Delay between scan and surgery lessen MDCT staging accuracy for pancreatic lesions

Multidetector CT (MDCT) is an effective staging tool for pancreatic cancer surgery, but it’s accuracy diminishes as the time between scan and surgery increases, according to a study published online this month in the American Journal of Roentgenology.

Pancreatic adenocarcinoma is a fast-moving malignancy with a five-year survival rate of less than 5 percent and the only curative option for patients is a complete surgical resection of the localized malignancy.

In the diagnosis and staging of pancreatic cancer, MDCT plays a vital role in lesion identification and detection of distant metastatic disease. In terms of determining the resectability of pancreatic cancer, MDCT has a reported accuracy rate of between 70 and 85 percent. However, in the case of pancreatic adenocarcinoma, a tumor that was initially thought to be resectable can become unresectable due to vascular involvement or metastatic disease in a matter of weeks.

“This study examines the relationship between the interval between imaging and surgery and the accuracy of MDCT in determining the presence or absence of metastatic disease at surgery in patients with pancreatic cancer,” the authors, including Siva P. Raman, MD, of John Hopkins University Medical School in Baltimore, wrote.

For the study, the researchers identified patients who had undergone surgery for pancreatic cancer and had also received a MDCT exam.

“Findings from the preoperative MDCT report were correlated with the operative findings, as well as the time between imaging and surgery,” Raman and colleagues wrote.

The study cohort consisted of 256 patients, median age of 67 years, who underwent 290 MDCT scans to stage pancreatic adenocarcinoma. The researchers found that the median time between MDCT and surgery was 15.5 days and that MDCT correctly predicted the absence of metastatic disease in 85 percent of the patients.

Additionally, Raman and team found that MDCT was more accurate if surgery occurred within 25 days of the scan and regression models showed that the negative predictive value of a scan decreased after four weeks.

“Unfortunately, partly as a result of the lack of supporting data in the literature, obtaining an additional MDCT closer to surgery has until now been quite difficult, because insurance carriers have been reluctant to provide reimbursement for repeat MDCT scans without a medical appeal from the treating physician, thereby placing a potentially large financial burden on the patient,” the authors concluded.  “This study provides evidence supporting the need to rescan patients with a long interval between their initial scan and the date of surgery to avoid an unnecessary nontherapeutic laparotomy, and in particular, to perform a CT scan as close in time as possible to the patient's surgery.”