Background Air pollution is associated with poorer survival among cancer patients. However, much of the evidence is from studies of ambient air pollution rather than acute exposures like from fires. In this study, we examined the effect of a 2014 coalmine fire in regional Australia, which shrouded nearby communities in smoke for six weeks. Methods We analysed Victorian Cancer Registry data on new cancers diagnosed between January 2009 and February 2014, the start of the coalmine fire, and survival up to August 2019. Tumours were grouped by location and subtypes for breast and lung cancers. The exposure group was based on residence at diagnosis: Morwell (most exposure), the rest of Latrobe Valley (less exposure), and the rest of Victoria excluding Melbourne (little to no exposure). Those who were diagnosed in Morwell or the Latrobe Valley but died before the fire were classified as unexposed. Months of survival post-fire were compared using Cox proportional hazards frailty and discrete survival models. Results In Morwell 488 total cancers were diagnosed, 1738 in the rest of the Latrobe Valley, while 42,738 were unexposed. There was no detectable overall effect. However, there were significant reductions in survival among cancers of female reproductive organs in Morwell and breast in the rest of Latrobe Valley. Conclusion There were no overall changes in cancer survival and isolated increases in two subtypes, although not consistent across exposure sites. Reduced survival from female reproductive cancers were plausibly related to smoke exposure, though numbers were small and there is a high likelihood this was a chance finding. Otherwise, we found little evidence that medium-duration exposure to smoke from the Hazelwood coalmine fire shortened survival among cancer patients. However, owing to limited statistical power, we could not rule out an effect of smoke on cancer survival.

The authors have declared no competing interest.

This work was funded by the Victorian Department of Health. The paper presents the views of the authorsand does not representthe views of the Department.

I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained.

Yes

The details of the IRB/oversight body that provided approval or exemption for the research described are given below:

The Monash University Human Ethics Research Committee of Monash University gave ethical approval for this work.

I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals.

Yes

I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance).

Yes

I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable.

Yes

All data are confidential and cannot be shared.