Confidence intervals cancers

Confidence Intervals CCDF for Latent Cancer Fatalities Internal and... 

In a case-control study of the relation between occupational exposures to various suspected estrogenic chemicals and the occurrence of breast cancer, the breast cancer odds ratio (OR) was not elevated above unity (OR=0.8 95% 01=0.2-3.2) for occupational exposure to endosulfan compared to unexposed controls (Aschengrau et al. 1998) however, the sample sizes were very small (three exposed seven not exposed), and co-exposure to other unreported chemicals also reportedly occurred. Both of these factors may have contributed to the high degree of uncertainty in the OR indicated by the wide confidence interval. 

In animal experiments exposures can be carefully controlled, and dose-response curves can be formally estimated. Extrapolating such information to the human situation is often done for regulatory purposes. There are several models for estimating a lifetime cancer risk in humans based on extrapolation from animal data. These models, however, are premised on empirically unverified assumptions that limit their usefulness for quantitative purposes. While quantitative cancer risk assessment is widely used, it is by no means universally accepted. Using different models, one can arrive at estimates of potential cancer incidence in humans that vary by several orders of magnitude for a given level of exposure. Such variations make it rather difficult to place confidence intervals around benefits estimations for regulatory purposes. Furthermore, low dose risk estimation methods have not been developed for chronic health effects other than cancer. The... 

Figure 15.1 Hazard ratios and 95 per cent confidence intervals for death from any cause (panel (a)) and recurrence (panel (b)) by treatment group (Sargent DJ, Goldberg RM, Jacobson SD, MacDonald JS et al., A pooled analysis of adjuvant chemotherapy for resected colon cancer in elderly patients. New England Journal of Medicine, 345, 1091-1097. (2001) Massachusetts Medical Society.)...

Selected characteristics were compared between cases and controls by using test. The analyses of data were performed using the computer software SPSS for Windows version 11.5. Max type 1 error was accept as 0.05. Binary logistic regression was performed to calculate the odds ratios (ORs), and 95% confidence intervals (Cls) to assess the risk of breast cancer. 

Finally, the statistical methods used to obtain estimates of relative risk, absolute rates of cancer, confidence intervals and significance tests, and to adjust for confounding should have been clearly stated by the authors. The methods used should preferably have been the generally accepted techniques that have been refined since the mid-1970s. These methods have been reviewed for case-control studies (Breslow Day, 1980) and for cohort studies (Breslow Day, 1987). 

In the REMARK system, estimated effects (e.g., hazard ratios) with confidence intervals for the marker were recommended for univariant and key multivariable analyses, and a Kaplan-Meier plot was recommended to represent the effect of a tumor marker in a time-to-event outcome. The discussion section should interpret the results in the context of the pre-specified hypothesis and describe limitations of the study as well as implications for future research and clinical value. These guidelines were advocated for reporting of tumor marker studies in breast cancer research and treatment (63). 

Olsen et al. (1995) studied mortality among a cohort of 548 male l,2-dibromo-3-chloropropane production workers. This was an update of an earlier study performed by Heam et al. (1984). The workers were identified on the basis of employment records or self-declaration of exposure to l,2-dibromo-3-chloropropane and were followed from 1957 through 1989. A total of 68 deaths were identified (standardized mortality ratio (SMR), 0.8) and overall cancer mortality was similar to expected (SMR, 1.0 n = 19), based on mortality of white men in the United States. There were seven lung cancer deaths compared with 7.1 expected (SMR, 1.0 95% confidence interval (Cl), 0.4-2.0), but an excess of lung cancer (SMR, 3.4 95% CI, 0.7-9.6), based on three cases, was... 

Austin and Schnatter (1983a) conducted a cohort study of 6588 white male workers employed at a petrochemical plant in the United States between 1941 and 1977. The study was conducted to investigate a cluster of brain tumours that was reported earlier in the same population (Alexander et al., 1980). There were 765 deaths (SMR, 0.8) and 150 cancer deaths (SMR, 0.9) observed. A greater than expected number (based on national rates) of brain cancers (SMR, 1.6 95% confidence interval (CI), 0.8-2.8, based on 12 cases) was observ ed. Austin and Schnatter (1983b) also conducted a nested case-control study to examine the relationship between the risk of primary brain tumours and exposures at the facility. No significant association with 1,2-dichloroethane exposure was observed. 

Cook et al. (1986) examined mortality between 1940 and 1979 among 2189 men involved in the manufacture of 2,4,5-trichlorophenol and 2.4.5-T. There were 298 deaths observed (standardized mortality ratio (SMR), 0.91), including 61 from cancer (SMR, 0.96) and five from non-Hodgkin lymphoma (SMR, 2.4 95% confidence interval (Cl), 0.8-5.6). 

Carpenter et al. (1988) carried out a nested case-control study of cancer of the central nervous system among workers at two nuclear facilities located in Tennessee (United States). They identified 89 cases (72 males and 17 females) who had died between 1943 and 1979. Four controls, living at the time the case was diagnosed, were matched to each case. Job history records were scrutinized by an industrial hygienist to assess potential exposure to each of 26 chemicals or chemical groups. Toluene, xylene (see this volume) and 2-butanone (methyl ethyl ketone) were evaluated as one chemical group the matched relative risk was 2.0 (95% confidence interval (Cl), 0.7-5.5 n = 28) in comparison with unexposed workers. Almost all cases had had low exposure, according to the classification used and there was no dose-response trend. The authors stated that the relative risks w ere adjusted for internal and external exposure to radiation. 

In the Montreal case-control study carried out by Siemiatycki (1991 see the monograph on dichloromethane in this volume), the investigators estimated the associations between 293 workplace substances and several types of cancer. Isopropanol was one of the substances. About 4% of the study subjects had ever been exposed to isopropanol. Among the main occupations to which isopropanol exposure was attributed in this study were fire fighters, machinists and electricians. For most types of cancer examined (oesophagus, stomach, colon, rectum, pancreas, prostate, bladder, kidney, skin melanoma, lymphoma), there was no indication of an excess risk due to isopropanol. For lung cancer, based on 16 cases exposed at the substantial level, the odds ratio was 1.4 (90% confidence interv al, 0.8-2.7). [The interpretation of the null results has to take into account the small numbers and presumed low levels of exposure.]... 

Figure 20.1 Odds ratios and 95% confidence intervals of selected cancers for the highest vs. the lowest levels of vegetable consumption. Italy, 1991-2005.

The study of oral and pharyngeal cancer (Table 20.1) showed that total flavonoids were inversely related to the risk of this neoplasm [Rossi et al., 2007b]. The ORs for the highest versus the lowest quintile of all classes of flavonoid intake were below unity. The OR was 0.51 (95% confidence interval,... 

---