, around 40% of cervical cancer patients have locally advanced disease at the time of their diagnosis, meaning that the cancer extends to the vagina, parametrium, and/or lymph nodes. At this stage, cervical cancer is inoperable but potentially curable with chemotherapy and radiation. The authors note the importance of staging the cancer, as undetected disease beyond the field of radiation treatment can result in undertreatment; alternately, if the undetected disease is disseminated, it can be overtreated. This study aimed to determine whether adding fludeoxyglucose F 18 PET/CT to CT staging of the abdomen and pelvis detected more extensive disease and influenced treatment selection.

The study included 168 adult patients with newly diagnosed stage IB to IVA squamous cell carcinoma, adenosquamous carcinoma, or adenocarcinoma of the cervix recruited at 6 regional cancer centers in Ontario, Canada. Because of low enrollment, the trial was discontinued before reaching the planned target of 288 participants.

Of the 168 patients, 112 underwent PET/CT imaging. Although PET/CT did not have a substantial impact on the detection of distant metastatic disease, it did increase detection of paraaortic or common iliac adenopathy: 21.4% of patients in the PET/CT group received extended field radiation therapy (EFRT) to paraaortic nodes compared with 14.3% in the CT-only group, and 12.5% of the PET/CT group received EFRT to common iliac nodes compared with 5.4% in the CT-only group. This difference was not statistically significant, a fact which the authors attribute to the small sample size.

"We met our goal of determining whether adding PET detects more extensive disease and influences treatment. The study showed that patients who had PET were twice as likely to have a change in their treatment," explained co-principal investigators Anthony Fyles, MD, MSc, radiation oncologist at Princess Margaret Cancer Centre, and Lorraine Elit, MD, MSc, gynecologic oncologist at Hamilton Health Sciences' Juravinski Cancer Centre.

Although the National Comprehensive Cancer Network guidelines for cervical cancer recommend PET/CT for the initial workup of stage II to IV cervical cancer, this recommendation is based on "lower-level evidence there is uniform consensus that the recommendation is appropriate". In the published paper, the authors note, "Our trial is the only randomized clinical trial that we know of in the contemporary era that actually addresses the utility of PET/CT for [locally advanced cervical cancer]. Although our trial was underpowered, it is reasonable to consider the results within the context of the National Comprehensive Cancer Network recommendations that are based on observational data. Our results provide higher-quality evidence to support current practice."

Dr. Fyles remarked, "With PET we always learn more about disease, but does that knowledge change what we do in treating patients? In this instance it did, and it's extremely gratifying to provide new evidence that changes clinical practice."

Dr. Elit echoed this sentiment: "As a result of our research, the access to PET scans for women with this disease has expanded in Ontario."

For More Information

Elit LM, Fyles AW, Gu CS, et al (2018). Effect of positron emission tomography imaging in women with locally advanced cervical cancer: a randomized clinical trial. JAMA Network Open, 1(5):e182081. DOI:10.1001/jamanetworkopen.2018.2081

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