Understanding lung cancer subtypes: How precision medicine has changed treatment

Personalising Lung Cancer treatment— moving beyond one size fits all. Lung cancer remains the most common cause of cancer-related deaths worldwide. Back in the early 1990s, chemotherapy was the only systemic treatment available for lung cancer. At that time, identifying the specific subtype of a patient’s cancer didn’t change the treatment much—everyone essentially received the same harsh treatment. 

The discovery of Gefitinib, an early EGFR inhibitor initiated the shift in the paradigm of treatment. By identifying the genetic mutations causing the cancer, we have now developed a whole range of drugs which treat specific subtypes of lung cancer. Defining the subtype of lung cancer thus leads to a more personalised and better treatment. As a result of this shift, lung cancer patients now live much longer and lead more productive and healthy lives. 

Lung cancers are broadly classified into two major categories: Small Cell Lung Cancer (SCLC) and Non-Small Cell Lung Cancer (NSCLC). They are further classified on their appearance under the microscope. From a treatment perspective, it is useful to further classify Lung Cancer by the genetic and immunological profile of the cancer. We now have several advanced tools to classify and identify the best possible treatment for the individual patient. 

To identify the subtype of cancer, doctors use a variety of diagnostic tools, including immunohistochemistry, next-generation sequencing (NGS), and other advanced molecular tests. While tumour tissue obtained through a biopsy remains the standard source for analysis, liquid biopsy, which uses a blood sample to detect tumour-related genetic changes, is increasingly used in selected situations. These investigations help identify specific mutations or biomarkers that can guide the use of targeted therapies, immunotherapy, chemotherapy, or combinations of these approaches. 

Targeted therapy has revolutionised the way lung cancer is being treated. Medications that target specific gene mutations like EGFR mutations, ALK rearrangements and ROS1 mutations, among others, improve the quality of treatment with less toxic side effects than those offered by chemotherapeutic agents. 

Another effective modality is immunotherapy, which boosts the immune system’s ability to detect and fight cancers. Biomarkers such as the expression of PD-L1 and micro-satellite instability (MSI) enable clinicians to predict which patients are most likely to respond to immunotherapy. 

Thus, in a span of a few decades, lung cancer treatment has evolved from non-selective chemotherapy to very selective targeted or immunotherapy based on the tumour profile. 

Patients with similar stages of lung cancer may sometimes receive very different treatments depending on their tumour genetics, general health status, and personal preferences. The newer treatment methods have proved to be better and more effective than the older ways of treating cancer. Patients are not only living longer but are also leading more meaningful and productive lives with the advent of these newer modalities. 

Side effects too are usually more tolerable with these new treatments. Lung cancer patients can look to a bright future with renewed hope as we continue to find novel targets and treatment approaches.