Follow-up questionnaire
We planned to send a follow-up questionnaire to all subjects who had completed 5 years in the study. The purpose of this was to update risk factor information, in particular family history, and to check on the reliability of the data by estimating agreement/disagreement rates between the first and second enquiry. For example, although parity and number of affected relatives might both increase over the period of the study, they cannot decrease. The approval of clinical staff managing the subject's surveillance was sought before sending the questionnaire. The items of information in the questionnaire were as follows:
ever in employment (yes/no)
educational level attained
weight and height
parity
breastfeeding
menopausal status/age at menopause
HRT use
tamoxifen use
update to family history (relatives diagnosed with breast cancer since recruitment).
Results
So far, 5462 follow-up questionnaires have been sent out and 2760 (51%) returned. Data have been entered and successfully linked with FH01 baseline data for 2705 (98%) of these. shows the distributions of risk factors reported in the follow-up questionnaire. Understandably, the proportion of postmenopausal subjects is higher in the follow-up survey than at baseline, and the parity distributions are similar (see Chapter 3, Table 2). Substantial numbers reported a relative diagnosed with cancer since their initial family history was taken at recruitment, 13% reporting a diagnosis in their mothers and 9% in their sisters.
Risk factor distributions from the follow-up questionnaire
shows the individual baseline responses tabulated against the follow-up responses for the binary variables menopausal status and HRT use. gives the baseline responses for parity cross-tabulated with the corresponding follow-up responses. For menopausal status, the agreement rate was 80%. It is plausible that the 402 subjects whose status was premenopausal at baseline and postmenopausal at follow-up did indeed change their status during the study. The eight subjects (< 1%) who reported being postmenopausal at baseline but premenopausal at follow-up suggest a small element of response error at one or both occasions. Results for HRT use suggest a similarly small error rate.
Baseline responses vs follow-up responses for binary factors
Parity reported at baseline vs parity reported at follow-up
For parity, there was 89% agreement and the small numbers with lower parity reported at follow-up than at baseline (115 subjects, 5%) suggest a small degree of response error for this factor.
The family history factors are rather more difficult to interpret. For maternal breast cancer, 13% report a diagnosis since their original family history was taken at recruitment. For sisters, the figure is 9%. shows the original baseline response tabulated against the report of new diagnoses in the follow-up questionnaire. The vast majority of those reporting a new diagnosis in mother or sister already had such a report at baseline, on average 5–6 years before. Although some of the reports may pertain to recurrences or new primaries in the same relative, or to cancer in different sisters, it is likely that the reports refer to the original cancer in the affected relative. The subjects were posted the questionnaire and did not have their baseline responses to hand when completing it. There has been at least one study where a postal questionnaire was considered adequate for taking a family history of colorectal cancer.76 However, another study investigating personal history of all cancers found rather poor sensitivity of a postal questionnaire.77 The results here suggest that if a family history is to be updated without a face-to-face interview, then it would be reasonable simply to request the entire family history again, rather than ask the individual to qualify the reported history with respect to previous responses.
Baseline status of mother or sister with breast cancer tabulated against follow-up reporting
