ASCENT: What the Breast Cancer Trial Found

Why triple-negative is a hard place to start

Most breast cancers carry something a drug can aim at. Hormone receptors let a team use endocrine therapy. HER2 lets them use HER2-directed drugs.

Triple-negative breast cancer has none of the three. It is defined by absence, and for years that left chemotherapy as the main option after the first ones stopped working.

ASCENT tested a drug built to create a target where the usual ones are missing.

The drug, in three parts

Sacituzumab govitecan is an antibody-drug conjugate. The published report describes it precisely: an antibody aimed at Trop-2, a protein the authors note is present on most breast cancers, joined by a breakable linker to SN-38, a topoisomerase I inhibitor.

SN-38 is the active form of irinotecan, an established chemotherapy drug. So the payload is not new. What is new is the delivery.

How the trial was run

ClinicalTrials.gov records NCT02574455 as a phase 3 trial that opened on 7 November 2017 and reached primary completion on 30 March 2020, with 529 participants.

The main published analysis covered 468 people without brain metastases. Two hundred and thirty-five received sacituzumab govitecan. Two hundred and thirty-three received a single chemotherapy drug chosen by their physician from four options: eribulin, vinorelbine, capecitabine or gemcitabine.

Median age was 54. Every participant had already had taxane chemotherapy, and all had relapsed or refractory metastatic disease.

That comparison arm deserves attention. It was not a placebo. It was real treatment, picked by the treating doctor. Our page on clinical trials compared with standard treatment explains why that design carries more weight.

What was found

Median progression-free survival was 5.6 months with sacituzumab govitecan and 1.7 months with chemotherapy. The hazard ratio was 0.41.

Median overall survival was 12.1 months against 6.7 months, with a hazard ratio of 0.48.

Tumors shrank enough to count as a response in 35% of the sacituzumab govitecan group and 5% of the chemotherapy group.

Both survival results were highly statistically significant, and the trial measured overall survival directly rather than through a substitute measure. That is worth noting, because many trials cannot.

What it cost

The same report sets out the harms in the same detail.

Severe neutropenia, meaning a dangerously low count of infection-fighting white cells, occurred in 51% of the sacituzumab govitecan group and 33% of the chemotherapy group. Severe low white cells overall occurred in 10% against 5%. Severe diarrhea occurred in 10% against under 1%. Severe anemia occurred in 8% against 5%. Febrile neutropenia, fever with a very low count, occurred in 6% against 2%.

Three people in each group died from adverse events. None of those deaths was considered related to sacituzumab govitecan.

The current label carries a boxed warning, FDA's strongest, for exactly the two problems the trial found most: neutropenia and diarrhea.

Where the drug sits now

The current prescribing information covers unresectable locally advanced or metastatic triple-negative breast cancer after two or more prior systemic therapies, which is the ASCENT setting. It has since expanded to a first-line indication and to hormone receptor-positive, HER2-negative breast cancer.

For context, the American Cancer Society projects about 321,910 new female breast cancer diagnoses in the United States in 2026 and about 42,140 deaths. Median age at diagnosis is 64.

Six percent of cases are found after distant spread, where five-year relative survival is 33.8%. Across all stages it is 91.9% for people diagnosed from 2016 through 2022. Triple-negative disease is a minority of breast cancer, and these pooled figures do not separate it out. Our overview of breast cancer covers the subtypes.

What to keep in perspective

• The trial studied people whose cancer had already progressed through at least two systemic treatments. A result in that setting says nothing about earlier treatment.
• Median survival figures describe the middle of a distribution. Half the group did better and half did worse, and no individual gained exactly 5.4 months.
• People with brain metastases were excluded from the main analysis, so the headline numbers do not describe that group.
• The side-effect rates above are not footnotes. Severe neutropenia in half of a trial population is a defining feature of this drug, and the label reflects it.
• A trial population is generally fitter and more closely monitored than everyone with the same diagnosis. Our page on questions to ask about a clinical trial covers what to raise with a care team.

Sources

• NCBI eutils: Bardia et al., N Engl J Med 2021;384:1529-41 (ASCENT, PMID 33882206)
• ClinicalTrials.gov API v2: NCT02574455 (ASCENT)
• openFDA drug label API: TRODELVY (sacituzumab govitecan-hziy)
• NCI SEER Stat Facts: Female Breast Cancer

How this article was prepared

An AI-assisted editorial system helped prepare this page. No named medical reviewer has reviewed it unless one is listed.

See an error, old source, or unclear wording? Tell us.