The Voice

Evaluating Success: How Lung Cancer Treatment Outcomes Are Measured

By Grace Ballenger

Answering whether lung cancer treatment has been successful involves a complex process. Because success looks different for every patient—ranging from total remission to stabilizing the disease—oncologists rely on a framework of continuous evaluation.

To understand where a patient stands, medical teams look at three critical areas:

What are outcome measures?

To standardize how oncologists measure treatment success, they use a system called RECIST (Response Evaluation Criteria in Solid Tumors). This framework categorizes a patient’s response into four clear stages:

• Complete Response: Also known as No Evidence of Disease (NED), meaning all signs of the cancer have disappeared on scans.
• Partial Response: The treatment is working well, and the tumors have shrunk by at least 30%.
• Stable Disease: The cancer hasn’t shrunk, but it hasn’t grown either; the treatment is successfully holding steady.
• Progression: While “progress” sounds positive in everyday language, in oncology it means the opposite—the cancer has grown or spread despite treatment.¹  

How are cancer treatments measured?

To evaluate how well a treatment is working, oncologists primarily rely on two diagnostic tools: imaging scans and blood-based testing.

• Imaging Scans: Tools like CT, MRI, PET scans, and X-rays allow doctors to visually compare the tumor before, during, and after treatment. By tracking these visual shifts, medical teams can see if a tumor has shrunk, remained stable, or grown, while also evaluating changes in blood flow directly to the cancer cells.
• Blood Tests (Biomarkers): Tumors often shed specific proteins, enzymes, or chemicals into the bloodstream. By monitoring these distinct “biomarkers” through routine blood draws, doctors can track the cancer’s activity. A steady decline in these marker levels is a strong indicator that the treatment is successfully destroying cancer cells and shrinking the tumor.

By comparing scans before, during and after treatment, doctors can see whether lung cancer tumors have grown, shrunk or stayed the same, and even details about blood flow to tumors.¹ Also common are blood tests, where doctors draw blood and are looking for certain proteins, chemicals or enzymes that tumors give off when they grow. If doctors see less of these markers in a patient’s blood, it may indicate that the lung cancer tumors have shrunk.² 

There are also indicators that are more difficult to measure on a medical test, so they depend on self-reports. These include an improvement in symptoms like pain, fatigue or persistent coughing.^2,3 If a patient is experiencing significant bleeding or pain and treatment lessens those symptoms, that may be one of the first signs that treatment is working, well before scans are reliable.²  Or mental/emotional improvements, like decreased anxiety or a more positive outlook.¹ These signs may be easier to capture in a survey or diary than through traditional medical tests.¹ Although wearable fitness trackers won’t be able to measure the impact of treatment on cancer directly, they can give an important idea of patients’ vitals before and after treatment, help to quantify how side effects are impacting patients, and may encourage patients to exercise more, which could have a positive impact on treatment.⁴  This information contributes significantly to quality of life for lung cancer patients.

Treatment type effects speed of results 

How often you need follow-up tests—like blood work or imaging scans—isn’t one-size-fits-all. The timing depends on your specific type of treatment, your cancer stage, and even your health insurance coverage.²

While chemotherapy, targeted therapies, and radiation treatments often use similar tests, their schedules can look very different:

• Chemotherapy & Targeted Therapy: Generally, doctors order scans every 3 to 6 weeks from the start of treatment to see how well it is working. However, if your symptoms change or worsen, they will scan more frequently.¹ Once the cancer stabilizes, that timeline usually stretches out to every 2 to 3 months.
• Radiation Treatment: Because radiation has a delayed effect on tumor cells, doctors typically recommend scans weeks or even months after your treatment ends. However, depending on your specific protocol, some cases may require daily imaging during active treatment for precise targeting.²

Because immunotherapy works differently than radiation and chemotherapy, doctors use a variety of different data points, including a scoring system called iRECIST to evaluate its effectiveness. Usually, imaging is done after three months.³ In radiation, chemotherapy and targeted treatment, tumor growth is seen as evidence of progression, and a serious sign. 

However, in immunotherapy what looks like tumor growth may be immune cells rushing to the area to counteract the effects of tumors. This is called pseudo progression and happens in 6 to 17% of lung cancer cases treated with immunotherapy.³ As a result, if immunotherapy patients see what could be pseudo progression or could be tumor growth they must have another scan in 4 to 8 weeks.³ Fortunately, there are two bloodborne markers that are particularly useful  in tracking the effectiveness of immunotherapy before scans are helpful. These are circulating tumor DNA, which goes down when immunotherapy works, and lactate dehydrogenase which is part of a standard blood test and will usually go down in the first few treatments if immunotherapy is effective.³ 

Although for other treatment types, seeing symptoms disappear is encouraging. For immunotherapy, however, it can be a good sign to see rashes, thyroid issues or other inflammatory responses, as it means that the immune system is active, and hopefully targeting tumors as well. This inflammatory response, however, does not happen in all successful immunotherapy cases. Immunotherapy is also unique in that it activates the body’s immune system to work against cancer cells, and these effects can continue working long after treatment stops. As a result, oncologists have come up with the term durable response, which is mostly used to describe complete or partial immunotherapy treatments where the effects of the treatment last for at least six months after the treatment stops.⁴

Sources 

1. Signs Chemo Is Working for Lung Cancer | Treatment Guide | careyourlungs
2. Is My Radiation Treatment Working? | SERO
3. How to Tell If Immunotherapy Is Working | ScienceInsights
4. Do Wearable Fitness Trackers Help Cancer Patients? | City of Hope