LUNG CANCER DIAGNOSTIC TESTS
3.8 DIAGNOSTIC TOOLS
3.81 Chest X-Ray
The most widely used diagnostic tool is the chest x-ray. It has the following advantages:
1. Economical and easy to use. A chest x-ray could take as little as ten minutes and cost less than $100.
2. Detects tumors of at least one centimeter The ease of use can be unfortunately deceiving. Doctors and radiologists may be called upon to make life-saving distinctions based upon an almost imperceptible shadow. For very small tumors in this one centimeter range, some have estimated a margin of error as high as 25%. Many smaller tumors whose early detection could be critical to the patient's survival are missed with the chest x-ray. Where a chest x-ray is not clear and the patient is a smoker, the sensible physician orders a Ct Scan (see below) a far more sensitive, accurate and therefore reliable test.
Although chest x-ray is the most commonly performed examination, it often is inadequately performed. In an FDA survey, over 40% of the chest x-rays were judged inadequate by a panel of radiation physicists and physicians. It is important that the examination you have be a good one.
Why Poor Quality
Chest x-rays are the most difficult of all radiographic examinations to perform because the chest contains tissues of such different consistency. The lungs are composed nearly entirely of air next to thick soft tissue and bone. Adequately producing an image which provides clear definition of all structures in the chest requires meticulous technique and attention to detail. The machine (film processor) used to develop the film must be working properly. This is rarely achieved. In the same FDA study noted above, over 50% of the film processors surveyed were judged inadequate." www.chest.x-ray.com.
Chest-x-rays should be read by a qualified radiologist whose findings are set forth in a written report, they should not be read only by an internist or family physician,
As seen here, follow-up is critical. Where cancer is a possibility based upon a smoking or family history, complaints of shortness of breath, chest pain, or other indicia of disease, follow up testing, preferably using a CT scan (see below(or other sensitive diagnostic tool should be utilized. The patient should consider a pulmonologist to carefully assess the status of any abnormality of any chest x-ray and arrange for careful and frequent follow- up.
3.82 Sputum Cytology
Sputum cytology is a microscopic analysis of cells from the lungs. The patient does a deep cough and the liquid or sputum is analyzed by a pathologist and a report prepared. Using sputum cytology, a man named Saccamanno in a landmark study was able to detect the progression of lung cancer in a smoker. This test has the following benefits and limitations
1. Effective at diagnosing very small microscopic cancers where treatment will be most effective. The Stage 0, or microscopic cancers which generate an excellent prognosis are usually the product of sputum cytology.
2. More effective at diagnosing central squamous cell carcinomas than peripheral adenocarcinomas. The nature of the test is to retrieve liquid in the lungs, and the patient is more likely to cough up liquid from the larger more central parts of the bronchial tree than the parts of the smaller airways that produce adenocarcinoma. While squamous cell remains the most common form of cancer, with low tar cigarettes smokers are inhaling more deeply creating more adenocarcinomas in the peripheral airways, some of which could be undetected by sputum cytology.
3. The European Cancer Institutes states, "Sputum cytological analysis is greater for squamous (93%) or small cell (89%) histotypes than for adenocarcinoma (25%) and large cell carcinoma (54%). www.sias.it/start/chap-13/chap13-2.htm
4. Cost-effective A company named Lungcheck offers sputum cytology with a detailed analysis of seven components of possible disease in the smoker's lungs for less than $100.00.
Overall, sputum cytology is an excellent tool, not used as often as it could be to save lives through early detection.
3.83 Computerized Tomography or CT Scan
Computerized tomography or CT uses an x-ray beam that rotates around the boy to produce a series of x-rays taken from different angles. See www. Colorado Health Net, org./cancerlung.symptoms.html. This information is then processed by computer to produce a cross-section of a specific area. CT can reveal the existence of a tumor, and specifics about its location and size.
CT is the most reliable non-invasive test to determine the existence and extent of lung cancer. A recent study found twenty people diagnosed early with CT Scan still living today, approximately two years later. This excellent mortality rate indicates CT Scan, in particular helical CT Scan, is an excellent way of diagnosing lung cancer at its earliest and most treatable stages. Its benefits: extremely sensitive and reliable, will detect lung cancers at early stages where they may be missed by other tests. Drawbacks:
1. Costly, may range as much as $800 for a test; HMO's may balk at the cost. However, anyone at possible risk should take the test, and the cost is small compared with that of a life.
2. Early diagnosis of cancers are critical, and the medical profession needs to be far more aggressive in using available technology so that lung cancers are diagnosed when they are most treatable. Present and former smokers should have the test done, and the HMO will back down in the face of legal action.
Although it is accurate and reliable, especially when compared with diagnostic tools other than biopsy, it is not foolproof. The excellent website, chestx-ray.com explains,
"Accuracy of CT to detect lymph node metastases
A meta-analysis of 42 studies published between 1980 and 1988 found (using a node size greater than 1.0 cm as abnormal) a pooled sensitivity of 83%, specificity of 81% and accuracy of 81%. The 20% false negative rate is largely due to microscopic metastases to normal sized lymph nodes and the 20% false positive rate is due to enlarged nodes from pre- or coexisting inflammatory disease." chestx-ray.com/StaginglungCa/Lung Cancer
3.831 Understanding Test Specificity and Accuracy
Let us review these terms which are frequently used with medical tests. A false negative occurs where the patient has a disease or characteristic and the test fails to detect that. Thus, the test is false negative, it should have been positive. Another word for false negative is accuracy. That is, what percentage of persons with a given disease are detected. The CT is 80% accurate in detecting lymph node metastases. The 20% missed are microscopic in nature and cannot be seen on the test.
