The heart and cancer may seem unrelated at first glance but a growing body of research reveals a complex interplay between these seemingly disparate systems.

Advances in cancer treatments have led to increased survival rates. However, the cardiovascular side effects of these therapies have become a significant concern.

There are three major non-surgical treatments for cancer: chemotherapy, immunotherapy and radiotherapy. Each one of them could impact the heart, leading to a range of adverse effects that vary in severity and clinical significance.

Can cancer affect the heart directly?

Yes, and by multiple ways:

1, For starters, heart disease and cancer tend to share multiple risk factors including smoking, obesity, sedentary lifestyle, unhealthy diet and old age.

2, The systemic effects of cancer, such as inflammation with associated release in the blood of special molecules called “cytokines”, can result in depressed cardiac function. These same molecules are responsible for body-wasting or cachexia and decreased appetite in cancer patients.

3, Metastatic cancer cells can infiltrate cardiac tissues through the bloodstream, leading to secondary tumours in the heart, a condition known as cardiac metastasis.

4, “Malignant pericardial effusion” constitutes a significant manifestation of advanced cancer's impact on the cardiovascular system. This condition arises when cancer cells infiltrate the pericardium, or the protective sac surrounding the heart, leading to the accumulation of cells and fluid in this space. As more liquid build up, it exerts pressure on the heart, compromising its ability to function properly. This can lead to cardiac tamponade, a critical condition where the heart's pumping capacity is severely impeded. It causes symptoms of shortness of breath, chest pain, and low blood pressure.

How can chemotherapy affect the heart?

Chemotherapy, a cornerstone of cancer treatment, exerts its effects on rapidly dividing cells, including cancer cells and certain healthy tissues, too. Unfortunately, this includes cardiac cells.

As an example, anthracyclines, such as doxorubicin, are widely used chemotherapeutic agents known for their powerful anticancer effects. However, their use is limited by their potential to induce cardiac toxicity, leading to heart failure that may or may not be reversible.

The mechanisms of anthracycline-induced cardiotoxicity involve oxidative stress, derangement of essential cellular components called “mitochondria” and “tubules”, and disruption of calcium physiology at a microscopic level, all leading to heart cells’ death.

Studies have shown that patients with baseline heart disease are more prone to chemotherapy-related side effects.

Recent research has highlighted the importance of early detection and monitoring of heart function in patients undergoing anthracycline-based chemotherapy. Various strategies, including the use of cardiac protective agents, along with serial heart imaging studies and blood markers, are being explored to mitigate this type of toxicity, without compromising the anti-tumour effects of chemotherapy.

How can immunotherapy affect the heart?

Immunotherapy, particularly a group of biological agents known as “immune checkpoint inhibitors”, has revolutionised cancer treatment by enhancing the body’s immune system against cancer cells.

However, the activation of immune responses can also lead to autoimmune-related adverse events where the strong anticancer immune reaction attacks some healthy organs along the way, including the heart.

Myocarditis, an inflammation of the heart muscle, has emerged as a rare but potentially fatal complication of immunotherapy.

Early recognition of myocarditis symptoms such as chest pain, arrhythmias, and elevated cardiac biomarkers, is crucial for timely intervention. Management often involves CI discontinuation and the administration of immunity suppressing agents, in order to tone down the strong and maladaptive immune reaction.

How can radiation therapy affect the heart?

Radiotherapy plays a pivotal role in cancer treatment, utilising ionising radiation to target and destroy cancer cells. However, adjacent healthy tissues, including the heart, can also be exposed to radiation, leading to radiation-induced cardiovascular disease.

It encompasses a spectrum of conditions, including accelerated ageing of the coronary vessels (atherosclerosis), pericardial sac thickening, and “cardiomyopathy”, or heart muscle damage.

The mechanisms of these side effects involve oxidative stress along with inflammation of the coronary vessels’ lining and of the pericardium. Newer techniques such as intensity-modulated radiotherapy and proton therapy aim to minimise cardiac exposure during radiation treatment, reducing the risk of cardiac toxicity.

In addition, numerous studies have investigated the association between chest radiation therapy in childhood cancer patients and subsequent cardiac problems in the following decades. They found a significantly increased risk of premature coronary artery disease but also heart failure and valves ageing after chest wall irradiation in kids.

The risk was especially elevated in very young survivors with rapidly growing and developing hearts and in those treated with higher doses of radiation: age and dose-dependent relationship.

What patients with cancer can do

While research is ongoing to find more potent and less toxic cancer therapies, healthcare providers’ alertness and patients’ education remain pivotal in fostering awareness of the intricate interactions between cancer and cardiovascular health.

Individuals undergoing cancer treatment should be informed about potential cardiac complications associated with chemotherapy, immunotherapy, and radiotherapy.

Empowering patients with the knowledge of warning signs such as shortness of breath, chest pain, leg oedema and palpitations can expedite timely medical intervention.

In addition, encouraging a heart-healthy lifestyle, comprising regular exercise, balanced nutrition, and stress management, can synergistically promote both cancer recovery and cardiac wellbeing.

• Joe Yammine, MD is a consultant cardiologist at the Bermuda Hospitals Board. The information here is not intended as medical advice or as a substitute for professional medical opinion. Always seek the advice of your physician