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THERE are approximately 145 000 new cancer cases diagnosed each year in Australia, which also has one of the highest global cancer survival rates with a 69% 5-year relative survival.
Significant advances in cancer treatment, including improved chemotherapy regimes, introduction of immunotherapies and targeted therapies, and increased access to cutting-edge radiation therapy techniques have all contributed to improved survival outcomes.
However, it is well documented that many of these cancer therapies have cardiovascular effects with potential resultant cardiotoxicity. This can affect the administration of optimal cancer therapies, patients’ quality of life, and overall survival.
Cardiovascular disease (CVD) is one of the major competing causes of death in patients with cancer and can overtake cancer as the greatest cause of death in certain cancer subsets, such as early stage breast cancer.
As a result, we have witnessed the emergence of cardio-oncology, a relatively new discipline dedicated to managing the cardiac health of cancer patients and survivors. We believe cardio-oncology should be an integral part of the multidisciplinary team approach to cancer care, and that more awareness and understanding of this field can help ensure optimal patient outcomes.
Cardiac considerations in medical oncology
Numerous chemotherapies, targeted therapies and immunotherapies used to treat melanoma, lymphoma, multiple myeloma, leukaemia, colorectal and breast cancers are known to cause cardiotoxicity.
These therapies can result in heart failure, systemic and pulmonary hypertension, arrhythmias, myocardial ischaemia and myocarditis, among other complications, and can occur at the time of treatment delivery or years later.
For example, in certain patient populations, anthracycline chemotherapy may increase the risk of heart failure decades after administration. Even without a detectable decrease in left ventricular function, prior anthracycline exposure causes cellular damage and adverse cardiac remodelling. This can increase the consequence of future cardiac insults, such as myocardial infarction. This is colloquially referred to as the “multiple hits” paradigm.
Enrolling patients receiving certain therapies, such as anthracycline chemotherapy or trastuzumab, into a cardio-oncology echo surveillance program enables early detection of potential cardiac issues. Timely intervention and appropriate treatment can then be administered to help normalise cardiac function and minimise interruptions to cancer treatment.
Minimising exposure to the heart during radiotherapy
Advances in radiation therapy technology are allowing clinicians to target tumours more precisely than ever before, helping to reduce many treatment-related side effects. However, as survivorship from cancer improves, prioritisation of cardiac health is paramount.
Exposing the heart to ionising radiation increases the long term risk of ischaemic heart disease, proportional to the mean heart dose received. The exposure also heightens the susceptibility of the heart to traditional cardiovascular risk factors such as hypertension, dyslipidaemia and obesity, with the increase being multiplicative in nature. For example, the risk of CVD with hypertension in a patient who has previously received radiotherapy is four to five times greater than if they had not received this treatment.
Minimising radiation dose to the heart has been a focus of radiation oncologists over the past decade. Techniques to reduce dose to the myocardium and coronary vasculature are now standard of care and include dose sculpting and deep inspiration breath hold (DIBH).
Managing cardiotoxicity in patients with breast cancer
Breast cancer is an archetypal disease that can benefit from cardio-oncology. The 5-year relative survival is now greater than 90%, and in certain breast cancer cohorts, cardiovascular death overtakes cancer-related death within 10 years of diagnosis.
Patients with breast cancer treated with neo-adjuvant or adjuvant treatments such as chemotherapy, targeted therapy or radiotherapy are at increased risk of treatment-induced cardiotoxicity. This risk is higher in patients with pre-existing CVD risk factors.
Breast cancer patients receiving radiotherapy may specifically benefit from referral to cardio-oncology clinics, given the ability to detect and manage coronary artery calcification (CAC) found on radiotherapy planning computed tomography. The presence of CAC is the best predictor of cardiovascular events, and is found in approximately one in four patients with breast cancer before therapy. This is especially important considering one in three women with CAC would have been considered low risk on traditional risk factors, and an opportunity to intervene with preventive therapy would otherwise be missed.
