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  • br Statistical power and analysis A description of the stati

    2019-04-26


    Statistical power and analysis A description of the statistical analysis of the study has been published previously [23]. For the analysis of the results at the 5-year time point, comparisons were expressed graphically using 95% confidence intervals. Statistical analysis was performed using SPSS version 19.0.0, 2010.
    Results Between December 2003 and October 2005, 131 postmenopausal, surgically treated breast cancer patients were recruited from oncology clinics in Leeds and Sheffield, UK. A total of 50 recruited patients were identified as having osteopenia at the time of the baseline scan. 68 had normal BMD and 13 had enkephalin prior to starting anastrozole. The CONSORT diagram in Fig. 1 shows the disposition of patients at baseline and their subsequent course on study. The baseline characteristics of the patients recruited to the trial have been previously published [23]. The median age of the study population was 64.8 years and the stratification factors (centre, time from menopause, previous HRT and previous chemotherapy) for the randomised patients were well balanced between the two treatment groups.
    BMD results The BMD changes from baseline for the osteopenic and osteoporotic patients are shown in Fig. 2a–c and Table 1. Osteopenic patients (ibandronate group): Of the 20 patients randomised to ibandronate and evaluable at the 2 year visit, BMD increased in the majority (13/20) with a mean overall increase in LS BMD of +3.19%. In 17/20 patients initially randomised to ibandronate with a mean T-score of −1.11 (range 0.0 to −2.2) at 2 years, study medication was stopped and the patients followed up on anastrozole alone till year 5 because BMD T scores were >−2. The improvements in BMD accrued during the first 2 years were lost at both the LS (−3.21%) and TH (−5.0%). As a consequence, at 5 years, 14 patients had T-scores in the osteopenic range and one had an osteoporotic T-score. Of the three offered an open label bisphosphonate for the remaining 3 years of the study; at the 2 year visit, two of these patients had a T-score of between −2 and −2.5 and in one the T-score was <−2.5. In these three patients, BMD increased in 2 and 1 and fell in 1 and 2 at the LS and TH respectively (Data not shown). Two patients still had a T-score of <−2.5 at LS and/or TH after 5 years of ibandronate. Osteopenic patients (placebo group): The mean change in LS BMD at the 2 year time-point in the 16 patients who were randomised to placebo and who remained on study until the 5 year visit was −4.52%. Eight patients with high rates of bone loss during years 0–2 (LS −7.1%, TH −7.3%) and a BMD result at 2 years showing either severe osteopenia (T-score <−2.0 to −2.5; n=5) or osteoporosis (t-score <−2.5; n=3) went on to receive open label ibandronate in years 2–5 alongside continued anastrazole, while 8 with less marked bone loss (LS −1.0%, TH −0.5%) were observed on anastrazole alone. Osteoporotic patients: Nine of the 13 patients initially identified as having osteoporosis were assessed at the 5 year visit. These patients showed steady increases in BMD through the 5 years of the study. Mean changes in BMD at the LS were +3.03% and +9.65% after 2 and 5 years respectively. At the TH BMD improved by +3.18% after 2 years and stabilised at +2.72% after 5 years. After 5 years only 2 out of the 9 patients remaining on study still had a T score of <−2.5. Fig. 3 shows the changes in BMD grouping for the 50 patients with osteopenia through the 5 years of the study. The number of patients with osteoporosis at either the LS or TH increased from 0 to 4 to 7 at the baseline, 2 year and 5 year endpoints respectively. Six out of the 11 patients (54%) who were offered ibandronate from 2–5 years developed or still had osteoporosis at 5 years.
    Study withdrawals From 2 to 5 years on study, one patient out of the 21 patients who were initially randomised to ibandronate withdrew from the study (patient choice). After 2 years, 19 patients who were randomised to placebo remained on study. Of these 3 patients came off study prior to the 5 year visit (patient choice n=1, death n=1, investigator recommendation n=1). 2 osteoporotic patients came off study following the 2 year visit (investigator recommendation n=2). Three patients withdrew from the study following their 2 year visit due following a recommendation from the treating clinician. In each of these 3 cases the treatment was discontinued because of problems related to the anastrozole rather than any changes in BMD.