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What is the difference between cancer screening & diagnostic assessment?

 

While most people might think that cancer diagnosis and screening for cancer are the same, diagnosis of cancer is actually performed for symptomatic individuals in several means such as blood test, urine test, imaging test, and biopsy to confirm the presence of cancer whereas screening of cancer is done regularly as a body check for high-risk individuals who do not show any signs of cancer but have a family history of cancer.

 

Diagnosis of CancerScreening for Cancer
TargetSymptomatic IndividualsAsymptomatic Individuals
Aims
  • Confirm whether the signs and symptoms are caused by cancer or other diseases
  • Localize the site of primary cancer and perform cancer staging for treatment planning
  • Enable early detection and treatment for better treatment and survival
  •  

    In case of any cancer suspicion, individuals are advised to seek medical help from family doctor or general practitioner. Doctor will first review on your medical and family history, perform basic physical examination, and then order other types of examinations if necessary.

     

    Our centre offers a wide range of examination for diagnosis of cancer. Should you receive any referral letters, please send us a copy via WhatsApp ‪(852) 6168 9195‬ and our team will advise you on the most appropriate investigation needed for accurate diagnosis. Here is the introduction of different means for diagnosing cancer.

    Common Tests for Diagnosing Cancer

     

    Most people might think that only one examination is needed for confirming the diagnosis of cancer, yet doctors rely on more than one to confirm whether the signs and symptoms are induced primarily from the cancer. Taking breast cancer as an example, even when calcification is suspected by doctor from a 3D mammogram, further investigation with fine needle aspiration or core biopsy is often needed to differentiate whether it is benign or malignant.

     

    Common tests for diagnosing cancer includes blood test, urine test, imaging test, biopsy and genetic test. Apart from diagnosing cancer, these investigations can also localise the primary site, differentiate the specific cancer cell type, perform cancer staging, identify whether there is metastasis, formulate treatment plan, monitor disease progression and detect recurrence. Below is the information regarding different tests.

    Diagnosis of Cancer

    Routine Tests (Blood Test, Urine Test)

     

    Through performing routine tests such as blood test and urine test to examine the change of concentration of different metabolites, doctors can deduce the proper functioning of different organs. However, a positive result does not directly confirm the presence of cancer and doctor will perform further investigations to confirm the diagnosis.

    Moreover, to monitor the side effects of cancer treatment and overall health status, cancer patients will undergo regular blood test throughout the entire course of treatment to observe the change in red blood cell, white blood cell and platelet cells.

    Patients should always be aware of the use of carcinoembryonic antigen (CEA) level in monitoring treatment progress and detecting recurrence rather than making a diagnosis. Numerous health conditions such as acute hepatitis, urethritis, pregnancy may also trigger a rise in CEA level. Should there be any concerns, patients should always seek medical help from doctors.

    Diagnosis of Cancer

    Imaging Tests

     

    Imaging tests for diagnosing cancer generally includes ultrasound, CT, PET/CT and MRI. Different types of imaging modalities have their own strengths and limitations. Patients should seek advice from doctors for the most appropriate tests needed for accurate diagnosis at different stage of the disease.

     

    超聲波

    Ultrasound

    Applications:

    • Localize the site of primary cancer
    • Guide biopsy
    • Detect pathological change of tissues and vascular flow

    Strengths:

    • No radiation is involved
    • Short examination time
    • Real-time monitoring of change is allowed

    Limitations:

    • Low penetration power to deep tissues
    • Low spatial resolution
    • Operator-dependent result
    電腦掃描

    CT

    Applications:

    • Localize the site of primary cancer
    • Detect pathological change of tissues
    • Guide biopsy
    • Allow cancer staging
    • Formulate treatment plan
    • Evaluate treatment effectiveness
    • Detect recurrence

    Strengths:

    • Short examination time

    Limitations:

    • Radiation is unavoidable
    • Relatively low spatial resolution for soft tissue structures such as muscle and nerve
    • Risk of contrast allergy
    正電子掃描

    PET-CT

    Applications:

    • Localize the site of primary cancer
    • Detect pathological change of tissues
    • Guide biopsy
    • Allow cancer staging
    • Predict prognosis
    • Formulate treatment plan
    • Evaluate treatment effectiveness
    • Detect metastasis or recurrence

    Strengths:

    • High sensitivity in picking up cancer at early stage
    • High accuracy

    Limitations:

    • Radiation is unavoidable
    • Injection of radiotracers is needed
    • Might not be suitable for diabetic patients
    磁力共振

    MRI

    Applications:

    • Localize the site of primary cancer
    • Detect pathological change of tissues
    • Differentiate benign tumor from malignant cancer
    • Formulate treatment plan (i.e. localisation for surgical planning or radiation therapy)
    • Monitor treatment progress
    • Evaluate treatment effectiveness
    • Detect recurrence

    Strengths:

    • No radiation is involved
    • Better image resolution for soft tissue structures such as muscle and nerve
    • Multi-planar 2D and 3D images are available
    • Contrast allergy is rare

    Limitations:

    • Metallic object is contraindicated in a MRI suite
    • Risk of claustrophobia
    • Long examination time

    Diagnosis of Cancer

    Biopsy

     

    Biopsy is commonly performed to confirm the diagnosis of cancer. Doctors will first take out a small sample of pathological tissue and pathologists will examine it under a microscope to determine whether it is a cancer type.

     

    There are 3 methods for biopsy

    1. Fine needle aspiration: A thin needle is inserted into an area of abnormal-appearing tissue or body fluid. This method is commonly used in breast, prostate and liver biopsy
    2. Endoscopy: a thin and flexible tube with a light and camera at the end is inserted either from mouth or anus into the body. Doctors will visually examine the organs inside, take out sample of tissue and remove abnormal-appearing tissue in case of a pathological finding. Taking colonoscopy as an example, polyps can be removed in the process and sent to the laboratory for further investigation.
    3. Surgery: entire or part of the abnormal-appearing tissue is removed during surgical procedure
    Biopsy

    Diagnosis of Cancer

    Genetic Testing

     

    Sample of tissue taken from biopsy cannot only be used to identify pathological change, but also test for genetic mutation. Liquid biopsy is a fast, cheap and non-invasive approach to tumour molecular profiling without having to obtain tumour tissue by performing genetic testing with blood sample, which is useful for targeted therapy. It is particularly helpful among patients who have poor health conditions or is not suitable for undergoing surgery. However, liquid biopsy is still limited in usage due to its low sensitivity.

     

    With the emergence of an advanced DNA sequence technology (next generation sequencing), entire human genome can be sequenced within a single day using the DNA sample taken from liquid biopsy or traditional biopsy, facilitating the formulation of an effective target therapy.

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