Variables affecting survival after second-line therapy initiation. (A) Impact of NT-proBNP progression on survival after second-line therapy initiation (P = .002). Solid line, no NT-proBNP progression (40 patients, median survival 62 months); dashed line, NT-proBNP progression (20 patients, median survival 17 months). (B) Impact of dFLC progression on survival after second-line therapy initiation (P = .004). Dashed line, patients with “high-risk dFLC progression” (60 patients, median survival 46 months); all of the following are required to define “high-risk dFLC progression”: dFLC >20 mg/L, dFLC >20% of baseline value, and dFLC increase by >50% of value reached at best response. Solid line, all other patients (32 patients, median survival not reached).