The New Era of Women’s Precision Health: What Guardant360

Can Reveal From a Blood Test

From breast cancer genomics to emerging treatment resistance, Dr. Corina Ianculovici examines how liquid biopsy is reshaping personalized care for women - and why advanced women’s health must extend far beyond routine hormone management.

By Dr. Corina Ianculovici, DNP, FAAMFM, ABAAM-HP, AGNP
Founder and Medical Director, Mirelle Institute for Longevity & Regenerative Medicine

Women’s health is entering a new era.

For much of modern medicine, women’s health was divided into separate compartments: reproductive medicine, gynecology, menopause, cardiometabolic health, cancer care and aging.

But biology does not operate in compartments.

The same woman who comes to us at 48 with vasomotor symptoms, sleep disruption, loss of muscle mass and declining estrogen may also have questions about breast density, family cancer history, cardiovascular risk, metabolic dysfunction, bone health and how her hormonal environment may influence her long-term health.

That is why I believe the future of women’s medicine must be personalized, preventive and increasingly molecular.

At Mirelle Institute for Longevity & Regenerative Medicine, our philosophy has always been that menopause care should not simply consist of treating hot flashes or prescribing hormones.

It should involve understanding the whole woman—her hormones, metabolic health, cardiovascular risk, bone health, body composition, cognition, sexual health, family history and, when appropriate, emerging advances in precision medicine.

One of the most remarkable advances occurring outside traditional menopause medicine is liquid biopsy.

And one of the most established examples is Guardant360®.

For women—particularly those affected by advanced breast cancer—the implications are becoming increasingly important.

What Is Guardant360?

Guardant360 is a blood-based form of comprehensive genomic profiling, commonly referred to as a liquid biopsy.

Rather than requiring another piece of tumor tissue, the technology analyzes genetic material circulating in a patient’s bloodstream.

Tumors can release fragments of DNA into the blood.

This tumor-derived genetic material is called circulating tumor DNA, or ctDNA.

By analyzing ctDNA, sophisticated sequencing technology can sometimes identify molecular changes occurring inside a cancer from a relatively simple blood draw.

The newest FDA-approved assay, Guardant360 Liquid CDx, received FDA approval in May 2026 and uses next-generation sequencing to detect small genomic variants across 741 genes, along with selected amplifications, losses and rearrangements.

Think about what that represents.

We are no longer limited exclusively to asking:

“Where is the cancer?”

We can increasingly ask:

“What is driving this cancer at the molecular level?”

That represents a profound evolution in medicine.

Why This Matters to Women’s Health

You may reasonably ask:

What does an oncology liquid biopsy have to do with a menopause and women’s health practice?

The answer is that sophisticated women’s health cannot exist in isolation from oncology.

Breast cancer remains one of the most consequential diseases affecting women.

Hormone biology is deeply intertwined with many breast cancers.

Estrogen receptors matter.

HER2 matters.

Endocrine therapy matters.

And increasingly, the molecular evolution of the tumor itself matters.

For clinicians working extensively with women during perimenopause, menopause and beyond, understanding these developments is essential.

It does not mean that Guardant360 is a menopause test.

It is not.

It means that modern women’s-health clinicians must understand the rapidly changing landscape surrounding breast health, cancer survivorship, hormone-sensitive malignancies and precision oncology.

That becomes particularly relevant when caring for women who have:

• a personal history of cancer;
• a strong family history of malignancy;
• previous breast cancer treatment;
• concerns regarding hormone therapy after cancer;
• complex survivorship needs;
• questions about new oncology technologies they encounter online or through their specialists.

Women deserve clinicians who understand not only hormones, but the broader medical landscape in which hormone decisions are made.

A Blood Test That Can Read Tumor Biology

Our bloodstream normally contains small fragments of DNA known as cell-free DNA, or cfDNA.

In someone with cancer, some of that material may come from cancer cells.

That portion is ctDNA.

Guardant360 uses sophisticated next-generation sequencing to analyze that circulating genetic material.

