Cancer is the leading cause of death, followed by cardiovascular disease (CVD), which is the second leading cause of death in Japan. The relationship between cancer and CVD is increasingly recognized as a critical area of research in the field of cardio-oncology. Both diseases are leading causes of morbidity and mortality worldwide, and they share numerous overlapping risk factors and pathophysiological mechanisms [1]. Cancer and CVD are multifactorial diseases with highly overlapping risk factors, including smoking, obesity, metabolic syndrome, hypertension, diabetes, and inflammation. These commonalities suggest a bidirectional relationship where each condition can potentially influence the onset and progression of the other. For example, heart failure has been associated with an increased risk of cancer due to shared mechanisms such as inflammation and oxidative stress [2]. A study, examines the CVD mortality risk among US cancer survivors, which revealed that CVD mortality risk can surpass cancer mortality risk in certain cases and is particularly high shortly after cancer diagnosis [3]. Another study also revealed that adult cancer survivors have independently higher risk of CVD, especially heart failure [4]. In addition, cancer treatments, including chemotherapy, radiotherapy, and targeted therapies, have been shown to increase the risk of CVD complications. These treatments can lead to cardiotoxicity, manifesting as heart failure, arrhythmias, or coronary artery disease [5]. For example, anthracyclines and trastuzumab are well-known for their potential to cause heart damage by reducing cardiac pumping ability. It is important to monitor CVD in cancer patients before, during, and after treatment to mitigate long-term CVD risks. Conversely, there is emerging evidence that CVD itself may predispose individuals to cancer. The physiological stress associated with heart disease can promote tumor growth through mechanisms such as increased circulating inflammatory markers [2]. Additionally, some studies report that certain medications used in managing CVD, like angiotensin-converting enzyme inhibitors (ACEIs) and aspirin, have been linked to altered cancer risks [6]. The relationship between cancer and CVD has become clear, and care for both is important.

On the other hand, there is little epidemiological data to show the relationship between cancer and CVD in relatively young people under the age of 65. Suzuki et al. investigated the relationship between cancer history and CVD risk in individuals with hypertension by analyzing 747,620 individuals aged 45–64 years with hypertension, including 26,531 with a cancer history from the JMDC database [7]. They revealed that a history of cancer was associated with a greater risk of developing composite CVD events, which are defined as myocardial infarction (MI), angina pectoris (AP), stroke, heart failure (HF), and atrial fibrillation (AF), among individuals with hypertension [7]. In addition, they also revealed that patients who had received chemotherapy for cancer had a particularly higher risk of developing CVD compared to those who did not undergo chemotherapy [7]. Furthermore, they revealed that cancer history is associated with higher hazard ratio for each component of composite CVD events; MI, AP, stroke, HF, and AF, respectively. From these results, they concluded that individuals with hypertension and a history of cancer, especially those treated with chemotherapy, have a higher risk of developing CVD.

The study provides significantly important insights about the close relationship between cancer and CVD among individuals with hypertension. However, there are a few points to keep in mind when interpreting the article. First, the study using the JMDC database is limited to individuals aged 45–64 years, which makes it difficult to generalize to the overall population. Generally speaking, cancer and CVD events are more commonly observed in individuals aged 65 and above, and the data may appear insufficient to accurately demonstrate the relationship between cancer and cardiovascular diseases. It is important to use a database that is tailored to the age group of those affected by cancer or CVD. Second, as the authors state in their limitations, the database lacks detailed cancer-related information (e.g., type and stage of cancer) and smoking history. Distinguishing between different types and stages of cancer is crucial because they indicate complications, severity, and prognosis. This study combines all cancer types, but it is challenging to analyze all cancer types and stages as the same. For example, pancreatic cancer requiring surgery and prostate cancer diagnosed based on elevated markers are clearly different. Analysis that takes into account the type and severity of cancer is required. Third, the group with a history of cancer is significantly older (52 years vs. 59 years) and the gender composition differs significantly in both groups. Therefore, the results of Kaplan-Meier curves should be interpreted with caution. Fourth, it does not clarify whether the increased risk of CVD is due to cancer itself or the chemotherapy treatment because this study lacks detailed information of chemotherapy. While some chemotherapy treatments directly lead to cardiovascular disease, it is important to note that this article is intended to explore the relationship between cardiovascular disease and cancer, not the potential cardiotoxic effects of chemotherapy. Finally, this study is a database observational study, and therefore, it is difficult to show causality.

Despite the limitations mentioned above, Suzuki et al. provide important information in that they reveal the close relationship between cancer and cardiovascular disease, even in individuals under the age of 65. The importance of long-term follow-up for cancer survivors, focusing on cardiovascular health, cannot be overstated. The Childhood Cancer Survivor Study has provided valuable insights into the long-term CVD risks in childhood cancer survivors [8], emphasizing the need for similar long-term studies in adult cancer survivors. The interplay between cancer and CVD necessitates a multidisciplinary approach in patient care. Oncologists and cardiologists must collaborate to balance effective cancer treatment with CVD risk management. This includes lifestyle interventions such as smoking cessation and weight management, alongside regular cardiovascular assessments for cancer survivors. Preventive strategies that could benefit both cancer and CVD outcomes, such as exercise interventions or dietary modifications, should be further explored. For example, exercise interventions during and after cancer treatment can improve cardiovascular fitness and potentially reduce the risk of both cancer recurrence and CVD [9].

As the field of cardio-oncology evolves, it is crucial to develop evidence-based guidelines for managing cardiovascular health in cancer patients. Further research is needed to fully understand the complex interactions between these diseases and to optimize therapeutic strategies that minimize adverse cardiovascular outcomes while maintaining effective cancer control. By fostering collaboration across specialties, both cardiologists and oncologists can improve outcomes for patients navigating the complexities of both cancer and CVD. Further collaboration between these specialists is required.