Mammograms: Major Variables Studied And Their Definitions (Other (Not Listed) Sample)

Mammograms
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Article 1CitationMorrell, S., Taylor, R., Roder, D., Robson, B., Gregory, M., & Craig, K. (2017). Mammography service screening and breast cancer mortality in New Zealand: A national cohort study 1999–2011. British Journal of Cancer. doi: 10.1038/bjc.2017.6.Conceptual FrameworkRandomized trials have, in the past, provided insights into breast cancer mortality and screening mammography and subsequently informed screening recommendations. Some meta-analyses have indicated the contribution of mammography screening to reduced breast cancer mortality. However, the exclusion of meta-analyses studies with randomization bias has suggested that mammography screening does not translate to reduced breast cancer mortality. Therefore, the researchers employ the BreastScreen Aotearoa (BSA) program to investigate several hypotheses regarding the breast cancer mortality rates in the never-screened and ever-screened women, and the regularly screened and less regularly screened. Design/MethodThe present study was a retrospective cohort study that investigated breast cancer mortality with reference to screening mammography. The BSA program along with the death and cancer registries provided data of the women in New Zealand who had undergone screening or diagnosis between 1999 and 2011. Sample/settingThe sample comprised women from New Zealand aged between 45 years and 69 years. The setting was New Zealand, and the sample excluded the never-screened women. Major variables studied and their definitionsThe major variables comprised age and ethnicity of the women included in the study. The age ranged between 45-69 years and ethnicity comprised the Pacific and Maori with “other” women implying women of European descent residing in New Zealand. The outcome variable in this study referred to breast cancer mortality for every cohort year.MeasurementThe breast cancer mortality for every cohort year served as the outcome measure did not require a scale because it was direct. Data analysisData analysis involved calculating breast cancer mortality with respect to participation and non-participation in the screening mammography service between 2000 and 2011. For ever-screen women, the researchers determined the years each person participated in screening right from the first screen. It also determined the years that the never-screened did not participate in the BSA program. The researchers used negative binomial regression for the adjustment of the repeated measures and Poisson regression in case the negative binomial model did not apply. FindingsThe ever-screened group achieved significant reductions in the overall breast cancer mortality when compared to the never-screened population. The regularly screened also had relatively lower mortality rates compared to the less screened counterparts. Further, the ever-screened women had better prognostic factors when compared to their never-screened counterparts due to early detection.Appraisal/Worth to PracticeIt proved challenging to eliminate the lead-time bias. However, the researchers managed to eliminate the predisposition of the study to lead time bias. It is also not possible to determine the exact causes of variations in breast cancer mortality for the ever-screened and never-screened populations. The study was subject to screening selection bias.Article 2CitationJohns, L. E., Coleman, D. A., Swerdlow, A. J. & Moss, S. M. (2017). Effect of population breast screening on breast cancer mortality up to 2005 in England and Wales: An individual-level cohort study. British Journal of Cancer, 116, 246–252.Conceptual FrameworkVarious countries set up population breast screening based on evidence in previous randomized trials that suggested the ability of mammographic screening to bring down breast cancer mortality. Even so, controversies exist regarding the value of putting in place these screening programs with respect to breast cancer mortality. As such, this called for the evaluation of the efficacy of these programs based on the existing individual-level data.Design/MethodThe study examines breast cancer screening histories, including the day of death of persons with breast cancer from the screening call and recall databases. The researchers coded the data of the people with breast cancer depending on their death causes.Sample/settingThe cohort sample included 988, 090 women residing in Wales and a third of those in England within the age range of 49 and 64 years.
