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Background and Importance Inavolisib has recently been approved in combination with palbociclib and fulvestrant for the treatment of adult patients with PIK3CA-mutated, oestrogen receptor (ER)-positive, HER2-negative, locally advanced or metastatic breast cancer, following recurrence during or within 12 months after completing adjuvant endocrine therapy.In the pivotal INAVO120 trial, inavolisib demonstrated a benefit over palbociclib-fulvestrant, with a median overall survival (OS) of 34.0 vs 27.0 months (7.0-month difference) and a hazard ratio of 0.67 (95% CI, 0.48–0.94), with data maturity of 47.4%. However, the median OS may not fully represent clinical benefit, as it reflects only a single point on the survival curve and does not capture differences occurring earlier or later in follow-up.Aim and Objectives To apply the modified Seruga–Fénix area under the curve (AUC) method to estimate mean OS from Kaplan–Meier data of the inavolisib trial and to compare the results with the median OS reported in the pivotal study.Material and Methods Kaplan–Meier curves from the pivotal trial were digitised using WebPlotDigitizer v5, and AUCs were calculated for both the inavolisib and control arms. The reference area was defined as the rectangle bounded by the y-axis, the vertical cut-off line representing the minimum number of patients at risk (≥10 per group or ≥30 in total), and the upper boundary of the survival curve. The mean OS values obtained were then compared with the published medians to assess possible over- or underestimation of survival benefit.Results The total reference time was 52.8 months, and 79.7% of patients were included in the analysis (those with OS data).The estimated mean OS was 29.27 months for the inavolisib arm and 24.37 months for the control arm, a difference of 4.9 months, lower than the 7.0-month difference reported in the pivotal trial.Conclusion and Relevance Inavolisib achieved a mean OS of 29.27 months compared with 24.37 months for the control arm in the AUC based method. Compared with the pivotal trial (34 vs 27 months), the AUC based method showed a smaller survival difference, suggesting that the pivotal trial measurements may be overestimating the clinical benefit.References and/or Acknowledgements 1. Fenix-Caballero S, et al. New graphic AUC based method to estimate overall survival benefit: pomalidomide reanalysis. J Clin Pharm Ther. 2016 Feb;41(1):1–3.Conflict of Interest No conflict of interest