Can Precision Diagnostics Help Reduce Overtreatment in Breast Cancer?
By Dr B.A. Savitha,
Until many years ago, the default treatment choice for breast cancer, and many other forms, was to treat the disease aggressively. Earlier, clinicians had very few tools to determine whether a patient would require an intensive treatment approach or if they could forgo the standard chemotherapy regimen for a patient. They had no reliable way to distinguish a tumor that would recur from one that never would. Hence, they usually opted for a one-size-fits-all approach.
Over the last decade, precision diagnostics has transformed different aspects of healthcare. Oncologists now know that patients with identical cancers with the same histology, stage, and clinicopathological features can have different responses to the same treatment approach. They have seen the impact of precision medicine on the quality of life of patients, the way it reduces financial burden and how it has led to optimum treatment plans for patients.
Dr B.A. Savitha, Senior pathologist and Lab Director, OncoStem Diagnostics
From ‘treating everyone’ to ‘treating who need it’
Oncologists have long known that two cancers may look identical under the microscope, but they can behave very differently from each other. What they didn’t have an explanation for was: Why do they behave differently? Precision diagnostics explains why. It analyses the unique biological characteristics of a patient’s tumor. It evaluates the genomic, proteomic, transcriptomic, epigenomic, and metabolomic profiles to understand disease behavior and treatment response. Among all cancers, breast cancer has been at the forefront of demonstrating the clinical utility of precision medicine.
One of the earliest applications of precision medicine in breast cancer is in the area of tumour subtyping. When a patient is diagnosed with breast cancer, oncologists look at hormone receptor status (estrogen and progesterone) and HER2 expression (HER2 protein present on tumour cells ). These three biomarkers form the basis of the entire treatment plan. It allows clinicians to decide whether a patient needs neoadjuvant therapy or if they can choose between chemotherapy, endocrine therapy, and HER2-targeted drugs.
Precision medicine goes beyond the classification. For individuals with hormone receptor-positive, HER2-negative early breast cancer, a set of validated assays can now estimate the actual risk of metastasis rather than leaving oncologists to infer it only from conventional parameters like tumor size and grade alone. Simply put, it allows clinicians to answer one of the most critical questions in breast cancer treatment: Will this patient truly benefit from chemotherapy, or can it be safely avoided?
Precision diagnostics relies on genomic technologies such as RT-PCR and tissue microarrays, as well as newer proteomic assays that utilize immunohistochemistry combined with artificial intelligence. Some of these have been validated through randomized clinical trials and have been incorporated into international treatment guidelines.
In the last few years, precision oncology has also expanded the use of predictive molecular testing. Identification of actionable mutations such as “BRCA1”, “BRCA2”, “ESR-1” and “PIK3CA” enables the use of targeted therapies. This offers a more personalized and effective treatment option while avoiding unnecessary toxicity.
Why does precision medicine matter to Indian patients?
The number of breast cancer cases has been increasing in India over the years. As per GLOBOCAN 2024, breast cancer constitutes 30.4% of all cancers diagnosed in Indian women. That’s approximately 2,37,000 new cases annually. An important aspect to note is that nearly 70% of these patients have hormone receptor-positive, HER2-negative disease. This is the subcategory of patients that derive the most benefit from precision prognostic testing.
A practical challenge in implementing precision diagnostics in India has been the limited validation of several internationally used prognostic assays in Indian populations. Most of the tests are validated on international patients, and it may not always translate directly to Indian clinical practice. Additionally, cost has been a significant barrier to mass adoption of these international tests. Recognizing the need for an affordable Indian alternative, a test that is ideal for the Indian population as it was developed using tumour samples from Indian patients and has been globally validated and published in studies involving more than 3,000 patients, including over 1,100 Indian patients.
Adoption gap in precision diagnostics
Even though there is availability of precision diagnostic tools, the adoption has been slow. Currently, less than 10% of eligible patients are undergoing testing. Treatment decisions continue to depend on conventional clinical and pathological factors such as tumor size, grade, nodal status, and ER/ PR/ Her2 Status. Though these conventional factors form the foundation of diagnosis, they do not adequately capture the underlying biological aggressiveness of individual tumors. This leads to overtreatment, particularly in patients with limited lymph node involvement, irrespective of menopausal status. Many of these patients end up receiving adjuvant chemotherapy even though they may get little benefit from it, exposing them to long-term side effects of chemotherapy. Few published studies suggest that nearly half of these patients may not benefit from chemotherapy when assessed using validated prognostic assays.
On the other hand, relying only on conventional clinicopathological features may also result in undertreatment. Some patients, particularly those who are young, can have a small tumour, but it may be more aggressive and may have a higher risk of recurrence. Without using precision diagnostic testing, many of these patients may be suggested to skip chemotherapy, thereby impacting long-term outcomes.
Precision diagnostics enables oncologists to look beyond conventional risk assessment by integrating tumor biology into treatment decisions. In this approach, they are able to offer chemotherapy to patients who are most likely to benefit while safely avoiding unnecessary treatment to those with biologically low-risk disease.
A decade from now, precision medicine will not be a buzzword. It will be the standard for how breast cancer is treated. Instead of a one-size-fits-all approach, doctors will decide the optimum treatment plan on the basis of each patient’s tumor biology and risk of recurrence. This will be a significant shift from where we are now. The impact will be substantial. Patients will have a better quality of life because cancer treatment will be tailored to that individual rather than a standard treatment protocol.
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