The FDA-approved Guardant360 Liquid CDx can detect:

• single nucleotide variants;
• small insertions and deletions;
• selected gene amplifications;
• selected gene losses;
• selected gene rearrangements.

The current FDA-approved platform evaluates small genomic variants across 741 genes.

That information can sometimes identify a mutation that helps an oncology team determine whether a particular targeted treatment may be appropriate.

This is the essence of precision oncology.

Two Women Can Have the Same Cancer—and Very Different Biology

Imagine two women who are both told that they have metastatic breast cancer.

At first glance, the diagnosis sounds identical.

Biologically, however, their cancers may be very different.

One tumor may carry one molecular alteration.

Another may carry an entirely different driver or resistance mutation.

Those differences can affect how the cancers behave and which therapies may work.

This is why oncology has moved well beyond treating malignancies solely according to the organ where they began.

The modern question is increasingly:

What molecular pathway is driving this particular patient’s disease?

Guardant360 can contribute to answering that question.

ESR1: An Especially Important Example for Women

One of the most compelling examples involves the ESR1 gene.

ESR1 encodes estrogen receptor alpha.

This matters enormously in hormone receptor-positive breast cancer because estrogen signaling can drive tumor growth.

During treatment with endocrine therapy, some cancers can evolve.

Under treatment pressure, tumor cells may acquire ESR1 mutations that allow estrogen-receptor signaling to behave differently and contribute to resistance.

Until relatively recently, clinicians often recognized treatment resistance because the cancer became visibly worse on imaging or because symptoms progressed.

Liquid biopsy creates another possibility:

Detecting molecular evidence of resistance before traditional imaging shows obvious progression.

That is an extraordinary concept.

A Major 2026 Development in Breast Cancer

In September 2026, the FDA granted accelerated approval to camizestrant (Etcamah) in combination with a CDK4/6 inhibitor for certain patients with hormone receptor-positive, HER2-negative locally advanced or metastatic breast cancer when an ESR1 mutation is detected during therapy using an FDA-authorized test.

Guardant360 CDx was simultaneously approved as a companion diagnostic for identifying those ESR1 mutations.

Even more remarkable is the concept underlying this approach.

In the pivotal SERENA-6 strategy, circulating tumor DNA was used to identify emerging ESR1 mutations before clinical or radiographic disease progression. Guardant reported that the associated ctDNA-guided treatment strategy reduced the risk of progression or death by 56% in the trial setting.

That begins to change the paradigm.

Traditionally:

Treatment → wait → scan → identify progression → change therapy.

We are beginning to envision:

Treatment → molecular surveillance → detect emerging resistance → potentially intervene earlier.

That is precision medicine in action.

Guardant360 and Other Breast Cancer Treatments

Guardant360 has also received FDA companion-diagnostic indications for additional therapies involving ESR1-mutated breast cancer.

In May 2026, for example, the FDA approved vepdegestrant for certain adults with ER-positive, HER2-negative, ESR1-mutated advanced or metastatic breast cancer following progression after endocrine therapy, with Guardant360 CDx approved as a companion diagnostic.

The FDA’s companion-diagnostic database also lists Guardant360 Liquid CDx for certain breast-cancer therapies associated with specific ESR1 alterations.

This illustrates why molecular testing is becoming increasingly intertwined with treatment selection.

The test is not merely producing interesting genetic information.

In specific settings, the molecular result can determine whether a patient meets the biomarker criteria for a particular FDA-approved therapy.

This Is Why Women’s Medicine Must Keep Evolving

For those of us caring for women through menopause and aging, there is an important lesson here.

Medicine is advancing rapidly.

The vocabulary of women’s health increasingly includes terms such as:

• genomics;
• epigenetics;
• ctDNA;
• precision medicine;
• pharmacogenomics;
• molecular biomarkers;
• metabolic phenotyping;
• personalized risk assessment.

Women are reading about these technologies.

They are asking about them.

