My talk will focus on cancer incidence rates in Lambton County, - PDF document

• My talk will focus on cancer incidence rates in Lambton County, incidence being the number of new cases of a disease diagnosed in a given population within a specified time frame. • This analysis has been conducted as part of our public health mandate to monitor the health status of the population, but it is also seeks to answer some of the questions raised by the Lambton Community Health Study Board and by community members. • This word cloud is based on a survey conducted as part of the Lambton Community Health Study public consultation phase in 2010. We asked residents how they think pollution from local industry affects the health of Lambton residents. And it is clear that cancer is a top concern. 1

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What I find is that this is a disease that evokes a lot of emotion, that most have been affected by this disease, whether it is a family member, friend or co-worker The fact is that it likely will affect us all… 2 out of 5 Canadians are expected to develop cancer in their lifetime 1 out of 4 are expected to die from it 3

There is clearly a perception that it does in this community. And while there is a relatively small proportion of the population who actively voice their concerns, I think there are many others who think that there is a higher risk of developing cancer here and either accept it or don’t think there is anything we can do about it. So, answering this question of whether it affects us more is really important. 4

• After the Lambton Community Health Study Board conducted a literature review and public consultation activities in 2010, several research questions were identified, including these three questions related to cancer … • Analyses related to the first two questions are hypothesis generating studies that may reveal important research questions to be pursued further. So, the data presented here today cannot determine why people get cancer in Lambton, but answers the first simple, but important question of whether we differ from other areas of the province. • While I haven’t included it in this presentation, the second question is being addressed by a team of researchers I’ve been working with at Cancer Care Ontario and U of T. • The first several slides will show data for all cancers combined to give a general overview. Since there are more than 100 types of cancer, I will then go on to highlight the most common sites and those where our rates deviate from the provincial average. 5

• All the data shown here are taken from the Ontario Cancer Registry (distributed to health units through Cancer Care Ontario). We receive this data at the public health unit level. The most recent release includes data up to 2009. • Significant lag time to get new data, as it is a very labour intensive process. • It is a passive registration system, meaning no one is legally required to report each case to a coordinating body. The registry is reliant on administrative records from hospitals, regional cancer centres, pathology reports and death certificates. Records for each case are linked together to create the final registry or listing of Ontario cancer cases. • Finally, data within the cancer registry is based on place of residence at time of diagnosis, not on the location where treatment or care is received. 6

First we can look at the number of cases. This is useful for illustrating the burden of disease on the health care system. Certainly if you are thinking about service provision you want to know how many people you need to serve. 7

• Number of cases in Lambton County has increased from 564 in 1989 to 840 in 2009. 8

• Similarly, the number of cases has increased in the past 20 years in Ontario. • Why might there be an increase? Why is the increase larger in Ontario vs. Lambton? 9

• Virtually no growth in Lambton; nearly 30% increase in Ontario. More people=more cases of cancer. • So, we know that the number of cases has increased in both Lambton and Ontario. We can guess that the increase in total population accounts for some of this increase in Ontario, but not Lambton. But, that is all we know and we cannot directly compare the two populations because they are different sizes. 10

We can compare two populations by simply dividing the number of cases by the total population. 11

• We can now show Lambton and Ontario on the same graph and see that the crude rate has been higher in Lambton vs. Ontario over the last 20 years. • After accounting for the increase in Ontario's population, the percent increase is 33% vs. 71%. Similar to the number of cases, Lambton's rate increased by 49%. • However, there is a problem if the two populations are different with respect to factors that are related to the outcome of interest. When talking about most health outcomes, including cancer, the outcome is strongly related to age. If you have an older population, you will have higher cancer rates than a younger population. So, you need to account for this. 12

You can calculate separate rates for each age and/or sex specific group. 13

• Here are age and sex-specific rates for males for the 10 year period, 2000-2009 combined. • Age-specific rates among males under 55 are very similar in Lambton and Ontario. Rates are higher in Lambton males over 55 compared to the province. 14

• Age-specific rates in Lambton females are similar to those in Ontario for most age categories, but the rate does appear slightly higher in the 65-74 year age category. • Age-specific rates can be very informative, but it is still difficult to make a direct comparison between populations due to the number of different categories and rates. 15

Standardized or adjusted rates can help us to make these comparisons. We force two populations to look the same with respect to age and produce estimates that can be compared. 16

• By adjusting for age we have accounted for the fact that the population is aging in both Lambton and Ontario and also the fact that Lambton's population is older than Ontario's. The percent increase over time is smaller and similar in Lambton and Ontario and Lambton's rates are closer to Ontario's. 17

• Sometimes we like to go beyond comparing Lambton to the provincial average. The provincial average is influenced by rates in the GTA and larger cities, where population characteristics can be very different. For many chronic diseases, including most types of cancer, health units in the GTA have the lowest rates in the province. • Here is a map based on the most recent three year period, 2007-09. It shows health units that have incidence rates of all cancers that are lower, similar to or higher than the provincial average. • Health units that are higher than the provincial average are in Southern, Central and Northern Ontario. 18

• Each bar represents one of Ontario’s 36 health units; green line represents the provincial average; error bars represent 95% confidence intervals – if these cross the provincial average we can generally conclude that there is no significant difference between that health unit and the provincial average. • Lambton ranks 11/36 health units with respect to age-standardized incidence of all cancers for the most recent three year period (2007-09). 19

• Top three in males account for 58% of all cases (Total cases=468) • Top three in females account for 50% of all cases (Total cases=372) 20

• Standardized rate ratios allow us to compare Lambton rates to Ontario rates for a number of cancer sites. • The standardized rate ratio tells us if the rate in Lambton is higher or lower than the rate in Ontario. • If the SRR is higher than 1, the rate is higher in Lambton vs. Ontario. If it is lower than 1, it is lower. If the 95% confidence interval (vertical line) does not cross 1, we say the difference is statistically significant. • For males: All cancers (9%), colorectal (14%), lung (16%) and prostate (8%) are slightly but significantly elevated. Melanoma is about 1.7 times or 70% higher than Ontario. Mesothelioma is over 5 times higher. • There are significantly fewer cases of liver cancer in Lambton County males as compared to Ontario. 21

• For females, all sites (4%) and lung (23%) are slightly, but significantly higher than Ontario. Mesothelioma is 3.3x higher among Lambton females, cancer of the larynx is 2 time higher and melanoma (skin) is 1.6 or 63% higher than the Ontario average. Notice the large confidence intervals on larynx and mesothelioma. This is a reflection of the small number of cases, even during a ten year period (17 larynx, 11 mesothelioma cases). • There are significantly fewer cases of stomach and thyroid cancers in Lambton County females compared to Ontario. 22

• Based on the 10 year period, 2000-2009: • Rates are significantly elevated for: melanoma (males & females) mesothelioma (males & females) larynx (females) • Rates are slightly but significantly elevated for: lung (males & females) colorectal (males) prostate • Rates are significantly lower for: liver (males) stomach (females) thyroid (females) 23