Cancer Question Answer Sample Assignment

Question 1

Of 2,872 persons who had received radiation treatment in childhood because of an enlarged thymus, cancer of the thyroid developed in 24 and a benign tumor developed in 52. A comparison group consisted of 5,055 children who had received no such treatment (brothers and sisters of the children who had received radiation treatment). During the follow-up period, none of the comparison group developed thyroid cancer, but benign thyroid tumors developed in 6. Calculate the relative risk for benign thyroid tumors.

Correct Answer:

The correct answer is 15.2. Children who were exposed to radiation treatment due to enlarged thymus were 15.2 times more likely to develop benign thyroid tumors.

Relative risk = incidence rate of benign tumors in the group exposed to radiation treatment/incidence rate of benign tumor among children non exposed to radiation treatment

Incidence rate among exposed = 52 benign tumors/2,872 persons exposed = 0.01811

Incidence rate among the non exposed = 6 benign tumors/5,055 persons non-exposed =0.00119

Relative risk = 0.018/0.0011 = 15.2

Question 2

In a small pilot study, 12 women with uterine cancer and 12 with no apparent disease were contacted and asked whether they had ever used estrogen. Each woman with cancer was matched by age, race , weight, and parity to a woman without disease. The results are shown below:

Pair no.

Women with Uterine Cancer

Women without Uterine Cancer

1

2

3

4

5

6

7

8

9

10

11

12

Estrogen user

Estrogen nonuser

Estrogen user

Estrogen user

Estrogen user

Estrogen nonuser

Estrogen user

Estrogen user

Estrogen nonuser

Estrogen nonuser

Estrogen user

Estrogen user

Estrogen nonuser

Estrogen nonuser

Estrogen user

Estrogen user

Estrogen nonuser

Estrogen nonuser

Estrogen nonuser

Estrogen nonuser

Estrogen user

Estrogen user

Estrogen nonuser

Estrogen nonuser

What is the estimated relative risk of cancer when analyzing this study as a matched-pairs study?

Correct Answer: 3.00

Response Feedback:

Estimated relative risk is the term used for odds ratio

a, pairs (both were exposed) =2

b, pairs (case exposed, control not exposed) = 6

c, pairs (case not exposed, control exposed) = 2

d, pairs (both non exposed) = 2

Create the following 2 x 2 table

PAIRS

Control

Exposed

Not exposed

Case

Exposed

(a) 2

(b) 6

Not exposed

(c) 2

(d) 2

Odds ratio (matched pairs) = b/c = 6/2= 3.0

Women with uterine cancer were 3 times more likely to have been used estrogen than the women without uterine cancer.

Question 3

In a small pilot study, 12 women with uterine cancer and 12 with no apparent disease were contacted and asked whether they had ever used estrogen. Each woman with cancer was matched by age, race , weight, and parity to a woman without disease. The results are shown below:

Pair no.

Women with Uterine Cancer

Women without Uterine Cancer

1

2

3

4

5

6

7

8

9

10

11

12

Estrogen user

Estrogen nonuser

Estrogen user

Estrogen user

Estrogen user

Estrogen nonuser

Estrogen user

Estrogen user

Estrogen nonuser

Estrogen nonuser

Estrogen user

Estrogen user

Estrogen nonuser

Estrogen nonuser

Estrogen user

Estrogen user

Estrogen nonuser

Estrogen nonuser

Estrogen nonuser

Estrogen nonuser

Estrogen user

Estrogen user

Estrogen nonuser

Estrogen nonuser

Unmatch the pairs. What is the estimated relative risk of cancer when analyzing this study as an unmatched study design?

Correct Answer: 4.00

Response Feedback:

Estimated relative risk is the term used for odds ratio

Create the following 2 x 2 table

Control

Exposed

Not exposed

Case

Exposed

(a) 8

(b) 4

Not exposed

(c) 4

(d) 8

These numbers are derived by counting the number of estrogen users and non users in each column.

Odds Ratio = ad/bc =( 8x8)/(4x4) = 64/16=4.0

Question 4

In a study of a disease in which all cases that developed were ascertained, if the relative risk for the association between a factor and the disease is equal to or less than 1.0, then:

Correct Answer: There is either no association or a negative association between the factor and the disease

Question 5

Talbot and colleagues carried out a study of sudden unexpected death in women. Data on smoking history are shown in the following table.

