Depth of Response From Fixed-Duration Treatment Is Associated With Superior Survival in Waldenstrom Macroglobulinemia.

As the treatment paradigm for Waldenström macroglobulinemia (WM) continues to evolve, the debate surrounding the prioritization of depth of response versus disease control as therapeutic goals gains significant relevance. However, the impact of depth of response from fixed-duration therapy on overall survival (OS) was unclear. This multicenter study evaluated the prognostic impact of depth of response using a landmark survival analysis. A total of 440 patients with WM treated with frontline fixed-duration regimens were included. Attaining a major response (MaR) was associated with superior outcomes, including significantly longer OS. The estimated 5-year PFS rates for patients with MaR at 6 months versus not were 50% versus 32%, respectively, p < 0.001, and the estimated 5-year OS rates for patients with MaR at 6 months versus not were 89% versus 70%, respectively, p < 0.001. In a multivariable analysis, MaR at 6 months was independently associated with superior PFS (HR 0.66, p = 0.007) and OS (HR 0.28, p < 0.001). Similar results were seen when considering deeper responses (CR + VGPR vs. PR). Depth of response at 6 months is an important prognostic marker in WM and an independent predictor of PFS and OS. These results support its utilization as a suitable endpoint in clinical studies in WM.