In a patient with history of successfully treated locally advanced H&N cancer, how do you discern between a metachronous second primary locally advanced lung SCC vs. metastatic head and neck SCC?

Solitary, particularly long interval, N0-N1, treat like lung primary. Multiple lesions, short interval, advanced neck disease, likely metastases.

This is a difficult clinical situation and unfortunately, too common. If you look at VAMC data, the incidence of a metachronous or synchronous lung cancer in the setting of HN cancer is approximately 20%. This data was prior to the increase in HPV related malignancies so most patients were smokers. ...

This scenario does come across in clinical settings often. As such, there are no bio-markers between squamous cell lung vs squamous cell H&N which can help differentiate though the presence of p16 can help.

The radiological appearance of lung lesions can be helpful especially if prior CT scans which...

Agree with the above suggestions of looking for help from pathology and radiology colleagues.

Would also consider circulating tumor DNA from a tissue-informed assay like Signatera. If initial tissue of the h/n derived genomic alterations are present as cell free DNA, then would be more likely to con...