Endpoints in Gynaecological Oncology Clinical Trials

Clinical trials in gynaecological oncology have delivered a wave of practice-changing results, especially over the past two years, from surgical de-escalation studies to immunotherapy and PARP inhibitor combinations.

However, there is an uncomfortable truth for clinical teams. Strong progression-free survival results do not always translate into a genuine overall survival benefit, and this says as much about clinical trial design as it does about the drugs themselves.

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The Clinical Compass for Smarter Gynaecological Oncology Trials

Over the past decade, two parallel shifts have reshaped gynaecologic oncology. Surgery has become more conservative for many early-stage patients, while systemic therapy has become more aggressive and biomarker-driven for advanced disease.

A recent review of the field, spanning cervical, endometrial, and ovarian cancer, catalogued the trials that have most shaped practice in a single year (2025), but nearly every major result came with a caveat that changes how it should be read.

A separate ten-year review of surgical trials in gynaecologic oncology reached a similar conclusion from the operating theatre. Several landmark studies challenged long-standing surgical dogma, and not every challenge succeeded.

For sponsors and trial designers, these reviews and others spanning almost 20 years and the for the year 2024 show the same underlying trend that endpoint choice and control-arm design now matter as much as the intervention itself.

Lessons From Surgical De-Escalation Trials

What changed in vulvar and cervical cancer

A cluster of trials tested whether less extensive surgery could match the outcomes of the traditional, more radical approach.

• GROINSS-V - GROINSS-VIII found that omitting groin lymph node removal was safe for women with early vulvar cancer and a negative sentinel node, with 10-year survival above 90% in that group.
• GROINSS-V II showed radiotherapy could replace lymphadenectomy for small-volume sentinel node involvement, though full lymphadenectomy remained the safer option once involvement exceeded 2 mm.
• SHAPE found simple hysterectomy as safe as radical hysterectomy for low-risk early cervical cancer, with fewer urinary complications and better quality-of-life scores.
• ConCerv supported conservative surgery, including conisation, for very low-risk early cervical cancer, with a low recurrence rate at two years.

• LACE confirmed laparoscopic hysterectomy as equivalent to open surgery for stage I endometrial cancer, with no difference in disease-free or overall survival.

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Why the LACC trial remains a cautionary tale

Not every de-escalation hypothesis held up.

The LACC trial found that minimally invasive radical hysterectomy produced a lower rate of disease-free survival than open surgery in early cervical cancer, reversing what had been the assumed trend in surgical practice.

The finding was significant enough that international guideline bodies moved to recommend this the studied type of open abdominal approach for radical hysterectomy.

But, a minimally invasive or conservative approach is not automatically equivalent just because it is less invasive.

Each surgical hypothesis in gynaecologic oncology still needs its own randomised evidence, not an assumption carried over from a different disease setting.

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When Progression-Free Survival Does Not Predict Overall Survival

In systemic therapy, the more striking findings sit in ovarian cancer maintenance trials, where clear progression-free survival (PFS) does not always hold up once mature overall survival data arrive.

None of this means the underlying drugs failed or that PFS is not a valuable clinical endpoint (or that in every case overall survival is more valuable than PFS). It means the clinical trial design made the true effect difficult to isolate.

When a control arm can access the experimental drug class after progression, or when it omits a treatment that has since become standard, overall survival comparisons need to be planned and interpreted with that in mind from the outset.

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Where Immunotherapy and Biomarkers Are Delivering Durable Gains

Set against that caution, several trials produced results robust enough to change practice outright.

In locally advanced cervical cancer, KEYNOTE-A18 added pembrolizumab to chemoradiotherapy and became the first Phase III trial in this setting to show a statistically significant overall survival benefit, cutting the risk of death by roughly a third at the second interim analysis.

INTERLACE showed that a short course of induction chemotherapy before chemoradiotherapy meaningfully improved both progression-free and overall survival.

In endometrial cancer, four separate Phase III trials, NRG-GY018, RUBY, AtTEnd, and DUO-E, tested adding immunotherapy to first-line chemotherapy. Across all four, the largest benefit consistently appeared in patients with deficient mismatch repair (dMMR) tumours, often with hazard ratios for disease progression below 0.4, against far more modest gains in mismatch repair-proficient disease.

This pattern established dMMR status as a genuine predictive biomarker, not simply a prognostic one.

• Deficient mismatch repair (dMMR) status in endometrial cancer, where immunotherapy benefit is largest and most consistent.
• Homologous recombination deficiency (HRD) in ovarian cancer, where PARP inhibitor benefit is substantially greater than in HRD-negative disease.
• PD-L1 expression in cervical cancer, where KEYNOTE-A18 showed benefit regardless of status, making it a weaker predictive signal than dMMR or HRD.

What Gynaecological Cancer Endpoint Data Mean for Clinical Development Teams

For sponsors running gynaecological oncology clinical trials, four practical lessons emerge from this body of evidence.

Firstly, control arms need to reflect the actual current standard of care at the time of analysis, not the standard from when the protocol was written. Overall survival analyses need a pre-specified plan for crossover, since many control-arm patients in maintenance settings will access the experimental drug class regardless.

Biomarker stratification, whether dMMR, HRD, or another signal, should sit inside the primary analysis rather than arrive as an after-the-fact subgroup analysis

And as the field faces growing criticism that its results generalise poorly beyond trial populations, sponsors should track the parallel push toward pragmatic, real-world-reflective designs coming from groups such as the Gynecologic Cancer InterGroup, which is actively building a roadmap for trials that better reflect routine care.

At Pharmatica, we analyse how endpoint selection, control-arm design, and biomarker strategy shape real clinical outcomes across the Clinical Compass. Our Insights connect trial evidence to the operational decisions that clinical development leaders face before a protocol goes to committee review.

Pharmatica: Insight. Connection. Impact.

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