Of 2872 persons who had received radiation treatment in chil

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 thyroid 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: _____

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Solution

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 thyroid 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: _____

Please show calculations

The relative risk or risk ratio is given by

Total

benign thyroid tumor

No tumour

Incidence

Treatment

a

b

a+b

a/(a+b)

control

c

d

c+d

c/(c+d)

Relative risk=

(a/(a+b)) / (c/(c+d))

Total

benign thyroid tumor

No tumor

Incidence

Treatment

52

2,820

2,872

52/2872=0.0181

control

6

5,049

5,055

6/5055=0.0012

Relative Risk = 0.0181/0.0012=15.08