University of Washington, Seattle, WA
E. Gabriela Chiorean , Daniel D. Von Hoff , Thomas J. Ervin , Francis P. Arena , Jeffrey R. Infante , Venu Gopal Bathini , Tina Evans Wood , Paul N. Mainwaring , Robert T. Muldoon , Philip R. Clingan , Volker Kunzmann , Ramesh K. Ramanathan , Josep Tabernero , David Goldstein , Amy Ko , Brian Lu
Background: nab-P + G showed promising efficacy in a phase I/II study in MPC, and decreases in CA19-9 correlated with OS. In MPACT, patients (pts) who received nab-P + G vs G had improved median OS (8.5 vs 6.7 mo; HR 0.72; p = 0.000015), PFS (5.5 vs 3.7 mo; HR 0.69; p = 0.000024) and ORR (23% vs 7%; p = 1.1 × 10−10). Here we present a prespecified exploratory analysis of CA19-9 from the MPACT trial. Methods: 861 previously untreated pts with MPC were randomized 1:1 to receive nab-P 125 mg/m2 + G 1000 mg/m2 days 1, 8, and 15 every 4 weeks or G alone 1000 mg/m2 weekly for 7 weeks followed by a week of rest (cycle 1) and then days 1, 8, and 15 every 4 weeks (cycle ≥ 2). CA19-9 was evaluated at baseline and then every 8 weeks. OS comparisons at different CA19-9 criteria were performed by stratified Cox proportional hazards model (P by stratified log-rank test using randomization criteria). Results: 750 pts had an evaluable CA19-9 at baseline. More pts in the nab-P + G arm vs the G arm demonstrated a best CA19-9 decrease from baseline of ≥ 20% and ≥ 90% (61% vs 44% and 31% vs 14%, respectively; Table). At the first postbaseline assessment (week 8), greater proportions of pts in the nab-P + G arm vs the G arm had CA19-9 decreases of ≥ 20% and ≥ 90% (Table). At that time point, for pts with a decrease of ≥ 20% in CA19-9, nab-P + G demonstrated a significantly longer OS vs G. The risk reduction for pts with a ≥ 90% decrease was greater than in pts with a ≥ 20% decrease. In pts with an 8-week CA19-9 decrease < 20%, median OS for nab-P + G vs G was 8.3 vs 8.0 mo (HR 0.92; p = 0.705). The relationship of CA19-9 kinetics with OS will also be examined. Conclusions: Higher proportions of pts in the nab-P + G arm had CA 19-9 responses of ≥ 20% and ≥ 90% vs the G arm. Pts who achieved a CA19-9 decrease at 8 weeks of ≥ 20% or ≥ 90% had significantly longer OS with nab-P + G than with G. Clinical trial information: NCT00844649.
nab-P + G n = 379 |
G n = 371 |
||
---|---|---|---|
Best CA19-9 decrease ≥ 20%, n (%) | 230 (61) | 162 (44) | |
8-week CA19-9 decrease ≥ 20%, n (%) | 196 (52) | 140 (38) | |
Median OS, mo | 13.2 | 9.4 | |
1-year OS, % | 53 | 34 | |
HR | 0.59 | ||
p | < 0.001 | ||
Best CA19-9 decrease ≥ 90%, n (%) | 117 (31) | 51 (14) | |
8-week CA19-9 decrease ≥ 90%, n (%) | 59 (16) | 33 (9) | |
Median OS, mo | 13.4 | 9.4 | |
1-year OS, % | 57 | 20 | |
HR | 0.44 | ||
p | 0.0022 |
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