OVARIAN CANCER: EXAMPLE OF AN UNSUCCESSFUL CANCER SCREENING STRATEGY
In contrast to the documented clinical utility of cytological screening for cervix cancer, there is currently no evidence of a benefit associated with screening for another, even more difficult gynecologic malignancy, e.g., ovarian cancer.
Important differences between the two disease entities help explain the lack of efficacy for ovarian cancer screening. First, although the cervix is very accessible to visual inspection and routine cytological analysis, the small ovaries are protected deep in the pelvis and present a serious problem for direct visualization.
Second, especially in premenopausal females, the ovaries are in constant change during the menstrual cycle. Thus, “abnormalities” observed on radiographic evaluation (e.g., ultrasound) may simply represent physiologic changes and not serious pathology. Even the common finding of cysts on ultrasound examination may be viewed in most women, more as a variant of normal physiology and anatomy rather than as a cause of serious concern.
Third, although obtaining frequent cytological analysis of the cervix is quite simple and associated with minimal discomfort, the biopsy of an ovary requires a surgical procedure (e.g., laparoscopy) and is associated with a concern for surgical morbidity and small risk of loss of ovarian function.
Fourth, although cervix cancer has well-defined premalignant (i.e., severe dysplasia) and early malignant (i.e., carcinoma in situ) components that can be diagnosed and easily treated, there are currently no established precursor lesions for cancer of the ovary.
Finally, the natural history of cervix cancer, from precursor lesions to invasive cancer, has been well documented. It is recognized that by finding and treating premalignant and early-stage malignancy the prognosis is greatly improved.
In the case of ovarian cancer, it remains completely unknown if the finding of “stage 1” disease during the performance of any screening test (e.g., abnormal vaginal ultrasound, elevated serum CA-125 antigen level) will have a favorable impact on survival from the malignancy (9,10). For example, despite the fact that the cancer appears to be confined to the organ of origin, microscopic metastatic disease may already be present at the time of diagnosis. Also, as it is known that
approx 10–20% of patients with ovarian cancer currently are found to have surgically documented stage 1 ovarian cancer, without the use of any screening strategy, it remains uncertain if screening will actually favorably impact on the percentage of individuals presenting at this early stage of disease. An alternative hypothesis is that nonscreened individuals who are destined to have stage 1 ovarian cancer will be essentially the same patient population whose cancers are discovered by any screening strategy to be confined to the ovary.
In view of these considerations it should not be surprising that several analyses of the cost-effectiveness of ovarian cancer screening have concluded that, with available techniques, such screening is highly unlikely to be a useful approach to decrease the morbidity and mortality associated with this difficult malignancy in a general patient population without a family history of ovarian cancer.
CONCLUSION
Cancer will ultimately affect one-third of all individuals and two-thirds of all families in the United States. Early in this new century, malignant disease will surpass heart disease as the leading cause of death in this country. Thus, it is important that we carefully and critically examine any and all strategies that have the potential to effectively lessen the morbidity and mortality associated with malignancy. Cancer screening is an obvious approach to accomplish this goal. However, despite the promise of this therapeutic strategy, we must be careful to avoid the temptation to accept the clinical usefulness of a proposed cancer screening program until it has been thoroughly tested in randomized controlled trials to document that the “costs” associated with the approach (e.g., monetary, time, inconvenience, anxiety, unnecessary procedures for falsepositive testing) are justified by a favorable impact on survival. The costeffectiveness of all proposed cancer screening strategies, as well as careful definitions of target populations, should be established before any approach is accepted as a component of routine medical care.
From: Cancer Screening: A Practical Guide for Physicians
Edited by: K. Aziz and G. Y. Wu © Humana Press Inc., Totowa, NJ
REFERENCES
1. Sparen P, Gustafsson L, Friberg L-G, et al. (1995) Improved control of invasive cervical cancer in Sweden over six decades by earlier clinical detection and better treatment. J Clin Oncol 13:715–725.
2. Cannistra SA, Niloff JM. (1996) Cancer of the uterine cervix. N Engl J Med 334:1030–1038.
3. Adami H-O, Ponten J, Sparen P, et al. (1994) Survival trend after invasive cervical cancer diagnosis in Sweden before and after cytologic screening. Cancer 73:140–147.
4. Austin RM, McLendon WW. (1997) The Papanicolaou smear. Medicine’s most successful cancer screening procedure is threatened. JAMA 277:754,755.
5. Fahs MC, Mandelblatt J, Schechter C, et al. (1992) Cost effectiveness of cervical cancer screening for the elderly. Ann Intern Med 117:520–527.
6. Koss LG. (1989) The Papanicolaou test for cervical cancer detection. A triumph and a tragedy. JAMA 61:737–743.
7. Marshall CJ, Rowe L, Bentz S. (1999) Improved quality-control detection of falsenegative pap smears using the Autopap 300 QC system. Diag Cytopath 20(3):170–174.
8. Cannistra SA. (1993) Cancer of the ovary. N Engl J Med 329:1550–1559.
9. NIH Consensus Development Panel on Ovarian Cancer. (1995) Ovarian cancer. Screening, treatment, and follow-up. JAMA 273:491–497.
10. DePriest PD, Gallion HH, Pavlik EJ, et al. (1997) Transvaginal sonography as a screening method for the detection of early ovarian cancer. Gynecol Oncol 65: 408–414.
11. Schapira MM, Matchar DB, Young MJ. (1993) The effectiveness of ovarian cancer screening. A decision analysis model. Ann Intern Med 118:838–843.