And increasingly, they expect their clinicians to understand them.

At Mirelle Institute for Longevity & Regenerative Medicine, our commitment is not to adopt every new technology simply because it is new.

That is not evidence-based medicine.

Our responsibility is to continually examine emerging science and ask:

Is it validated?

Who is it intended for?

What does it actually tell us?

Will it change clinical management?

What are its limitations?

That distinction between innovation and evidence-based innovation, is critical.

Guardant360 Is NOT a Routine Cancer Screening Test

This is perhaps the most important clarification in this article.

Guardant360 Liquid CDx is not intended as a general blood test for healthy women who want to know whether they have cancer.

The FDA indication is for patients who have already been diagnosed with a solid malignant neoplasm and need tumor molecular profiling in conjunction with other clinical information.

That distinction matters.

A test designed to characterize an existing cancer is different from a screening test designed to search for cancer in an asymptomatic population.

Guardant Health produces other products for different purposes, but Guardant360 should not be marketed or understood as a universal cancer-detection blood test.

Could I Order Guardant360 During a Routine Menopause Evaluation?

Generally, no.

There is no evidence-based rationale for ordering Guardant360 simply because a woman is menopausal, uses hormone therapy or wants an extensive wellness evaluation.

It is an oncology test.

Its appropriate use begins with a known malignancy and a clinically relevant oncology question.

This is an important part of responsible precision medicine.

Advanced medicine does not mean ordering every sophisticated test available.

Sometimes the most sophisticated clinical decision is knowing when not to order one.

Liquid Biopsy Versus Traditional Tissue Biopsy

Traditionally, genomic profiling requires tumor tissue.

That may involve:

• surgery;
• needle biopsy;
• bronchoscopy;
• image-guided biopsy;
• another invasive procedure.

Those procedures remain enormously important.

But obtaining tissue may sometimes be difficult.

A tumor may be located close to important structures.

A metastatic lesion may be challenging to access.

The patient may have limited tissue remaining from an earlier biopsy.

Or another invasive procedure may carry meaningful risk.

Liquid biopsy provides another potential source of molecular information.

A simple blood draw is clearly less invasive than obtaining another tumor specimen.

But Liquid Biopsy Does Not Replace Every Tissue Biopsy

This is where clinical nuance becomes essential.

A negative Guardant360 test does not necessarily mean that a mutation is absent from the tumor.

Some cancers shed substantial amounts of ctDNA into circulation.

Others shed very little.

Therefore, a tumor may contain an important genomic alteration even when it cannot be detected in plasma.

The FDA specifically warns that a negative plasma result does not ensure that the tumor itself is negative and recommends tissue testing for relevant biomarkers when appropriate and feasible.

In other words:

A positive liquid-biopsy finding may be highly informative.

A negative result may sometimes require another question.

That distinction is fundamental.

One Tumor Is Not Necessarily One Disease

Cancer is remarkably heterogeneous.

Even within the same patient, different populations of cancer cells can possess different genomic characteristics.

A biopsy from one metastatic lesion captures the biology of the tissue that was actually sampled.

But another metastasis may contain additional molecular changes.

Because ctDNA may enter the bloodstream from multiple tumor sites, a liquid biopsy can sometimes provide a broader view of the molecular heterogeneity occurring throughout the body.

This does not make blood testing universally better than tissue testing.

It makes the two approaches potentially complementary.

Cancer Evolves Under Treatment

This is another concept that patients need to understand.

A cancer's molecular profile is not necessarily permanent.

Treatment exerts evolutionary pressure.

Cancer cells susceptible to therapy may die.

Other populations may survive.

Eventually, resistant clones may emerge.

That means the molecular profile identified at initial diagnosis may not completely represent the biology of the tumor years later.

This is one reason repeat liquid biopsy can become clinically useful.

Instead of viewing cancer genomics as a single test performed once, oncology is increasingly exploring dynamic molecular monitoring.

