Symptoms and day-to-day function
An improvement in pain, breathing, appetite, energy or another cancer-related symptom may suggest benefit. A new or worsening symptom may prompt an earlier assessment rather than waiting for the next planned scan.
Symptoms are important but not definitive. Treatment side effects, infection, another health condition or anxiety can change how someone feels. Some cancers cause few symptoms even when they are changing.
Clinical examination
An examination may show whether a lump has changed, fluid has built up, swelling has improved, or a person’s general condition is different. What can usefully be examined depends on where the cancer is.
Blood tests and tumour markers
Routine blood tests can show how the bone marrow, kidneys, liver and other organs are coping with treatment. This helps the team judge whether it is safe and reasonable to continue, change a dose or allow more time for recovery. In some cancers, a tumour marker can provide additional information about response.
Tumour markers are not suitable for every cancer. They can change for reasons other than cancer, and a result should not usually be interpreted in isolation. The pattern over time may be more useful than one number.
Scans
CT, MRI, PET, ultrasound, X-ray or other imaging may be used, depending on the clinical question. The team compares new images with earlier ones and looks for shrinkage, stable disease, growth or new areas.
The timing matters. A scan performed too early may be difficult to interpret, and some treatments can temporarily create changes that resemble worsening. This is one reason cancer scans are planned at particular intervals rather than performed as often as possible.
Pathology and other specialist tests
In certain situations, a repeat biopsy, endoscopy, bone marrow test or specialised blood test may be needed. These are used when the result could clarify what is happening or alter the plan, not as a routine step for everyone.
What counts as success depends on the aim
If treatment is intended to cure cancer, doctors may be looking for no detectable disease and for it not to return over time. If treatment is intended to control advanced cancer, stable disease, symptom improvement or slower growth may be a meaningful success.
The most important question is not always “Has it disappeared?” It is “Is the treatment achieving the outcome it was chosen to achieve, with an acceptable effect on the person receiving it?”
No single result tells the whole story
A scan can improve while side effects make treatment difficult to continue. Symptoms can improve before a scan changes. A tumour marker can fall while another part of the assessment remains uncertain. Doctors therefore look at the overall pattern, including treatment tolerance and what matters to the patient, rather than allowing one number or image to decide everything.
You may hear response terms such as complete response, partial response, stable disease or progressive disease. After treatment intended to cure cancer, you may also hear remission or no evidence of disease. These phrases describe different clinical situations; none should be interpreted without the context of the cancer, treatment and tests used.
The separate guides to response categories and remission, no evidence of disease and “cancer-free” explain that terminology in more detail.
Waiting for an assessment can be difficult. The articles on coping with scanxiety and living between cancer scans discuss that period more directly.
Questions to ask
- What is the aim of my treatment?
- Which tests will show whether it is helping?
- When is the first useful assessment?
- What result would lead us to continue or change treatment?
- Which symptoms should I report before the planned review?
Your clinical team should explain both the evidence they are using and the uncertainty that remains.