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common_problems_in_abortion-breast_cancer_studies [2015/10/19 11:30]
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common_problems_in_abortion-breast_cancer_studies [2017/05/16 07:52] (current)
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 Many design errors can skew the results of epidemiological [[studies_on_the_abortion-breast_cancer_link|studies]]. Some of these biases and problems include: Many design errors can skew the results of epidemiological [[studies_on_the_abortion-breast_cancer_link|studies]]. Some of these biases and problems include:
  
-=====1. Incomplete ​questionnairelow user responseunsuitable circumstances ​for obtaining data=====+=====1. Incomplete ​QuestionnaireLow User ResponseUnsuitable Circumstances ​for Obtaining Data=====
  
 In the Nurses Study II, the basis of the Michels study, over half of respondents did not completely answer the study’s question on induced and spontaneous abortion history. Rather than leaving these questions half-blank, the authors filled in the blank halves of their responses with “no.” The Brauner study relied on a national survey to which over 60 percent of those invited to participate declined. In the Nurses Study II, the basis of the Michels study, over half of respondents did not completely answer the study’s question on induced and spontaneous abortion history. Rather than leaving these questions half-blank, the authors filled in the blank halves of their responses with “no.” The Brauner study relied on a national survey to which over 60 percent of those invited to participate declined.
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 =====2. Health/ Survivor bias===== =====2. Health/ Survivor bias=====
  
-Women who have died of breast cancer prior to the study time cannot be accounted for, and women who have been diagnosed with breast cancer prior to the study time are often deliberately excluded from its sample. Some studies exclude women with [[biology_of_the_abortion-breast_cancer_link|in situ]]((There are invasive and in situ cancers of both the milk ducts and milk glands. When cancer cells form but do not penetrate the basement membrane, or outer layer of the duct or gland, a cancer is said to be an in situ cancer. These cancers are curable, because they cannot spread to other parts of the body. Invasive cancers have penetrated the basement membrane and can spread throughout the body, becoming metastatic and life-threatening. Most invasive cancers start as in situ cancers.)) breast cancer.((//​In situ// breast cancer will likely account for over 60,000 cases of breast cancer among women in 2013 in the U.S. and over 20 percent of breast cancer cases. (See American Cancer Society, “Cancer Facts & Figures 2013” [Atlanta: American Cancer Society, 2013]: 9. “An estimated 232,340 new cases of invasive breast cancer are expected to be diagnosed among women in the US during 2013; about 2,240 new cases are expected in men…In addition to invasive breast cancer, 64,640 new cases of //in situ// breast cancer are expected to occur among women in 2013. Of these, approximately 85% will be ductal carcinoma in situ [DCIS].”) It is treated with surgery, radiation, and drugs, and it may be serious enough that a woman requires a mastectomy. Furthermore,​ most of these cancers develop into invasive breast cancers, though it may take 10 or more years for ductal carcinoma in situ to become invasive. (See Stephen ​P. Povoski and Sanford ​H. Barsky, “Chapter 10: In Situ Carcinomas of the Breast: Ductal Carcinoma in Situ and Lobular Carcinoma in Situ” ​in //The Breast: Comprehensive Management of Benign and Malignant Disorders//,​ eds. Kirby I. Bland and Edward M. Copeland III, 4th ed. (Philadelphia:​ Saunders Elsevier, 2009), 212: “Clearly the evidence is incontrovertible that DCIS can and often progresses to frank invasive adenocarcinoma.”) Regardless: women with //in situ// cancer doubtless consider their condition to be “real” breast cancer, as do their doctors. Hence, to not account for these women is misleading.)) This survivor or “health” bias may alter the results of the analysis concerned. It is somewhat higher in studies with representative population samples (rather than case-control studies), in studies whose populations are older (because breast cancer resulting from an induced abortion will most likely show up around a decade thereafter),​ and in studies that deliberately eliminate women with cancer history. (Depending on the age of the analysis, exclusion of controls with breast cancer may skew results away from or toward induced abortion-breast cancer linkage or have no effect.)+Women who have died of breast cancer prior to the study time cannot be accounted for, and women who have been diagnosed with breast cancer prior to the study time are often deliberately excluded from its sample. Some studies exclude women with [[biology_of_the_abortion-breast_cancer_link|in situ]]((There are invasive and in situ cancers of both the milk ducts and milk glands. When cancer cells form but do not penetrate the basement membrane, or outer layer of the duct or gland, a cancer is said to be an in situ cancer. These cancers are curable, because they cannot spread to other parts of the body. Invasive cancers have penetrated the basement membrane and can spread throughout the body, becoming metastatic and life-threatening. Most invasive cancers start as in situ cancers.)) breast cancer.((//​In situ// breast cancer will likely account for over 60,000 cases of breast cancer among women in 2013 in the U.S. and over 20 percent of breast cancer cases. (See American Cancer Society, “Cancer Facts & Figures 2013” [Atlanta: American Cancer Society, 2013]: 9. “An estimated 232,340 new cases of invasive breast cancer are expected to be diagnosed among women in the US during 2013; about 2,240 new cases are expected in men…In addition to invasive breast cancer, 64,640 new cases of //in situ// breast cancer are expected to occur among women in 2013. Of these, approximately 85% will be ductal carcinoma in situ [DCIS].”) It is treated with surgery, radiation, and drugs, and it may be serious enough that a woman requires a mastectomy. Furthermore,​ most of these cancers develop into invasive breast cancers, though it may take 10 or more years for ductal carcinoma in situ to become invasive. (See S.P. Povoski and S.H. Barsky, “Chapter 10: In Situ Carcinomas of the Breast: Ductal Carcinoma in Situ and Lobular Carcinoma in Situ,” //The Breast: Comprehensive Management of Benign and Malignant Disorders//,​ eds. Kirby I. Bland and Edward M. Copeland III, 4th ed. (Philadelphia:​ Saunders Elsevier, 2009), 212: “Clearly the evidence is incontrovertible that DCIS can and often progresses to frank invasive adenocarcinoma.”) Regardless: women with //in situ// cancer doubtless consider their condition to be “real” breast cancer, as do their doctors. Hence, to not account for these women is misleading.)) This survivor or “health” bias may alter the results of the analysis concerned. It is somewhat higher in studies with representative population samples (rather than case-control studies), in studies whose populations are older (because breast cancer resulting from an induced abortion will most likely show up around a decade thereafter),​ and in studies that deliberately eliminate women with cancer history. (Depending on the age of the analysis, exclusion of controls with breast cancer may skew results away from or toward induced abortion-breast cancer linkage or have no effect.)
  
