Lung cancer in Sweden : incidence, diagnosis and survival

Abstract

Globally, lung cancer is the most commonly diagnosed form of cancer, as well as the number one cancer-related cause of death. This thesis includes four population-based studies that considered different aspects of lung cancer, covering incidence, diagnosis and survival.

Study I considered the incidence of lung cancer in relation to use of antimuscarinic medications to treat overactive bladder. We identified first-time users of antimuscarinic medications and matched them with individuals not exposed to antimuscarinic medications. Exposed individuals had lower incidence of lung cancer than those unexposed. The inverse association became more pronounced over time from the start of treatment and with the amount of medication from filled prescriptions. Our finding of an inverse association generates hypotheses regarding the prevention of cancer and new treatment strategies for patients with cancer.

In study II, we identified individuals with incident non-small cell lung cancer and compared characteristics and survival by smoking status at diagnosis. We found that women, adenocarcinoma, and epidermal growth factor receptor mutation were overrepresented among never-smokers. Furthermore, compared to current smokers, survival was longer for never-smokers. Our findings emphasise the need for an improved understanding of lung cancer among never-smokers that may help to prevent lung cancer and improve survival.

Patients with incident lung cancer were identified in study III and matched with individuals free of lung cancer. We investigated patterns of recent use of antibiotics as an indicator of early symptoms of lung cancer. We found that a diagnosis of lung cancer was associated with increased likelihood of recent pre-diagnostic use of antibiotics. The likelihood became more pronounced with the number of filled prescriptions and with proximity to the diagnosis. Our findings further emphasise the importance of ruling out lung cancer following pneumonia treatment.

In study IV, we identified patients with incident adenocarcinoma or squamous cell carcinoma of the lung and investigated temporal trends in relative survival. We found that relative survival increased between 1995 and 2016. The increase was most pronounced among women, patients with stage III cancer, patients with adenocarcinoma, and never-smokers. These findings corroborate results from other countries. The increase in relative survival for patients with lung cancer in recent decades can probably be attributed to the improvements in diagnostic procedures and new treatments.