Cervical Screening and Cervical Cancer Death in Older Women
Cervical Screening and Cervical Cancer Death in Older Women
Among 47 potentially eligible cases, 4 were excluded because no medical records were available, and 3 were excluded because they had likely received care outside the health plan. Among controls with sufficient enrollment duration, the most common reason for exclusion was evidence of hysterectomy before the reference date (n = 69), followed by lack of availability of medical records (n = 18), and documentation of outside health care (n = 16). These exclusions left 40 potential cases, and 80 controls were identified as eligible for inclusion in the study. After medical record abstraction, 1 case with less than 6 years of prediagnosis enrollment was excluded, leaving 39 cases and 80 controls available for the analysis.
There were no appreciable differences between cases and controls in most measured demographic characteristics (Table 1). A majority of study subjects (61%) were younger than 65 years at diagnosis; half of cases (49%) were younger than 65 years at death. Cases were more likely to be current smokers at the time of diagnosis (31%) than were controls (14%), and cases had higher body mass index values than controls (32% vs. 15% with body mass index ≥35). The overwhelming majorities of both cases (95%) and controls (97%) were white. Controls were more likely than cases to have been married at the reference date (68% vs. 56%). Cases were more likely than controls have had 3 or more births (72% vs. 50%). Among cases, the most common cervical cancer histology was SCC (51%), followed by adenocarcinoma (31%), undifferentiated carcinoma (10%), unknown histology (5%), and adenosquamous (3%) carcinoma.
Screening histories differed substantially between cases and controls. In the 7 years prior to the index date, 51% of cases and 81% of controls received cervical cytology screening. The univariate odds ratio associated with 1 or more screens was 0.24 (95% confidence interval (CI): 0.10, 0.56) (Table 2). After adjustment for covariates (smoking status, marital status, and race/ethnicity), screening was associated with a 74% reduction in cervical cancer death (odds ratio (OR) = 0.26, 95% CI: 0.10, 0.63). Inclusion of all measured covariates did not alter the magnitude of the association (OR = 0.26, 95% CI: 0.09, 0.77).
Exclusion of 10 subjects with less than 7 years of enrollment prior to the reference date did not affect the magnitude of the calculated odds ratio (adjusted OR = 0.26, 95% CI: 0.10, 0.67). In sensitivity analyses, the length of the DPP was varied from 5 to 6.5 years prior to the index date (Table 3). As the DPP shortened, the magnitude of the risk estimate was not appreciably affected. Similarly, the use of conditional logistic regression did not alter the primary odds ratio (Table 2 substantively (adjusted OR = 0.25, 95% CI: 0.09, 0.68), nor did it substantively alter the interpretation of any other analyses.
In the first exploratory analysis, associations did differ somewhat by age (<65 years vs. ≥65 years at reference date; Table 4, but a reduced risk associated with screening was present in both age groups. Second, when subjects were stratified by year of diagnosis (1999 or earlier vs. 2000 or later), the reduction in cervical cancer death associated with screening was similar during the 2 intervals (Table 4). Finally, restriction to cases with SCC tumor histology (n = 20) yielded a lower adjusted odds ratio (OR = 0.13, 95% CI: 0.03, 0.54) (Table 5).
Results
Among 47 potentially eligible cases, 4 were excluded because no medical records were available, and 3 were excluded because they had likely received care outside the health plan. Among controls with sufficient enrollment duration, the most common reason for exclusion was evidence of hysterectomy before the reference date (n = 69), followed by lack of availability of medical records (n = 18), and documentation of outside health care (n = 16). These exclusions left 40 potential cases, and 80 controls were identified as eligible for inclusion in the study. After medical record abstraction, 1 case with less than 6 years of prediagnosis enrollment was excluded, leaving 39 cases and 80 controls available for the analysis.
There were no appreciable differences between cases and controls in most measured demographic characteristics (Table 1). A majority of study subjects (61%) were younger than 65 years at diagnosis; half of cases (49%) were younger than 65 years at death. Cases were more likely to be current smokers at the time of diagnosis (31%) than were controls (14%), and cases had higher body mass index values than controls (32% vs. 15% with body mass index ≥35). The overwhelming majorities of both cases (95%) and controls (97%) were white. Controls were more likely than cases to have been married at the reference date (68% vs. 56%). Cases were more likely than controls have had 3 or more births (72% vs. 50%). Among cases, the most common cervical cancer histology was SCC (51%), followed by adenocarcinoma (31%), undifferentiated carcinoma (10%), unknown histology (5%), and adenosquamous (3%) carcinoma.
Screening histories differed substantially between cases and controls. In the 7 years prior to the index date, 51% of cases and 81% of controls received cervical cytology screening. The univariate odds ratio associated with 1 or more screens was 0.24 (95% confidence interval (CI): 0.10, 0.56) (Table 2). After adjustment for covariates (smoking status, marital status, and race/ethnicity), screening was associated with a 74% reduction in cervical cancer death (odds ratio (OR) = 0.26, 95% CI: 0.10, 0.63). Inclusion of all measured covariates did not alter the magnitude of the association (OR = 0.26, 95% CI: 0.09, 0.77).
Exclusion of 10 subjects with less than 7 years of enrollment prior to the reference date did not affect the magnitude of the calculated odds ratio (adjusted OR = 0.26, 95% CI: 0.10, 0.67). In sensitivity analyses, the length of the DPP was varied from 5 to 6.5 years prior to the index date (Table 3). As the DPP shortened, the magnitude of the risk estimate was not appreciably affected. Similarly, the use of conditional logistic regression did not alter the primary odds ratio (Table 2 substantively (adjusted OR = 0.25, 95% CI: 0.09, 0.68), nor did it substantively alter the interpretation of any other analyses.
In the first exploratory analysis, associations did differ somewhat by age (<65 years vs. ≥65 years at reference date; Table 4, but a reduced risk associated with screening was present in both age groups. Second, when subjects were stratified by year of diagnosis (1999 or earlier vs. 2000 or later), the reduction in cervical cancer death associated with screening was similar during the 2 intervals (Table 4). Finally, restriction to cases with SCC tumor histology (n = 20) yielded a lower adjusted odds ratio (OR = 0.13, 95% CI: 0.03, 0.54) (Table 5).
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