By Billy Candra 
Physicians caring for survivors of childhood cancer must now consider an expanded understanding of risk factors for secondary malignancies, with new research from St. Jude Children’s Research Hospital unequivocally demonstrating that survivors’ inherent genetics, in addition to their life-saving initial cancer treatments, play a critical role in determining their long-term susceptibility. This seminal finding, published today in The Lancet Oncology, quantifies the distinct contributions of various factors to the risk of a second cancer, a leading cause of mortality among long-term survivors of pediatric malignancies. The study leveraged extensive data from two of the world’s foremost childhood cancer survivor cohorts, the St. Jude Lifetime Cohort Study (St. Jude LIFE) and the Childhood Cancer Survivor Study (CCSS), both housed at St. Jude.
A Deeper Dive into Secondary Cancer Risk: Beyond Treatment Exposures
For decades, the medical community has recognized the long-term sequelae of aggressive childhood cancer treatments, particularly the increased risk of developing new, unrelated cancers later in life. However, the precise proportional contributions of different risk factors – genetic predisposition, specific treatment modalities, and lifestyle choices – have remained largely unquantified at a population level. This knowledge gap posed a significant challenge for developing truly personalized surveillance and prevention strategies for this vulnerable population. The new St. Jude study meticulously addresses this, providing a comprehensive attribution of risk factors.
"We found the burden of second cancer in survivors of childhood cancer is largely contributed by pediatric treatment exposures and genetic predisposition," stated Yadav Sapkota, PhD, corresponding author and a faculty member in the St. Jude Department of Epidemiology and Cancer Control. Dr. Sapkota emphasized the groundbreaking nature of the quantification: "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 attribution provides an unprecedented roadmap for clinicians and researchers to refine risk stratification and intervention strategies.
The Power of Cohort Studies: Unlocking Complex Interactions
The ability to dissect these complex interactions stems from the unparalleled scale and depth of the St. Jude LIFE and CCSS cohorts. These studies represent a monumental, decades-long effort to track the health outcomes of thousands of childhood cancer survivors, meticulously collecting data on their original cancer diagnoses, treatment regimens, genetic profiles, lifestyle factors, and subsequent health events. Collectively, these cohorts comprise over 10,000 survivors, making them the largest such survivor cohort in North America.
Co-author Greg Armstrong, MD, MSCE, chair of the St. Jude Department of Epidemiology and Cancer Control, underscored the unique capacity of these resources. "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 noted. The sheer volume of data, coupled with detailed genetic information, enabled researchers to move beyond correlational studies to a more precise quantification of risk contributions. This includes comprehensive records of radiation exposure, chemotherapy agents, genetic information spanning common and rare variants, lifestyle habits, and the subsequent development (or absence) of a second cancer.
Radiation’s Enduring Legacy: A Significant but Mitigated Risk
Among the quantified risk factors, radiation exposure emerged as the most significant contributor to secondary cancer risk, accounting for approximately 40% or more of the overall risk. This finding reinforces decades of prior research documenting the long-term adverse effects of therapeutic radiation, including its carcinogenic potential. Early childhood cancer treatments, particularly in the mid to late 20th century, often involved higher doses and broader fields of radiation, given the nascent understanding of its late effects and the imperative to cure the primary cancer.
In response to accumulating evidence of radiation-induced toxicities, including secondary malignancies, modern pediatric oncology has undergone a paradigm shift. Contemporary treatment protocols have dramatically reduced radiation doses, narrowed treatment fields, or eliminated radiation entirely where effective alternative therapies exist. This study provides further compelling evidence supporting these ongoing efforts to minimize radiation exposure while maintaining high cure rates for childhood cancer. The continuous evolution of treatment strategies, driven by such research, aims to improve not only survival but also the long-term quality of life for survivors.
Genetics: An Underestimated Force in Secondary Cancer Risk
While the impact of radiation was stark, the study unveiled more nuanced and, in some cases, surprising relationships concerning chemotherapy and genetic predisposition. Chemotherapy’s contribution to subsequent cancer risk varied significantly depending on the specific cancer type, ranging from 8% to 35%. The potential late effects of various chemotherapeutic agents, such as alkylating agents and topoisomerase inhibitors, on subsequent cancer development have been well-documented. However, the extent of genetic predisposition’s contribution was less clearly defined until now.
