In a Danish population-based retrospective cohort study reported in The Lancet Oncology, Kjaer et al identified the cumulative incidence of second primary cancers among cancer survivors aged ≥ 40 years who were alive 1 year after diagnosis.
Study Details
The study involved data from 457,334 patients diagnosed with 27 types of cancer between January 1997 and December 2014. Follow-up was from date of first cancer diagnosis and lasted up to 24 years, ending in December 2020.
Key Findings
Among all survivors, the cumulative incidence of second primary cancer was 6.3% (95% confidence interval [CI] = 6.2%–6.4%) at 5 years after diagnosis, 10.5% (95% CI = 10.4%–10.6%) at 10 years after diagnosis, and 13.5% (95% CI = 13.4%–13.7%) at 15 years after diagnosis.
The highest cumulative incidence of second primary cancer at 10 years after diagnosis was among survivors of laryngeal cancer (21.8%), oropharyngeal and oral cavity cancer (19.5%), and bladder and urinary tract cancer (18.5%). Most cancer types (17 of the 27 investigated) were associated with a 10-year cumulative incidence of second primary cancer between approximately 10% and 15%. Survivors of liver (2.5%), pancreatic (2.5%), and lung cancer (3.9%) had the lowest 10-year cumulative incidence of second primary cancer.
Lung cancer was the most frequent or second most frequent second primary cancer for 7 of the 10 primary cancer types associated with the highest 10-year cumulative incidence of second primary cancer. The sites of second primary cancer varied among patients with the remainder of the investigated primary cancer types.
Survivors of cancers related to alcohol (hazard ratio [HR] = 1.09, 95% CI = 1.06–1.13), smoking (HR = 1.73, 95% CI = 1.68–1.78), diets high in red or processed meat (HR = 1.32, 95% CI = 1.24–1.39), and viral infections (HR = 1.23, 95% CI = 1.13–1.35) were at an increased risk of developing a second cancer with the same etiology. Survivors with a hormone-related first cancer had a lower risk of a second hormone-related cancer (HR = 0.77, 95% CI = 0.73–0.81).
The investigators concluded, “Our results could help optimize prevention efforts targeting modifiable risk factors to reduce risk of developing a second primary cancer.”
Trille Kristina Kjaer, PhD, of the Danish Cancer Institute, Copenhagen, is the corresponding author for The Lancet Oncology article.
Disclosure: The study was funded by the Nordic Cancer Union and The Health Foundation. For full disclosures of the study authors, visit thelancet.com.