 **__To avoid__**: Studies should commence with women who procure an induced abortion and track them for a minimum of eight to 10 years thereafter. This would eliminate health or survivor bias from studies. Researchers can also avoid introducing health or survivor bias, or reduce its effects, by not excluding any women who have, or who have had, invasive or in situ breast cancer and by limiting their analysis to women still in their reproductive years or just past them. Researchers should not exclude women who die of breast cancer; the relatives or friends of deceased women can be interviewed. **__To avoid__**: Studies should commence with women who procure an induced abortion and track them for a minimum of eight to 10 years thereafter. This would eliminate health or survivor bias from studies. Researchers can also avoid introducing health or survivor bias, or reduce its effects, by not excluding any women who have, or who have had, invasive or in situ breast cancer and by limiting their analysis to women still in their reproductive years or just past them. Researchers should not exclude women who die of breast cancer; the relatives or friends of deceased women can be interviewed.
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 =====3. Incorrect Time Frame===== =====3. Incorrect Time Frame=====
  
-An [[biology_of_the_abortion-breast_cancer_link|individual breast cancer cell]] requires around eight to 10 years to grow into a clinically detectable cancer one centimeter in diameter.((J. Gershon-Cohen,​ S.M. Berger, and Herbert ​S. Klickstein, “Roentgenography of breast cancer moderating concept ​of ’biologic predeterminism,’” //Cancer// 16, no. 8 (August ​1963): 961-964.)) However, some studies neglect this time frame. Some studies do not follow induced abortions for at least eight to 10 years after they are reported, and, though they may eventually produce breast cancer, the cancer does not yet show. This skews the data away from linkage of induced abortion and breast cancer.+An [[biology_of_the_abortion-breast_cancer_link|individual breast cancer cell]] requires around eight to 10 years to grow into a clinically detectable cancer one centimeter in diameter.((J. Gershon-Cohen,​ S.M. Berger, and H.S. Klickstein, “Roentgenography of Breast Cancer Moderating Concept ​of Biologic Predeterminism,’” //Cancer// 16, no. 8 (1963): 961-964.)) However, some studies neglect this time frame. Some studies do not follow induced abortions for at least eight to 10 years after they are reported, and, though they may eventually produce breast cancer, the cancer does not yet show. This skews the data away from linkage of induced abortion and breast cancer.
  
 In analyses of the relationship between time of an induced abortion and breast cancer diagnosis, wrongly-bounded time frames may obscure induced abortion’s effect. In analyses of the relationship between time of an induced abortion and breast cancer diagnosis, wrongly-bounded time frames may obscure induced abortion’s effect.
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-This entry draws heavily from [[http://​marri.us/​abortion-breast-cancer|Induced Abortion and Breast Cancer]].)) in analyses will obscure the influence of induced abortion on breast cancer risk. For example, the effect of induced abortion among nulliparous (or childless) women will be muted if nulliparous women with induced abortions are compared to nulliparous women with no induced abortions (never-pregnant women). The breast cancer risk of never-pregnant women is greater than that of parous women (or women who have born offspring); the risk associated with induced abortion will thus be muted.+This entry draws heavily from [[http://​marri.us/​research/​research-papers/​induced-abortion-and-breast-cancer/|Induced Abortion and Breast Cancer]].)) in analyses will obscure the influence of induced abortion on breast cancer risk. For example, the effect of induced abortion among nulliparous (or childless) women will be muted if nulliparous women with induced abortions are compared to nulliparous women with no induced abortions (never-pregnant women). The breast cancer risk of never-pregnant women is greater than that of parous women (or women who have born offspring); the risk associated with induced abortion will thus be muted.
  
 **__To avoid__**: Rather than disregarding the differences between women with different reproductive histories, advanced research should parse out their effects. Researchers ought to conduct sophisticated analyses and assess the effect of the timing of an induced abortion in a woman’s reproductive life (i.e., whether the induced abortion preceded or followed a first birth, if any, and the span of time between the abortion and any subsequent first birth). Researchers also ought to assess the influences of repeated induced abortions and maternal age and gestational period at induced abortion(s). **__To avoid__**: Rather than disregarding the differences between women with different reproductive histories, advanced research should parse out their effects. Researchers ought to conduct sophisticated analyses and assess the effect of the timing of an induced abortion in a woman’s reproductive life (i.e., whether the induced abortion preceded or followed a first birth, if any, and the span of time between the abortion and any subsequent first birth). Researchers also ought to assess the influences of repeated induced abortions and maternal age and gestational period at induced abortion(s).