167MO - Longitudinal evaluation of serum assessed non-adherence to tamoxifen (TAM) among premenopausal patients (pts) in the prospective multicenter CANTO cohort

Background

Using TAM serum assessment, we demonstrated that 1 in 6 premenopausal pts with early breast cancer (EBC) are non-adherent to TAM at 1 year (Y1) from treatment initiation. Most of them did not overtly declare non-adherence. We now evaluate the longitudinal evolution of non-adherence to TAM by using serum assessment and pts’ self-declarations at year 3 (Y3).

Methods

CANTO COMPLETE, a sub-study of CANTO cohort (NCT01993498), evaluates prevalence and predictors of non-adherence to adjuvant endocrine therapy in premenopausal pts at several time points from treatment initiation by drug serum levels and pts’ self-declarations. TAM was measured by liquid chromatography-tandem mass spectrometry on 50 μL of serum (lower limit of quantification [LLOQ]= 10 ng/mL). Pts were considered as biochemically non-adherent if TAM <60 ng/mL. Pts’ declarations were collected at the same time points. We used multivariable logistic regression and longitudinal multivariable mixed models to evaluate non-adherence at Y3.

Results

718 pts were evaluable at Y3. Median age 46 (IQR 42–49), partnered 536 (78.7%), post-graduation education 362 (52.6%), stage I BC 333 (46.4%) and received chemotherapy 444 (61.8%). At Y3, serum assessment showed that 260 (36.2%) pts were non-adherent, of whom 226 (31.5%) with TAM Definition TAM at Y1 (ng/mL) TAM at Y3 (ng/mL) N pts (%) * Early discontinuation <60 <60 83 (13.1) Later discontinuation ≥60 <60 144 (22.8) Interruption <60 ≥60 14 (2.2) Persistence ≥60 ≥60 392 (61.9)

*85 missing at Y1

Conclusions

At Y3 from initiation of TAM, more than 1 patient out of 3 was poorly adherent to adjuvant TAM, showing that non-adherence sharply increased from Y1 to Y3. Serum assessment was able to identify a higher proportion of pts who have dropped out from treatment early.

Clinical trial identification

NCT01993498.

Editorial acknowledgement

Legal entity responsible for the study

UNICANCER.

Funding

Institut National Cancer-France grant (SHS-E-SP 18-129) to Barbara Pistilli, a Career Catalyst Research grant from Susan G. Komen (CCR17483507) to Ines Vaz-Luis, a Fondation ARC pour la recherche sur le cancer grant (CANTO-WORK-programme labillisé) to Ines Vaz-Luis and Gwenn Menvielle and the Philanthropic Odyssea Gustave Roussy Program. The CANTO study is supported by the French Government under the “Investment for the Future” program managed by the National Research Agency (ANR), grant n° ANR-10-COHO-0004.

Disclosure

B. Pistilli: Honoraria (institution), Advisory/Consultancy: Puma Biotechnology; Speaker Bureau/Expert testimony: Pierre Fabre; Honoraria (institution), Advisory/Consultancy, Speaker Bureau/Expert testimony, Travel/Accommodation/Expenses: Novartis; Speaker Bureau/Expert testimony: Myriad Genetics; Travel/Accommodation/Expenses: MSD Oncology; Honoraria (institution), Travel/Accommodation/Expenses: AstraZeneca; Honoraria (institution), Travel/Accommodation/Expenses: Pfizer; Honoraria (institution): Merus. A.R. Ferreira: Advisory/Consultancy, Travel/Accommodation/Expenses: Roche; Advisory/Consultancy, Travel/Accommodation/Expenses: Novartis. A. Bardet: Advisory/Consultancy: Roche SAS. P.H. Cottu: Honoraria (self), Travel/Accommodation/Expenses: Pfizer; Honoraria (self), Honoraria (institution), Travel/Accommodation/Expenses: Roche; Honoraria (self): Lilly; Honoraria (institution): Novartis. S. Michiels: Advisory/Consultancy: IDDI; Advisory/Consultancy: Janssen Cilag; Speaker Bureau/Expert testimony: Hexal; Speaker Bureau/Expert testimony: Steba; Speaker Bureau/Expert testimony: IQVIA; Speaker Bureau/Expert testimony: Roche; Speaker Bureau/Expert testimony: Sensorion; Speaker Bureau/Expert testimony: Biophytis; Speaker Bureau/Expert testimony: Servier; Speaker Bureau/Expert testimony: Yuhan. I. Vaz Luis: Speaker Bureau/Expert testimony: Novartis; Speaker Bureau/Expert testimony: Amgen; Speaker Bureau/Expert testimony: AstraZeneca; Advisory/Consultancy: Kephren. All other authors have declared no conflicts of interest.