Second primary tumors and field cancerization in oral and oropharyngeal cancer: Molecular techniques provide new insights and definitions

Second primary tumors (SPTs) are a significant problem in treating oral and oropharyngeal squamous cell carcinoma and have a negative impact on survival. In most studies the definition of SPT is based on the criteria of Warren and Gates, published in 1932. These criteria, however, are ill-defined and lead to confusion. Recent molecular studies have shown that a tumor can be surrounded by a mucosal field consisting of genetically altered cells. Furthermore, evidence has been provided that SPTs (defined by classical criteria) can share some or even all genetic markers with the index tumor, indicating that both tumors have arisen from a common cell clone. We propose that these secondary neoplastic lesions should not be considered SPTs, implying that the present concept of SPT needs revision. This review describes a novel classification of the secondary tumors that develop after treatment of a carcinoma in the oral cavity or oropharynx. On the basis of the molecular analysis of the tumors and the genetically altered mucosal field in between, we propose definitions for a "true SPT," a local recurrence, a "SFT" (second field tumor derived from the same genetically altered mucosal field as the primary tumor), and a metastasis. Considering the etiologic differences of these lesions, we believe that an accurate molecular definition is essential to make headway with the clinical management of oral and oropharyngeal cancer.