Endometrial Cancer

Aspirin has one of the stronger gynaecological evidence signals in endometrial cancer.

The case is still built mainly on observational data. Even so, the pattern is unusually coherent. Prevention signals, obesity-linked subgroup effects, and supportive post-diagnosis data all point in the same direction.

Overview

Endometrial cancer is tightly linked to obesity, oestrogen excess, and chronic inflammatory signalling.

That matters because aspirin directly intersects with this biology. It suppresses COX-driven prostaglandin signalling, lowers TXA2 activity, and may weaken the inflammatory loop that helps drive endometrial proliferation and malignant change. Read the meta-analysis

Compared with ovarian cancer, this looks like the clearer aspirin page in gynaecological oncology. The signal is more consistent, the mechanism is more direct, and one retrospective study also suggests a survival benefit after diagnosis. Read the gynaecological review

Key human data

Prevention and risk reduction

The strongest endometrial-cancer pattern is not simple long duration. It is frequency of aspirin use.

• Meta-analysis of 18 studies: Aspirin use was associated with lower endometrial-cancer risk in both case-control and cohort data. Reported effect sizes were OR 0.88 in case-control studies and RR 0.92 in cohort studies. Read the meta-analysis

• Higher-frequency use: Women using aspirin at least twice weekly showed a stronger signal, with an odds ratio of 0.63 in one synthesis. Read the gynaecological review

• Australian National Endometrial Cancer Study: Use of two or more tablets per week was associated with an odds ratio of 0.54, which is close to a 50% relative risk reduction. Read the gynaecological review

• Overweight and obese women: A 2024 QIMR Berghofer analysis reported about 15% lower risk in overweight or obese women using aspirin or NSAIDs more than once weekly. Read the QIMR summary

This obesity signal matters. Endometrial cancer is one of the clearest cancers where adipose inflammation, prostaglandins, and local oestrogen production reinforce each other.

Survival after diagnosis

Direct treatment-trial data is still missing.

But one multicentre retrospective study reported that low-dose aspirin use after diagnosis was associated with better 5-year disease-free survival and overall survival. Read the report summary

This should be treated as supportive, not definitive. Still, few non-colorectal aspirin pages have both a prevention signal and a post-diagnosis survival signal.

Mechanistic relevance

COX-2, PGE2, and oestrogen amplification

This is the main biological reason the page matters.

In obesity-linked endometrial cancer, excess adipose tissue raises local oestrogen production and inflammatory prostaglandins at the same time. COX-2 drives PGE2 production. PGE2 can increase aromatase activity in adipose tissue. That increases local oestrogen production, which then further supports endometrial proliferation. Read the meta-analysis

Aspirin interrupts this loop upstream. It reduces prostaglandin production and may blunt the inflammatory-oestrogen feedback cycle that is especially active in obese patients.

Low-dose aspirin has also been reported to reduce basal systemic PGE2 biosynthesis by about 55% in healthy women. That gives this mechanism a direct pharmacodynamic anchor. Read the meta-analysis

PIK3CA relevance

Endometrial cancer is also a plausible PIK3CA-linked aspirin setting.

PIK3CA mutations occur in roughly 30% to 35% of endometrial cancers. That is one of the highest rates among solid tumours. Read the AACR pan-cancer analysis

That does not mean aspirin is validated here the way it now is in biomarker-selected colorectal cancer. It does mean the biology overlaps with the same mutation-defined logic that made the ALASCCA colorectal result so important.

Platelet and TXA2 biology

Platelet signalling may add a second layer of relevance.

Aspirin irreversibly blocks platelet COX-1 and sharply lowers TXA2 generation. That matters because TXA2 can suppress immune surveillance during metastatic spread. For the broader mechanism, see Aspirin and Thromboxane A2 (TXA2).

Clinical positioning

Practical interpretation

Endometrial cancer is one of the more biologically coherent aspirin pages outside colorectal cancer.

The useful patient-level questions are:

1. Has the tumour had genomic profiling, especially for PIK3CA?

2. Was the cancer strongly linked to obesity, metabolic syndrome, or chronic inflammatory pressure?

3. Is the main discussion about prevention, recurrence risk, or post-diagnosis adjunctive use?

4. Given bleeding risk and GI history, is low-dose aspirin a reasonable discussion with the gynaecological oncology team?

The main limit is still trial quality. Most evidence here is observational. But the overall picture is stronger than the old placeholder version suggested.

References

• 2020 meta-analysis of aspirin and endometrial-cancer risk — 18 studies, pooled prevention signal. Read the meta-analysis

• 2020 review of aspirin in gynaecological cancers — includes higher-frequency endometrial findings. Read the review

• QIMR Berghofer 2024 — lower endometrial-cancer risk in overweight and obese women using aspirin or NSAIDs. Read the summary

• Multicentre retrospective report — low-dose aspirin and survival after endometrial-cancer diagnosis. Read the report summary

• Yang et al., Nature 2025 — platelet TXA2, immune escape, and metastasis. Read the University of Cambridge summary

• AACR pan-cancer analysis — PIK3CA mutation frequency context across tumour types. Read the analysis

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