4.6 Prostate Cancer Analysis
We give a brief background for prostate cancer, the second most common cancer among men in the United States, usinghttp://www.cancer.gov/cancertopics/types/prostate. Age is a strong risk factor and prostate cancer occurs more often in African-American men than in white men. Dietary factors play a role, with the risk increasing with greater intake of vitamin E, folic acid, dairy and calcium.
The geographic variation in mortality from prostate cancer was examined across the United States in the period 1970–19897. A previous study indicates that 10% to 30% of the geographic variation in prostate cancer mortality rates in segments of the United States may relate to variations in access to medical care.8 A number of studies have been carried out subsequently.9–11 Geographical examination of prostate cancer was analyzed across electoral wards in Great Britain, using a variety of techniques including disease mapping.12
eFigure 37 gives the expected numbers for prostate cancer and we see high counts across the map. eFigure 38 shows that the SMRs show a wide range, 0–4.82 and 0–5.19, without and with adjustment for income, respectively. Interestingly, the SMRs tend to be increased in higher income quintiles (eFigure 39), which could be a reflection of more a✏uent men being more likely to seek out screening, and therefore have prostate cancer detected.
The multiple cluster Kulldor↵method results are mapped in eFigure 40 and show 4 and 2 clusters without and with adjustment for income. The most significant cluster is in the north of the study region.
The Bayesian method indicates similar cluster regions with the aforementioned northern cluster having a high posterior probability of being a genuine cluster as seen in eFigure 41 and eFigure 43. Both without and with income adjustment the modal number of clusters is 3 (eFigure 42). The cluster in the north of the state would seem to warrant further investigation; it consists of 34 census tracts containing 1917 cases, 1504.5 income unadjusted expected counts yielding an SMR of 1.27, and 1446.2 income adjusted expected counts yielding an SMR of 1.33.
Income Unadjusted Income Adjusted Expected Counts [0.146,20.7] (20.7,32.6] (32.6,47.1] (47.1,68.7] (68.7,109]
Income Unadjusted Income Adjusted
Seattle
Income Unadjusted Income Adjusted
Tacoma
eFigure 37: Maps of income unadjusted (left column) and income adjusted (right column) expected counts of prostate cancer.
Income Unadjusted Income Adjusted SMR [0,0.869] (0.869,1.15] (1.15,1.64] (1.64,3.22] (3.22,5.19]
Income Unadjusted Income Adjusted
Seattle
Income Unadjusted Income Adjusted
Tacoma
eFigure 38: Maps of income unadjusted (left column) and income adjusted (right column) standardized morbidity ratios for prostate cancer.
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Income Unadjusted Income Adjusted
0.25 0.50 1.00 2.00 4.00
1 2 3 4 5 1 2 3 4 5
Income per capita bracket
SMR (log−scale)
Prostate Cancer
eFigure 39: Boxplots of prostate cancer SMR for each income quintile bracket.
p−value 1e−04 0.0151 0.0185 0.021
Kulldorff for Income Unadjusted Prostate
p−value 1e−04 0.0024
Kulldorff for Income Adjusted Prostate
p−value 1e−04 0.0151 0.0185 0.021
Seattle
p−value 1e−04 0.0024
Seattle
p−value 1e−04 0.0151 0.0185 0.021
Tacoma
p−value 1e−04 0.0024
Tacoma
eFigure 40: Maps of income unadjusted (left column) and income adjusted (right column) Multiple cluster Kulldor↵ results for prostate cancer.
Income Unadjusted Income Adjusted Probability [1.03e−18,0.0567] (0.0567,0.268] (0.268,0.578] (0.578,0.857] (0.857,1]
Income Unadjusted Income Adjusted
Seattle
Income Unadjusted Income Adjusted
Tacoma
eFigure 41: Maps of income unadjusted (left column) and income adjusted (right column) posterior probabilities of prostate cancer cluster membership.
0.00 0.25 0.50 0.75 1.00
0 1 2 3 4 5 6 7
Number of clusters/anti−clusters
Probability
Probability Type Prior
Posterior (Income Unadj.) Posterior (Income Adj.)
Prostate Cancer
eFigure 42: Prior/posterior probabilities of the number of prostate cancer clusters/anti- clusters.
Income Unadjusted Income Adjusted Relative Risk [0.867,0.91] (0.91,0.972] (0.972,1.05] (1.05,1.2] (1.2,1.6]
Income Unadjusted Income Adjusted
Seattle
Income Unadjusted Income Adjusted
Tacoma
eFigure 43: Maps of income unadjusted (left column) and income adjusted (right column) posterior estimates of the relative risk of prostate cancer.
