Question

Researchers were interested in assessing the relationship between obesity and breast cancer recurrence and fatality in postmenopausal African-American and Caucasian women with primary breast cancer. Data was collected on women with primary breast cancer and included the following variables:

Age

Age at diagnosis of breast cancer

Weight

Height

Data of diagnosis of breast cancer

Menopausal status

Diagnosis and coding of tumor (histopathology and topography)

Stage of tumor

Size of tumor

Number of positive lymph nodes

Estrogen receptor analysis

Progesterone receptor analysis

Site of distant metastasis

First course of treatment (surgery, radiation, chemotherapy)

Additional treatment

Five-year recurrence and survival rates

Recurrence and survival status were determined by reviewing the cancer registry follow-up data and medical record information across the multiple healthcare sites involved in this study. The cancer registries were accredited by the American College of Surgeons and used active follow-up on all cancer patients. Postmenopausal status was determined as subjects older than 55 years. In those subjects younger than age 55, determination was made by consulting the cancer registry data, the medical record, and physician’s office records. Premenopausal patients and patients whose menopausal status could not be determined from the data were excluded from the study. Body mass index (BMI) was based on height and weight collected from the medical record or cancer registry at the date of diagnosis only. Values greater than 27 were considered to indicate obesity. The effect of weight changes during the follow-up period was not evaluated.

 QUESTIONS:

1. What type of study design is this? If it was found that obesity and breast cancer recurrence were related what type of study could be conducted to test whether changes in diet may make a difference in the recurrence of breast cancer in women who have had primary breast cancer?

 

2. Why is it important to collect the other variables when studying the relationship between obesity and breast cancer recurrence?

 

3. This study did not examine pre-menopausal women. It did not look at other races besides African American and Caucasian women. Is this a limitation? Why or why not?

 

Answer 1

1) The study design is retrospective cohort study. In order to find if there is any relation between changes in diet makes a difference in the recurrence of breast cancer prospective cohort study can be conducted.

2) Confounding variables such as alcohol use, smoking, number of children, breastfeeding, physical activity etc. may be associated with both obesity and breast cancer. So, it is important to collect other variables also.

3) Excluding pre menopausal women and women belonging to other races will decrease the accuracy and validity of the study. So, this is considered as a limitation for this study.