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  • br Methods br Patient selection and data collection

    2022-07-25


    2. Methods
    2.1. Patient selection and data collection
    The registry data are from both patients who give consent (C) and those who did not give consent (NC) within the period 2000-2012. Eligible patients are defined by registry criteria applied at that time:
    • no breast cancer history before 1st of June 2000; • diagnosed with invasive carcinoma or ductal carcinoma in situ (DCIS) but not lobular carcinoma in situ (LCIS) alone;
    • Auckland region resident at first surgery, or Auckland region re-sident who had first surgery outside Auckland and came back to Auckland for adjuvant treatment; • New Zealand permanent resident (including Cook Island resident) at the time of diagnosis.
    The registry collates information on baseline, treatment and follow-up data, including data on diagnosis and treatment of local/regional recurrence and metastatic disease, from both the public and private health care facilities to which registry data managers have been given access. These systems include all public hospitals, private hospitals and all private practitioners known to be treating breast cancer patients within the Auckland region. Mortality data is obtained by regular MK0683 by the Ministry of Health between the study database and na-tional mortality records using the patient’s unique National Health 
    2.2. Statistical analysis
    Consented and NC groups were compared using Kaplan Meier sur-vival analysis, chi square and log-rank tests [3]. Direct standardisation used the whole patient group as the standard population, with con-fidence limits [4]. Stata statistical software (version 13) was used for the statistical analysis [5]. A sensitivity analysis, of survival left-cen-sored at 90 days after diagnosis, thus excluding patients with less than 90 days follow-up, was done to assess the effects of bias arising from completion of the consent process being delayed up to 90 days post-diagnosis.
    3. Results
    3.1. Invasive cancer: survival by consent status
    3.2. Overall survival comparing the overall cohort and consented group (invasive)
    The overall survival rates for all patients are consistently lower than those of the subgroup who give active consent (Table 1), the differences at 2, 5 and 10 years respectively being 1.6, 2.4, and 2.4%. The survival rates based on all patients lie below the 95% confidence limits for the rates based only on the consented patients.
    Fig. 1. Invasive cancer: disease-specific survival of consented and non-consented patients, with 95% confidence bands. Logrank statistic chisq 400.1, p < 0.0001.
    Table 2
    Proportions of patients not consented, by age and ethnicity.
    Consented Non- % non 95% CL
    consented consented
    Age and ethnicity mutually standardised by direct method.
    Subjects with missing data on ethnicity excluded (6.0% of consented, 5.8% of non-consented).
    3.3. Features of consented and non-consented patients
    The group of non-consented patients with invasive cancer differs from the consented group in demographic features, disease character-istics, treatment, and survival. For demographic factors, age and eth-nicity are correlated. The proportions not consented increased regularly with age; after adjustment for ethnicity, from 8.4% at ages < = 49 to 26.5% at ages 80 and over, the differences being significant (Table 2). By ethnicity, adjusted for age, and compared to NZ European women (9.9% non-consented), the non-consented proportions was similar in Maori (9.8%), but significantly higher in Pacific women (14.4%). Asian women and those of ‘other’ ethnicities had non-significantly higher proportions than NZ Europeans. Omitting missing data, non-consented patients had features asso-ciated with a poorer prognosis (Table 3); they were more often clini-cally rather than screen detected, and 13% had metastatic disease compared with 3% of consented patients. Non-consented patients more often had no primary surgery (26.2% compared with 4.0% of consented patients), and less frequently had chemotherapy, radiotherapy, hor-monal therapy, or biological therapy (all p < 0.001), in part because more non-consented patients declined these treatments. They had more often positive tumour margins (p = 0.05). However, they did not differ by tumour size, histological type, or hormone receptor status, and