Surgeons Combat PET Scan Limitations by Illuminating Lung Tumors

Each year, pulmonary nodules are found in approximately 250,000 Americans. Although PET scans can be highly effective in detecting malignant nodules, they are limited by the inability to detect tumors smaller than a centimeter and cannot distinguish between cancerous growths and benign inflammatory diseases.

To bridge this gap, the authors of a study published in Annals of Surgery combined intraoperative molecular imaging (IMI) with PET scans. The near-infrared contrasting agent OTL38 was used to make the tumor cells glow.

In the study, investigators combined PET imaging and IMI for 50 patients undergoing surgery to remove lung nodules. A preoperative PET scan was conducted in all the patients within 30 days of their procedure. A total of 66 nodules were identified in the scans.

Using IMI, 91% of the previously known nodules were identified during the operation. The physicians were also able to identify 9 additional nodules using IMI that were undetected by the PET scan or by traditional intraoperative monitoring.

The investigators identified a total of 75 nodules between PET and IMI. The PET scan accurately determined if nodules were malignant in 68% of cases compared with IMI alone in 91% of cases.

Diagnostics were further improved in 30% of patients who underwent IMI, helping surgeons identify cancer that would have otherwise been missed in 10% of the patients.

“This shows that the contrast agent is allowing us to remove more cancer from the patient than we would have with PET imaging along,” said senior author Sunil Singhal, MD.

Dr Singhal stressed, however, that the study does not devalue the role of PET scans, but rather provides insight into how to improve treatment.

“PET imaging still has an important role to play in developing treatment plans for patients, but given its limitations, it’s clear that IMI with this contrast agent can improve the picture surgeons are seeing,” Dr Singhal said. “That’s especially true when you’re talking about nodules that are only a centimeter or smaller.”

Currently, investigators are examining the role of OTL38 and IMI. The technology is being evaluated in a formal, multi-center trial, which will be the first phase 2 study of molecular imaging in the United States, according to the authors.

Other areas being explored are the efficacy of additional contrast agents—–some of which are expected to be available in clinic within a few months––as well as tracking these patients to find out whether the improved surgeries increased survival.