Targeted therapy: its status and promise in selected solid tumors. Part II: Impact on selected tumor subsets, and areas of evolving integration.

This second article in our two-part series on targeted therapies in solid tumors covers the emergence of targeted therapies for the treatment of two common malignancies: lung cancer and breast cancer. In these two tumors, the identification of a promising target has led to successful preliminary applications, and eventually to further advances through drug development and the fine tuning of patient selection. As a result, the percentage of patients with breast or lung cancer who are benefiting from targeted agents has steadily increased, even if the majority are still treated with conventional cytotoxic regimens.

Targeted therapy: its status and promise in selected solid tumors part I: areas of major impact.

"Targeted therapy" is becoming the centerpiece of current therapeutic strategies, and is often mentioned as the desirable direction for future progress. Why and how it is replacing past approaches in the management of solid tumors is the subject of this two-part overview. Here, in Part I, we describe areas where major inroads were initially achieved by targeting angiogenesis (central to the biology of renal cell carcinoma and hepatocellular cancer) and by unraveling pathways in the heterogeneous tumors of mesenchymal origin--spurred by the identification of c-Kit-activating mutations in gastrointestinal stromal tumors (GIST) and the regressions that ensued when tumors harboring these mutations were exposed to the tyrosine kinase inhibitor imatinib (Gleevec).