Participants
Between December 2009 and October 2010, 144 women (out of a total of 160 who were eligible) being cared for by multidisciplinary breast teams in Cardiff, Sheffield and Newcastle upon Tyne in the UK, were invited to take part in the study. Seventy women consented, of whom 62 (88.6%) participated in the study before surgery, in accordance with the protocol; 48 of these women accessed the questionnaire after accessing BresDex and before their surgery (all women included in the current study accessed BresDex). The mean age of these 48 women was 53.15 years (range 29–80), with less than half (47.9%) educated to college level or higher. Seventy-five per cent (n=36) of the women opted for BCS; there was no statistically significant difference in age between those who opted for BCS (mean = 52.92 years) compared with those who opted for mastectomy (mean = 54 years). The number of days between receiving their diagnosis at the results clinic and having surgery ranged from 2 to 56 days (median = 21 days).
Main outcome measures
Views about the surgical options were assessed using items designed to measure constructs in the extended TPB. One item directly assessed intentions to opt for BCS; a second item assessed intentions to opt for mastectomy. Participants responded to these items on a 7-point scale ranging from −3 (I definitely do not intend to choose a lumpectomy/mastectomy) to +3 (I definitely do intend to choose a lumpectomy/mastectomy). Responses to these items were significantly negatively correlated (r = −.785, p < .01). Differential scores were calculated by subtracting intentions for mastectomy from intentions for BCS. Scores could range from −6 to +6; higher negative scores reflect increasing intentions to opt for mastectomy, while higher positive scores reflect increasing intentions to opt for BCS.
‘Direct’ measures of attitudes to opting for BCS and opting for mastectomy were calculated by averaging responses to the items stating
For me, choosing BCS/mastectomy would be … harmful/beneficial, wrong/right. Responses to these items were measured on 7-point scales ranging from −3 (harmful/wrong) to +3 (beneficial/right). Thus the higher the score, the more positive were attitudes towards the surgery option in question. There was a significant negative correlation between the BCS and mastectomy direct attitude scores (
r = −.582,
p < .001). A differential attitudes measure was calculated by subtracting the mastectomy direct attitudes score from the BCS direct attitudes score [
35].
a The higher the resulting score, the more positive were women’s attitudes towards BCS.
Behavioural beliefs about each surgery option were assessed by asking participants to rate five statements (e.g., Having a lumpectomy/mastectomy would be disfiguring) for each surgical option on 7-point scales with endpoints labelled ‘extremely unlikely’ and ‘extremely likely.’ Outcome evaluations were assessed using four itemsb corresponding to the behavioural belief statements (e.g., Having an altered appearance after surgery would be…), to which participants responded on a 7-point scale with the endpoints labelled ‘extremely undesirable’ and ‘extremely desirable.’
To compute an indirect measure of attitudes to BCS and mastectomy, behavioural belief scores were multiplied by the corresponding outcome evaluation scores. Reliability analyses were carried out on the computed variables. For the BCS attitudes scale one item was deleted to achieve a Cronbach’s alpha of .623. The remaining items were averaged to calculate a BCS attitudes scale score. For the mastectomy attitudes scale one item was deleted to achieve a Cronbach’s alpha of .663. The remaining items were averaged to calculate a mastectomy attitudes scale score.
The belief-based attitudes scales were then correlated with their direct attitude counterparts. The belief-based BCS attitudes score was positively, albeit not significantly, correlated with its direct attitude counterpart (r = .248, p =.097). The belief-based mastectomy attitudes score was significantly positively correlated with its direct attitude counterpart (r = .373, p < .05).
Subjective norms were measured by six items, three for each type of surgery. Each participant was asked to rate whether three salient referents (her closest friends, her partner/spouse, her breast surgeon) felt that she should choose to have BCS or mastectomy. Responses were made on 7-point scales with endpoints labelled ‘definitely should not’ and ‘definitely should.’ There was good internal consistency among the items relating to both BCS (α = .712) and mastectomy (α = .749). BCS subjective norms and mastectomy subjective norms were calculated by averaging scores on the relevant items. A subjective norms differential score was then calculated by subtracting the mastectomy subjective norm score from its BCS counterpart. The higher the score on the resulting differential measure, the stronger were women’s subjective norms in favour of BCS.
Two further items measured descriptive norms by asking participants to indicate on a 7-point scale the extent to which they agreed or disagreed with the statement ‘Most women who find themselves in my situation would choose to have a lumpectomy/mastectomy’. Scores on the two items were strongly correlated (r = −.451, p < .01). A differential descriptive norms score was calculated by subtracting the mastectomy score from the BCS score. The higher the resulting score, the stronger was the descriptive norm in favour of BCS.
Participants’ perceived behavioural control (PBC) relating to the decision about which surgery to choose was assessed by two items (e.g., Which treatment to have is mostly up to me). Responses were measured on 7-point scales ranging from −3 (strongly disagree) to +3 (strongly agree). Scores on the two items were strongly correlated (r = .652, p < .001) and were averaged to form an index of PBC. The higher the score, the greater the control participants felt they had over choosing their surgery.
Anticipated regret was assessed by asking participants to imagine (in turn) that they had chosen BCS or mastectomy. They were then asked to rate on a 7-point scale the degree to which they thought they would feel anxious, relieved, regretful and confident (endpoints labelled ‘not at all’ and ‘extremely’). These four items were averaged to calculate anticipated regret (BCS α = .744; mastectomy α = .668) by averaging scores on the relevant items. A differential anticipated regret score was calculated by subtracting the mastectomy score from the BCS score. Higher scores on the resulting measure reflect greater anticipated regret in relation to BCS.
Objective data were collected on participants’ choice of surgery; the clinical breast teams notified the research team of the type of surgery participants went on to have (i.e., either mastectomy or BCS).
Analysis
Hierarchical multiple regression analysis was used to examine the utility of the extended TPB in predicting participants’ surgery intentions. The basic TPB constructs (attitudes, subjective norms, PBC) were entered at step 1. At step 2 the extended TPB constructs (descriptive norms, anticipated regret) were added. Logistic regression was used to examine the utility of the TPB in predicting participants’ surgery choices. Here intentions and PBC were entered in block 1; attitudes, subjective norms, descriptive norms and anticipated regret were entered in block 2c.
T-tests were used to examine differences at the item or construct level between women who opted for BCS and those who opted for mastectomy; we report the results based on equal variances not assumed where Levene’s test for equality of variances was found to be statistically significant.