Multiple regression analysis for survival post-progression (SPP).

¶Older agents were defined as those that had been developed before newer drugs (i.e., docetaxel, paclitaxel, vinorelbine, gemcitabine, irinotecan) were introduced clinically (see Methods section).
§Defined as agents acting on known specific molecular targets, such as tyrosine kinase inhibitors, neutralizing antibodies, matrix metalloproteinase inhibitors, and antisense oligonucleotides (see Methods section).