In New Zealand, the fellow reviewed the literature on factors of age-related disparities in colon and lung cancer survival and found that while age is one of the most important prognostic factors, age-related disparities in colon and lung cancer survival have so far been understudied in population-based research. Moreover, the included studies were highly heterogeneous and often of poor quality. The magnitude of age disparities in survival varied greatly by sex, ethnicity, socio-economic status, stage at diagnosis, cancer site, and morphology, the number of nodes examined, and treatment strategy. Although results were inconsistent for most characteristics, we consistently observed greater age disparities for females with lung cancer compared to males. Also, age disparities increased with more advanced disease for colon cancer and decreased with more advanced disease for lung cancer. This work is published in BMJ Open.
The fellow described the role of patient-related and clinical factors on age-related disparities in colon cancer survival among patients aged 50-99 years at diagnosis in New Zealand. The excess mortality in older patients was minimal for localized cancers, maximal during the first six months for regional cancers, the first 18 months for distant cancers, and over the three years for missing stages. Overall, the results showed that factors reflecting timeliness of cancer diagnosis (eg. stage at diagnosis and emergency diagnosis) affected the most age-related disparities in cancer survival, probably by impacting treatment strategy. This work is published in the Journal of Geriatric Oncology.
The fellow did similar work on lung cancer. In contrast to colon cancer, age-related disparities decreased as the disease was more advanced. We also observed a greater disparity in cancer survival in females compared to males, likely explained by the role of sex hormones but this needs to be confirmed. Like in colon cancer, comorbidity and socio-demographic played a minor or even no role in age-related disparity in lung cancer survival. This work is published in Lung cancer.
The Fellow presented these works at the NCRI virtual conference in November 2020, the Nuffield Department of Population Health symposium at the University of Oxford in March 2021, the SIOG 2021 virtual annual conference, and at 3 webinars (Canada, New Zealand and SIOG NAH webinar).
In England, the Fellow focused on describing treatment patterns and outcomes in relation to age.
Observational data are often used to study the effectiveness of treatment but these data are prone to several biases including the immortal time bias (ITB). ITB occurs in longitudinal studies (e.g. cohort studies, time-to-event studies) when the exposure is defined based on information available after the start of participants' follow-up. Using simulated data, we compared estimates from a time-fixed exposure model to three methods addressing ITB: time-varying exposure, delayed entry, and landmark methods, and we estimated the effect of surgery performed within 6 months of diagnosis on one-year overall survival in patients diagnosed with stage IV colon cancer aged 50-74 and separately, in those aged 75-99. In simulations, the magnitude of ITB is larger among older patients when their probability of early death increases, or the treatment is delayed. The bias is corrected using appropriate methods. In real data, appropriate methods yielded smaller effects of surgery than the time-fixed exposure approach, but effects were generally similar in both age groups. While ITB may be exacerbated in older patients, this was not obvious in our real data, because of the possible highly selected older population. The manuscript is circulating among co-authors.
The Fellow also described the patterns of chemotherapy use and associated outcomes in >18 000 patients with stage III or IV non-small cell lung cancer (NSCLC) and >8000 patients with stage III or IV small cell lung cancer (SCL) in relation to age using the national Systemic Anti-Cancer Treatment dataset. In NSCLC, the treatment plan was modified more often in patients aged 75+ than younger ones. The difference in survival based on age was small, except for patients with stage IV NSCLC who first received curative treatment.
In SCLC, despite a similar chemotherapy pattern in patients aged below 75 and older ones, the 30-day mortality rate (in stage IV SCLC) and overall survival were poorer in older patients.
Two manuscripts are in preparation and will be submitted in 2022. These results were presented at the SIOG 2021 virtual conference and the Fellow was awarded the SIOG Nursing and Allied Health investigator award for her work on NSCLC.
The Fellow could not answer the 3rd specific objective because the relevant data were not accessible for use in this project.
The Fellow was invited by the Union for International Cancer Control (UICC), a NGO advocating for better cancer control, as an expert in epidemiology of cancer in older people.
