Abstract discussant Anand Devaraj, MD, PhD, Professor in Thoracic Radiology at Royal Brompton and Harefield Hospitals, and Professor of Thoracic Radiology at the National Heart and Lung Institute, Imperial College London, highlighted the increased risk of second primary tumors among current smokers. “Greater than 70% of the causes of death in this group were from lung cancer, illustrating the importance of combining smoking cessation with screening not just at baseline when participants are first invited but also [later] for participants who have an ongoing smoking history,” said Dr. Devaraj.

Dr. Devaraj also discussed data regarding pathology. Although most synchronous tumors occurred when the primary lung cancer was adenocarcinoma, a significant proportion (approximately one-quarter) also occurred when the primary tumor was squamous cell carcinoma, he explained. Furthermore, he said, between 38% and 46% of synchronous or metachronous tumors had the same histology as the primary tumor. 

“I mentioned these two points because we often face the dilemma in clinical practice of differentiating synchronous or metachronous tumors from metastatic disease or recurrence,” Dr. Devaraj explained. “When faced with multifocal synchronous, subsolid lesions on a computed tomography scan, for example, many of us can feel confident that we’re dealing with synchronous primary tumors. But, in the setting of bilateral solid nodules, especially in stage II or III disease when the primary is squamous cell carcinoma, it becomes much more challenging.”

According to Dr. Devaraj, the gold standard for confirming a synchronous or a metachronous tumor is showing differential pathology between the primary and the secondary lung tumors. 

“However, as was shown in this study, a significant portion of synchronous tumors [between 38% and 46% in this study] can manifest as the same pathology as the primary tumor,” he continued. “In this setting, subcategorization with molecular analysis can be of use.” 

DISCLOSURE: Dr. Devaraj disclosed financial relationships with Boehringer Ingelheim, Brainomix, Roche, Galecto Biotech, and Galapagos.