When to call the cardio-oncologist? At the Global Cardio-Oncology Summit 2025, Dr. Christine Brezden-Masley, Medical Director of the Cancer Program at Sinai Health and Professor of Medicine at the University of Toronto, addressed one of the most pressing clinical questions in modern oncology
The session highlighted the increasingly intertwined relationship between cancer and cardiovascular health. Cardiovascular disease remains the leading cause of death worldwide, followed closely by cancer. Both conditions share common risk factors such as obesity, smoking, diabetes, and hypertension, making collaboration between the two specialties essential.
The evolving therapeutic landscape
The rapid expansion of modern cancer therapy has introduced new challenges. In 2024 alone, nearly one-third of all new oncology trials involved cell and gene therapies, multispecific antibodies, and antibody-drug conjugates (ADCs). These treatments have improved survival but are also linked to cardiotoxic effects.
Tracking the cardiac impact of new therapies is increasingly difficult as the global research pipeline accelerates. China, for example, has doubled its number of active cancer compounds since 2015 and is now among the top contributors of novel therapeutics. This progress has redefined survival outcomes in several cancers, notably HER2-positive metastatic breast cancer, where median overall survival now exceeds 40 months thanks to ADCs like trastuzumab deruxtecan (T-DXd). Yet with prolonged survival comes a rising burden of long-term cardiovascular complications.
The growing importance of survivorship
Improved outcomes have turned millions of cancer patients into long-term survivors. There are currently 53 million people worldwide within five years of a cancer diagnosis, a number projected to reach 83 million by 2050. This demographic shift makes survivorship care an essential part of oncology.
Cardiovascular complications can appear years after therapy. The cumulative effects of chemotherapy, radiotherapy, targeted drugs, and immunotherapies often manifest as heart failure, arrhythmias, or ischemic disease long after remission. Survivorship clinics now play a central role in early detection and prevention, bridging oncology and cardiology long after the last treatment cycle.
Clinical cases: early collaboration saves lives
Two case studies demonstrated how timely cardiology involvement changes outcomes.
The first involved a 32-year-old woman with de novo metastatic HER2-positive breast cancer. At diagnosis, her baseline ejection fraction was 51%. Following chemotherapy and targeted therapy, it dropped to 45–50%, warranting cardio-oncology referral for monitoring and management.
In another case, a 46-year-old man with locally advanced HER2-positive gastroesophageal adenocarcinoma underwent chemoradiation, surgery, and adjuvant immunotherapy. He later presented with mild cardiac biomarker elevations suggestive of possible myocarditis, a known complication of immune checkpoint inhibitors. Multidisciplinary evaluation allowed treatment optimization without compromising cancer control.
These examples illustrate that collaboration should begin early—before symptoms or irreversible damage occur. Baseline ECGs, echocardiography with strain imaging, and cardiac biomarkers such as troponin and BNP should be standard in patients receiving potentially cardiotoxic therapies.
Cardiotoxicity in the era of novel therapeutics
Antibody-drug conjugates have redefined oncology but also expanded the spectrum of cardiotoxicity. Trastuzumab deruxtecan is associated with ejection fraction declines of 3–12%, a slightly higher rate than with earlier HER2-targeted drugs. Determining whether therapy can continue safely in patients with mild dysfunction is the focus of the SCHOLAR-2 trial, led by Dr. Daryl Leong in Canada. This international study examines whether HER2-targeted therapy can be maintained with close cardiac monitoring rather than discontinued at the first sign of toxicity.
The results will help shape future cardio-oncology protocols, balancing life-saving cancer treatment with long-term cardiac safety.
Cardiotoxicity and modern therapeutics
New drug classes such as antibody-drug conjugates (ADCs) have revolutionized cancer therapy but introduced new layers of cardiac risk. Trastuzumab deruxtecan (T-DXd), for example, is associated with ejection fraction declines ranging from 3% to 12%, somewhat higher than seen with prior HER2-targeted therapies.
The question of whether treatment can continue despite mild cardiotoxicity is being investigated in the ongoing SCHOLAR-2 trial, led by Dr. Daryl Leong in Canada. This global study aims to determine whether HER2-targeted therapy can safely proceed in patients with mild left ventricular dysfunction under close cardiology supervision.
Such studies, she noted, are essential to guide the real-world management of patients receiving potentially cardiotoxic but life-prolonging therapies.
Optimizing survivorship and lifestyle intervention
The rise of survivorship brings renewed emphasis on prevention and lifestyle modification. Smoking cessation, balanced diet, and regular physical activity remain cornerstones of reducing both cardiac and oncologic risk. Exercise, in particular, has emerged as a potent therapeutic ally.
Recent trials have shown that high-intensity interval training (HIIT) during breast cancer therapy reduced mortality by nearly 80%, while the CHALLENGE trial in colorectal cancer demonstrated a 7% improvement in eight-year overall survival among patients who maintained structured exercise routines. These findings reinforce the notion that lifestyle interventions can deliver survival benefits comparable to—or greater than—some modern drug regimens.
Building bridges: when to call the cardio-oncologist?
Cardio-oncology partnerships are no longer optional—they are essential. Coordinated care enables patients to receive optimal cancer therapy without compromising heart health. Since the founding of the Canadian Cardio-Oncology Network (CCON) in 2011, the field has evolved from a small initiative of 35 professionals in Ottawa to a global collaborative platform that unites oncologists, cardiologists, and researchers.
Shared expertise, standardized protocols, and mutual trust now allow clinicians to safely “push the limits” of cancer treatment while preserving cardiovascular function. The success of this model has inspired similar networks worldwide, ensuring that patients benefit from multidisciplinary expertise regardless of where they receive care.
Conclusion
Modern cancer therapies have transformed survival but introduced new cardiovascular risks. The future of oncology depends on an integrated approach that combines innovation with vigilance, science with prevention, and oncology with cardiology.Collaboration between these specialties is not just about managing toxicity—it’s about ensuring that every patient can survive cancer without sacrificing heart health.
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