Smoking History for Cases as ASHD sudden Death and Controls (Current Smoker, 1+ Pack/Day) (Matched Pairs), Allegheny County, 1980

Cases

Controls

Smoking 1+ Pack/Day

Smoking <1 Pack/Day

Total

Smoking 1+ Pack/Day

Smoking < 1 Pack/Day

Total

2

8

10

36

34

70

38

42

80

Calculate the matched-pairs odds ratio for these data.

Correct Answer:

The correct answer is 4.5 See page 224-225.

Odds ratio for matched pair = b/c = 36/8 = 4.5

Question 6

Talbot and colleagues carried out a study of sudden unexpected death in women. Data on smoking history are shown in the following table.

Smoking History for Cases as ASHD sudden Death and Controls (Current Smoker, 1+ Pack/Day) (Matched Pairs), Allegheny County, 1980

Cases

Controls

Smoking 1+ Pack/Day

Smoking <1 Pack/Day

Total

Smoking 1+ Pack/Day

Smoking < 1 Pack/Day

Total

2

8

10

36

34

70

38

42

80

Using data from the table, unmatch the pairs and calculate an unmatched odds ratio.

Correct Answer:

The correct answer is 6.3 Those who dies suddenly were 6.3 times more likely to have smoked more than one pack a day than those who didn’t die suddenly.

Cell a 2 smokers who died suddenly (cases)and 2 smokers who didn’t die suddenly (controls)

Cell b 36 smokers who died suddenly (cases) and 36 non smokers who didn’t die suddenly (controls)

Cell c 8 nonsmokers who died suddenly (cases) and 8 smokers who did not die suddenly (controls)

Cell d 34 nonsmokers who died suddenly (cases) and 34 nonsmokers who didn’t die suddenly (controls)

Therefore the unmatched 2 x 2 table is as follows:

Smoking History for Cases as ASHD sudden Death and Controls (Current Smoker, 1+ Pack/Day) Allegheny County, 1980

Smoking Status

Sudden Death

YES

NO

Total

Smoking 1+ Pack/Day

Smoking <1 Pack/Day

Total

38

42

80

10

70

80

48

112

160

Odds ratio = ad/bc=(38x70)/(10 x 42) = 2660/420 = 6.3

Question 7

What are the odds that the controls smoke 1+ pack/day?

Correct Answer:

The correct answer is 1:7. You get this from the 2 x 2 table comparing cell b to cell d.

Question 8

Questions 8 and 9 are based on the information given in the table below:

Rates of Atherosclerotic Heart disease (ASHD) per 10,000 population, By Age and Sex, Framingham, Massachusetts

Men

Women

Age at Beginning of Study (yr)

ASHD Rates at Initial Exam

Yearly Follow-up Exams (mean Annual Incidence)

ASHD Rates at Initial Exam

Yearly Follow-up Exams (Mean Annual Incidence)

29-34

35-44

45-54

55-62

76.7

90.7

167.6

505.4

19.4

40.0

106.5

209.1

0.0

17.2

111.1

211.1

0.0

2.1

29.4

117.8

The relative risk for developing ASHD subsequent to entering this study in men compared to women is:

Correct Answer:

Lowest in the oldest age group

Response Feedback:

The correct answer is e.

Relative risk = incidence rate in exposed/ incidence rate among nonexposed

In this case the exposed are the men and the nonexposed are the women

Relative risk =Incidence rate among men/incidence rate among women for each age category

29-34 RR is undefined (cannot divide by 0)

35-44 RR= 40/2.1 = 19

45-54 RR=106.5/29.4 = 3.6

55-62 RR = 209.1/117.8 = 1.8

Question 9

Rates of Atherosclerotic Heart disease (ASHD) per 10,000 population, By Age and Sex, Framingham, Massachusetts

Men

Women

Age at Beginning of Study (yr)

ASHD Rates at Initial Exam

Yearly Follow-up Exams (mean Annual Incidence)

ASHD Rates at Initial Exam

Yearly Follow-up Exams (Mean Annual Incidence)

29-34

35-44

45-54

55-62

76.7

90.7

167.6

505.4

19.4

40.0

106.5

209.1

0.0

17.2

111.1

211.1

0.0

2.1

29.4

117.8

The most likely explanation for the differences in rates of ASHD between the initial examination and the yearly follow-up examinations in men is:

Correct Answer:

The initial examination measures the prevalence of ASHD, whereas the subsequent examinations primarily measure the incidence of