Cancer clusters are defined by the Centers for Disease Control and Prevention (2013) or CDC as “greater-than-expected number of cancer cases that occurs within a group of people in a geographic area over a period of time.” In order to determine if cancer clusters exist in a particular area, it would be useful for epidemiologists to first survey the usual occurrence of cancer in such an area. If the numbers are unusually higher than what is expected, the area may be considered as a cancer cluster.

The Centers for Disease Control and Prevention (2013) recommends a four-step approach to determine suspected cancer clusters. The first step involves initial contact and response. The second step includes an assessment as well as the calculation of the SIR or the standardized incidence ratio. The third step is to determine the feasibility of conducting an epidemiologic study. Once this has been considered, the surveyor can then proceed to assessing the association between cancers and environmental causes by conducting an epidemiologic study. Additionally, to know whether the prevalence rate of cancer may be confirmed as a cancer cluster, the current data must be cross-checked with previous data for unusual difference in incidence rate.

Some additional information may also be required in order to conclude the occurrence of a cancer cluster. According to the CDC (2013), besides the unexpected number of observed cases, the cancer must be of the same type and scientifically proven to be of the same cause. Also, it must occur within a specific group of people “carefully defined by factors such as race/ethnicity, age, and gender, for purposes of calculating cancer rates” (CDC, 2013). Moreover, a cancer cluster may be confirmed if it happened within a specific area and over a specified period of time (CDC, 2013).

In the case of the ABC investigation on breast cancer cases within their company, the specific group affected was the female population. There were 10 women who acquired breast cancer out of the 550 women who were employed in the same company and area at the time. To calculate the ratio between the occurrences of breast cancer against the total number of affected group (females), we divide 10 by 550. This results to 1 out of 55 women having breast cancer or 18 per 1000 occurrences of breast cancer in ABC as shown below:

Figure 1A. Formula for Incidence rate

Figure 1B. Calculation for Incidence rate

As an epidemiologist, developing a surveillance system for chronic diseases at a national level would necessitate the use of strategies prescribed by the World Health Organization. The World Health Organization or WHO has a predefined approach called STEPS and describes such an approach as the following:

“The WHO STEPwise approach to Surveillance (STEPS) of NCDs is based on sequential levels ofsurveillance of different aspects of noncommunicable diseases, allowing flexibility and integration ateach step by maintaining standardized questionnaires and protocols to ensure comparability over timeand across locations.”

(WHO, 2003)

Assuming that 6 years would be spent in completing the project, with 2 years for each a step, an outline of the plan for a surveillance system for chronic diseases is presented in a table below:

STEP 1:           Questionnaires

• Includes demography (i.e. age, sex, education, rural/ urban)
• Nutrition (i.e. dietary patterns, oil used for cooking)
• Physical activities (minutes of activity)
• Others (i.e. risk factors to cancer: radiation, carcinogens, etc.)

STEP 2:           Physical measurements

• Physical exam (i.e. changes in physical appearance, pain, alopecia)
• Weight (i.e. gain or loss)

STEP 3:           Biochemical measurements

• Complete Blood Count (CBC)
• Biopsy for individuals with tumors

In addition to the STEPS provided by the World Health Organization, the National Cancer Institute also created the Surveillance, Epidemiology, and End Results Program. In this program, various data are consolidated in order to form a database of cancer cases that can also be accessed online. The Surveillance, Epidemiology, and End Results Program disseminates data through the following figure:

Case Study on Serum Ferritin and Cardiovascular Disease

The following answers are based on the case study on Serum Ferritin and Cardiovascular Disease by Knuiman et. al. (2003):

1. How many years were followed up a person who had an incident stroke the 15 of July 1990 and died the 31 of December 1992? (1 mark)

The number of years of follow up for a person who had an incident stroke the 15th of July 1990 and died the 31st of December 1992 was 17 years.

1. How many years were followed up a person that only reported arthritis on the 30 of August 2000? (1 mark)

For persons who only reported arthritis on the 30 of August 2000, the number of years for follow up was 4 years.

1. What it is the advantage of using “case-cohort sampling”? When it should be used? (2 marks)

The advantages of using “case-cohort sampling” was that it reduced costs and preserved stored serum (Knulman et. al., 2003)

1. “The target population was all adults on the electoral roll (registration to vote is compulsory in Australia) in the Shire of Busselton; the overall response rate for the 1981 survey was 64 percent.” Discuss implications for internal validity (1 mark).

The implication for internal validity is that, in causal relationships, it is able to approximate truths about a particular inference, in this case, the cause and effect of serum ferritin on cardiovascular diseases. The internal validity is applicable only for causal relationships.

1. “A viable blood serum sample was available for about 75 percent of the eligible disease-free cohort.” Discuss what authors did to avoid potential bias because of this(2 marks)

To avoid potential bias because of this, the researchers used a total number of assayed sera samples of 626.

1. What was the statistical rationale to select a random subset of 450 individuals (2 marks)

The statistical rational in selecting a random subset of 450 individuals was that “provided the study with 89 percent power to detect a hazard ratio of 1.3 for CHD for a one standard deviation change in a continuous risk factor” (Knulman et. al., 2003).

10. If each measurement of ferritin cost UD$10. How much money would be saved in this study, compared to a typical prospective cohort study? (1 mark)

If each measurement of ferritin cost $10, the money that would be saved in this study compared to a typical prospective cohort study would be more than 50%.

.

References

Centers for Disease Control and Prevention (2013). Cancer Clusters. [Online] Retrieved

from: <http://www.cdc.gov/NCEH/clusters/default.htm>

Centers for Disease Control and Prevention (2013). Investigating Suspected Cancer Clusters

and Responding to Community Concerns: Guidelines from CDC and the Council of

State and Territorial Epidemiologists [Online]. Retrieved from:

<http://www.cdc.gov/mmwr/preview/mmwrhtml/rr6208a1.htm>

Knuiman, M.W., Divitini, M.L., Olynk, J.K., Cullen, D.J., and Bartholomew, H.C. (2003).

Serum Ferritin and Cardiovascular Disease: A 17-Year Follow-up Study in Busselton,

Western Australia. American Journal of Epidemiology, 158(2), 144-149.

National Cancer Institue (2012). SEERS [Online]. Retrieved from:

<http://seer.cancer.gov/about/factsheets/SEER_brochure.pdf>

World Health Organization (2003). STEPS: A framework forsurveillance.

Noncommunicable Diseases and Mental Health [Online]. Retrieved from:

<http://www.who.int/ncd_surveillance/en/steps_framework_dec03.pdf>

Do you need an Original High Quality Academic Custom Essay?