Why This Is Particularly Fascinating in Hormone-Sensitive Breast Cancer

Hormone receptor-positive breast cancer provides an extraordinary example of the intersection between:

hormones + genetics + treatment + tumor evolution.

For decades we have known that estrogen signaling can profoundly influence certain breast cancers.

Now we are becoming increasingly capable of watching the tumor's estrogen-receptor biology evolve molecularly.

That is especially relevant to clinicians practicing women's hormonal medicine.

It reinforces something I emphasize frequently:

Hormones are neither universally “good” nor universally “bad.”

Biology is contextual.

Estrogen has important physiologic roles in:

• bone;
• brain;
• cardiovascular physiology;
• genitourinary health;
• sexual health;
• body composition;
• connective tissue;
• numerous other systems.

At the same time, estrogen-receptor signaling can play an important role in specific cancers.

Good women's medicine requires understanding both realities simultaneously.

Fear-based medicine oversimplifies hormones.

So does indiscriminate hormone prescribing.

Precision medicine requires context.

Menopause Care After Cancer Requires Nuance

Another reason menopause specialists should understand advances such as Guardant360 is the growing population of cancer survivors.

Many women enter premature or abrupt menopause as a result of:

• chemotherapy;
• ovarian suppression;
• endocrine therapy;
• surgery;
• radiation;
• other cancer treatments.

They may experience:

• severe hot flashes;
• insomnia;
• sexual dysfunction;
• vaginal and urinary symptoms;
• accelerated bone loss;
• unfavorable body-composition changes;
• cognitive complaints;
• cardiometabolic changes.

Their menopause management can be substantially more complicated than routine hormone replacement.

The appropriate strategy depends upon the cancer type, receptor status, treatment history, recurrence risk and oncology recommendations.

A clinician working in advanced menopause care needs to understand that broader context.

That is part of what comprehensive women's health should mean.

Is Guardant360 an Inherited Cancer-Risk Test?

Not primarily.

Another distinction patients frequently misunderstand is the difference between somatic and germline mutations.

Somatic mutations

These develop in cells during life and can occur within a tumor.

Germline mutations

These are inherited variants present from birth and can potentially be passed to children.

Guardant360 primarily examines tumor-related molecular alterations circulating in plasma.

A finding may sometimes raise the possibility of an inherited variant, but tumor genomic profiling by itself should not automatically be interpreted as proof of hereditary cancer risk.

When hereditary cancer risk is suspected, dedicated germline testing and appropriate genetic counseling may be indicated.

Precision Medicine Is More Than Genetics

Genomic medicine is powerful.

But I want to emphasize something particularly important from a longevity perspective.

A woman's health cannot be reduced to her genome.

Genetics is one layer.

So are:

• metabolic health;
• insulin sensitivity;
• muscle mass;
• visceral adiposity;
• blood pressure;
• lipid biology;
• sleep;
• inflammation;
• physical activity;
• nutrition;
• environmental exposures;
• reproductive history;
• hormone status;
• psychosocial health.

Precision medicine means integrating these layers - not becoming obsessed with one sophisticated laboratory result.

That is the philosophy we bring to women's health at Mirelle Institute.

What Should Women Ask Their Clinicians?

If you or someone you love has been diagnosed with an advanced solid tumor, useful questions for the treating oncology team may include:

Has comprehensive genomic profiling been performed?

Was tissue sufficient for molecular testing?

Could liquid biopsy provide additional information?

Are there actionable mutations?

Does my tumor have a biomarker associated with an FDA-approved targeted therapy?

Could repeat molecular testing become appropriate if my disease progresses?

If my plasma test is negative, should tissue still be evaluated?

For women with advanced hormone receptor-positive breast cancer, questions regarding ESR1 mutation testing may now be particularly relevant depending upon treatment history and disease status.

What Guardant360 Cannot Tell Us

Guardant360 is sophisticated, but it is not omniscient.

