Temporal trends in the risk of second primary cancers among survivors of adult-onset cancers, 1980 through 2013: an Australian population-based study

Background: The authors' systematic review indicated an increasing trend in the risk of second primary cancers (SPCs) from the 1980s to 2000 when considering studies from the United States and Australia. It is uncertain whether this trend has continued to increase since 2000.

Methods: The current study was a population-based study of 51,802 individuals with adult-onset cancers identified in the Tasmanian Cancer Registry. Patients with a first cancer diagnosis made between 1980 and 2009 were followed up to December 2013. SPC risks were quantified using standardized incidence ratios (SIRs) and absolute excess risks (AERs). Trends in SPC risk were assessed using multivariable Poisson models.

Results: With a median follow-up of 4.8 years (mean, 6.9 years), a total of 5339 SPCs were observed. The SIRs for any SPC increased from 0.98 (95% confidence interval, 0.90-1.07) after a first cancer diagnosis in 1980 through 1984 to 1.12 (95% confidence interval, 1.05-1.20) in 2005 through 2009. In multivariable Poisson models accounting for patient sex, age at the time of the first cancer diagnosis, follow-up interval, and first cancer type, the trend in SIRs increased significantly from 1980 through 2009 for all SPCs (P for trend <.001) and for specific SPCs of the head and neck, lung, digestive tract, and prostate (all P for trend <.05). From 2000 onward, the AER for specific SPCs after specific first cancers was highest for prostate cancer after first cancers of the urinary tract (AER, 54.3 per 10,000 person-years).

Conclusions: In Tasmania, the risk of SPCs among survivors of adult-onset cancers has increased with periods of first cancer diagnosis from 1980 through 2009. Increased cancer screening and improved medical imaging may have contributed to the greater risk in recent years.