[Treatment of cancer of unknown primary, today and future]

Cancer of unknown primary(CUP)is a malignant disease with metastases such as lymph nodes, lung or liver metastasis, and without an identified primary site. CUP constitutes 5% of all human malignant diseases. CUPs are divided into two sub-groups, favorable and unfavorable, based on their clinical output. In the unfavorable group, platinumbased CUPs or those combined with taxane regimens have been examined in phase II trials and practically conducted with high frequency. However, no standard regimens have thus far been established. Chemotherapy based on the primary site is not applicable for the treatment of CUP. It is very difficult to apply any regimens without information on the primary sites. To resolve this problem, molecular diagnostic technologies using a gene expression profiling platform to identify the primary site of CUP are now applied. Primary site-dependent chemotherapy could be conducted in accordance with the result of the molecular diagnosis of the primary site. On the other hand, the idea that the unfavorable group is an independent entity of malignancy is supported. The unfavorable CUPs might have a common molecular mechanism. Identification of the underlying mechanism that is specific to the unfavorable CUP may be a clue to develop a novel treatment for CUP.