The association between different night shiftwork factors and breast cancer: a case-control study.

BACKGROUND: Research on the possible association between shiftwork and breast cancer is complicated because there are many different shiftwork factors, which might be involved including: light at night, phase shift, sleep disruption and changes in lifestyle factors while on shiftwork (diet, physical activity, alcohol intake and low sun exposure). METHODS: We conducted a population-based case-control study in Western Australia from 2009 to 2011 with 1205 incident breast cancer cases and 1789 frequency age-matched controls. A self-administered questionnaire was used to collect demographic, reproductive, and lifestyle factors and lifetime occupational history and a telephone interview was used to obtain further details about the shiftwork factors listed above. RESULTS: A small increase in risk was suggested for those ever doing the graveyard shift (work between midnight and 0500 hours) and breast cancer (odds ratio (OR)=1.16, 95% confidence interval (CI)=0.97-1.39). For phase shift, we found a 22% increase in breast cancer risk (OR=1.22, 95% CI=1.01-1.47) with a statistically significant dose-response relationship (P=0.04). For the other shiftwork factors, risks were marginally elevated and not statistically significant. CONCLUSION: We found some evidence that some of the factors involved in shiftwork may be associated with breast cancer but the ORs were low and there were inconsistencies in duration and dose-response relationships.

Second cancer incidence and cancer mortality among chronic lymphocytic leukaemia patients: a population-based study.

BACKGROUND: Patients with chronic lymphocytic leukaemia (CLL) are known to have increased risks of second cancer. The incidence of second cancers after CLL has not been reported in detail for Australia, a country with particularly high levels of ultraviolet radiation (UVR). METHODS: The study cohort comprised of all people diagnosed with a primary CLL between 1983 and 2005 in Australia. Standardised incidence ratios (SIRs) and standardised mortality ratios (SMRs) were calculated using Australian population rates. RESULTS: Overall, the risk of any second incident cancer was more than double that of the general population (SIR=2.17, 95% confidence interval (CI)=2.07, 2.27) and remained elevated for at least 9 years after CLL. Risks were increased for many cancers, particularly melanoma (SIR=7.74, 95% CI=6.85, 8.72). The risk of melanoma increased at younger ages, but was constant across >9 years of follow-up. Chronic lymphocytic leukaemia patients also had an increased risk of death because of melanoma (SMR=4.79, 95% CI=3.83, 5.90) and non-melanoma skin cancer (NMSC; SMR=17.0, 95% CI=14.4, 19.8), suggesting that these skin cancers may be more aggressive in CLL patients. CONCLUSION: We speculate that a shared risk factor, such as general immune suppression, modulated by UVR exposure may explain the increased risk of melanoma and NMSC in CLL patients.

Hypotheses for mechanisms linking shiftwork and cancer.

Shift work has been associated with various adverse health outcomes. In particular, there has been a recent flourish in investigating potential cancer risk associated with working night shifts and other shift schedules. Epidemiologic studies have revealed generally weak associations due to several methodological challenges such as lack of standard classifications of shift or night work. The field also has been hindered by a lack of clarity about the possible mechanisms by which shiftwork could have an effect on cancer risk. One possible mechanism is reduced production of melatonin caused by exposure to light at night. Although there is a growing body of evidence that provides some support for this mechanism, several other mechanisms also make sense from a biological point of view. Further, the relatively weak magnitude of the associations between light at night and melatonin level suggests that multiple factors may be operating along the pathway between shift work and adverse health consequences (including cancer risk). Here we propose four additional mechanisms that should be considered for a comprehensive investigation of these potential pathways. These are: phase shift; sleep disruption; lifestyle factors (such as poor quality diets, less physical activity and higher BMI); and lower vitamin D. Consideration of all these mechanisms is necessary in order to design effective preventative workplace strategies. In developed countries, approximately 20% of the population undertake shiftwork and, while we are unlikely to be able to eliminate shiftwork from current work practices, there are aspects of shiftwork that can be modified and there may be facets of individual susceptibility that we may be able to identify and target for prevention.

Merkel cell carcinoma in Western Australia: a population-based study of incidence and survival.

BACKGROUND: Merkel cell carcinoma (MCC) is an uncommon but aggressive cutaneous skin cancer. Even with the appropriate treatment, MCC is prone to recurrence, and metastases are common. Exposure to ultraviolet radiation has been suggested as contributing towards the development of MCC. MCC has not been extensively investigated in Australia, even though Australia has the highest incidence of sun-related cancers in the world. OBJECTIVES: To describe the demographics and determine trends of incidence and survival of MCC cases in Western Australia (WA). METHODS: All reported invasive cases of MCC incident between 1 January 1993 and 31 December 2007 were extracted from the WA Cancer Registry. Age-adjusted incidence rates for MCC were calculated using direct standardization to the U.S. standard 2000 population. Cause-specific survival was investigated using Kaplan-Meier and Cox proportional hazards analysis. results: Two hundred and fifteen cases were confirmed by pathological review as being definite cases of MCC. Patients were mainly males (65%) and elderly (median age 77 years). Standardized age-adjusted incidence rates were higher in men (1·0/100,000) than in women (0·63/100,000) and higher in older ages (15·5/100,000 in the 85+year age group) than younger ages (0·1/100,000 in the 30-34 year age group). Five-year cause-specific survival was 64%. CONCLUSIONS: Incidence of MCC in WA is the highest reported in the literature. In addition, MCC has worse survival than melanoma. The high rates and demographic and anatomical distribution are consistent with sun exposure playing a causal role.

Deaths from non-melanoma skin cancer in Western Australia.

OBJECTIVES: Non-melanoma skin cancer (NMSC) is common, slow growing, and rarely metastasizes. However, there are still nearly 400 deaths from NMSC in Australia annually. We aimed to investigate the accuracy of NMSC death coding and to describe the characteristics of these deaths and the potential for prevention. METHODS: Histology reports for all deaths coded as NMSC (ICD-10 C44.0-C44.9) by the Western Australian Cancer Registry for the years 1996-2005 were reviewed for type of cancer, body site (primary tumor and metastases), and level of available documentation. RESULTS: Of 368 deaths recorded as being due to NMSC only 3 were found to be miscoded. An additional 53 deaths contained inadequate information to confirm NMSC as the cause of death. Of the confirmed cases, 219 were due to squamous cell carcinoma, 53 to Merkel cell carcinomas, and 40 to other skin cancers. Cases were mainly males and were elderly. Most of the primary squamous and Merkel cell carcinomas were in areas of maximum sun exposure (face, ears, and hands, and scalp in males). CONCLUSIONS: Misclassification of NMSC deaths in WA was minimal. The majority of NMSC deaths were due to squamous cell carcinomas; had primary sites associated with significant sun exposure; and occurred in older men.