Abstract P4-13-02: Treatment patterns of post-disease progression in the PALOMA-1/TRIO-18 trial
Authors: Finn RS , Crown JP , Ettl J , Pinter T , Thummala A , Shparyk Y , Patel R , Randolph S , Kim S , Huang X , Nadanaciva S , Huang Bartlett C , Slamon DJ 
Published: May 2016

Abstract
Background
Palbociclib (P) is an oral CDK4/6 inhibitor. In PALOMA-1/TRIO-18, a randomized phase 2 trial, addition of P to letrozole (L) significantly prolonged progression-free survival (PFS) (20 mo with P+L vs 10 mo with L alone; HR = 0.488, P=0.0004; Finn et al, Lancet Oncol, 2015) in postmenopausal women with estrogen-receptor-positive (ER+), HER2-negative advanced breast cancer (ABC) in the first-line setting. At the time of final PFS analysis, overall survival (OS) was immature.
Objectives
It is clinically important to understand whether patients (pts) benefit from standard of care endocrine therapy (ET) after they progressed on P+L as first-line treatment for ABC. We report patterns of post-progression treatment in the next line of therapy immediately following participation in the PALOMA-1 trial.
Methods
Postmenopausal women with ER+ and HER2- ABC who had not received any treatment for their advanced disease were randomized to receive P+L (N = 84) or L alone (N = 81) in the first-line setting. The primary endpoint was investigator-assessed PFS. Tumor assessment was performed every 8 weeks. Post-progression treatment data was captured and analyzed.
Results
As of the data cut-off (Nov 29, 2013), 40 progression events had occurred in the P+L arm and 59 in the L alone arm. 50% of pts in the P+L arm vs. 64% in the L alone arm received ET after progression on study treatment. 60% of pts in the P+L arm vs. 66% in the L alone arm received chemotherapy (CT) after progression on study treatment. The time to 1st subsequent ET/ CT after progression on study treatment, duration of 1st subsequent ET/CT, and choice of 1st subsequent ET/ CT are shown in Table 1.
Table 1 P + LL N=84N=81Patients (pts) with Disease Progression, NN (%)a40 (47.6)59 (72.8)Pts who received subsequent Endocrine Therapy (ET) after progression on study treatment, n(%)b20 (50.0)*38 (64.4)*Time from randomization to 1st subsequent ET (days), median (range)465.5 (239-1100)368.5 (65-1102)Duration of 1st subsequent ET (days), median (range)**153 (24-592)151 (16-1135)Choice of 1st subsequent ET, n(%)bFulvestrant9 (22.5)15 (25.4)Exemestane6 (15.0)9 (15.3)Medroxyprogesterone4 (10.0)1 (1.7)Letrozole1 (2.5)5 (8.5)Tamoxifen08 (13.6)Pts who received subsequent Chemotherapy (CT) after progression on study treatment, n(%)b24 (60.0)*39 (66.1)*Time from randomization to 1st subsequent CT (days), median (range)388.5 (69-918)281 (46-1013)Duration of 1st subsequent CT (days), median (range)**92 (1-457)120 (1-1143)Choice of 1st subsequent CT, n(%)bCapecitabine1 (2.5)10 (17.0)Mitoxantrone13 (32.5)1 (1.7)Paclitaxel013 (22.0)Other10 (25)15 (25.4)apercentages are based on N as denominator; bpercentages based on NN as denominator; *some patients had both ET and CT after progression; **calculated as treatment stop date minus treatment start date +1; if treatment was ongoing at time of data cut-off, stop date was imputed as Nov 29, 2013.
Conclusions
P+L delayed the time to ET/CT as compared to L alone. Pts benefited from standard of care ET/CT after they progressed on P+L as first-line treatment for ABC as demonstrated by the length of time on subsequent therapies; no difference was observed from the L alone arm.
Clinical Trial Information: NCT00721409
Funding Source: Pfizer.
Citation Format: Finn RS, Crown JP, Ettl J, Pinter T, Thummala A, Shparyk Y, Patel R, Randolph S, Kim S, Huang X, Nadanaciva S, Huang Bartlett C, Slamon DJ. Treatment patterns of post-disease progression in the PALOMA-1/TRIO-18 trial. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P4-13-02.