Early diagnosis of particular pathological conditions of the human body can provide patients with adequate time to make well informed decisions regarding the treatment of their pathological condition, as well as prepare for the potential incapacitation of the patient. One such pathological condition is colon cancer. The American Chemical Society has reported that colon cancer is the second most common cause of cancer in the United States (Fleischer, D. et al. Detection and Survival of Colorectal Cancer (1989) JAMA 261(4):580. It has been estimated that approximately 145,000 new cases of colon cancer are reported yearly in the United States, and the overall mortality rate of this pathological condition is almost 60%. Moreover, a diagnosis of colon cancer has been estimated to shorten that patient's life by six to seven years (Id). Consequently, early detection of this pathological condition offers a patient the best hope of survival.
Approximately three principal screening tests for the early detection of colon cancer or precancerous polyps are presently available to physicians. One such test is the Fecal Occult Blood Test (FOBT). Basically, this test is designed to test whether blood is present in the fecal material of the patient. Hence, this effectiveness of this test is dependent upon the assumptions that blood in the fecal material is indicative of the presence of colonic neoplasms, and that these neoplasms will bleed in sufficient quantity in order to cause a positive FOBT result.
However, it is because of these necessary assumptions that applicants believe the FOBT contains significant shortcomings as a screening tool for colon cancer. For instance, it has been shown that not all colonic neoplasms bleed sufficiently into the colon. As a result, this test is readily capable of giving false negative results.
In addition, there are other factors which could result in a false positive result for this test. For example, it has been found that aspirin and other non-inflammatory analgesics have been known to cause irritation in the stomach and increased gastro-intestinal tract blood loss, thereby producing in a false positive result. The patient's ingestion or rare beef and fruits and vegetables which contain catalases and peroxidases within 24 hours of administering the test may also cause a false positive result.
Another screening test that is available is the Carcinoembryonic Antigen (CEA) test. CEA is a glycoprotein that may be produced by cancerous lesions in the colon. This test is desired to measure the concentration of CEA in the patient's blood to determine if it is elevated relative to normal levels. It is believed that an elevated level is due directly to the presence of colon cancer in the patient. Hence it was hoped CEA would act as a genetic marker for colon cancer. Immunological techniques are usually used to measure CEA levels in the blood.
However, soon after this test became available to health professionals, it was observed that this test was simply too insensitive to recognize numerous types of colon cancers. As a result, the CEA test was relegated to the detection of a recurrence of colon cancer after surgery is performed to remove cancerous lesions from the colon. Even in this role though, it has met with only limited success. In 1993, a study on the effectiveness of CEA testing in 1017 patients was published in the Journal of the American Medical Association. The study showed that 417 patients out of the original group developed recurrent colon cancer, and 247 of these had elevated CEA levels prior to diagnosis of recurrence. However, of the remaining 600 patients, 98 also had elevated CEA levels. Hence the rate of false negatives for the test was 41%, and the rate of false-positive results was 16%. (Moertel, C., et al. An Evaluation of the Carcinoembryonic Antigen (CEA) Test for monitoring Patients with resected Colon Cancer. JAMA 270(8):954 (1993).
In concluding their study, the authors questioned the efficacy of the CEA Test. In support of this conclusion, they explained that, based on their data, the maximum anticipated gain from CEA monitoring would probably be a small number of lives saved (less than 1% of patients monitored) after resection and hepatic metastasis. In addition, the authors specifically stated, “Since the most defensible objective of CEA monitoring is detection of potentially resectable hepatic metastasis, it would also seem appropriate to consider alternative strategies that might fulfill this objective in a more sensitive, specific, and cost-effective manner.” (Id)
Another method used to screen for colon cancer is to have the patient undergo a periodic sigmoidoscopic examination. The use of this screening test in a particular patient is dependent upon the age of the patient and whether he or she is a member of a high-risk population. Research on this screening technique has concluded this method to be the best known screening method for colon cancer presently available (see Selby, J. Sigmoidoscopy in the Periodic Health Examination of Asymptomatic Adults JAMA (1989) 261(4):595)
However, researchers have also acknowledged that this screening method contains inherent limitations. For example, the high cost for the specialized instruments required to perform this screening test, and the special training required in the operation of the instruments in order to perform the procedure safely are acknowledged. Moreover, general patient discomfort while undergoing this screening is believed to be one of the obstacles in providing mass screening for the general population. Finally, health professionals acknowledge that there is a very slight risk of perforating a patient's colon while undergoing the procedure. Consequently, applicants believe a simple, cost effective screening test for colon cancer is needed.
Another type of pathological condition, present exclusively in women, is ovarian cancer. Ovarian cancer comes from cells of the ovary that grow and divide uncontrollably. Applicants believe that statistical information on ovarian cancer indicates that approximately one woman out of every fifty-five (approximately 1.8%) will develop ovarian cancer some time in her lifetime, and it was believed that in 1996, approximately 26,000 women would be diagnosed with ovarian cancer and approximately 14,500 women would die of the disease. Moreover, 85 to 90% of women diagnosed with the condition before it spreads from the ovary are cured. However, there is only a 20 to 25% chance of living after diagnosis, if the diagnosis is made after the disease has spread beyond the ovary.
Presently, there are methods available to diagnose ovarian cancer, but such methods have inherent limitations. One such method is assaying the patient's blood for elevated levels of Cancer Antigen 125 (CA 125). It has been determined that eight out of ten women with advanced ovarian cancer, and in one out of two women with cancer localized in the ovary will have such elevated levels. However, endometriosis, pelvic inflammatory disease of the tubes and ovaries, uterine fibroids, and pregnancy can also elevate levels of CA 125 in the blood, resulting in false positives.
Another method involves screening the ovaries for a growth, surgically removing the growth, and then performing a biopsy on the growth. Screening can occur with a pelvic examination, during which the physician feels for growths on the ovary, or with special types of x-rays. If such a growth is discovered, it must be surgically removed, so that a biopsy can be performed. Another such screening method is ultrasound examination of the ovaries. However, like the pelvic examination, this method provides no definitive answer regarding the presence of cancer in the ovaries.
Another pathological condition for which early diagnosis would benefit the patient is testicular cancer. With this type of cancer, the patient develops a growth within the body of the testicle. The physician must then determine whether the growth is cancerous using presently available diagnostic procedures.
One such procedure is to perform a biopsy on the growth through the scrotum. However, such a procedure presents a problem to the patient in that it could contaminate the scrotum, which could then be a site for the development of cancer. Moreover such a biopsy could disturb the pattern of nodal metastases, and make points for subsequent surgery difficult to predict.
Another such procedure is inguinal orechiectomy, which is done through an incision made above the inguinal ligament. The testicle is then brought up through the inguinal canal and examined visually. However this procedure has limitations in that it is done surgically, like the biopsy, and is a qualitative inspection of the testes. Consequently, a false positive or false negative can result from this procedure.
Another method available for diagnosing testicular cancer is assaying the patient's blood for elevated levels of Human Chorionic Gonadotrophin, beta subunit (Beta HCG). However, this method contains inherent limitations in that it has been determined that low testosterone states, and marijuana use by the patient can produce false positives.