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About Cancer

Diagnosis of Cancer

1. Significance of early diagnosis

The choice in treatment methods is much wider and the chance of cure is much higher for early-stage cancers, as metastases do not happen at these stages. Therefore, early diagnosis is especially important. The studies conducted by American Cancer Society show that with early diagnosis, the five-year survival rates of breast, colon, rectal, cervical, prostate and testicle cancers increased to 95%. The commonly used diagnostic technologies include x-ray, ultrasound, CT, MRI, PET. The method include endoscopic examination, pathological examination, biochemical and hematological examinations, etc. the development of modern diagnostic technologies provides larger opportunities for successful early diagnosis and timely treatment of tumors. As important as these technologies themselves, proper adoption of the technology is equally critical to the right diagnosis. For example, contrast agents are used during x-ray imaging and very effective to diagnose brain tumor and subarachnoid cavity hemorrhage. However, they are not working well in diagnosis of parenchymal organs as it is difficult to deliver the agents into these organs. On the other hand, CT is the most suitable technique in these cases.

2. Methodology in tumor diagnosis
Tumor diagnosis is based upon results from a series of examinations. The diagnostic methods consist of general examination and specific examination. General examinations include study of medical history, physical examination and routine biochemical tests. Specific examinations include a variety of imaging examinations and pathological tests.

General examination
Like diagnoses of all other diseases, tumor diagnosis starts with a close look at the patient's medical history. Through conversations with the patient, information is gathered and analyzed to reach an initiative inference of the causes, types, staging of the tumor and strategies for following examinations. At this phase, clinical presentations demand special attention as 75% of the tumors manifest themselves in noticeable parts of the body and can be detected with conventional examination methods. The result of a patient's blood examination is listed as follows: Hb, 8.8g/L; MCV, 96 FL; MCHC, 31 g/L. Combined with the recent history of gastrointestinal disease and the symptom of emaciation, the doctor easily made the suspicion of a gastrointestinal tumor. The following fecal occult blood test and barium test generated positive results. A final diagnosis is reached that the patient had stomach cancer.

Imaging examinations

a. X-ray: X-ray is the oldest and the most widely chosen technology in imaging examinations. In conjunction with other examination methods, x-ray can be very effective in diagnosing many tumors. Combining with barium enema, x-ray imaging can detect tumors in stomach, intestine and other organs with cavities. Using contrast agents injected into bloodstream, x-ray images are useful in diagnosing hepatobiliary tumors.

b. CT: Computed Tomography is an imaging technology integrating x-ray radiography and the computer-generated three-dimensional image reconstruction. CT has very high resolution and can identify pathological changes around 1 mm in diameter. The current CT technologies include plain CT scan, contrast-enhanced CT scan and spiral CT scan, etc. Their clinical applications include the diagnosis and differentiation of occupying tumors, determining tumor stages and guidance for needle biopsy.

c. Ultrasound: Ultrasound imaging has the unique advantage of being harmless and pain-free. It can detect pathological area around 1 cm in diameter. Imaging technologies based upon ultrasound include color Doppler, energy imaging, bloodstream acoustic imaging, 3-D ultrasound and invasive ultrasound imaging. Ultrasound is the best in examining brain, eyes, mammary glands, liver, gallbladder, pancreas, stomach, uterus, etc. for space-occupying pathological changes and pleural effusion and ascites.

d. MRI: Magnetic Resonance Imaging has higher resolution than CT and generates clearer images of brain, chest, limbs, liver, gallbladder, pancreas and other organs. It has the unique benefit of imaging the chemical and physiological changes of the body. MRI is especially effective in detecting tumors in the central nervous system and providing evidence for stage determination. The high sensitivity of MRI imaging to the early-stage biochemical changes makes it a very desirable tool for early diagnosis of cancer. It is also an important diagnostic method in post-surgery and post-radiotherapy patients.

e. PET: Positron Emission Tomography is a latest imaging technology, which is safe and non-invasive. PET is the only receptor-originated imaging technology to reveal the function and metabolism of the tissues. PET reaches a resolution of 4 mm. It can detect pathological areas of 1 cm in diameter. Its clinical applications include diagnosis and guidance for tumor treatment, distinguishing benign and malignant tumors, rating the malignancy, clinical staging, locating primary and metastatic changes, evaluating treatment efficacy and foretelling relapse. PET has unparalleled strengths in diagnosing heart diseases, epilepsy, depression, cerebral vascular and neurodegenerative disorders.

Immunological examinations

The origination, development and prognosis of tumors are all closely related to human immunity. Therefore, immunological examinations provide important evidence in tumor diagnosis. The commonly used immunological test includes AFP, CEA, ferritin, iso-ferritin, FSA and anti-EB antibody etc. For example, the test of AFP is of certain value in the diagnosis of primary liver cancer. When tumors are excised, the CEA level in blood is usually lowered. When there is relapse, CEA will increase. Therefore, CEA could be used to judge the effect and prognosis of treatments.

Endoscopic imaging
Using endoscopes, images of cavities of the human body can be observed from outside and pictures can be taken simultaneously. Commonly used endoscopes include gastroscope, esophagoscopy and bronchoscope. To make examinations in the abdominal cavity, small hole needs to be opened on the abdominal wall to allow the scope to be inserted and to observe liver, gallbladder, intestine and stomach for outside conditions. At present, endoscopic technologies are being improved rapidly, which have become more and more important clinically.

Pathological examinations

Pathological examination is intended to look for desquamated cells and to use tissue sections to identify the biological characteristics of the tumor. The final diagnosis of tumors still depends on pathological and cytological examinations. Especially for malignant tumors, it is necessary to verify that the obtained tissues are malignant. Currently, the major methods are as follows:
a. Aspiration biopsy: A fine needle (#22) is penetrated into tissues to aspirate cells and is then placed on glass slides. The specimen is collected in a way very similar to using papanicolaou cervix smear, and then analyzed by the cytological pathologists.
b. Needle biopsy: A large needle (e.g. #18) is used to penetrate into tissues to obtain a tubular tissue. While the examination take more living tissue using the needle than using the fine aspiration needle, complications such as hemorrhage, may happen during biopsy. Yet it may be a worthwhile sacrifice as the larger tissue provides more defined evidence.
c. Incision biopsy: Before treatment, excise a tumor located on the body surface could be used for diagnosis.
d. Decisional biopsy: To completely remove a small tumor without damaging adjacent normal tissues has no therapeutic effects on malignant tumors. This method is usually adopted when local excision will not affect the ongoing treatment.
e. Staging laparotomy: It is usually used in Hodgkin's disease to make correct diagnosis.