By Billy Candra 
Physicians caring for survivors of childhood cancer later in life should be aware that survivors’ genetics, in addition to their lifesaving cancer treatment, contribute significantly and sometimes equally to the risk for secondary cancers. This critical finding emerges from a comprehensive study conducted by scientists at St. Jude Children’s Research Hospital, who have for the first time quantified the proportional contributions of different factors to the risk of a second primary malignancy. Secondary cancers represent the primary cause of mortality for long-term survivors of childhood cancer, making this research a pivotal advancement in understanding and mitigating this persistent threat. The groundbreaking study, which leveraged extensive data from the St. Jude Lifetime Cohort Study (St. Jude LIFE) and the Childhood Cancer Survivor Study (CCSS)—two of the world’s most prominent childhood cancer survivor investigations, both housed at St. Jude—was published in the esteemed journal The Lancet Oncology.
The research provides unprecedented clarity on the complex interplay of factors driving secondary cancer development. "We found the burden of second cancer in survivors of childhood cancer is largely contributed by pediatric treatment exposures and genetic predisposition," stated corresponding author Yadav Sapkota, PhD, from the St. Jude Department of Epidemiology and Cancer Control. While the association between treatment exposures, genetics, and secondary cancer risk has been recognized, Dr. Sapkota emphasized the study’s unique contribution: "This is the first time we’ve been able to attribute the proportion of their contributions to that risk at the population level." This quantification marks a significant leap forward, moving beyond mere association to providing a tangible understanding of each factor’s impact.
The Unseen Burden: Secondary Cancers in Focus
Childhood cancer, once a near-certain death sentence, has seen remarkable improvements in survival rates over the past half-century. Advances in chemotherapy, radiation therapy, and surgical techniques mean that more than 80% of children diagnosed with cancer now survive five years or more. However, this triumph comes with a significant challenge: the long-term health consequences faced by these survivors. Among the most serious and life-threatening of these late effects are secondary primary cancers, which are new cancers that develop years or even decades after the successful treatment of the initial childhood malignancy. These are distinct from recurrences of the original cancer and often arise in different tissues or organs.
The prevalence of secondary cancers is alarming. Studies have shown that by the age of 50, approximately one in five childhood cancer survivors will have developed a second primary cancer. This elevated risk stands in stark contrast to the general population and underscores why secondary cancers have become the leading cause of non-relapse mortality among long-term survivors. Understanding the root causes of these secondary malignancies is paramount to developing effective prevention, early detection, and treatment strategies, ultimately enhancing the quality and length of life for this vulnerable population.
A Landmark Investigation: The St. Jude LIFE and CCSS Cohorts
Previous research efforts have often examined how individual factors—such as specific treatment exposures, genetic predispositions, or lifestyle choices—might be associated with an increased risk of secondary cancers. However, a crucial knowledge gap persisted: the relative contribution of these factors when considered together at a population level. To address this, St. Jude scientists undertook an ambitious comparative analysis, utilizing data from over 10,000 survivors enrolled in the St. Jude LIFE and CCSS cohorts. Combined, these represent the largest and most comprehensive survivor cohort in North America, providing an unparalleled dataset for such an investigation.
The St. Jude LIFE study systematically evaluates the health of adult survivors of childhood cancer who were treated at St. Jude Children’s Research Hospital. It meticulously collects information on their treatment history, current health status, lifestyle factors, and genetic profiles, often following participants for decades. Similarly, the CCSS is a multi-institutional, retrospective cohort study that tracks over 35,000 long-term survivors of childhood cancer diagnosed between 1970 and 1999 across numerous participating institutions in the United States and Canada. The vastness and depth of these combined datasets, which included detailed information on past treatment exposures and outcomes, comprehensive genetic information, lifestyle factors, and the presence or absence of a second cancer, provided the robust foundation necessary to rigorously evaluate the proportionate contribution of these various factors.
"This kind of high-impact discovery is only possible in the CCSS and SJLIFE cohorts, that in combination, have more than 12,000 survivors with genetic sequencing," noted co-author Greg Armstrong, MD, MSCE, chair of the St. Jude Department of Epidemiology and Cancer Control. The sheer scale of genetic data, coupled with meticulously documented clinical histories, allowed researchers to move beyond correlational observations to a quantitative attribution of risk.
Dissecting the Risk Factors: A Quantitative Analysis
The study meticulously dissected the contributions of radiation exposure, chemotherapy, genetic predisposition, and lifestyle factors to secondary cancer risk. The findings offer a nuanced and sometimes surprising picture of their relative importance.
Radiation’s Enduring Legacy:
Radiation therapy, while a potent weapon against childhood cancers, has long been recognized for its potential long-term adverse effects. The St. Jude study further solidified this understanding, identifying radiation exposure as the most significant contributor to secondary cancer risk, accounting for approximately 40% or more of the overall risk. This finding resonates with decades of prior research that has meticulously documented the dose-dependent and site-specific risks of radiation-induced secondary malignancies, including sarcomas, breast cancers, thyroid cancers, and other solid tumors.