Major variables studied and their definitions
The major variables in this study included the socioeconomic status and age. The age ranged between 49 years and 64 years. MeasurementThe researchers employed the Townsend Index to provide estimates of the socioeconomic status of the participants in the study (Phillimore et al., 1994). It utilized postcode of residence of the women who took part in screening to develop socioeconomic estimates.Data analysisData analysis involved carrying out the intention-to-screen analyses. The researchers also adjust the results against the lead-time bias. It also involved performing a cumulative incidence analysis to take into account overdiagnosis as a result of screening. The standardized mortality rates allowed for the adjustment depending on age and year. The Poisson regression allowed for the calculation of rate ratios, confidence intervals, as well as p-values. FindingsThe mortality rate remained relatively lower at 17 percent for the invited than the uninvited women. However, the mortality rate rose to 21 percent after carrying out a lead-time bias adjustment with respect to age and socioeconomic status. The cumulative incidence rates stood at 3.02 with 0.3 percent representing overdiagnosis for the invited. Appraisal/Worth to PracticeThe current study addresses the limitations of past studies with respect to their inability to assess exposure with a great sense of accuracy, including employing the incidence-based mortality technique. However, the study suffered the healthy invitee bias, self-selection bias, and the pro-screening lead-time bias. Other limitations comprised inability to determine diagnosis dates for approximately 5 percent of those who succumbed to breast cancer and temporal differences noted in the exposed groups.Article 3CitationMassat, N. J., Dibden, A., Parmar, D., Cuzick, J., Sasieni, P. D., & Duffy, S. W. (2016). Impact of screening on breast cancer mortality: the UK program 20 years on. Cancer Epidemiology, Biomarkers & Prevention, 25(3).Conceptual FrameworkThe evidence of the randomized clinical trials led to the launch of population mammographic screening and subsequent expansion of the invitations to cover women aged 47-73 years. The evaluation of these programs can provide new insights into whether early detection is required regardless of better prognosis in the 21st century. The insights can elucidate whether breast cancer screening has a significant influence on mortality. Design/MethodThe study utilized the case-control study design and targeted women aged 47-89 years whose death occurred due to breast cancer in the period between 2008 and 2009. The researchers matched the 869 women in the cancer registry with one or two general population controls without breast cancer diagnosis based on screening locale and date of birth. Sample/settingThe sample comprised 869 women whose death certificate indicated breast cancer as the primary death cause and 1642 controls. The participants ranged between 47 and 89 years and resided in London. Major variables studied and their definitionsThe major variables included age, currently screened (0 to 60 months), formerly screened (more than 60 months), and never screened. MeasurementThe study did not employ any scale or measurement instrument because of the straightforwardness of the variables. Data analysisThe conditional logistic regression assisted in comparing participation in breast screening of the cases and controls. The resulting ORs underwent adjustment for self-selection bias. The researchers also executed a sensitivity analysis to eliminate the bias associated with screening time. FindingsThe mortality rates linked with breast cancer for screened women remained relatively lower that is 35 percent when compared to the never-screened group. Self-selection bias had no significant impact on study OR and attending the last invitation significantly influenced mortality rate reduction because it allowed for the detection of fatal cancers. Appraisal/Worth to PracticeThe study employed a new approach and contemporary data. The findings agree with those of other researchers who have employed contemporary data. The design provided for equal screening opportunity and minimized self-selection and lead time bias. Article 4CitationWeedon-Fekjжr, H., Romundstad, P. R., & Vatten, Lars J. (2014). Modern mammography screening and breast cancer mortality: Population study. BMJ, 348. Conceptual FrameworkPrevious studies provided evidence demonstrating the ability of mammography screening to lessen breast cancer mortality. Even so, the methods employed in these studies have received widespread criticism with the Cochrane Collaboration considering the estimated mortality benefits invalid. The recent advancements in breast cancer treatment have caused debate on the relevance of mammography screening and early cancer detection. Design/MethodThe study employed a prospective cohort study design to examine the efficacy of carrying out mammography screening on breast cancer mortality. The Norwegian cancer registry provided the data on screening invitations, as well as breast cancer diagnoses and deaths. Sample/settingThe sample consisted of all Norwegian women who participated in the screeni...