12. Carlson J, Skates SJ, Singer DE. (1994) Screening for ovarian cancer. Ann Intern Med 121:124–132.
13. Mackey SE, Creasman WT. (1995) Ovarian cancer screening. J Clin Oncol 13:783–793.
14. Landis SH, Murray T, Bolden S, et al. (1999) Cancer statistics, 1999. CA Cancer J Clin 49:8–31.
Important differences between the two disease entities help explain the lack of efficacy for ovarian cancer screening. First, although the cervix is very accessible to visual inspection and routine cytological analysis, the small ovaries are protected deep in the pelvis and present a serious problem for direct visualization.
Second, especially in premenopausal females, the ovaries are in constant change during the menstrual cycle. Thus, “abnormalities” observed on radiographic evaluation (e.g., ultrasound) may simply represent physiologic changes and not serious pathology. Even the common finding of cysts on ultrasound examination may be viewed in most women, more as a variant of normal physiology and anatomy rather than as a cause of serious concern.
Third, although obtaining frequent cytological analysis of the cervix is quite simple and associated with minimal discomfort, the biopsy of an ovary requires a surgical procedure (e.g., laparoscopy) and is associated with a concern for surgical morbidity and small risk of loss of ovarian function.
Fourth, although cervix cancer has well-defined premalignant (i.e., severe dysplasia) and early malignant (i.e., carcinoma in situ) components that can be diagnosed and easily treated, there are currently no established precursor lesions for cancer of the ovary.
Finally, the natural history of cervix cancer, from precursor lesions to invasive cancer, has been well documented. It is recognized that by finding and treating premalignant and early-stage malignancy the prognosis is greatly improved.
In the case of ovarian cancer, it remains completely unknown if the finding of “stage 1” disease during the performance of any screening test (e.g., abnormal vaginal ultrasound, elevated serum CA-125 antigen level) will have a favorable impact on survival from the malignancy (9,10). For example, despite the fact that the cancer appears to be confined to the organ of origin, microscopic metastatic disease may already be present at the time of diagnosis. Also, as it is known that
approx 10–20% of patients with ovarian cancer currently are found to have surgically documented stage 1 ovarian cancer, without the use of any screening strategy, it remains uncertain if screening will actually favorably impact on the percentage of individuals presenting at this early stage of disease. An alternative hypothesis is that nonscreened individuals who are destined to have stage 1 ovarian cancer will be essentially the same patient population whose cancers are discovered by any screening strategy to be confined to the ovary.
In view of these considerations it should not be surprising that several analyses of the cost-effectiveness of ovarian cancer screening have concluded that, with available techniques, such screening is highly unlikely to be a useful approach to decrease the morbidity and mortality associated with this difficult malignancy in a general patient population without a family history of ovarian cancer.
CONCLUSION
Cancer will ultimately affect one-third of all individuals and two-thirds of all families in the United States. Early in this new century, malignant disease will surpass heart disease as the leading cause of death in this country. Thus, it is important that we carefully and critically examine any and all strategies that have the potential to effectively lessen the morbidity and mortality associated with malignancy. Cancer screening is an obvious approach to accomplish this goal. However, despite the promise of this therapeutic strategy, we must be careful to avoid the temptation to accept the clinical usefulness of a proposed cancer screening program until it has been thoroughly tested in randomized controlled trials to document that the “costs” associated with the approach (e.g., monetary, time, inconvenience, anxiety, unnecessary procedures for falsepositive testing) are justified by a favorable impact on survival. The costeffectiveness of all proposed cancer screening strategies, as well as careful definitions of target populations, should be established before any approach is accepted as a component of routine medical care.
From: Cancer Screening: A Practical Guide for Physicians
Edited by: K. Aziz and G. Y. Wu © Humana Press Inc., Totowa, NJ
REFERENCES
1. Sparen P, Gustafsson L, Friberg L-G, et al. (1995) Improved control of invasive cervical cancer in Sweden over six decades by earlier clinical detection and better treatment. J Clin Oncol 13:715–725.
2. Cannistra SA, Niloff JM. (1996) Cancer of the uterine cervix. N Engl J Med 334:1030–1038.
3. Adami H-O, Ponten J, Sparen P, et al. (1994) Survival trend after invasive cervical cancer diagnosis in Sweden before and after cytologic screening. Cancer 73:140–147.
4. Austin RM, McLendon WW. (1997) The Papanicolaou smear. Medicine’s most successful cancer screening procedure is threatened. JAMA 277:754,755.
5. Fahs MC, Mandelblatt J, Schechter C, et al. (1992) Cost effectiveness of cervical cancer screening for the elderly. Ann Intern Med 117:520–527.
6. Koss LG. (1989) The Papanicolaou test for cervical cancer detection. A triumph and a tragedy. JAMA 61:737–743.
7. Marshall CJ, Rowe L, Bentz S. (1999) Improved quality-control detection of falsenegative pap smears using the Autopap 300 QC system. Diag Cytopath 20(3):170–174.
8. Cannistra SA. (1993) Cancer of the ovary. N Engl J Med 329:1550–1559.
9. NIH Consensus Development Panel on Ovarian Cancer. (1995) Ovarian cancer. Screening, treatment, and follow-up. JAMA 273:491–497.
10. DePriest PD, Gallion HH, Pavlik EJ, et al. (1997) Transvaginal sonography as a screening method for the detection of early ovarian cancer. Gynecol Oncol 65: 408–414.
11. Schapira MM, Matchar DB, Young MJ. (1993) The effectiveness of ovarian cancer screening. A decision analysis model. Ann Intern Med 118:838–843.
12. Carlson J, Skates SJ, Singer DE. (1994) Screening for ovarian cancer. Ann Intern Med 121:124–132.
13. Mackey SE, Creasman WT. (1995) Ovarian cancer screening. J Clin Oncol 13:783–793.
14. Landis SH, Murray T, Bolden S, et al. (1999) Cancer statistics, 1999. CA Cancer J Clin 49:8–31.
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