ABSTRACT

The improvements in cancer treatment prolonged survival in patients. Despite this survival benefit, chemotherapies, radiotherapies or combination therapies, and continuing exposure to the same carcinogenic agents may lead to secondary cancers. Multiple primary neoplasm is described as multiple tumors in a single patient posing distinct individual malignant characteristics with definite exclusion of one tumor is the metastasis of the other. According to the time of onset, these are considered to be synchronous or metachronous tumors. While synchronous tumors often occur due to carcinogen exposure, metachronous tumors often develop after treatments such as radiotherapy. Although the cause and developmental mechanisms of multiple primary tumors are not clear, several factors including immune deficiency, genetic instability, increased use of systemic chemotherapy and radiotherapy, increased survival, elderliness, and smoking have been implicated. The two developmental hypotheses in development of multiple primary tumors appear as field cancerization and common clonal origin. Multiple primary tumors often involve respiratory, gastrointestinal, and genitourinary systems. Transitional cell carcinoma of the urinary bladder may also rise as part of synchronous or metachronous multiple tumors. We still lack large scale studies relevant to the treatment of multiple primary cancers. Close follow-up in primary malignant tumor patients is of extreme importance for the risk of secondary cancers.