Specificity is the number of false positives. That is, how many tests are incorrectly read as positive. Here, the article explains that sometimes a person with inflamed nodes could have a CT Scan read as positive for spread of the cancer to the node. That is, why the ultimate test is analysis of tissue by a pathologist.
Some overall conclusions:
Chest x-rays and sputum cytology have limitations and are best used together as joint effective diagnostic tools for high risk individuals such as heavy smokers. Because x-rays are difficult to read, they must always be interpreted by a radiologist and approprirate followup is needed where results are unclear.
CT Scans need to be used more widely, since they are the most reliable non-invasive method of detecting cancers. Where x-rays are an older and less sensitive diagnostic tool, the modern physician uses the CT Scan with high-risk smokers where there any possibility of lung cancer given the need for prompt and early detection. Isnt saving the life of a 45 year old mother of three or a loved grandfather worth the $250.00 or $300.00 cost of a CT Scan. If you know a smoker, suggest a CT Scan and do not be afraid to fight your HMO to secure reimbursement. If they refuse to pay, you are right, and they are wrong because this test is designed to assess a serious disease in a high-risk group and its cost is appropriate and reasonable. With the new study in the 1999 Lancet magazine, its value has been shown in epidemiological studies.
If Ct Scan is the most reliable non-invasive test, bronchosopy is the reliable minimally invasive test. While bronchosophy should be viewed as a surgical procedure, its risks are generally minimal. The Virtual Hospital is an excellent site which describes bronchosopy:
"Bronchosopy is the examination of the airways under direct visualization. Bronchosopy began with the use of a candle and a rod with a polished metal disk to visualize the osopharaynx. It has evolved into a wide variety of precision optical instruments capable of visualizing the endobronchial tree to the 5th or 6th generation....
bronchosopy is used to obtain peripheral lung samples in the presence of lung parenchymal disease such as peripheral coin lesion(s), hilar adenopathy, or diffuse or focal parenchymal infiltrates. Finally, bronchosopy is useful in staging lung cancer, evaluating the airways in patients with normal radiographic findings and positive sputum cytology, and evaluating the airways after thoracic trauma, or if there is a suspected airway foreign body.
Virtual Hospital, Lung Ttumors: A Multidisciplinary Database, Bronchosopy, www.vh.org.Providers/Textbooks/LungTumors/Diagnosis/Bronchosopy/bronchosopy.htm.
3.841 Reliability of the Bronchosopy
Reliability seems to depend upon the location of the tumor.
"Tumors may be present in three ways in the lung, as central endoscopically visible lesions, as submucosal or extrinsic lesions, and as peripheral lung lesions. The diagnostic yield and bronscospic apropach to diagnose these lesions varies among these three presentations. In endobronchially visible lesions, bronchosopy will correctly diagnose the lesion in 94% of the cases if at least 5 samples of the lesion are obtained....
By contrast, direct forceps biopsy correctly diagnoses only 27% of patients with extrinsic airway compresiion or with submucosal or peribrohcial disease. The low yield is most likely due to the fact that the forceps biopsy does not sample tissue deep enough. Much better diagnostic results are obtained in this situation by using transbronchial needle aspiration. In this technigue, a 1 cm. needle attached to a catheter is placed through the mucosa using the bronchospe....
The diagnostic yield for peripheral lung lesions varies widely from 30-90% using transbronchial biopsies. In this technique, the forceps are passed through the airways distal to the directly visualized sites using fluroscopy." Virtual Hospital, Lung Ttumors: A
Multidisciplinary Database, Bronchosopy, www. vh.org.Providers/Textbooks/LungTumors /Diagnosis/Bronchosopy/bronchosopy.htm,
Sadly, some people have gone undiagnosed after a physician failed to detect a tumor during a bronchosopy. The above highlights that the following:
1) Bronchosopy is not a conclusive test. Where symptoms of lung cancer continue, and a definitive diagnosis of another disease is not made, additional diagnostic tests must be done. Our office is handling a medical malpractice claim where the physician essentially concluded treatment with a negative bronchosopy and the patient was diagnosed with lung cancer approximately one year later. Where a patient seems to fit the profile of a lung cancer patient- signficant smoking history, loss of weight, fatigue, chest pain, cough, and has other symptoms of the disease, a repeat bronchosopy, needle biopsy, or even a thoratomy (surgical biopsy) may be called for with a negative bronchosopy. Timely diagnosis of lung canceris critical.
2) Success in detecting the tumor will depend upon the tumors location and to some extent, the skill of the physician performing the procedure.
3) An adequate sampling is critical. Reports should clearly indicate how many samples have been taken so the extent of reliance on the bronchosopy can be determined by other physicians.
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