An antibody-drug conjugate extended survival in previously treated endometrial cancer

When advanced endometrial cancer returns after the standard first treatments — platinum chemotherapy and an immunotherapy drug — the options narrow quickly, and the chemotherapy used next tends to work only briefly. A phase 3 trial published in The Lancet on 26 October tested a newer kind of drug in exactly that situation [s1].

What the drug is

Sacituzumab tirumotecan, abbreviated sac-TMT, is an antibody-drug conjugate. The idea is to use an antibody as a guided delivery system: it recognises a protein called TROP2, which sits on the surface of many endometrial cancer cells, and carries a chemotherapy payload directly to the tumour, aiming to concentrate the toxic effect where it is needed and spare healthy tissue [s1]. It is a different strategy from the blunt, body-wide dosing of conventional chemotherapy.

The question TroFuse-005 set out to answer was whether, for people whose cancer had already progressed through chemotherapy and immunotherapy, this targeted approach would do better than simply giving another round of standard chemotherapy. TROP2 is a sensible target in this disease precisely because it is displayed on so many endometrial tumour cells, which is what gives the antibody something specific to home in on [s1].

How the trial was built

TroFuse-005 — also ENGOT-en23 and GOG-3095 — was a randomised, open-label, phase 3 trial registered as NCT06132958 [s1][s2]. It enrolled 776 people with advanced or recurrent endometrial cancer that had been treated with platinum-based chemotherapy and immunotherapy, and randomly assigned them to one of two arms [s1].

The 386 in the sac-TMT arm received the drug at 4 mg/kg intravenously on days 1 and 15 of each 28-day cycle [s1]. The 390 in the control arm received treatment of physician's choice — either doxorubicin at 60 mg/m² every three weeks, or paclitaxel at 80 mg/m² on days 1, 8 and 15 of each 28-day cycle — both long-established chemotherapy options for this setting [s1]. The trial had two primary endpoints, progression-free survival and overall survival [s1].

What it found

Both primary endpoints favoured the antibody-drug conjugate. Median progression-free survival was 7.2 months with sac-TMT against 3.9 months with physician's-choice chemotherapy, a hazard ratio for progression or death of 0.59 (95% CI 0.50–0.70; p<0.0001) [s1].

On overall survival, median survival was 19.0 months with sac-TMT versus 12.1 months with chemotherapy, a hazard ratio for death of 0.68 (95% CI 0.55–0.84; p=0.0001) [s1]. That the survival benefit reached significance is notable: in heavily pre-treated cancer, many new drugs delay progression on scans without clearly helping people live longer, and here both measures moved together. Because the trial set progression-free and overall survival as dual primary endpoints, the survival finding is a result the study was designed and powered to detect — not a secondary signal to be read cautiously, but a planned test the drug passed.

The trade-off was in side effects. Grade 3 or higher adverse events occurred in 69% of the sac-TMT group versus 57% of the chemotherapy group [s1]. More effective, in this trial, came with a higher rate of severe side effects — the opposite trade-off from the ideal, and a real consideration for patients weighing the two.

What is, and is not, established

What TroFuse-005 supports is clear: in advanced endometrial cancer already treated with chemotherapy and immunotherapy, sacituzumab tirumotecan produced longer progression-free and overall survival than the standard chemotherapy options it was tested against [s1]. For a setting where effective choices are scarce, a drug that extends median survival by nearly seven months is a meaningful advance, and the authors describe it as a new standard of care for this population [s1].

The qualifications are worth keeping in view. The trial was open-label, so neither patients nor doctors were masked to the treatment — progression-free survival can be influenced by that, which is one reason the overall survival result, harder to bias, carries particular weight [s1]. The higher rate of severe side effects means the benefit is not free, and the right choice will depend on an individual's circumstances and tolerance [s1]. And the result applies to the specific population studied — disease that has already progressed through platinum chemotherapy and immunotherapy — not to earlier treatment [s1].

Red flags: anyone receiving chemotherapy or an antibody-drug conjugate who develops a fever, mouth sores, severe diarrhoea, or unusual bruising or bleeding should contact their oncology team, as these can signal serious treatment effects. This article describes research and is not medical advice. Treatment decisions in recurrent endometrial cancer are for patients and their treating oncologists.