To elucidate the role of genetics, the researchers delved into hundreds of common genetic variants previously associated with cancer development in the general population, integrating them into a "polygenic risk score" (PRS). They also investigated rare genetic variants. This polygenic risk score approach revealed that genetic predisposition contributed between 5% and 37% of the second cancer risk, depending on the specific type of subsequent cancer.
"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," explained co-author Yutaka Yasui, PhD, from the St. Jude Department of Epidemiology and Cancer Control. "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 transition from a research tool to a clinically actionable one, particularly within specific high-risk populations like childhood cancer survivors.
Perhaps the most striking revelation from the genetic analysis challenged long-held assumptions within 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 stated. This finding represents a significant recalibration of understanding, suggesting that for certain secondary malignancies, a survivor’s inherited genetic blueprint might be a more potent determinant of risk than the specific chemotherapeutic agents they received. This paradigm shift underscores the necessity of incorporating genetic profiling into comprehensive survivor care plans.
Lifestyle Factors: A Long-Term Perspective
In contrast to the significant contributions of treatment and genetics, lifestyle factors such as diet and exercise appeared to contribute much less to second cancer risk in this study, accounting for a modest 1% to 6%. This finding, while seemingly downplaying the role of healthy living, comes with a crucial caveat. The survivors included in this study were primarily in their 20s and 30s, meaning that many of the long-term effects of lifestyle choices, which often manifest over decades, may not yet have become apparent.
Dr. Sapkota elaborated on this point, reiterating the broader importance of healthy habits. "We know healthy lifestyle choices are important for survivors," he affirmed. "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 perspective underscores that while lifestyle’s direct impact on secondary cancer risk may be limited in younger survivors, its overall contribution to health and mitigation of other treatment-related morbidities remains paramount.
Implications for Clinical Practice and Survivor Care
The findings of this study carry profound implications for the evolving landscape of childhood cancer survivor care. Historically, clinical attention to secondary cancer risk has largely focused on a survivor’s treatment history, particularly radiation exposure. This research mandates a broader, more integrated approach.
"Historically, we have paid attention to survivors’ treatment exposures when determining second cancer risk," Dr. Sapkota reflected. "Our study suggests that we need to better account for genetic predisposition in this population." This shift calls for the integration of genetic screening and risk assessment into routine follow-up care for childhood cancer survivors.
For survivors identified with a strong genetic predisposition, this could translate into more aggressive and frequent cancer screenings, tailored to their specific genetic risks. Early detection is paramount for improving outcomes, as secondary cancers caught at an earlier stage are generally more responsive to treatment. Furthermore, empowering survivors with knowledge of their unique combination of treatment-related, genetic, and lifestyle risk factors could enable them to engage more proactively with their healthcare providers, advocating for personalized screening protocols and preventative strategies. This move towards precision medicine for survivorship care holds the promise of significantly improving long-term health outcomes.
A Call to Action for Prevention, Detection, and Treatment
The ultimate goal of such research is to extend and enhance the lives of childhood cancer survivors. Second cancers remain the single leading cause of mortality for this population, often decades after their initial victory over cancer. By precisely quantifying the contributions of treatment, genetics, and lifestyle, this study provides a clearer roadmap for targeted interventions.
"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," Dr. Sapkota concluded. This enhanced understanding is expected to drive advancements in several key areas:
- Refined Risk Stratification: Developing more sophisticated algorithms that combine treatment history with genetic profiling to identify high-risk individuals for specific secondary cancers.
- Personalized Screening Guidelines: Moving beyond generalized recommendations to individualized surveillance plans based on a survivor’s unique risk profile.
- Targeted Prevention Strategies: Investigating gene-environment interactions to develop personalized preventative measures.
- Enhanced Patient Education and Counseling: Providing survivors and their families with clear, actionable information about their individual risks and how to manage them.
- Future Research Avenues: Stimulating further research into the specific mechanisms by which genetic variants interact with treatment exposures to drive secondary carcinogenesis, and exploring the long-term impact of lifestyle interventions in older survivor cohorts.
The study’s first author is Achal Neupane, of St. Jude. Other contributing authors from St. Jude include Siddhant Taneja, Jennifer French, Matthew Ehrhardt, Tara Brinkman, Rachel Webster, Jun Yang, Kirsten Ness, Melissa Hudson, Gregory Armstrong, Leslie Robison, and Yutaka Yasui. Additional collaborators 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.
This pivotal research was made possible through substantial support from grants provided by 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. The findings represent a significant leap forward in understanding the complex long-term health challenges faced by childhood cancer survivors, paving the way for more precise and effective interventions to improve their health and longevity.
