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 to the risk for secondary cancers. This critical finding, emerging from groundbreaking research by scientists at St. Jude Children’s Research Hospital, quantifies for the first time the proportional contributions of various factors to the risk of developing a second primary malignancy, which represents the leading cause of mortality for long-term survivors of pediatric cancer. The comprehensive new research leveraged extensive data from two of the world’s preeminent childhood cancer survivor studies, the St. Jude Lifetime Cohort Study (St. Jude LIFE) and the Childhood Cancer Survivor Study (CCSS), both centrally housed at St. Jude. The seminal study was formally published today in the esteemed medical journal, The Lancet Oncology.
The landscape of childhood cancer survival has undergone a dramatic transformation over the past several decades. What was once a grim prognosis for many pediatric cancer diagnoses has evolved into a narrative of increasing survivorship, with more than 85% of children diagnosed with cancer now surviving five years or more. This remarkable success, however, has brought into sharper focus the long-term health challenges faced by these survivors, prominent among them being the elevated risk of developing secondary cancers. These subsequent malignancies, often distinct from the original childhood cancer, pose a significant threat to the extended lifespans achieved through initial successful treatment. Understanding the multifaceted drivers of this risk is paramount for improving lifelong care.
Quantifying the Contributions to Secondary Cancer Risk
The St. Jude study marks a pivotal moment in this understanding, moving beyond identifying risk factors in isolation to attributing their relative contributions at a population level. Dr. Yadav Sapkota, a corresponding author from the St. Jude Department of Epidemiology and Cancer Control, articulated the core discovery: "We found the burden of second cancer in survivors of childhood cancer is largely contributed by pediatric treatment exposures and genetic predisposition. We’ve known treatment exposures and genetics were associated with second cancer risk, but 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 provides an unprecedented roadmap for clinical intervention and future research.
Previous investigations have meticulously explored how specific treatment exposures, genetic predispositions, and lifestyle choices correlate with an increased risk of secondary cancers. However, the comparative weight of these factors within the broader population of survivors remained an elusive piece of the puzzle. To bridge this critical knowledge gap, St. Jude scientists undertook a monumental task, analyzing data from over 10,000 survivors drawn from the St. Jude LIFE and CCSS cohorts. Combined, these cohorts represent the largest survivor population in North America, offering an unparalleled dataset for such an intricate analysis. The wealth of information included detailed records of initial cancer treatment exposures, subsequent health outcomes, comprehensive genetic information, various lifestyle factors, and, crucially, the presence or absence of a second primary cancer. This holistic approach allowed researchers to systematically evaluate the proportional contribution of each factor to the occurrence of these dreaded follow-up diseases.
Dr. Greg Armstrong, co-author and Chair of the St. Jude Department of Epidemiology and Cancer Control, underscored the unique nature of this research. "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," he stated, highlighting the extraordinary scale and depth of genetic data available for analysis.
Radiation Exposure: A Dominant but Evolving Risk
The study identified radiation exposure as the most significant contributor to secondary cancer risk, accounting for approximately 40% or more of the overall risk. This finding, while substantial, reinforces a well-established understanding within pediatric oncology. Decades of research have consistently described the long-term adverse effects of therapeutic radiation, particularly its carcinogenic potential. Consequently, modern therapeutic protocols have already seen a strategic shift towards reducing radiation doses or, where possible, eliminating radiation exposure entirely as other, equally effective treatments have emerged and advanced. This study provides further robust evidence supporting these ongoing modifications in treatment paradigms. The historical timeline of childhood cancer treatment illustrates this evolution: early protocols, especially for conditions like Hodgkin lymphoma or certain brain tumors, often involved extensive radiation fields. As understanding of late effects grew and systemic therapies improved, the focus shifted towards dose reduction and precision targeting, minimizing exposure to healthy tissues. This study’s data quantifies the legacy of past radiation practices and validates the current efforts to mitigate its long-term consequences.
Unmasking the Role of Genetics and Chemotherapy
While the impact of radiation exposure was relatively straightforward, the researchers uncovered more complex and nuanced relationships when examining the contributions of chemotherapy and genetic predisposition. Chemotherapy, a cornerstone of most childhood cancer treatments, was found to contribute between 8% and 35% of subsequent cancer risk, with the specific percentage varying depending on the type of secondary cancer. The potential late effects of various chemotherapeutic agents, including cardiotoxicity, infertility, and secondary malignancies, have been extensively documented. However, the contribution of genetic predisposition to secondary cancer risk in survivors has been less consistently recognized and quantified at this population level.
Driven by a desire to better understand this genetic component, the researchers meticulously investigated hundreds of common genetic variants previously associated with cancer development in the general population. These variants were integrated into what is known as a polygenic risk score (PRS). Additionally, they examined certain rare genetic variants. By analyzing the relationship between these genetic markers and the incidence of secondary cancers within the St. Jude LIFE and CCSS participants, a clearer picture emerged. The polygenic risk score approach revealed that, depending on the specific type of secondary cancer, genetic predisposition contributed a substantial 5% to 37% of the risk.
Dr. Yutaka Yasui, another co-author from the St. Jude Department of Epidemiology and Cancer Control, commented on the clinical utility of these scores. "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," he explained. "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 distinction is crucial: while PRS might have limited predictive power for the general population’s cancer risk, their utility significantly escalates within the context of childhood cancer survivors, where treatment exposures create a unique susceptibility landscape.
