By Billy Candra 
Physicians dedicated to the lifelong care of childhood cancer survivors must now integrate a deeper understanding of risk factors, as groundbreaking research from St. Jude Children’s Research Hospital unequivocally demonstrates that survivors’ genetic makeup, in conjunction with their life-saving cancer treatments, significantly contributes to their risk of developing secondary cancers. This pivotal finding, published today in The Lancet Oncology, marks a crucial advancement in understanding the complex etiology of these subsequent malignancies, which represent the leading cause of mortality for long-term survivors of childhood cancer. By meticulously quantifying the proportional contributions of various factors, scientists have provided an unprecedented clarity that promises to reshape long-term follow-up care and screening protocols for this vulnerable population. The study leveraged the unparalleled datasets from the St. Jude Lifetime Cohort Study (St. Jude LIFE) and the Childhood Cancer Survivor Study (CCSS), two of the most extensive and well-regarded childhood cancer survivor studies globally, both headquartered at St. Jude.
The scientific community has long recognized that childhood cancer survivors face a heightened risk of developing secondary cancers. This phenomenon, often a cruel irony following successful primary cancer treatment, has prompted extensive research into its causes. Historically, the focus has largely been on the adverse effects of therapeutic interventions such as radiation and chemotherapy. While these treatments are undeniably critical for eradicating primary cancers, their systemic impact can predispose survivors to new malignancies years, or even decades, later. However, the precise extent to which different factors contribute to this risk at a population level has remained largely unquantified, creating a significant knowledge gap that this new St. Jude research now addresses.
"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. Dr. Sapkota emphasized the novelty of the findings, noting, "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 is vital, moving beyond mere association to establish a clearer hierarchy of risk drivers, thereby enabling more targeted and effective preventative strategies.
The Enduring Threat of Secondary Cancers for Childhood Survivors
Childhood cancer, while devastating, has seen remarkable improvements in survival rates over the past few decades. In the 1970s, the five-year survival rate for childhood cancers was around 58%; today, it exceeds 80% and, for some cancers, approaches 90%. This medical triumph, however, has brought into sharper focus the long-term health challenges faced by these survivors. Among the myriad late effects—which can include cardiac issues, endocrine dysfunction, and neurocognitive deficits—secondary cancers stand out as the gravest. They are not merely a complication but the primary cause of premature mortality among long-term survivors, underscoring the urgency of understanding and mitigating this risk. The types of secondary cancers vary widely depending on the primary diagnosis and treatment, but can include leukemias, lymphomas, sarcomas, and carcinomas of the breast, thyroid, and skin, among others. The incidence of secondary cancers is estimated to be several times higher in childhood cancer survivors compared to the general population, with cumulative incidence rates continuing to climb decades after initial treatment.
Leveraging Unparalleled Data: The St. Jude LIFE and CCSS Cohorts
The robustness of the St. Jude study’s findings is largely attributable to the extraordinary depth and breadth of the data utilized from the St. Jude LIFE and CCSS cohorts. These two studies represent a colossal undertaking in longitudinal health research, meticulously tracking thousands of childhood cancer survivors over many years, often decades.
The St. Jude LIFE study enrolls adult survivors who were treated for childhood cancer at St. Jude Children’s Research Hospital, providing comprehensive follow-up care and collecting extensive clinical and genomic data. The CCSS, on the other hand, is a multi-institutional, retrospective cohort study that includes survivors from 31 institutions across North America, focusing on the long-term health outcomes of individuals diagnosed with cancer before age 21. Combined, these cohorts provide an unparalleled resource for understanding the long-term effects of childhood cancer and its treatment.
For this particular research, scientists compared data from over 10,000 survivors drawn from both St. Jude LIFE and CCSS, collectively representing the largest survivor cohort in North America with available genetic sequencing information. This vast dataset encompassed critical variables, including detailed records of treatment exposures (e.g., specific chemotherapy agents, radiation fields and doses), comprehensive genetic information (both common and rare variants), lifestyle factors (such as diet and exercise), and, critically, the presence or absence of a secondary cancer diagnosis. The sheer scale and granularity of this data allowed researchers to move beyond simple correlations and employ sophisticated statistical models to apportion the relative contributions of these factors to secondary cancer incidence at a population level.
Co-author Greg Armstrong, MD, MSCE, chair of the St. Jude Department of Epidemiology and Cancer Control, underscored the unique capability of these datasets: "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." The combination of detailed clinical histories with extensive genomic data is what truly sets this study apart, enabling insights that would be impossible with smaller, less comprehensive datasets.
Deconstructing Risk: Quantifying Contributions to Secondary Cancers
The study meticulously dissected the contributions of radiation exposure, chemotherapy, genetic predisposition, and lifestyle factors to the risk of secondary cancers, revealing a nuanced landscape of causality.
Radiation’s Enduring Legacy:
Radiation therapy emerged as the most significant single contributor to secondary cancer risk, accounting for approximately 40% or more of the observed risk, depending on the specific secondary cancer type. This finding reinforces decades of prior research that has consistently highlighted the long-term adverse effects of radiation. While radiation is highly effective in localizing and destroying cancer cells, it also damages surrounding healthy tissues, increasing the likelihood of new cancer development years later. Historically, radiation was a cornerstone of many childhood cancer treatment regimens, often delivered at high doses and to extensive fields. However, recognizing these long-term risks, modern pediatric oncology has progressively reduced radiation doses, narrowed treatment fields, and in many cases, entirely replaced radiation with other effective treatments, particularly for certain leukemias and lymphomas. The study’s quantification provides further empirical support for these ongoing shifts in clinical practice, validating the efforts to minimize radiation exposure whenever possible.
