Re: Distinguishing Second Primary Tumors From Lung Metastases in Patients With Head and Neck Squamous Cell Carcinoma

Extract

The recent paper by Leong et al. ( 1 ) highlights progress regarding a longstanding oncology dilemma in distinguishing a solitary metastatic deposit from a new cancer in patients with known prior cancer. The specific clinical scenario is familiar to those who frequent head and neck tumor boards—specifically, the patient with known head and neck cancer (squamous cell carcinoma) who simultaneously or subsequently manifests a solitary pulmonary nodule, which is similarly confirmed as squamous cell carcinoma.

Many head and neck oncologists have turned wistfully toward their tumor board pathologist with the simple question, “Is this a metastasis or a new primary tumor?” The promise of this published work by Leong et al. ( 1 ) is that we are moving closer to providing the clinician with molecular diagnostic tools to answer the question more precisely.

Judicious application of molecular techniques to complement clinical judgment in the “metastasis versus primary tumor” scenario will clearly prove beneficial in selected circumstances. Nevertheless, maximizing clinical thinking before soliciting molecular “truth telling” will be important. In their abstract, Leong et al. state “...a solitary SCC [squamous cell carcinoma] in the lung more likely represents a metastasis than an independent lung cancer.” However, this is largely dependent on the patient cohort selected. The study group in the paper by Leong et al. is dominated by patients with advanced, lymph nodepositive, and/or recurrent head and neck cancers. Of the 16 patients studied, 13 presented with stage IV tumors and 15 were lymph node positive at presentation. These represent compelling prognostic features for locoregional disease recurrence and eventual distant metastases. Thus, it is not surprising that 12 of 16 lung tumors appeared to represent metastases in this group of patients with highly advanced-stage disease for whom clinical judgment would largely dictate the same. This is by no means meant to detract from the importance of this work. Rather, it is suggested that such molecular analysis may prove far more important in patients with earlier stage disease for whom the clinical likelihood of distant metastasis is deemed far lower.