Abstract OT2-01-11: Phase II of POSEIDON: A phase Ib / randomized phase II trial of tamoxifen plus taselisib or placebo in hormone receptor positive, HER2 negative, metastatic breast cancer patients with prior exposure to endocrine treatment

Background: The combination of PI3K-AKT-mTOR pathway inhibitors with endocrine therapy can improve clinical outcomes of hormone receptor positive (HR+) metastatic breast cancer (MBC) patients. Taselisib is a potent and selective PI3K inhibitor, with greater selectivity against mutant (MUT) PI3Kα isoforms than wild-type (WT) via a unique mechanism. Phase Ib data of POSEIDON with Taselisib + tamoxifen (TAM) demonstrated encouraging activity in patients with heavily pre-treated MBC, with an acceptable toxicity profile (Baird et al, ASCO 2016). The recommended phase II dose (RP2D) was Taselisib 4mg plus TAM 20mg, both administered on a daily continuous schedule. ctDNA monitoring may have value in drug development by (1) assessing predictive biomarkers to therapy, (2) providing an early indication of treatment response, and (3) shedding light on potential mechanisms of acquired drug resistance. In some patients included in phase Ib of POSEIDON, tumor response was preceded by a corresponding early change in plasma PIK3CA ctDNA levels. Methods: The phase II portion of the POSEIDON trial is a two-arm, randomized, double blind study of Taselisib plus TAM versus placebo (PLA) plus TAM in pre- and postmenopausal women with HR+/HER2- MBC. In the first part of the Phase II, 180 patients will be randomized (1:1) to receive continuous TAM with either Taselisib at the RP2D or PLA until disease progression, unacceptable toxicity or patient / physician decision. Crossover is allowed upon progressive disease in those patients receiving PLA plus TAM, after collection of tumor and blood samples for exploratory biomarker analysis. Stratification is based on menopausal status, histology [lobular breast cancer (LBC) vs. ductal/others], PIK3CA mutation (WT vs. exon 9 vs. exon 20), prior everolimus, timing of recurrence/progression after prior endocrine therapy, number of prior chemotherapy (CT) lines, and treatment center. After recruiting the initial 180 patients, trial will focus in LBC, until a total number of 110 patients with LBC are enrolled. Other key eligibility criteria include presence of measurable or evaluable disease (RECIST 1.1), prior progression to endocrine treatment, maximum of 5 prior CT lines in the metastatic setting, absence of diabetes under medical treatment, and absence of chronic inflammatory bowel disease. Primary endpoint is investigator-assessed PFS. Key secondary endpoints are PFS in LBC, objective response rate, clinical benefit rate, safety, and exploratory biomarker analysis (including ctDNA). The study has a 90% power at a two-sided log-rank test significance level of 0.2 to detect an HR of 0.64, which corresponds to an increase in median PFS from 4.5 months in the PLA plus TAM arm to 7 months in the Taselisib plus TAM arm. Enrollment to POSEIDON Phase II started in June 2016 (Clinicaltrials.gov NCT02285179).

Citation Format: Oliveira M, Baird RD, van Rossum AGJ, Beelen K, Garcia-Corbacho J, Mandjes IAM, Vallier AL, van Werkhoven E, Garrigós L, Kumar S, van Tinteren H, Muñoz S, Linossi C, Rosing H, Miquel JM, Schrier M, de Vries Schultink A, Saura C, Gallagher WM, Bernards R, Tabernero J, Cortés J, Caldas C, Linn SC. Phase II of POSEIDON: A phase Ib / randomized phase II trial of tamoxifen plus taselisib or placebo in hormone receptor positive, HER2 negative, metastatic breast cancer patients with prior exposure to endocrine treatment [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr OT2-01-11.

Abstract P4-21-16: Phase III trial to evaluate patient´s preference for subcutaneous versus intravenous trastuzumab administration in patients with HER2 positive advanced breast cancer (ABC) under IV trastuzumab (IV-t) treatment for at least 4 months. ChangHER-SC study (GEICAM/2012-07)

Background: Patients with HER2-positive ABC, receive anti-HER2 treatment for several months or even years. IV-t is administered weekly or 3-weekly, mandating patients to visit the hospital on a regular basis to receive infusions. This has inconveniences for patients and increase treatment costs. Subcutaneous administration could improve convenience of trastuzumab therapy. This study was designed to evaluate patient's preference for IV-t or SC trastuzumab (SC-t) in ABC patients.

Methods:This is a phase III, open label, multicenter study inpatients with HER2 positive ABC, receiving IV-t for at least 4 months and without evidence of disease progression. Patients received 600 mg of SC-t, either from a vial or from a single injection device (SID), every 3 weeks for 4 cycles. Before starting SC-t, patients received an additional IV-t cycle. Patients were randomized 1:1 to arm A, receiving 2 cycles of SC-t with vial followed by 2 cycles with SID or arm B, receiving the opposite sequence. After cycle 4, patients decided to continue with IV-t or SC-t till disease progression. Stratification criteria were the associated therapy (Chemotherapy, Hormone-therapy or none) and its administration route (IV, oral or none). Patients completed a questionnaire of experiences and preferences at three time points: before starting SC-t, after cycle 2 and after cycle 4. Health Care Professionals completed a satisfaction questionnaire every 5 patients. The primary objective was to evaluate patient´s preference for IV-t or SC-t (after cycle 2) and, secondary objectives were, to evaluate patient´s preference between the two SC-t administrations (vial or SID) after cycle 4, Health Care Professional satisfaction, associated costs of the administration options (Time and Motion pharmacoeconomic study) and safety.