Chemotherapy’s Variable Impact:
The study found that chemotherapy contributed between 8% and 35% of subsequent cancer risk, a range that varied significantly based on the specific type of secondary cancer. The late effects of chemotherapy, including cardiotoxicity, neurotoxicity, and secondary malignancies, are also well-documented. Certain classes of chemotherapeutic agents, such as alkylating agents and topoisomerase inhibitors, are known to be particularly genotoxic and have been linked to an increased risk of secondary leukemias and solid tumors. The study’s findings underscore that while chemotherapy is indispensable for curing many childhood cancers, its specific protocols and agents must be continually evaluated for their long-term risk profiles.
The Unveiling of Genetic Predisposition:
Perhaps the most striking and novel finding of the study was the substantial and often underappreciated contribution of genetic predisposition to secondary cancer risk in survivors. While the late effects of treatment have been extensively described, the role of an individual’s inherent genetic susceptibility had not been quantified at this population scale. To explore this, researchers examined hundreds of common genetic variants previously associated with cancer development in the general population, integrating them into what is known as a polygenic risk score (PRS). They also assessed the impact of rare genetic variants.
The polygenic risk score approach revealed that, depending on the specific secondary cancer type, genetic predisposition contributed between 5% and 37% of the risk. This finding challenges conventional wisdom, as Dr. Sapkota articulated: "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 suggests that for certain types of secondary cancers, an individual’s inherited genetic susceptibility can be as, or even more, influential than the chemotherapy they received.
Yutaka Yasui, PhD, also from the St. Jude Department of Epidemiology and Cancer Control and a co-author, commented on the clinical potential of PRS: "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, when combined with detailed treatment histories, to offer a more precise and actionable risk assessment for childhood cancer survivors.
Lifestyle Factors: A Nuanced View:
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 cohort, accounting for a modest 1% to 6%. This observation, however, comes with an important caveat. The survivors included in this study were primarily in their 20s and 30s. The effects of lifestyle choices, both positive and negative, often accrue over longer periods and may not have had sufficient time to manifest as secondary cancers in this relatively young adult population.
Dr. Sapkota cautioned against misinterpreting this finding: "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 emphasizes that while lifestyle’s direct contribution to secondary cancer risk might be limited in younger survivors, its overarching importance for general health and other late effects remains undisputed.
Transforming Long-Term Care for Childhood Cancer Survivors
The implications of this comprehensive quantification are profound, signaling a paradigm shift in how healthcare providers assess and manage the long-term health of childhood cancer survivors.
Personalized Risk Assessment and Screening:
"Historically, we have paid attention to survivors’ treatment exposures when determining second cancer risk," Dr. Sapkota noted. "Our study suggests that we need to better account for genetic predisposition in this population." This new understanding mandates a more integrated approach, where genetic screening becomes a standard component of follow-up care for survivors. Identifying individuals with a strong genetic predisposition to certain cancers, combined with their specific treatment history, allows for the development of highly personalized surveillance plans. For instance, a survivor with a high polygenic risk score for breast cancer, coupled with chest radiation exposure, might warrant more frequent mammograms or earlier initiation of screening than current general guidelines suggest. This proactive, risk-stratified approach could lead to earlier detection of secondary cancers, when they are more amenable to successful treatment, ultimately improving survival outcomes.
Refining Treatment Protocols and Clinical Guidelines:
The findings will also inform ongoing efforts to refine initial cancer treatment protocols. As researchers gain a more detailed understanding of gene-treatment interactions, it may become possible to tailor primary therapies to an individual’s genetic profile, minimizing the use of highly toxic agents in those who are genetically predisposed to their late effects, without compromising treatment efficacy. This move towards precision oncology, often discussed in the context of primary cancer treatment, now extends significantly into survivorship care.
Empowering Survivors:
Armed with knowledge about their unique combination of treatment-related, genetic, and lifestyle risk factors, survivors can become more active participants in their own healthcare. They can better advocate for specific screenings and interventions with their healthcare providers, fostering a more collaborative and informed approach to managing their long-term health. Patient advocacy groups are likely to seize upon these findings to champion increased access to genetic counseling and comprehensive risk assessments for all childhood cancer survivors.
The Road Ahead: Future Research and Policy Implications
This landmark study represents a critical milestone, but it also paves the way for extensive future research. Scientists will likely delve deeper into specific genetic variants and their interactions with particular treatment exposures to identify even more precise risk predictors. Further studies are needed to explore how lifestyle factors might impact secondary cancer risk over longer follow-up periods, as survivors age into their 40s, 50s, and beyond. Understanding the biological mechanisms through which genetic predispositions interact with treatment-induced damage will also be a key area of investigation, potentially leading to novel preventative interventions.
From a policy perspective, these findings underscore the need for robust funding for long-term follow-up clinics and research initiatives focused on survivorship. Insurance coverage for genetic testing and enhanced, risk-stratified cancer screenings for childhood cancer survivors will become increasingly important considerations for healthcare systems.
As Dr. Sapkota concluded, "Second cancers remain the leading cause of mortality for childhood cancer survivors. 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 offers a beacon of hope, transforming the landscape of survivorship care from a reactive approach to a proactive, personalized strategy, ultimately aiming to ensure that childhood cancer survivors not only live, but thrive, free from the shadow of secondary disease.
The study’s first author is Achal Neupane, of St. Jude. Other authors include 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 generous grants from the National Cancer Institute (R01HL173881, R01CA216354, R21CA261833, U24CA55727, U01CA195547, and CA21765) and ALSAC, the dedicated fundraising and awareness organization for St. Jude Children’s Research Hospital.