TOPLINE:

A large SEER analysis found that the likelihood of developing a second primary cancer varied by age, birth cohort, and original cancer type among US survivors diagnosed between 1975 and 2019. Older age at diagnosis and a history of lung, bladder, or melanoma, for instance, were associated with a higher incidence of new cancers. Over time, incidence rose among some groups, such as female lung cancer survivors, but declined among others, including breast cancer survivors.

METHODOLOGY:

• Cancer survivors are known to face a higher risk for developing new primary cancers — distinct malignancies that arise in different anatomical sites or have different histological characteristics.
• To understand the most recent trends, researchers conducted a retrospective cohort study using Surveillance, Epidemiology, and End Results (SEER) 8 registries data from the US, which identified 3.36 million individuals diagnosed with a first primary cancer between 1975 and 2019. Survivors were followed through December 2022 to estimate incidence of subsequent primary cancers.
• Researchers conducted age-period-cohort analyses for the five most common index cancer sites among women (breast, lung and bronchus, colon and rectum, uterine corpus, and melanoma of the skin) and men (prostate, lung and bronchus, colon and rectum, urinary bladder, and melanoma of the skin).
• During 29.5 million person-years of follow-up, 510,340 subsequent primary cancers — 235,099 among women and 275,241 among men.

TAKEAWAY:

• Subsequent primary cancer incidence increased with age at index cancer diagnosis among both sexes. The incidence was more than two times higher in women aged 75-79 years vs those aged 35-39 (1980 vs 915 per 100,000 person-years), and in males across the same age groups (2945 vs 1228 per 100,000).
• Subsequent primary cancer incidence peaked in the 1935-1945 birth cohorts and declined in later cohorts overall, except among female survivors of lung cancer and male survivors of bladder cancer, where incidence continued to rise.
• Subsequent primary cancer incidence among female lung cancer survivors increased by 60% between 1975-1979 and 2015-2019 (incidence rate ratio [IRR], 1.60; P < .001), while breast cancer survivors decreased by 29% (IRR, 0.71; P < .001).
• Overall subsequent primary cancer incidence declined over calendar periods, with an annual percent change of -0.63% among women and -0.95% among men, but incidence remained higher — or continued to rise — among survivors diagnosed at older ages.

IN PRACTICE:

“These findings underscore the need for tailored survivorship care strategies that account for age, cohort, and index cancer site,” the study authors concluded.

SOURCE:

The study, led by Hui G. Cheng, Cancer Prevention and Survivorship Outcomes Research Lab, Massey Comprehensive Cancer Center, Virginia Commonwealth University in Richmond, Virginia, was published online on April 28 in PLoS Medicine.

LIMITATIONS: 

The study’s age-period-cohort analyses are descriptive and do not establish causal links between specific exposures and subsequent primary cancers. SEER data lack information on treatment modalities, genetic factors, and lifestyle variables such as smoking, ultraviolet exposure, and physical activity after index cancer diagnosis, which limits understanding of the mechanisms driving observed patterns. The study did not stratify analyses by subtypes of index cancers, which may obscure important heterogeneity within cancer sites. Individuals who migrated out of registry catchment areas were censored at migration, potentially affecting case counts and precision of estimates. SEER data may contain misclassification errors, particularly for histologically similar cancers at the same anatomical site, despite application of multiple primary rules.

DISCLOSURES:

This study received support from the US National Cancer Institute through grants RO1CA239714, RO1CA172145, and RO1CA226080 awarded to Oxana Palesh. Oxana Palesh disclosed serving as a consultant for Brigham Young University, University of Rochester, Shook Hardy and Bacon, Elsevier, Merck, NIH, Sage Publisher, and Monash University. Other authors reported haing no conflicts of interest relevant to this manuscript.

This article was created using several editorial tools, including AI, as part of the process. Human editors reviewed this content before publication.