It is common practice to continue treating metastatic breast cancer patients as long as responses are expected. NCCN recommends single agents mostly but also a few combinations for second line. However, there is little evidence to support this practice after the first few lines. NCCN on p. MS-43 recommends continuing Herceptin into consecutive line of therapy but says that the duration of that is unknown. It also says on MS-2that continuation of chemotherapy past third line is not recommended and only supportive care should be given.