Epidemiological studies of cervical cancer survival in New Zealand : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Epidemiology at Massey University, Wellington Campus, New Zealand

Abstract

In this thesis I describe a series of studies of the stage at diagnosis and subsequent survival of women registered with cervical cancer in New Zealand during the period 1994 to 2005, and the factors that may contribute to the demographic differences that were found in both stage at diagnosis and survival. The studies involved all of the cervical cancer cases registered on the New Zealand Cancer Registry between 1994 and 2005. The cases were linked to the National Mortality Collection (for mortality data), the National Cervical Screening Programme- Register (for screening history), and the hospital events on the National Minimum Dataset (for information on comorbid conditions). The studies assessed what proportions of the ethnic differences in late stage diagnosis (after adjustment for socioeconomic position) were due to various factors such as screening history and urban/rural residency, and what proportions of the ethnic differences in survival (after adjustment for socio-economic position) were due to various factors including stage at diagnosis, comorbid conditions, and travel time and distance to the nearest General Practitioner and cancer centre. Māori and Pacific women had a higher risk of late stage diagnosis compared with ‘Other’ (predominantly European) women. Screening history did not entirely explain the increased risk in Māori women, but did explain that in Pacific women. More than half of the women with cervical cancer had not been screened, while those that had been ‘regularly’ screened had a considerably lower risk of a late stage diagnosis. Stage at diagnosis accounted for some but not all of the ethnic differences in survival. Comorbidity explained a moderate proportion of the ethnic differences in survival, while travel time may account for a small proportion of the ethnic differences in stage at diagnosis, and to a lesser extent mortality, particularly for Pacific women. The higher risk of late stage diagnosis in Māori women remains largely unexplained, whereas in Pacific women it is almost entirely due to differences in screening history and travel time. More than one-half of the higher risk of mortality in Māori and Pacific women is explained by differences in stage at diagnosis and comorbid conditions.