Abstract 123P
Background
BC pts in China (median age 48-50 y), with est. 60% being premenopausal, are younger than those in western countries. As an effective ovarian function suppression therapy that improves survival for premenopausal hormone receptor-positive (HR+) BC pts, the 3-monthly goserelin 10.8 mg depot offers more convenience with reduced visits and clinician burden compared with the monthly 3.6 mg depot. We conducted the largest real-world study (RWS) to date in China with 8 years of data to validate the noninferiority of goserelin 10.8 mg to the 3.6 mg depot.
Methods
This multicenter, retrospective-prospective, noninferiority study used medical record data to compare goserelin 10.8 mg with 3.6 mg in suppressing estradiol (E2) levels in premenopausal HR+ BC pts. Propensity score matching (PSM) ensured baseline comparability. The primary endpoint was the proportion of pts with E2 suppression to postmenopausal level at Wk 12±4. Difference in proportions and 95% CI was calculated by Newcombe-Wilson score method. The noninferiority margin was -10%. Subgroup and sensitivity analyses assessed confounder effects and result robustness.
Results
From 1 Jan 2015 to 15 Dec 2023, 15,629 pts from 16 hospitals nationwide were screened, with 1,060 eligible pts included in the full analysis set (10.8 mg group: 382; 3.6 mg group: 678). Post PSM, the primary endpoint was analyzed in 590 pts (295 in each group). At Wk 12±4, the proportion of pts with E2 suppression was 99.1% (95% CI: 96.9%, 99.8%) for goserelin 10.8 mg and 95.3% (95% CI: 91.0%, 97.6%) for goserelin 3.6 mg. The difference was 3.8% (95% CI: 0.6%, 8.1%) with the lower limit of 95% CI greater than the noninferiority margin. All subgroup analyses, including those based on age (≤45/>45 y) and previous chemotherapy (yes/no), and all sensitivity analyses on the primary endpoint were consistent with the main analysis (Table). Table: 123P
Sensitivity analyses on the primary endpoint
| Analysis† | Timepoint, Wk | Proportion of Pts with E2 Suppression, % (n/N) | Difference in Proportions, % (95% CI) | P value | |
| 10.8 mg | 3.6 mg | ||||
| Endpoint redefined as the proportion of pts with E2 suppression in all measurements between Wk 4 and 16 | 4–16 | 99.2 (259/261) | 94.4 (185/196) | 4.8 (1.7, 9.0) | 0.002 |
| Excluded pts who switched between goserelin 10.8 mg and 3.6 mg dosages | 12±4 | 99.1 (223/225) | 94.7 (144/152) | 4.4 (0.9, 9.2) | 0.017 |
| For the goserelin 3.6 mg group, only pts who received ≥2 doses were included∗ | 99.1 (217/219) | 95.8 (159/166) | 3.3 (0.1, 7.6) | 0.043 |
†Three key analyses out of 11 conducted are shown. *Rematched with 279 included in each group.
Conclusions
This large RWS with rigorous design validated the noninferiority of goserelin 10.8 mg 3-monthly to 3.6 mg monthly in Chinese pts with HR+ BC.
Editorial acknowledgement
The authors. would like to thank Xuenan Liu from Costello Medical for writing assistance and editorial support, which was funded by the study sponsor AstraZeneca China.
Legal entity responsible for the study
AstraZeneca China.
Funding
AstraZeneca China.
Disclosure
All authors have declared no conflicts of interest.