Historically, radiation therapy was a cornerstone of many childhood cancer treatment protocols, often delivered in broad fields and at high doses. However, as the long-term consequences became clearer, and as other therapeutic modalities improved, there has been a significant shift in clinical practice. Modern therapies now prioritize reducing radiation doses, employing more precise delivery techniques (such as intensity-modulated radiation therapy and proton therapy), or even completely eliminating radiation exposure where other treatments prove equally effective. The current study’s robust quantification of radiation’s contribution to risk provides strong data-driven support for these ongoing efforts to minimize radiation exposure in pediatric oncology. It reinforces the imperative for continued innovation in radiation-sparing strategies to protect survivors from future health complications.
Chemotherapy’s Complex Role:
Chemotherapy, another vital component of childhood cancer treatment, also contributed substantially to secondary cancer risk, albeit with more variability depending on the specific cancer type. The study found that chemotherapy contributed from 8% to 35% of subsequent cancer risk. The late effects of various chemotherapeutic agents have been well-described, with certain drugs linked to specific types of secondary cancers. For instance, alkylating agents and topoisomerase inhibitors are known to increase the risk of therapy-related acute myeloid leukemia (t-AML), while other agents might be implicated in solid tumors.
The wide range in chemotherapy’s contribution highlights the heterogeneous nature of these drugs and their mechanisms of action. Different chemotherapy regimens are tailored to specific cancer types and stages, and their long-term toxicities vary accordingly. This complexity underscores the ongoing need for precise risk stratification based on specific agents, cumulative doses, and individual patient vulnerabilities.
Genetics: The Unfolding Predisposition:
Perhaps the most striking and paradigm-shifting finding of the study pertains to the role of genetic predisposition. While the potential late effects of chemotherapy have been extensively documented, the contribution of inherent genetic factors to secondary cancer risk in survivors has been less well recognized and certainly not quantitatively attributed at a population level until now.
To better understand this predisposition, the researchers explored two main types of genetic variants. First, they examined hundreds of common genetic variants that have been previously associated with an increased risk of developing cancer in the general population. These variants, individually, have small effects but collectively can contribute significantly to an individual’s overall cancer risk, summarized as a polygenic risk score (PRS). Second, they looked at rare genetic variants, which, though less common, can have a more pronounced impact on cancer susceptibility. By analyzing these variants in the St. Jude LIFE and CCSS participants, the researchers uncovered their relationship to secondary cancers.
The polygenic risk score approach revealed that, depending on the specific type of secondary cancer, genetic predisposition contributed to a substantial 5% to 37% of the risk. This finding challenges conventional wisdom in the field. "Our findings showed that genetics can be equally or more important than chemotherapy in some second cancers, which is counter to conventional wisdom in the field," Dr. Sapkota revealed. This implies that for certain secondary malignancies, a survivor’s inherited genetic makeup might be as, or even more, influential than the cytotoxic chemotherapy they received as children.
Yutaka Yasui, PhD, also from the St. Jude Department of Epidemiology and Cancer Control and a co-author, shed light on the broader implications of this genetic insight: "Polygenic risk scores are developed for all kinds of diseases for personalized medicine, but generally with precision below what is required for clinical utility in the general population. Among survivors of childhood cancer and for estimating their risk of certain types of subsequent cancer, however, they may provide useful information in conjunction with therapy exposures." This statement highlights the potential for PRS to become a valuable tool in personalized risk assessment for this specific, high-risk population, even if its utility is still developing for the general public.
Lifestyle Factors: A Nuanced Perspective:
In contrast to the significant contributions of treatment and genetics, lifestyle factors, such as diet and exercise, appeared to contribute much less to secondary cancer risk in this study, accounting for a modest 1% to 6% of the risk. This finding might seem surprising given the well-established links between lifestyle and cancer risk in the general adult population.
However, Dr. Sapkota offered a crucial caveat: "Survivors in this study were primarily in their 20s and 30s, which may mean that lifestyle factors did not yet have enough time for effects to become apparent." The cumulative impact of lifestyle choices on cancer development often manifests over many decades. It is plausible that the relatively young age of the cohort members meant that the long-term effects of, for instance, dietary habits or physical activity levels had not yet fully materialized in terms of secondary cancer risk.
Despite this, Dr. Sapkota strongly emphasized the continued importance of healthy lifestyle choices for survivors: "We know healthy lifestyle choices are important for survivors. In this study, we focused only on the risk of second cancers, which may not be strongly impacted by lifestyle at this young age. However, other research has shown the benefits of healthy choices on other late effects, such as protecting cardiac wellbeing, so it is still important for clinicians to encourage—and patients to seek—a healthy lifestyle." This underscores that while lifestyle’s direct contribution to secondary cancer at a young age might be limited, its overarching benefits for overall health, including mitigating other late effects of treatment, remain undeniable.
