704The preventable future burden of cancer in Australia

Background

Estimates of the future burden of invasive cancer attributable to current modifiable causal exposures can guide cancer prevention.

Methods

We linked pooled data from seven Australian cohort studies (N = 367,058) to national cancer and death registries, and estimated exposure-cancer and exposure-death associations using adjusted proportional hazards models. We estimated exposure prevalence from contemporary national health surveys and calculated population attributable fractions (PAFs) and 95% confidence intervals, using advanced methods accounting for competing risk of death.

Results

Current levels of past and current smoking explain 36.1% (95%CI 33.2%-38.9%), body fatness 13.6% (10.9%-16.2%) and alcohol consumption exceeding two drinks/day 2.3% (1.0%-3.6%) of cancers causally related to these exposures, corresponding to 210,000, 81,300 and 14,800 cancers in Australia in the next 10 years, respectively. Ever smoking is the leading modifiable cause of lung (82.1%), bladder (49.8%), oesophageal (42.8%), liver (39.8%), head and neck (35.6%), and pancreatic (21.3%) cancer burden. Body fatness is the leading modifiable cause of corpus uteri (42.5%), gastric cardia (33.6%), renal cell (29.1%), thyroid (20.1%), colorectal (12.6%) and postmenopausal breast (12.6%) cancer burden. The absolute numbers of cancers in the next 10 years attributable to smoking are highest for lung cancer (114,000). The numbers of cancers attributable to body fatness and alcohol are highest for colorectal cancer (23,000 and 9,900, respectively).

Conclusions

More reliable advanced methods demonstrate large proportions and numbers of cancers are preventable by modifying behaviours.

Key messages

Ever smoking and body fatness are the leading causes of preventable future burden of causally related cancers in Australia.

The preventable burden of endometrial and ovarian cancers in Australia: A pooled cohort study

OBJECTIVE

Evidence on the endometrial and ovarian cancer burden preventable through modifications to current causal behavioural and hormonal exposures is limited. Whether the burden differs by population subgroup is unknown.

METHODS

We linked pooled data from six Australian cohort studies to national cancer and death registries, and quantified exposure-cancer associations using adjusted proportional hazards models. We estimated exposure prevalence from representative health surveys. We then calculated Population Attributable Fractions (PAFs) with 95% confidence intervals (CIs), accounting for competing risk of death, and compared PAFs for population subgroups.

RESULTS

During a median 4.9 years follow-up, 510 incident endometrial and 303 ovarian cancers were diagnosed. Overweight and obesity explained 41.9% (95% CI 32.3-50.1) of the endometrial cancer burden and obesity alone 34.5% (95% CI 27.5-40.9). This translates to 12,800 and 10,500 endometrial cancers in Australia in the next 10 years, respectively. The body fatness-related endometrial cancer burden was highest (49-87%) among women with diabetes, living remotely, of older age, lower socio-economic status or educational attainment and born in Australia. Never use of oral contraceptives (OCs) explained 8.1% (95% CI 1.8-14.1) or 2500 endometrial cancers. A higher BMI and current long-term MHT use increased, and long-term OC use decreased, the risk of ovarian cancer, but the burden attributable to overweight, obesity or exogenous hormonal factors was not statistically significant.

CONCLUSIONS

Excess body fatness, a trait that is of high and increasing prevalence globally, is responsible for a large proportion of the endometrial cancer burden, indicating the need for effective strategies to reduce adiposity.

Reoperation after breast-conserving surgery for cancer in Australia: statewide cohort study of linked hospital data

OBJECTIVES

To investigate between-hospital variation in the probability of reoperation within 90 days of initial breast-conserving surgery (BCS), and the contribution of health system-level and other factors.

DESIGN

Population-based, retrospective cohort study.

SETTING

New South Wales (NSW), Australia.

PARTICIPANTS

Linked administrative hospitalisation data were used to define a cohort of adult women undergoing initial BCS for breast cancer in NSW between 1 July 2002 and 31 December 2013.

PRIMARY OUTCOME MEASURES

Multilevel, cross-classified models with patients clustered within hospitals and residential areas were used to examine factors associated with any reoperation, and either re-excision or mastectomy, within 90 days.

RESULTS

Of 34 458 women undergoing BCS, 29.1% underwent reoperation within 90 days, half of which were mastectomies. Overall, the probability of reoperation decreased slightly over time. However, there were divergent patterns by reoperation type; the probability of re-excision increased alongside a concomitant decrease in the probability of mastectomy. Significant between-hospital variation was observed. Non-metropolitan location and surgery at low-volume hospitals were associated with a higher overall probability of reoperation, and of mastectomy specifically, after accounting for patient-level factors, calendar year and area-level socioeconomic status. The magnitude of association with geographical location and surgical volume decreased over time.

CONCLUSIONS

Reoperation rates within 90 days of BCS varied significantly between hospitals. For women undergoing mastectomy after BCS, this represents a dramatic change in clinical course. Multilevel modelling suggests unwarranted clinical variation may be an issue, likely due to disparities in access to multidisciplinary breast cancer care and preoperative diagnostic procedures. However, the observed reduction in disparities over time is encouraging and indicates that guidelines and policy initiatives have the potential to improve regional breast cancer care.