br New Zealand like many other
New Zealand like many other countries has a national Cancer Registry, which is based on clinical and pathological data for all pa-tients diagnosed with a first invasive cancer. Such registration is routine and legally protected and there is no requirement for consent. As a result the registry can be complete and can give good information on cancer incidence, and by PSB 1115 with mortality data, on survival. Cancer Epidemiology 58 (2019) 178–183
However like many large-scale registries the data is extremely limited; for example, little information is collected on extent of disease or stage, treatment, or outcomes such as recurrence. Thus such data is useful background but is inadequate to address many current aspects of cancer management. Clinical registries such as the one described here provide greater detail, and can be operated in conjunction with routine medical records at little additional cost. To be most valuable, such registries need to be population-based and complete, and also need to be linked to other registries, national registries, and to mortality and other hospital data. To operate them efficiently can easily be blocked by inappropriate management or ethical committee decisions.
A registry which uses only the clinical and pathological information already collected and recorded on patients and kept in various places within hospital records should require no explicit consent to gather that data in one place where it can be usefully used for the benefit of all patients. Such is indeed the argument for the existence of national cancer registries without any consent requirement. Any further study requiring access to patients, or further requirements of the patients such as the use of tissues, would require consent and ethical review. r> 5. Conclusions
Data restricted to patients who give active consent to be included in the patient registry produced a bias in survival results, as the con-senting patients are a biased subgroup. In this study, the bias resulted in excluding a group of patients with low survival, and demographic and clinical differences related to this decreased survival. The overall sur-vival rates for invasive cancer up to 10-years are about 2% over-estimated if based only on consented patients; while a small difference, Divergent transcription means that survival rates based on all patients are below the 95% lower confidence limits based only on consented patients.. Analyses of clinical and pathological characteristics using only consented patients will also give misleading results. Clinical registries should aim to in-clude all patients, and opt-off consent systems may be appropriate.
Conflicts of interest
The authors declare no conflicts of interest.
This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.
Availability of data and materials
The datasets used in this study contain personal information and are not publicly available, but may be requested from the Auckland Breast Cancer Registry, subject to ethical approvals.
VH, MB, and RM developed the concept, and ME, ST, RM and MB analysed the data. All authors contributed to the interpretation of the data and to drafts of the report, and reviewed and approved the sub-mission.
We thank the New Zealand Breast Cancer Foundation and the Auckland Breast Cancer Registry for their support of these patient re-gistries. We thank all patients who contributed their data, the staff of the registries, and the Ministry of Health (New Zealand) for facilitating data linkages.
 Auckland District Health Board (ADHB). Auckland Breast Cancer Register, Auckland District Health Board (ADHB, 2015, http://www.adhb.govt.nz/ AucklandBreastCancerRegister/.
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