Shifting Paradigms in Survivor Care
The quantifiable insights from this study are poised to catalyze a significant shift in how secondary cancer risk is assessed and managed in childhood cancer survivors.
Personalized Screening and Surveillance:
"Historically, we have paid attention to survivors’ treatment exposures when determining second cancer risk," Dr. Sapkota explained. "Our study suggests that we need to better account for genetic predisposition in this population." This paradigm shift implies a move towards more personalized and genetically informed surveillance strategies. Survivors identified with a strong genetic predisposition, perhaps through a high polygenic risk score or the presence of rare high-impact variants, could potentially receive more regular and intense cancer screenings. This proactive approach could lead to earlier detection of a second cancer, when it is typically more amenable to treatment and offers a higher chance of successful outcomes. For example, a survivor with a genetic predisposition to breast cancer combined with radiation exposure to the chest might warrant earlier and more frequent mammograms or breast MRIs than a survivor without such genetic markers.
Genetic Counseling and Risk Stratification:
The findings underscore the growing importance of genetic counseling for childhood cancer survivors. Incorporating genetic testing and risk assessment into routine long-term follow-up care could provide invaluable information. This wouldn’t just be about identifying germline mutations in known cancer predisposition genes, but also leveraging polygenic risk scores to refine individual risk profiles. Such comprehensive genetic evaluations could enable clinicians to stratify survivors into different risk categories, allowing for tailored surveillance protocols and targeted preventive interventions.
Empowering Survivors:
Knowledge is power, and survivors armed with the understanding of their unique combination of treatment-related, genetic, and even lifestyle risk factors can become more effective advocates for their own health. They can engage more meaningfully with their healthcare providers about the need for specific screenings, lifestyle modifications, and ongoing surveillance. This personalized understanding fosters a more proactive approach to health management, moving beyond generic guidelines to truly individualized care plans. Patient advocacy groups are likely to champion the integration of these genetic insights into survivor care guidelines, ensuring equitable access to advanced risk assessment tools.
The Broader Impact: Research, Policy, and Lifespan Extension
The implications of this study extend beyond individual clinical practice to influence broader research agendas and healthcare policies. "Second cancers remain the leading cause of mortality for childhood cancer survivors," Dr. Sapkota reiterated. "Now that we have quantified the contributions of treatment, genetics and lifestyle to the risk of secondary disease, we have a better understanding of where to focus efforts to prevent, detect and treat these cancers, and hopefully extend these survivors’ lives."
This research provides a robust framework for future studies. It will guide investigations into specific genetic variants that interact with particular treatment exposures, leading to an even finer-grained understanding of risk. It will also stimulate the development and validation of clinical tools that integrate genetic information with treatment history to generate actionable risk predictions. Furthermore, the findings are likely to influence guidelines for long-term follow-up care for childhood cancer survivors, advocating for the routine inclusion of genetic risk assessment. Healthcare policymakers may also consider funding initiatives that support comprehensive genetic testing and counseling for this high-risk population.
Ultimately, by dissecting the complex etiology of secondary cancers, this study provides a crucial roadmap toward a future where childhood cancer survivors can not only overcome their initial diagnosis but also navigate their adult lives with a clearer understanding of their health risks and with proactive, personalized strategies to mitigate them. The goal remains clear: to prevent, detect early, and effectively treat secondary cancers, thereby extending the healthy lifespan of those who have already faced and triumphed over so much.
Methodological Rigor and Collaborative Excellence
The strength of this study lies in its methodological rigor and the unparalleled resources it drew upon. The combination of the St. Jude LIFE and CCSS cohorts provided a statistical power and depth of data rarely seen in oncology research. The meticulous collection of treatment details, long-term health outcomes, and comprehensive genetic sequencing on thousands of survivors allowed for a robust, population-level analysis that would be impossible with smaller, less comprehensive datasets. The collaboration between multiple institutions and researchers, as evidenced by the extensive author list, further underscores the scientific excellence and collaborative spirit driving this vital research.
Authorship and Funding
The study’s first author is Achal Neupane, of St. Jude. The study’s other authors are Siddhant Taneja, Jennifer French, Matthew Ehrhardt, Tara Brinkman, Rachel Webster, Jun Yang, Kirsten Ness, Melissa Hudson, Gregory Armstrong, Leslie Robison and Yutaka Yasui, all from St. Jude; Qi Liu from the University of Alberta; Cindy Im, Lucie Turcotte and Joseph Neglia from the University of Minnesota; Monica Gramatges from Baylor College of Medicine; Rebecca Howell from the University of Texas MD Anderson Cancer Center and Smita Bhatia from the University of Alabama at Birmingham.
The study was supported by grants from the National Cancer Institute (R01HL173881, R01CA216354, R21CA261833, U24CA55727, U01CA195547 and CA21765) and ALSAC, the fundraising and awareness organization of St. Jude.