The acute management of these issues and longer term surveillance is therefore critical to ensure patients experience the best possible life outcomes.
Lessons learnt from abroad
The current European Society of Medical Oncology (ESMO) and American Society of Clinical Oncology (ASCO) guidelines on the cardiac effects of cancer therapy are explicit in their statements:
ESMO states:
“Close and early collaboration between cardiologists, oncologists, haematologists and radiation oncologists is recommended to ensure lifelong [cardiovascular] health and to avoid unnecessary discontinuation of cancer therapy.”
ASCO recommends:
“Clinicians … perform a comprehensive assessment in patients with cancer that includes a history and physical examination, screening for cardiovascular disease risk factors … and an echocardiogram before initiation of potentially cardiotoxic therapies.”
Multiple other international organisations, such as the National Comprehensive Cancer Network, the International Cardio-Oncology Society, the American College of Cardiology, the European Society of Cardiology, the American Society of Echocardiography and the European Association of Cardiovascular Imaging, also endorse these principles.
Bridging the divide between our two biggest health burdens
As an emerging discipline, many patients currently undergoing cancer therapy are not referred on to cardio-oncology services as part of their multidisciplinary care. A recent study revealed only one in eight medical and radiation oncologists felt that asymptomatic cancer patients should be referred to a cardiologist and less than half believed their patients would benefit from such services. Referral to cardio-oncology clinics and active prospective data collection and trial enrolment of patients will be an important step to manage this issue.
Cancer survivors require ongoing surveillance to ensure optimal management of cardiac risk factors and treatment of therapy-related cardiotoxicity.
Surveillance by GPs and close collaboration with cardio-oncology services are important in cancer survivors, especially as oncology-specific follow-up decreases.
Ongoing collaboration between oncologists, surgeons, haematologists, breast care nurses, exercise physiologists, cardiologists and primary care practitioners and increased integration of cardio-oncology principles into multidisciplinary cancer care are an important step in continuing to see Australia’s, and the world’s, cancer survivorship improve.
The divide between oncology and cardiology, the leading causes of mortality in the world, is significant, but closing and not insurmountable. We propose that this divide can and should be bridged to ensure patients receive the optimal cancer care and afford survivors their best possible life outcomes.
More information on cardio-oncology available here.
Dr Daniel Cehic is the Chief Medical Officer and Clinical Lead for Cardio-oncology at GenesisCare. He is also an electrophysiologist. GenesisCare has cardio-oncology clinics in all mainland states and Dr Cehic practises in both the Adelaide and Sydney clinics. His other interests include health management and regulation, and he is the past Chairman of the Clinical Management Committee of GenesisCare – Cardiology – Adelaide and GenesisCare’s national Clinical Leaders’ Forum.
Dr Peter Dias is a GenesisCare cardiologist and a consultant cardiologist at Fiona Stanley Hospital, Perth in the state Advanced Heart Failure and Cardiac Transplant service. He also runs a cardio-oncology clinic, where he uses a multidisciplinary approach to provide the highest standard of cardiac care for patients who have received cancer treatments. Dr Dias is actively involved in recruiting patients for cardio-oncology clinical trials. His fields of specialty include heart failure, cardiac transplant and mechanical support, echocardiography and general cardiology.
Dr Joanne Toohey is a Sydney-based radiation oncologist at GenesisCare and St Vincent’s Hospital, and a visiting scientific officer at the Garvan Institute of Medical Research. She is a Conjoint Lecturer at University of New South Wales and was an active participant in University of Sydney SCORPIO oncology-based education sessions. Dr Toohey’s clinical interests include breast and gynaecological malignancies, lung and palliative care. Dr Toohey is heavily involved in GenesisCare’s cardio-oncology clinics, referring her at-risk patients with breast cancer to Dr Daniel Cehic.
The statements or opinions expressed in this article reflect the views of the authors and do not represent the official policy of the AMA, the MJA or InSight+ unless so stated.