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2.3.1. British Childhood Cancer Survivor Study

The British Childhood Cancer Survivor Study (BCCSS) is a large, population-based study of childhood cancer survivors who survived at least five years. The cohort was ascertained by using the population-based National Registry of Childhood Tumours (NRCT), which has

approximately a 99% ascertainment rate253_{. Demographic, cancer, and treatment-related}

consequence of the improvements in childhood cancer survival rates across recent decades, which has led to a growing population of living childhood cancer survivors. As it is internationally recognized that survivors of childhood cancer are a high-risk population with

specific health care needs254_{, it was imperative that these individuals be monitored for long-}

term outcomes, especially as these survivors have many decades of life remaining due to their young age at diagnosis. Thus, the main objective of the BCCSS is to assess adverse health

and social outcomes following childhood cancers255_{. Ethical and legal approval for the}

BCCSS was given by a Multi-Centre Research Ethics Committee and every Local Research

Ethics Committee in Britain.

Originally, to be eligible for inclusion, survivors had to be diagnosed with cancer in Britain before the age of 15 years, between January 1, 1940 and December 31, 1991, and to have survived at least five years from their original cancer diagnosis. The overall eligible population-based cohort comprised 17,980 survivors. These individuals were then linked to the Health and Social Care Information Centre, which are maintained at Southport (England

and Wales) and Edinburgh (Scotland)255. Through this linkage, three critically important

types of information were obtained for all individuals in the BCCSS cohort. Firstly, the vital status of each survivor was obtained by linking with the national death registration system. Secondly, all SPNs were identified by linking with the national cancer registration system. And, finally, the current general practitioner practice was identified for all survivors who were alive.

By ascertaining each survivor’s National Health Service status, the Study Coordinating Center was then able to identify the survivor’s current primary care physician. Using the primary

care physician’s details, a study package was then sent to all survivors who were alive, a British resident, and aged at least 16 years at time of questionnaire send out (median year 2002). The study package to the primary care physician contained the following items: (1) a covering letter indicating the need for the study and seeking their cooperation, (2) a consent form for the primary care physician to give their permission for their patient, the survivor, to be included in the study together with a reply paid enveloped addressed to the Study Coordinating Center, (3) a suggested draft letter for the primary care physician to send to the survivor with the study questionnaire inviting participating, and (4) a postage-paid package to be mailed to the survivor by the primary care physician after the inclusion of the suggested

draft letter255_{. The package of documents sent to the survivors contained the following items:}

(1) the suggested covering letter from the primary care physician inviting participation, (2) a covering letter from the Study Coordinating Center, (3) a short explanatory leaflet for the survivor, (4) a personalized copy of the study questionnaire in either the male or female version depending on the sex of the survivor, and (5) a reply paid envelope for the survivor to

return the completed questionnaire to the Study Coordinating Center255_{. Ethical approval for}

the questionnaire send-out was obtained from a Multi-Centre Research Ethics Committee and every Local Research Ethics Committee in England, Wales, and Scotland.

Of the 17,980 total survivors in the BCCSS cohort, 14,880 (82.8%) were alive, a British resident, and aged at least 16 years at questionnaire send out. Of those who were ineligible for a questionnaire, 2,780 (15.5%) had died subsequent to surviving at least five years, 245

(1.4%) had emigrated, and 75 (0.4%) were alive, a British resident and under 16 years age255_.

An additional 45 survivors were excluded from receiving a questionnaire because they were not traced with the Health and Social Care Information Centre (n=24), adopted subsequent to

diagnosis of childhood cancer (n=16), or had indicated as part of a pilot study that they did

not want to be contacted again (n=5)255_{. Thus, ultimately, 14,835 survivors were available to}

receive a postal questionnaire survey255.

In total, 10,488 completed questionnaires were returned to the Study Coordinating Center, which equated to a response rate of 70.7%. Each questionnaire contained a range of questions relating to the survivor’s life, including topics such as health status, marriage, pregnancies and children, family history, smoking and alcohol use, educational attainment, employment, life and medical insurance, and personal concerns. The full male and female questionnaires can be found in Appendix 1 and Appendix 2, respectively.

In 2014 the BCCSS was subsequently extended to include individuals diagnosed with childhood cancer from January 1, 1992 to December 31, 2006 in Britain and who had

survived at least five years from their childhood cancer. Ethical and legal approval was given

by the National Research Ethics Service (NRES) and national Confidentiality Advisory

Group (CAG). With the extension, the BCCSS comprises 34,489 five-year survivors of

childhood cancer. Information relating to vital status and SPNs is available for all survivors in the cohort. Information on social, economic, and health outcomes is available for only the survivors who completed the questionnaire survey (n=10,488). This thesis includes analyses on the BCCSS both before and after the extension; however, the study population under investigation will be described in the methods section of each of the subsequent chapters. Baseline characteristics of the original and extended cohorts can be found in Appendix 3.

2.3.2. Teenage and Young Adult Cancer Survivor Study

The Teenage and Young Adult Cancer Survivor Study (TYACSS) is a large, population based study of individuals diagnosed with cancers between the ages of 15 to 39 and who have

survived at least five years256_{. The cohort was established in collaboration with the Office for}

National Statistics (ONS) and Welsh Cancer Registry due to the international acknowledgement of the need for survivorship and late effects studies relating to individuals

diagnosed with cancer as teenagers and young adults6,256–261_{. As cancer incidence rates take}

up to five years after the end of a given calendar year to reach 100%262, ascertainment for this

cohort is expected to be essentially complete as the upper limit for diagnosis inclusion was

2006. Ethical and legal approval for the TYACSS was given by the National Research Ethics

Committee and Confidentiality Advisory Group.

In order to be included in the TYACSS cohort, individuals had to be diagnosed with a teenage

or young adult cancer from January 1, 1971 to December 31, 2006 in England or Wales and

survive at least five years. The total eligible population-based cohort comprises 200,945 survivors. These individuals were then linked to the Health and Social Care Information Centre, which provided the vital status of each survivor, via the national death registration system, and all cancer registrations, via the national cancer registration system. Baseline characteristics of the TYACSS cohort can be found in Appendix 4.