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~l The distribution of types of cancer were examined as well as age patterns. The four major cancers (lung, colon, female breast and prostate) account for more than 59% cancer cases in Orange County. Pediatric cancers comprise 1 % of the cases. And 81 % of the cases are of patients 50 years and over. Thus, the age pattern of these cases is quite consistent with what is normally seen with cancer cases, i.e. the majority of cancers occur at older ages. In examining the Mill Creek area of Orange county, the observed number of cases was compared to the expected number of cases. The expected number of cases is calculated assuming that the population had the same incidence rates as the State. The procedure used for calculating the expected number of cases for each block group was to apply the age/gender-specific cancer incidence rates for the State to the age/gender-specific populations of the census block groups in the study area. This gives an expected number of cases for each age and gender group.. These were added to arrive at an expected number for the entire census block group. The census block groups were summed to form an expected number of cases in the study area, as indicated in Table 3, *S Table 3. Observed and Ex ected Cases in Stud Area, 1990-2003 95% Confidence Interval" Site Observed Expected Observed/Expected (Lower,Upper) Liver <5 <5 1.67 (-0.:22, 3.55) Melanoma 12 7.7 1.56 (0,68, 2.44) Bladder 10 93 L08 (0.41, 1,74) Luna 32 39 0.82 0.54, 1.10 nnnressed to maintain confidentiality. There were fewer lung cancer cases observed than were expected and approximately the same number of bladder cancer cases as were expected. The observed cases for melanoma and liver cancer were somewhat higher than expected, but the difference was not statistically significant. Summary There were 1.56 times as many observed melanoma cancer cases in the study area than were expected. However, the 95% confidence interval for the ratio of observed to expected includes 1.0, indicating a lack of statistical significance. This is one tool used in evaluating the relevance of an association, but statistical significance does not imply causation, nor does the lack of statistical significance address the issue of biological relevance. One explanation for the slightly higher rate is that melanoma reporting in Orange County is better than statewide melanoma reporting, At this time, the data do not suggest a clustering of cancer cases in the MiII Creek area and no further studies are suggested.. a 95% Confidence Intervals were calculated fox the rate ratios using the method described by Breslow and L)ay in: Breslow NE and Da}' NE Stalirliral tbtelGadr iu Caucer RerearcG, Vnhuue II, Lyon, Prance: Bxtcrnationnl Agency for Research on Cancex, IARG Scienti£c Publications N0.32,1987,p 59 Page 39 of 47