PET/CT Scans Detect Recurrence, But Issues Over Clinical Use Linger

Eric J. Sherman, MD

Head and Neck Oncology

Memorial Sloan Kettering Cancer Center, New York, NY

The use of positron emission tomography/computed tomography (PET/CT) scans in the detection of early recurrence in patients with squamous cell carcinoma of the head and neck remains an open question despite recent research suggesting beneficial results.

A retrospective review of patients who had been treated with chemoradiation indicated that the routine use of PET/CT scans might improve the detection of locoregional regional recurrences before they become clinically apparent, potentially improving the outcome of salvage therapy that would be undertaken, according to research presented at the Multidisciplinary Head and Neck Cancer Symposium in January.¹

In the study, the charts of 234 patients who had been treated with chemoradiation between 2006 and 2010 and also received a posttherapy PET/CT scan were reviewed. Of those patients, 45 were identified who had achieved the status of no clinical evidence of disease at the time of imaging.

At 6 to 9 weeks, abnormalities requiring further analysis were found in 15 patients, and of those patients, 8 (53%) had malignancies that were identified through a biopsy. The imaging findings were falsepositive results in the remaining 7 cases (46%).

The relatively high rate of false-positives was not surprising, according to Eric J. Sherman, MD. “We know that in using PET scans this early, there’s an enormous potential for false-positives,” Sherman said. “This is a big problem.”

In addition, Sherman said a number of studies have shown that PET/CT imaging lacks effectiveness in helping to predict recurrence.

For example, in a study presented at the 2011 American Society of Clinical Oncology Annual Meeting, the Ontario Clinical Oncology Group (OCOG) examined the use of fluorodeoxyglucose (FDG) PET/CT to predict whether neck dissection should be performed following radiation therapy.²

In that study, 350 patients completed PET/CT imaging at a mean of 9.2 weeks after treatment (range, 4-19). Of the 201 patients who did not have neck dissection performed, 8 patients (4%) had neck recurrence on follow-up. Posttreatment PET/CT was positive in 4 of those 8 patients (50%). However, it was also positive in 24 of the 193 (12%) patients who had no neck recurrence on follow-up, suggesting that PET/CT scans are not a reliable indicator of residual nodal disease.

While PET/CT scans have prompted some changes in the management of head and neck cancer, the high rate of false-positive scans may diminish any benefit derived from those changes.

“There is a lack of prospective data showing that a PET/CT scan done six to nine weeks after the completion of radiation therapy leads to an improvement in survival or a decrease in morbidity,” Sherman said. “Meanwhile, PET/CT scans could potentially lead to issues such as an increase in cost, morbidity from unnecessary procedures due to the false-positive rate, and an increase in a patient’s worry about disease recurrence.”

References

1. Rudha Y, Aref A, Chuba P, et al. The value of PET scan in the routine follow up of patients with squamous cell carcinoma of the head and neck. Presented at: Multidisciplinary Head and Neck Cancer Symposium; January 26, 2012; Phoenix, AZ. Abstract 226.
2. Waldron JN, Gilbert RW, Eapen L, et al. Results of an Ontario Clinical Oncology Group (OCOG) prospective cohort study on the use of FDG PET/CT to predict the need for neck dissection following radiation therapy of head and neck cancer (HNC). J Clin Oncol. 2011;29(15)(suppl;abstr 5504).