Evidence-Based Oncology June 2015
Extending Cancer Care Past Remission: The Importance of Cardiac Toxicity Monitoring and Awareness
For example, a 2015 report published in JAMA Oncology1 provided encouraging news of the ongoing efforts against cancer. An analysis of the National Cancer Institute’s Surveillance, Epidemiology, and End Results (SEER) program of cancers diagnosed and treated between 1990 and 2010 demonstrated significant reductions in the risks of cancer-related deaths for colon, breast, prostate, lung, and liver cancers. Approximately 20% to 60% of those reductions were observed since 1990, and among those populations affected, the greatest survival benefit was observed for patients younger than 65 years.
In other words, there is mounting evidence that physicians, policy makers, and the scientific community are turning the tide in the so-called “War on Cancer.” However, despite the encouraging nature of such numbers, these improvements in survival statistics may come at some cost. Indeed, as cancer survivors live longer, treatment-related complications develop into significant concerns for a patient’s overall health.
Among the toxicities of cancer treatment, cardiac toxicity is generally the most feared by physicians, as it may erode the gains in life expectancy that result from ever-more effective therapies. Cardiac toxicity has the ability to induce heart failure from treatment-related damage done to the heart muscle directly or indirectly through promotion of coronary vessel blockage, arrhythmias, elevated blood pressure, and blood clots. Once inflicted, cardiac damage may be irreversible for many patients, and strategies for managing cardiac failure may be temporizing at best. Furthermore, cardiac toxicity due to cancer therapy usually does not manifest itself for years. Despite these potential outcomes, there is currently no standard protocol sanctioned by the American College of Radiation Oncology or the American Society for Radiation Oncology for cardiac follow-up an oversight that may put the patient at risk.
We at 21st Century Oncology are acutely aware of the pernicious effects of cardiac toxicity, especially as these effects may go undiscovered until it’s too late. Therefore, our oncologists preemptively try to identify patients who may be predisposed to severe cardiac damage from cancer treatment, and administer therapies that mitigate the risks of heart failure while still achieving meaningful levels of effectiveness.
Common, and generally effective, chemotherapy agents can lead to deterioration of the heart’s ability to contract efficiently. In fact, a potentially fatal weakening of the heart was observed in nearly 40% of patients treated at higher doses of chemo drugs associated with congestive heart failure.2 Additionally, targeted anticancer therapies that inhibit specific molecules within cancer cells and block their ability to multiply may also adversely affect cardiac cells that express the same target molecule.
With this in mind, we follow a number of processes for the monitoring and management of drug-induced cardiotoxicity, which greatly benefit the patient over the course of treatment and long past the completion of treatment. Customized to the individual patient’s needs, we will order routine initial and follow-up testing of cardiac function; asymptomatic patients demonstrating adverse changes upon routine testing may be directed toward more aggressive medical treatment.
Specifically, patients with known cardiac risks who are scheduled to undergo drug therapy may receive a baseline evaluation of cardiac function through an echocardiogram, followed by regular retesting thereafter. Abnormal test results during therapy may be addressed with drug dose reductions or discontinuation, and abnormal test findings after completion of therapy may be addressed with medical interventions to reduce blood pressure and lipid levels, as well as counseling on smoking cessation and lifestyle modifications.
Medical monitoring and counseling can help us track and contain many harmful effects of cancer drug-induced cardiotoxicity. Patient engagement from the very beginning, along with medically advanced testing methods, can help us surmount cardiotoxicity and better ensure that patients receive only the benefits of essential cancer treatment.
In addition to drug-induced cardiotoxicity, radiation therapy to the breast and chest has also been reported as a risk factor for subsequent development of heart disease among long-term cancer survivors. Because of the large number of radiation oncologists in our network and our focus on safety, we also pay particular attention to the effects of radiotherapy induced cardiotoxicity.
When assessing radiotherapy-induced cardiotoxicity, it is important to consider its unique attributes, many of which are outlined in a New England Journal of Medicine report3:
- Younger patients with curable cancer treated with radiotherapy to the chest are at highest risk for treatment-related cardiac toxicity.
- Additional factors, such as treatment with chemotherapy or targeted therapies, diabetes, hypertension, and smoking may contribute to the risk of radiation-induced cardiotoxicity.
- The nature of the cardiac injury related to radiation depends upon the extent of cardiac exposure during treatment.
Considering cardiotoxicity’s almost direct relation to radiation exposure to the heart, it is vital that radiation therapy be precise. Fortunately, more modern methods involve the use of CT scans to accurately define and distinguish the tumor from nearby healthy organs, and sophisticated treatment planning software to design radiation treatment fields that allow for the delivery of effective radiation doses to the tumor while sparing surrounding organs. Furthermore, modern radiotherapy equipment can very precisely shape a treatment field to closely match the size and shape of the tumor while greatly limiting the exposure of tissues just beyond the tumor. This beam-shaping technology is referred to as conformal or intensity-modulated radiation therapy.
Additionally, modern treatment equipment referred to as image-guided radiation therapy is capable of capturing an X-ray image of the treatment field prior to each radiation session as verification that organs such as the heart are excluded from exposure as much as possible. Together, these technical improvements allow for greater precision and accuracy in the delivery of radiotherapy and improved sparing of the heart, which could subsequently reduce exposure-related cardiac risks. Put simply, innovation is truly guiding our ability to combat cardiotoxicity.
In order to supplement advances in technology, we at 21st Century also maintain clinical guidelines that provide safe dose limits for our patients’ treatment with radiation therapy. This way, we can ensure that no matter the equipment used, patients are receiving safe levels of radiation something that provides an additional level of security down the road.
In the end, even as technology continues to drive us forward in both traditional oncology and radiation oncology, we must never lose sight of cardiotoxicity. Ensuring our patients’ health begins at diagnosis, but it must extend into remission. Our duty as oncologists must include attentive follow-up to sustain our patients’ health. We must also increase awareness of the risks of cardiotoxicity. As patients battle for their lives and even after they have beaten back the disease they do not consider the future effects of their treatments.
In addition to patients, private and public payers are not necessarily aware of the long-term effects and costs of cardiotoxicity. Among private payers, claims adjudications through utilization of inappropriately narrow clinical pathways and onerous authorization processes may further inhibit the diagnosis and treatment of such patients. However, all payers share a common concern when it comes to the high costs of avoidable hospitalizations and procedures. Effective risk management of cardiac toxicity due to treatment would help mitigate those costs an effort that, once again, begins with awareness. Managing cardiotoxicity makes sense from every perspective in our healthcare system. Increased communication among various stakeholders is the call of the hour.
Through coordinated efforts and enhanced patient education, consistent lifelong management of cardiotoxicity is becoming a reality for those in the 21st Century Oncology network. We hope our efforts can serve as a model; more so, further research, improved treatments, and increased collaboration among stakeholders will prove vital in years to come. EBO