A lung cancer diagnosis is often described through familiar terms such as the stage, size and location of a tumour. But there is another layer of information that can be equally important when doctors are deciding how to treat the disease: what is happening inside the cancer cells themselves.
This is where molecular profiling comes in. The test can identify genetic changes driving a tumour and help doctors determine whether a patient may be suited to a targeted treatment rather than relying only on a more general approach. Dr Vinayak Maka, Consultant, Department of Medical Oncology, Ramaiah Memorial Hospital, Bengaluru, explains why understanding the biology of a tumour can make a difference to lung cancer treatment.
What exactly is molecular profiling?
Molecular profiling is a laboratory test that looks for specific genetic changes inside cancer cells that may be responsible for their growth.
Dr Maka points out that this is different from the genetic testing people often associate with inherited diseases. Molecular profiling in cancer is primarily looking at changes that have occurred in the tumour itself, rather than mutations a person was born with.
The distinction matters because some of these tumour changes may be linked to treatments designed to target particular molecular pathways.
In simple terms, instead of asking only, "What type and stage of lung cancer does this person have?", doctors can also ask, "What is driving this particular tumour?"
Why can two people with the same lung cancer need different treatment?
Cancer does not behave identically in every patient.
Two people may have the same broad subtype of lung cancer but have different molecular changes driving their tumours. That means a treatment that works particularly well for one patient may not necessarily have the same effect in another.
This is one of the reasons comprehensive biomarker testing has become an important part of modern lung cancer care. Current ASCO guidance recommends broad tissue and/or blood-based biomarker testing for patients with non-small cell lung cancer, alongside relevant protein testing such as PD-L1.
Dr Maka explains that molecular profiling helps doctors move away from a one-size-fits-all approach and towards treatment based on the biology of an individual's cancer.
Who should consider molecular profiling?
One common misconception is that molecular profiling is relevant only to people who have smoked.
That is not the case.
Dr Maka specifically highlights that people who have never smoked can also develop lung cancers with actionable molecular changes. For patients with advanced non-small cell lung cancer, molecular profiling can therefore be an important part of treatment planning, irrespective of smoking history.
Current clinical guidance also emphasises broad biomarker testing rather than selecting patients based simply on characteristics such as smoking history.
How is the test performed?
Molecular profiling is commonly performed using tissue obtained during a biopsy.
However, obtaining additional tissue is not always straightforward. In some situations, doctors may consider a liquid biopsy, which uses a blood sample to look for tumour-derived genetic material.
Dr Maka explains that advances in next-generation sequencing, or NGS, allow laboratories to examine several biomarkers from a single sample. This can potentially reduce the need for multiple separate tests and provide a broader picture of the molecular changes involved.
Recent ASCO guidance also recognises validated tissue and blood-based broad multi-gene panels as part of comprehensive biomarker testing for NSCLC. It notes that combining tissue and blood testing may increase the chances of detecting relevant molecular alterations.
Why does timing matter?
One of the most important points is when molecular profiling is done.
Dr Maka says its value is greatest when the testing is completed before treatment begins. Starting treatment without knowing whether a tumour carries a potentially actionable alteration could mean that an appropriate targeted option is not considered at the right point in the treatment journey.
That is why timely testing has become an important part of precision oncology. The aim is to have relevant biomarker information available when treatment decisions are being made. Current ASCO guidance specifically states that biomarkers should be available at the time of decision-making.
Is molecular profiling the same as a regular biopsy?
Not exactly.
A biopsy can provide the tissue needed to diagnose the cancer, determine its type and examine its physical characteristics. Molecular profiling uses a tumour sample, where available, to look deeper into the genetic alterations that may influence treatment.
The two therefore serve different but complementary purposes.
A biopsy can tell doctors what the tumour looks like, while molecular profiling can provide information about the molecular changes driving it.
In some cases, a blood-based liquid biopsy can also be considered when obtaining sufficient tissue is difficult. However, a blood test does not necessarily replace tissue testing in every situation, and interpretation depends on the clinical context. Current guidance notes that tissue has advantages and that false-negative results can occur with liquid biopsy.
What does this mean for patients?
For someone diagnosed with lung cancer, molecular profiling may sound like another complicated medical test. But its purpose is relatively straightforward: to understand the cancer better before deciding how to treat it.
The field of lung cancer treatment is increasingly moving towards precision medicine, where therapy is selected according to the characteristics of the tumour rather than relying solely on broad cancer categories.
Dr Maka says the important question after a lung cancer diagnosis should therefore extend beyond the stage and type of cancer. Patients and families can also ask their treating team whether the tumour has been appropriately profiled.
The broader goal is simple: the more doctors know about the biology of a tumour, the better equipped they may be to identify treatment options that are suited to that particular cancer.
Disclaimer: Tips and suggestions mentioned in the article are for general information purposes only and should not be construed as professional medical advice.
Also read:
Lung cancer symptoms: 5 signs of the fatal condition, other than persistent cough
