# Temporal trends in the risk of multiple primary cancers and competing mortality among adult-onset cancer patients

2018 , 'Temporal trends in the risk of multiple primary cancers and competing mortality among adult-onset cancer patients', PhD thesis, University of Tasmania.

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## Abstract

$$Background:$$ Cancer patients are at risk of developing multiple primary cancers (MPCs). MPCs and non-cancer events compete with first cancers as the cause of death. This thesis aims to investigate temporal trends in the risk of MPCs and competing mortality due to MPCs and non-cancer events among adult-onset cancer patients in Tasmania.
$$Methods:$$ A systematic review of temporal trends in the risk of MPCs was performed. Original data were extracted from the population-based Tasmanian Cancer Registry in Australia. Patients with a first cancer registered between 1980-2009 were followed for incident second cancers to 2013 and for deaths to 2014. For non-cancer mortality, patients with a first cancer registered between 2006-2013 were followed up to 2015. MPC risks were quantified and trends in MPC risk were assessed in multivariable Poisson models. Mortality due to MPCs and non-cancer events were assessed in competing risk models.
$$Results:$$ The systematic review indicated an increasing trend in the risk of MPCs from the 1980s to 2000 in studies from Australia and the USA. In Tasmania, there was an increasing trend in the risk of any second cancer from 1980-2013. The competing mortality due to MPCs increased from the 1980s to a peak for first cancers diagnosed in 1995-1999. From 2006-2015, the competing mortality due to cardiovascular events increased significantly with age at first cancer diagnosis and exceeded other competing events at age 65 years or older.
$$Conclusions:$$ In Tasmania, the risk of MPCs has increased with periods of first cancer diagnosis from 1980-2009. The competing mortality due to MPCs increased for first cancers diagnosed in the 1990s possibly indicating overdiagnosis of non-fatal first cancers in the 1990s. Cardiovascular events were the leading cause of competing mortality among Tasmanian patients diagnosed with a first cancer from 2006-2013 suggesting potential opportunities for preventive interventions