Introduction

Lung cancer diagnosis is the key to establishing any abnormal growth in the lung and to determining the most appropriate treatment. It is a condition in which cells in the lung tissue grow uncontrollably and may form a mass (a tumor) that can affect your ability to breathe and metastasize to other parts of the body. The diagnosis and staging of the disease is, of course, absolutely fundamental to enabling the doctor to arrive at the most appropriate treatment for that individual patient.

Diagnosis of lung cancer is not a single test. You've got to look at the symptoms, the patient's medical history and smoking history, the physical examination, the imaging, and the labs. A tissue sample is generally required to make the diagnosis. Patients must understand the diagnostic process so that they are as well prepared as possible for their appointments and can make informed decisions about their own care.

When is a diagnosis of lung cancer actually needed?

Doctors will look for lung cancer in a patient if they have any of the classic symptoms (persistent cough, coughing up blood, unexplained weight loss, chest pain, recurrent chest infections, breathlessness, etc.). Of course, those symptoms could be due to infection or other lung diseases as well, so further investigation would be required to establish the cause.

Lung cancer can be picked up quite occasionally even before any symptoms at all. A fairly common example of this would be someone having chest imaging for some other reason who is found to have an abnormality which then requires further investigation.

People who meet the eligibility criteria may be offered low-dose CT lung cancer screening. This is for people at increased risk of lung cancer who have absolutely no symptoms. It is not a diagnostic test (a test that would be used on someone who is thought to have a disease). It is a screening test.

1. Medical History and Physical Examination

   The diagnosis will generally begin with a full consultation with the doctor, who will take a full history of your symptoms, including when they started, how often they occur, and whether they've changed at all. Medical history will almost certainly include current and past smoking, exposure to secondhand smoke, exposure at work to noxious substances, family history of lung cancer, and any previous respiratory illness. The doctor will want to know about any previous cancer treatment or radiation exposure. They'll listen to your lungs, assess your breathing, check your oxygen levels, and look for any other findings that might explain your symptoms. This first test would not prove the presence of lung cancer, but would only help identify which other tests are needed.

2. Chest X-Ray

   A chest X-ray is the primary diagnostic imaging test used to diagnose lung cancer. This test shows the image of the lungs and surrounding structures, including the heart. An X-ray might show a suspicious mass, abnormal shadowing, or fluid around the lungs, which would, of course, require further investigation. Chest X-rays won't pick up all lung tumors. Small lesions can be very hard to see, and some benign conditions can look like cancer on a chest X-ray. A normal chest X-ray therefore doesn't exclude the possibility of lung cancer in a clinically unwell patient.

3. Computed Tomography (CT) Scan

   A CT scan develops a series of detailed cross-sections of the chest using X-rays and computer reconstruction. It provides much more information about the size, shape, and position of any lesion than a plain chest X-ray. The doctor can rely on CT to diagnose whether there is a tumor or an enlarged lymph node and to evaluate the surrounding anatomy. Contrast can be administered to make the blood vessels and some tissues visible. CT used to perform biopsies is a very useful diagnostic modality, but it doesn't, in itself, tell you whether an abnormality is malignant. You may well need further investigation.

4. PET-CT Scan

   A PET-CT combines metabolic and anatomical imaging: a small amount of a radioactive tracer is administered, and the scanner then detects where the tracer has accumulated. As many cancer cells are metabolically active, they will appear as 'suspicious' areas on the PET-CT scan, and the scan can be used to assess whether the lung cancer has influenced the lymph nodes or other parts of the body. Moreover, inflammation and infection may cause tracer accumulation, which means that the PET/CT scan alone cannot confirm the diagnosis of cancer. This test needs to be combined with the results of other diagnostic methods and the patient's clinical information.

5. Biopsy: Diagnosis of Lung Cancer

   The most important step in confirming a diagnosis of lung cancer may be the biopsy. This involves taking a tissue or cell sample from the site in question and sending it to the pathologist. The approach will be determined by the lesion's site and the patient's general condition.

   Common biopsy procedures include:

   • Bronchoscopy: This method involves inserting a thin, flexible tube equipped with a camera into the breathing passages via the mouth or nose to collect specimens for examination under different instruments.
   • Needle biopsy: The process involves passing a needle through the chest wall into a lung mass to collect a tissue specimen.
   • Endobronchial ultrasound (EBUS): is a form of bronchoscopy in which a bronchoscope with an ultrasound probe is used to obtain samples from the lymph nodes and the surrounding tissue.
   • Surgical biopsy: In selected cases, a surgical procedure will be required to obtain the sample where other methods are inappropriate or unlikely to give a result.

   The procedure we end up with will be dictated by the tumor's location, the risks, and the information we need to plan treatment.

6. Laboratory and Pathology Tests

   Following biopsy, the lab people will look at the cells or tissue under the microscope to see if it's cancerous and, where possible, to establish what type of cancer it is. Lung cancer is identified as either non-small cell or small cell, which is itself split into adenocarcinoma and squamous cell carcinoma. It's of the utmost importance to know which type you have, as the different types of cancer will respond to treatment in very different ways. Molecular testing may be indicated to detect specific genetic alterations in the tumor cells. In some cases, tests for specific proteins (for example, PD-L1) may also be done to help inform your treatment. These tests may identify patients who would benefit from targeted therapy or immunotherapy. Whether a patient is appropriate will depend on the type and stage of cancer, the test results, and the individual clinical situation.

How is lung cancer staged after diagnosis?

Once lung cancer is confirmed, the doctor will go on to stage it. Staging describes the size of the tumor, the extent of lymph node involvement, and whether it has spread to distant sites.

The investigation could well involve CT scans, PET-CT, brain MRI, and a lymph node biopsy. NSCLC is typically staged as stage I to IV. SCLC is generally described as either limited-stage or extensive-stage disease. The exact staging system and the details of the investigation will depend on the type of cancer.

Accurate staging will enable the doctor to assess the likely behavior of the disease and to select the most appropriate treatment (this could be surgery, radiotherapy, chemotherapy, targeted therapy, immunotherapy or some combination of these).

What's the situation after a diagnosis of lung cancer?

Following a review of the test results, the medical team will discuss the diagnosis and next steps with the patient. The treatment options will be dictated by the type and stage of the cancer, the molecular findings, the symptoms, the patient's general health, and their own individual preferences. The patient may be referred to a multidisciplinary team (which would normally include a lung specialist, an oncologist, a radiologist, a pathologist, and a surgeon) to ensure that the diagnosis and management are considered from several different medical perspectives.

Patients are, of course, free to ask any questions they have about their results, the rationale for each test, possible side effects, and the various treatment options. A second opinion may be appropriate in circumstances where further reassurance or clarification is required.

Conclusion

Lung cancer diagnosis is a multi-stage affair involving a medical history and physical examination, imaging, biopsy, lab tests and staging (where appropriate). Each of the individual tests gives you a different piece of information which the doctor uses to determine whether or not there is cancer, what type of cancer it is and how far it's spread. A normal scan can be absolutely terrifying, but an abnormality in itself doesn't mean you have cancer. You'll often require further investigation to reach a diagnosis. If you've got any ongoing respiratory symptoms or you're coughing up blood, you absolutely need to see a doctor rather than carry on ignoring it.

A proper and accurate diagnosis allows the clinician to recommend the appropriate treatment and gives the patient a much clearer understanding of what's happening and their options.

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