Early detection of cancer becomes very necessary for having high survival outcomes in patients. The current screening techniques for cancer mainly comprise of imaging techniques like CT scans, X-rays, PET-scans, MRIs, blood and urine tests detecting cancer specific markers and antigens, endoscopic methods like gastroscopy and bronchoscopy, biopsy and cytology. Imaging tests use X-rays, magnetic fields, sound waves, or radioactive substances to create images of the inside of body. A CT scan uses x-rays to make detailed cross-sectional images of your body. It can also show the size, shape, and position of any tumor and can help find enlarged lymph nodes that might contain cancer that has spread. If a suspected area of cancer is deep within the body, a CT scan might be used to guide a biopsy needle into this area to get a tissue sample to check for cancer. Like CT scans, MRI scans show detailed images of soft tissues in the body. But MRI scans use radio waves and strong magnets instead of x-rays. MRI scans are most often used to look for possible spread of lung cancer to the brain or spinal cord. Mammograms use low-dose x-rays that can help find breast cancer. For screening of breast cancer, an early mammogram combined with a breast MRI is usually recommended. For a PET-scan, a slightly radioactive form of sugar (known as FDG) is injected into the blood, which collects mainly in cancer cells. Often a PET scan is combined with a CT scan using a special machine that can do both tests at the same time. This lets the doctor compare areas of higher radioactivity on the PET scan with a more detailed picture on the CT scan. This is the type of PET scan most often used in patients with lung cancer. Symptoms and the results of certain tests may strongly suggest that a person has cancer, but the actual diagnosis is made by looking at cells in the lab. The cells can be taken from a suspicious area using a needle or surgery (biopsy). A hollow needle is used to get a small sample from a suspicious area (mass). Endoscopic techniques are often used for detection of cancers located in the hollow structures of body like gastric cancers, lung cancers. Endoscopic technique like Bronchoscopy can help the doctor find some tumours or blockages in the larger airways of the lungs, which can often be biopsied during the procedure.
All these techniques are routinely used for screening of cancer. However, there are certain drawbacks of these techniques. The drawback of biopsy is that only a small amount of tissue is removed and in some cases, the amount of tissue removed might not be enough to both make a diagnosis and to perform more tests on the cancer cells that can help doctors choose anticancer drugs. Also, the nature of this technique is invasive. Imaging studies can expose the person to large amount of radiations, endoscopic techniques can cause bleeding or more serious complications like bowel tear (colon cancer). False positives and false negatives can hamper diagnosis of cancer.