Abstract LB129: Survival of most commonly diagnosed second primary cancers among adult cancer survivors
Authors: Sung Hyuna , Nisotel Lauren , Sedeta Ephrem , Islami Farhad , Jemal Ahmedin 
Published: April 2023

Abstract
Background Second primary cancer (SPC) burden is increasing in the US, but few studies comprehensively examined survival in persons diagnosed with SPCs in relation to survivors’ antecedent cancer types.
Methods Persons aged ≥20 years and diagnosed with one of the six most common SPCs (female breast, prostate, bladder, lung, colorectum, corpus uteri) from 2000-2013 were identified from 17 Surveillance, Epidemiology, and End Results registries (n=152,204). For comparison, persons diagnosed with same type cancers occurring as first primary cancers (FPCs) were also identified (n=2,131,953). For each cancer type, differences in the risk of cancer-specific or all-cause death between SPC and FPC were estimated using multivariable Cox proportional hazards models adjusted for potential confounders. Subgroup analyses were conducted to estimate the risk difference between SPC and FPC by antecedent cancer types of those with SPCs.
Results During a median follow-up of 6.5 years (interquartile range, 1.8-10.6), cancer-type specific death occurred among 34% of persons with SPCs and among 32% of persons with FPCs. The corresponding proportions for all-cause death were 67% and 53%, respectively. In multivariable models, the risk of cancer-specific death was statistically significantly higher in persons with SPC than in persons with FPC for breast (hazard ratio [HR]=1.43; 95% confidence interval [CI]=1.40-1.48), bladder (HR=1.19; 1.09-1.29), corpus uteri (HR=1.10; 1.05-1.15), and colorectal (HR=1.05, 1.03-1.07) cancer, whereas it was lower for lung cancer (HR=0.78; 0.77-0.79). The risk did not vary between groups for prostate cancer (HR=0.92; 0.79-1.06). Subgroup analyses showed large variations in HRs across survivors by antecedent cancer types. In particular, the highest HR associated with SPC (vs FPC) was among ovarian cancer survivors for colorectal cancer (HR=1.31; 1.10-1.56), gallbladder cancer survivors for breast cancer (HR=1.78; 1.09-2.91), head and neck cancer survivors for uterine cancer (HR=1.69, 1.05-2.72), gallbladder cancer survivors for bladder cancer (HR=1.87; 1.06-3.22), while the lowest HR for lung cancer was among testicular cancer survivors (HR=0.54; 0.38-0.76). Associations were generally consistent across strata of diagnosis years, race/ethnicity, household income, and urbanicity. The risks of all-cause death were also higher among persons with SPC vs FPC, including prostate cancer. Persons with second primary prostate cancer were almost twice as likely to die from all causes as persons with first prostate cancer (HR=1.83; 1.80-1.87).
Conclusion Persons with SPC generally have a higher risk of cancer-specific and all-cause death than those with FPC, suggesting that intensive SPC surveillance may benefit those at increased risk of developing SPC. Importantly, the risk difference substantially varied by survivors’ antecedent cancer type, highlighting a need for targeted strategies for treatment and survivorship care for persons with SPCs.
Citation Format: Hyuna Sung, Lauren Nisotel, Ephrem Sedeta, Farhad Islami, Ahmedin Jemal. Survival of most commonly diagnosed second primary cancers among adult cancer survivors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 2 (Clinical Trials and Late-Breaking Research); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(8_Suppl):Abstract nr LB129.