Poster Presentation Clinical Oncology Society of Australia Annual Scientific Meeting 2026

Obesity, metformin prescription and risk of advanced prostate cancer in non-diabetic men: findings from the 45 and Up Study (146453)

Visalini Nair-Shalliker 1 , Albert Bang 1 , Rani Radhika-Chand 1 , Karen Chiam 1 , Manish Patel 2 , Anthony Joshua 3 , Jerry Greenfield 3 , Michael David 1 , David Smith 1
  1. The Daffodil Centre, The University of Sydney, a joint venture with Cancer Council New South Wales, Sydney, New South Wales, Australia
  2. The University of Sydney, Sydney, NSW
  3. University of New South Wales, Sydney

Background

The aim is to determine the independent and interactive effects of obesity and metformin-use in predicting prostate cancer (PC) risk.

Methods

We used male participants from the Sax Institute’s 45 and Up Study (Australia), recruited between 2005-2009. Participants completed a questionnaire at recruitment which included information on self-reported body mass index (BMI; kg/m2). Participants’ baseline data were linked by the Centre for Health Record Linkage to the NSW Cancer Registry and to Services Australia to identify prescription claims for diabetic medications. Multivariable Joint Cox regression analyses were used to examine associations between BMI, and diabetic medications, by cancer spread.

Results

Of 94,674 eligible participants, there were 5265 incident PC cases (localised n=2638, regional n=925, metastatic n=1514 and unknown; n=1514) diagnosed between January 2012 and December 2019. Risk of metastatic PC was higher in BMI>30kg/m2 (versus <30kg/m2; HRadjusted=1.67;95%CI:1.10-2.54). Risk of localised PC diagnosis was lower in metformin-users (versus non-users; HR-metformin only=0.65;95%CI:0.50-0.84 and HRmetformin-combination=0.51; 95%CI:0.34-0.77). The lower risk of localised PC diagnosis in metformin-users (versus non-users) was evident across all BMI categories. 

Conclusion

Metformin-use in obese men may subsequently reduce their risk of PC diagnosis if PC is detected early. Further research could inform the repurposing of metformin for PC control.