It cannot independently tell us:

• whether every detected mutation is driving the cancer;
• whether every theoretically targeted treatment will work;
• whether a patient is cured;
• whether an asymptomatic healthy person has cancer;
• whether a negative plasma result means no actionable tumor mutation exists;
• whether a mutation is necessarily inherited;
• which treatment is best without considering the rest of the patient's clinical picture.

Precision medicine still requires clinical judgment.

Technology supports medicine.

It does not replace it.

The Mirelle Institute Perspective: Innovation With Clinical Context

At Mirelle Institute for Longevity & Regenerative Medicine, our mission in women's health extends beyond simply treating symptoms.

We believe women deserve care that evolves as medicine evolves.

That means continually examining developments across:

• menopause medicine;
• hormone biology;
• cardiometabolic health;
• osteoporosis prevention;
• cognition;
• sexual medicine;
• body composition;
• regenerative medicine;
• genomics;
• precision diagnostics;
• cancer survivorship;
• healthy longevity.

Not every emerging test belongs in routine practice.

Not every innovation is ready for every patient.

And not every “advanced” intervention is actually evidence-based.

Our responsibility as clinicians is to understand the difference.

Guardant360 represents an excellent example.

It is a remarkable technology.

It has important FDA-authorized applications.

It is changing aspects of precision oncology.

And in breast cancer, recent developments involving ESR1 mutations demonstrate just how rapidly molecular medicine is advancing.

But it remains an oncology tool—not a routine longevity or menopause screening test.

That distinction is exactly what evidence-based personalized medicine requires.

The Bigger Picture: The Future of Women's Health Is Precision Health

For too long, women have heard variations of:

“Your labs are normal.”

“You're just getting older.”

“This is menopause.”

“There is nothing else to investigate.”

That era is changing.

The future of women's health is not about indiscriminately ordering more tests.

It is about asking better questions.

It is about understanding:

Which woman?

Which risk?

Which biomarker?

Which intervention?

At what time?

And perhaps most importantly:

Will knowing this information actually change what we do?

That is precision health.

The Bottom Line

Guardant360 represents one of the most compelling examples of how blood-based molecular diagnostics are changing modern oncology.

For appropriately selected patients with known cancer, liquid biopsy can potentially:

• identify actionable mutations;
• help guide targeted therapy;
• provide molecular information when tissue is difficult to obtain;
• reveal emerging treatment resistance;
• capture aspects of tumor heterogeneity;
• allow repeat molecular assessment over time.

For women with certain advanced breast cancers, the implications are especially significant.

The September 2026 FDA approval involving Guardant360 CDx, ESR1 detection and camizestrant demonstrates how circulating tumor DNA may increasingly influence treatment decisions even before conventional imaging demonstrates disease progression.

That does not mean every woman needs Guardant360.

It means every clinician committed to advanced women's health should understand what technologies like this are telling us about the future of medicine.

Because the future is not simply about treating disease after it appears.

It is about understanding biology with greater precision—and using that information intelligently.

At Mirelle Institute for Longevity & Regenerative Medicine, that is the standard toward which we believe women's healthcare should continue to evolve.

About the Author

Dr. Corina Ianculovici, DNP, FAAMFM, ABAAM-HP, AGNP, is the founder and medical director of Mirelle Institute for Longevity & Regenerative Medicine. Her clinical work focuses on women's health, menopause and hormone optimization, functional and metabolic medicine, healthy aging and personalized longevity strategies.

Her approach emphasizes the integration of established clinical medicine with emerging evidence in precision health, with particular attention to helping women navigate the complex biological changes that occur during perimenopause, menopause and beyond.

Medical Disclaimer

This article is provided for educational purposes only and is not intended to diagnose, treat, cure or prevent disease. Guardant360 is an oncology diagnostic and is not recommended as routine screening for healthy or asymptomatic individuals. Cancer diagnosis, genomic testing and treatment decisions should be made in collaboration with appropriately qualified oncology specialists based on the patient's individual diagnosis, pathology, disease stage, treatment history and clinical circumstances.