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A detailed spatial analysis on contrasting cancer incidence patterns in thyroid and lung cancer in Toronto women

View Article: PubMed Central - PubMed

ABSTRACT

Background: Thyroid cancer has been rapidly rising in incidence in Canada; however, in contrast, lung cancer appears to be decreasing in incidence in Canadian men and stable in women. Moreover, disease-related mortality risk is generally very low in TC but high in LC. We performed a geographic spatial analysis in metropolitan Toronto, Canada to determine if there is regional variability of respective risks of thyroid cancer (TC) and lung cancer (LC), among women. Women were of particular interest for this study, given their known predilection for thyroid cancer.

Methods: The postal codes of all females with TC or LC, residing in metropolitan Toronto from 2004 to 2008, were geocoded to point locations according to 2006 Canadian Census data. The data were analysed using a log-Gaussian Cox Process, where the intensity of age-adjusted cancer cases was modelled as a log-linear combination of the population at risk, explanatory variables (race, immigration, and median household income), and a residual spatially varying random effect. For each respective malignancy, statistical models were fit to make quantify the relationship between cancer incidence and explanatory variables.

Results: We included 2230 women with TC and 2412 with LC. The distribution of TC and LC cases contrasted inversely among Toronto neighbourhoods with the highest TC incidence in the Northeast and the highest LC incidence in the Southeast. A higher proportion of Asian ethnicity was associated with higher regional risk of TC and lower risk of LC. A higher proportion of recent immigrants was associated with increased LC and lower TC risk, whereas median household income and proportions of African ethnicity were not significantly associated with risk of either cancer, after adjustment for other socio-demographic variables.

Conclusions: We observed contrasting regional distributions of female TC and LC cases in Toronto. The differences were partly attributed to ethnic composition variability and the proportion of recent immigrants, but substantial unexplained residual variation of incidence patterns of these malignancies exists, suggesting that more individual-level research is needed to explain the regional variability of incidence of these malignancies.

No MeSH data available.


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Prior and posterior distributions for selected model parameters. Legend: a. Thyroid cancer range ϕ.b. Thyroid cancer standard deviation δ.c. Lung cancer range ϕ.d. Lung cancer standard deviation δ
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Fig3: Prior and posterior distributions for selected model parameters. Legend: a. Thyroid cancer range ϕ.b. Thyroid cancer standard deviation δ.c. Lung cancer range ϕ.d. Lung cancer standard deviation δ

Mentions: Upon examining the regional distribution of female TC and LC cases, we observed a relatively higher density of TC cases in the Northeast part of the city (Fig. 2a), and a higher density of LC cases in the Southeast (Fig. 2c). Lung cancer risk in Toronto is lower than the Canadian average and thyroid cancer is more common in Toronto than elsewhere in Canada, which is reflected in relative risk for LC being below 1.1 and relative risk for TC being above 1.5 throughout the city. From the map of residual spatial random effect for LC (Fig. 2d), a strong spatial effect is observed in the Central Southeast. However, the map of TC cases does not show the same pattern (Fig. 2b). These data strongly suggest that the risks for TC and LC are highly variable regionally, but that the risk for each of these malignancies appears to be independent. Table 1 shows parameter estimates for both models along with 95 % posterior credible intervals, and the larger range parameter for LC of 7.2 km (against 3.3 km for TC) reflects the smoother contour lines for residual LC risk in Fig. 2b. The standard deviation parameter is larger for LC, however, at 0.21 versus 0.15 for TC, which is reflected in the surface in Fig. 2b showing relative risks for TC closer to 1.0 than the comparable values for LC in Fig. 2d. Figure 3 shows prior and posterior distributions for the range and standard deviation parameters, with the larger LC dataset shifting posterior distributions further from their priors than the smaller number of TC cases do.Fig. 2


A detailed spatial analysis on contrasting cancer incidence patterns in thyroid and lung cancer in Toronto women
Prior and posterior distributions for selected model parameters. Legend: a. Thyroid cancer range ϕ.b. Thyroid cancer standard deviation δ.c. Lung cancer range ϕ.d. Lung cancer standard deviation δ
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC5016996&req=5

Fig3: Prior and posterior distributions for selected model parameters. Legend: a. Thyroid cancer range ϕ.b. Thyroid cancer standard deviation δ.c. Lung cancer range ϕ.d. Lung cancer standard deviation δ
Mentions: Upon examining the regional distribution of female TC and LC cases, we observed a relatively higher density of TC cases in the Northeast part of the city (Fig. 2a), and a higher density of LC cases in the Southeast (Fig. 2c). Lung cancer risk in Toronto is lower than the Canadian average and thyroid cancer is more common in Toronto than elsewhere in Canada, which is reflected in relative risk for LC being below 1.1 and relative risk for TC being above 1.5 throughout the city. From the map of residual spatial random effect for LC (Fig. 2d), a strong spatial effect is observed in the Central Southeast. However, the map of TC cases does not show the same pattern (Fig. 2b). These data strongly suggest that the risks for TC and LC are highly variable regionally, but that the risk for each of these malignancies appears to be independent. Table 1 shows parameter estimates for both models along with 95 % posterior credible intervals, and the larger range parameter for LC of 7.2 km (against 3.3 km for TC) reflects the smoother contour lines for residual LC risk in Fig. 2b. The standard deviation parameter is larger for LC, however, at 0.21 versus 0.15 for TC, which is reflected in the surface in Fig. 2b showing relative risks for TC closer to 1.0 than the comparable values for LC in Fig. 2d. Figure 3 shows prior and posterior distributions for the range and standard deviation parameters, with the larger LC dataset shifting posterior distributions further from their priors than the smaller number of TC cases do.Fig. 2

View Article: PubMed Central - PubMed

ABSTRACT

Background: Thyroid cancer has been rapidly rising in incidence in Canada; however, in contrast, lung cancer appears to be decreasing in incidence in Canadian men and stable in women. Moreover, disease-related mortality risk is generally very low in TC but high in LC. We performed a geographic spatial analysis in metropolitan Toronto, Canada to determine if there is regional variability of respective risks of thyroid cancer (TC) and lung cancer (LC), among women. Women were of particular interest for this study, given their known predilection for thyroid cancer.

Methods: The postal codes of all females with TC or LC, residing in metropolitan Toronto from 2004 to 2008, were geocoded to point locations according to 2006 Canadian Census data. The data were analysed using a log-Gaussian Cox Process, where the intensity of age-adjusted cancer cases was modelled as a log-linear combination of the population at risk, explanatory variables (race, immigration, and median household income), and a residual spatially varying random effect. For each respective malignancy, statistical models were fit to make quantify the relationship between cancer incidence and explanatory variables.

Results: We included 2230 women with TC and 2412 with LC. The distribution of TC and LC cases contrasted inversely among Toronto neighbourhoods with the highest TC incidence in the Northeast and the highest LC incidence in the Southeast. A higher proportion of Asian ethnicity was associated with higher regional risk of TC and lower risk of LC. A higher proportion of recent immigrants was associated with increased LC and lower TC risk, whereas median household income and proportions of African ethnicity were not significantly associated with risk of either cancer, after adjustment for other socio-demographic variables.

Conclusions: We observed contrasting regional distributions of female TC and LC cases in Toronto. The differences were partly attributed to ethnic composition variability and the proportion of recent immigrants, but substantial unexplained residual variation of incidence patterns of these malignancies exists, suggesting that more individual-level research is needed to explain the regional variability of incidence of these malignancies.

No MeSH data available.


Related in: MedlinePlus