Results: From September-13 to July-15, 166 patients were randomized (81 arm A, 85 arm B) in 26 Spanish sites from GEICAM. Median age was 60 years (35-93), 88% of patients were postmenopausal and 123 and 42 had an ECOG PS of 0 and 1, respectively. The median duration of prior IV-t for ABC was 1.8 years (range: 0.3-14). Patients received a median of 2 previous lines of Chemotherapy and/or Hormone-therapy (range: 1-9). Twenty patients were receiving pertuzumab at inclusion. According to patient questionnaires completed after cycle 2, 137 patients preferred the SC-t (66 arm A, 71 arm B), 11 the IV-t (6 arm A, 5 arm B), 11 didn't have a preference (4 arm A, 7 arm B), and 7 didn't answer (3 progressed, 2 withdrew participation before cycle 2 and 2 unknown reason). Three of the 11 patients choosing IV-t were receiving IV treatment as accompanying therapy; after cycle 4 five of these 11 patients finally continued with SC-t, 5 with IV-t and 1 progressed. From the 11 patients without any preference 7 received SC-t, 2 receive IV-t and 2 progressed; from the 137 patients preferring SC-t, 125 actually received it, 3 received IV-t and 9 progressed.

Conclusions: Our study shows that 82.5% of patients preferred the SC-t over the IV-t. Treatment choice was not influenced by the accompanying therapy.

Citation Format: Ciruelos EM, Montaño Á, Rodríguez CA, González-Flores E, Lluch A, Garrigós L, Quiroga V, Antón A, Malón D, Chacón JI, Velasco M, Gonzalez-Cortijo L, Jolis L, Pascual T, Amigo Y, Casas M, Cámara MC, Carrasco E, Casas A. Phase III trial to evaluate patient´s preference for subcutaneous versus intravenous trastuzumab administration in patients with HER2 positive advanced breast cancer (ABC) under IV trastuzumab (IV-t) treatment for at least 4 months. ChangHER-SC study (GEICAM/2012-07) [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P4-21-16.

Abstract OT3-01-03: Phase III clinical trial to evaluate patient's preference for subcutaneous (SC) versus intravenous (IV) trastuzumab administration in patients with HER2 positive, advanced breast cancer (ABC) under IV trastuzumab treatment for at least 4 months and without disease progression. ChangHER-SC study (GEICAM/2012-07)

Background: Patients with HER2-positive, ABC, usually receive anti-HER2 treatment for several months or even years. Trastuzumab IV is administered weekly or 3-weekly, mandating patients to visit the hospital on a regular basis to receive infusions that are prepared in the hospital's pharmacy and administered to patients over 30-90 minutes. These mean some inconveniences for the patients and increase treatment costs. Subcutaneous administration could improve convenience of trastuzumab treatment. This study was designed to evaluate patient's preference for IV or SC trastuzumab.

Trial Design: Phase III, open label, multicenter study, running in 27 Spanish sites. HER2 positive, ABC patients, receiving IV trastuzumab (in monotherapy or in any combination), without evidence of disease progression for at least 4 months, and a life expectancy of at least 3 months, are eligible. Patients are randomized to receive SC trastuzumab, either from a vial or from a single injection device (SID), at a fixed dose of 600 mg, every 3 weeks, for 4 cycles. Before starting SC administration, patients receive an additional IV cycle. Patients in arm A receive 2 SC cycles using the vial and then two cycles more with the SID. In arm B patients receive the opposite sequence. After these four cycles, patients continue with SC or IV trastuzumab, depending on their decision, until disease progression. The primary objective is to evaluate patient's preference for IV or SC trastuzumab and, secondary objectives are, to evaluate patient's preference for the SC administration using the vial or the SID, the Health Care Professional satisfaction, the associated costs of the different administration options (with a Time and Motion pharmaco-economic study) and the safety of the different treatment administrations. Assuming a 65% rate of patients preferring SC trastuzumab and with a precision ±7.5%, a total of 195 patients have to be recruited to allow for a 20% of expected drop-out rate. Recruitment started in September 2013 and 158 patients have been included so far. Analysis of the primary endpoint will take place once the last patient has completed the 4 cycles of the study treatment. (ClinTrials.gov reference NCT01875367).

Citation Format: Ciruelos E, González E, Lluch A, Garrigós L, Quiroga V, Antón A, Pascual T, Montaño Á, Angulo MdM, Cámara MdC, Amigo Y, Carrasco E, Casas A. Phase III clinical trial to evaluate patient's preference for subcutaneous (SC) versus intravenous (IV) trastuzumab administration in patients with HER2 positive, advanced breast cancer (ABC) under IV trastuzumab treatment for at least 4 months and without disease progression. ChangHER-SC study (GEICAM/2012-07). [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 OT3-01-03.