Perhaps one of the most surprising findings, challenging conventional wisdom in the field, was the revelation that genetics can be equally or even more important than chemotherapy in the development of some secondary cancers. Dr. Sapkota emphasized this point: "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." This paradigm shift underscores the necessity of integrating genetic risk assessment more prominently into long-term survivor care plans.
Lifestyle Factors: A Long-Term Perspective
In contrast to radiation, chemotherapy, and genetics, lifestyle factors—such as diet and exercise—appeared to contribute much less to secondary cancer risk in this particular study, accounting for a modest 1% to 6% of the risk. This finding, however, comes with a critical caveat: the survivor population included in this analysis was primarily in their 20s and 30s. At this relatively young age, the cumulative effects of lifestyle choices on cancer development may not yet have had sufficient time to manifest.
Dr. Sapkota provided important context for interpreting these results: "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 distinction highlights that while lifestyle’s direct impact on secondary cancer risk might be less immediate at younger ages, its broader benefits for overall health and the prevention of other long-term complications remain undeniable and crucial for survivor well-being.
Transforming Care for Childhood Cancer Survivors
The implications of this comprehensive study for the ongoing care of childhood cancer survivors are profound and far-reaching. Historically, clinical attention to secondary cancer risk has predominantly focused on survivors’ treatment exposures, particularly radiation doses and specific chemotherapy regimens. "Our study suggests that we need to better account for genetic predisposition in this population," Dr. Sapkota asserted. This shift in understanding necessitates a re-evaluation of current risk stratification models and screening protocols.
For survivors identified with a strong genetic predisposition to certain cancers, this knowledge could translate into more personalized and intensified surveillance programs. Regular and more frequent cancer screenings, tailored to their specific genetic risks and treatment history, could lead to earlier detection of secondary cancers, significantly improving the chances of successful treatment and ultimately, survival. Empowered with the knowledge of their unique combination of treatment-related, genetic, and lifestyle risk factors, survivors can also become more proactive advocates in their own healthcare journeys, engaging in informed discussions with their healthcare providers about the necessity and type of screening required.
The broader medical community, including oncologists, primary care physicians, and survivorship specialists, will need to integrate these new insights into their clinical practices. Educational initiatives and updated guidelines will be essential to ensure that this nuanced understanding of risk factors reaches all practitioners involved in the long-term care of these vulnerable patients. This might involve wider adoption of genetic testing for survivors, particularly those with a strong family history of cancer or specific treatment exposures.
"Second cancers remain the leading cause of mortality for childhood cancer survivors," Dr. Sapkota reiterated, emphasizing the urgency of these findings. "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 improved understanding promises to refine risk prediction models, optimize screening strategies, and ultimately, enhance the quality and longevity of life for a growing population of childhood cancer survivors.
Methodology and Cohort Power
The power of this study rests significantly on the unparalleled resources provided by the St. Jude Lifetime Cohort Study (St. Jude LIFE) and the Childhood Cancer Survivor Study (CCSS). The CCSS, initiated in 1994, is a multi-institutional cohort study designed to investigate the long-term health outcomes of individuals diagnosed with cancer before age 21. It includes more than 35,000 survivors from 31 participating institutions across the United States and Canada, making it the largest cohort of its kind globally. The St. Jude LIFE study, established in 2007, specifically focuses on survivors treated at St. Jude Children’s Research Hospital, offering an even deeper level of detailed clinical and genetic data, including comprehensive assessments of late effects, advanced imaging, and biospecimen collection. The synergy of these two cohorts, with their extensive follow-up periods and meticulous data collection, provided the robust foundation necessary to disentangle the complex interplay of factors contributing to secondary cancer risk. The ability to combine such a large number of survivors with extensive genetic sequencing information truly set this study apart.
Looking Ahead: Future Research and Policy Implications
This research opens several avenues for future investigation. Further studies could delve into the specific genetic variants and pathways that most significantly interact with particular treatment exposures to elevate risk. Research could also focus on developing more precise polygenic risk scores, potentially incorporating additional genetic markers or environmental factors, to achieve even greater predictive accuracy. Longitudinal studies will also be crucial to understand how the contribution of lifestyle factors evolves over a survivor’s lifespan, particularly as they reach older adulthood.
From a policy perspective, these findings could advocate for broader coverage of genetic counseling and testing services for childhood cancer survivors, recognizing their unique vulnerability. It could also influence national guidelines for survivorship care, recommending more personalized surveillance protocols based on an integrated assessment of genetic and treatment-related risks. Patient advocacy groups will likely leverage this research to empower survivors and their families, ensuring they are aware of these critical insights and can advocate for the most comprehensive and personalized care available.
Authorship and Funding
The study’s first author is Achal Neupane, affiliated with St. Jude. The extensive list of co-authors includes 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. Other contributing authors include 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 vital research was supported by substantial grants from the National Cancer Institute (R01HL173881, R01CA216354, R21CA261833, U24CA55727, U01CA195547, and CA21765). Additional crucial support was provided by ALSAC, the dedicated fundraising and awareness organization that sustains St. Jude Children’s Research Hospital. These funding bodies are instrumental in enabling the pioneering research that continues to redefine the understanding and treatment of childhood cancer and its long-term effects.