Estimates of PFS, TTNT Per Treatment Line and their Relationship for Multiple Myeloma Patients

Abstract

The aim of this research was to study how progression free survival (PFS) and time to next treatment (TTNT) changed by line of treatment among multiple myeloma (MM) patients and assess the relationship between the two. Consecutive patients diagnosed with MM between 2000 and 2011 at various medical centers in Sweden were included. TTNT and PFS were defined as the time between the start date of the administered drugs in the current treatment line and the start date of the administered drugs in the next treatment line; or until progressive disease respectively. In both cases, death was defined as an event. Multi-variate Cox model including prognostic factors and line of treatment were used in the analysis. Among the 1616 total MM population 1125 patients were not eligible for stem cell transplant. Their median PFS and median TTNT decrease significantly as the line of treatment increases and the difference between these two endpoints decreases by treatment lines. Median PFS and TTNT in months (with 95% CI) in 1st line are: 8.5 (7.9, 9.2), 12.3 (11.1, 13.3), in 7th line 3.0 (1.5, 5.2), 3.9 (2.2, 7.2). The risk of disease progression or death increased significantly by line of treatment with a more profound increase between 2nd line vs. 1st line (hazard ratio, HR, 1.39 [1.26, 1.53]) than line 3+ vs. their corresponding previous lines (HR 1.18 [1.12, 1.23]). The same trend was observed for TTNT. Median survival times and HRs have similar significant pattern for stem cell transplant eligible patients. The time to progression and TTNT decrease the most after the first line treatment, suggesting that an effective treatment in first line could have a bigger impact on survival than an effective treatment in later lines.