A Flinders University study shows that bowel cancer survivors face an elevated risk of developing multiple primary cancers (MPCs) - for prostate, lung, breast and blood cancer.
In a new article in Cancer Medicine, the South Australian bowel cancer researchers say the trend, which is linked to advancements in treatment and increased survival rates, presents a clinical challenge as the population ages.
Based on South Australian Cancer Registry data, the Flinders University researchers analysed the likely incidence and risk of MPCs using thousands of individual colorectal cancer (CRC) cases diagnosed between 1982 and 2017. The study included 26,729 CRC survivors.
"While patient outcomes have improved over time, CRC survivors already face an increased risk of developing one or more cancers in another part of the colon or other primary sites," says study leader Mulugeta Melku, from the Flinders Health and Medical Research Institute (FHMRI) Bowel Health Service.
"This study shows that CRC survivors are at increased risk of subsequent cancers compared to the general population, highlighting the need for targeted surveillance, particularly for early detection and treatment of prostate, lung, breast and blood cancers," he says.
Senior researcher Associate Professor Erin Symonds, also from the Southern Adelaide Local Health Network, says: "Estimating the incidence, trend and risk of other kinds of MPCs after a diagnosis of CRC will help service delivery, testing and treatment in the coming years, as the population continues to age and survivors live longer."
The study indicated that the most common MPCs over time in CRC survivors were prostate cancer, subsequent CRC, lung cancer, haematological malignancies, breast cancer, urinary tract organ cancers and skin melanoma.
Colorectal cancer (CRC) is the fourth most diagnosed cancer in Australia, and second-highest cause of cancer-related death. Over the past 40 years, however, significant advances in screening for early detection of CRC, improved diagnostic tools, more targeted treatment options and improved awareness in the community about cancer and prevention have improved survival rates.
The Australian five-year relative survival over time has risen from 54.9% in 1991-95 to 71.3% in 2016-2020.
Associate Professor Symonds says studies such as this increase understanding of MPCs risks which, in turn, helps to develop suitable strategies to enhance and refine surveillance programs for early detection of subsequent cancers.
"Further research will also help to improve treatment outcomes and overall survival," she says.
In 2000, there were around 88,000 cases of cancer diagnosed in Australia, rising to around 169,000 last year. This rise of more than 90% in all types of cancers over the past 24 years is mainly due to rising population size and increasing numbers of people reaching older ages for which cancer rates are higher. These factors are expected by push the number of cancer diagnoses to around 209,000 by 2034.
The researchers have also published a second new paper covering some of the risk factors for developing a second cancers after bowel cancer
Risk Factors of Multiple Primary Cancers Among Colorectal Cancer Survivors (2025) by Mulugeta Melku, Oliver G Best, Jean M Winter, Lauren A Thurgood, Muktar Ahmed, Ganessan Kichenadasse, Molla M Wassie and Erin L Symonds has been published in Cancers DOI: 10.3390/cancers17132145.
The research paper, 'Incidence, Risk and Trends of Multiple Primary Cancers in Patients With Colorectal Cancer: Evidence From the South Australian Cancer Registry' (2025) by Mulugeta Melku, Oliver G Best, Jean M Winter, Lauren A Thurgood, Muktar Ahmed, Ganessan Kichenadasse, Murthy Mittinty, Molla M Wassie and Erin L Symonds was published in Cancer Medicine.
Acknowledgements: The authors would like to thank the South Australian Cancer Registry, Dr Rosie Meng from Epidemiology and Research, Preventive Health SA, Flinders University and the Australian Government International Postgraduate Research Scholarship, which sponsored MM's PhD study.
