Landmark study dispels myths about the effects of radiation therapy on the hearts of breast cancer patients
A landmark study by a breast cancer specialist at the Lynn Cancer Institute offers conclusive evidence that for patients with HER-2 positive breast cancer who are treated with both chemotherapy and modern radiation therapy (RT) , radiation therapy itself brings little or no additional risk of damage to the heart, despite the proximity of this vital organ to the RT-treated breast.
The findings were presented last October at the American Society for Radiation Oncology (ASTRO) annual meeting in Chicago and recently published in the Society’s peer-reviewed professional journal.
The study, considered the largest of its kind, demonstrates that adding modern RT to treatment results in no significant increase in cardiotoxicity in women with HER-2 positive breast cancer, its researcher says main, Youssef Zeidan, MD, Ph.D.a radiation oncologist with Lynn Cancer Institute at Boca Raton Regional Hospital, part of Baptist Health South Florida.
What the research team learned should be good news for women with HER-2 positive breast cancer, which doctors say accounts for 20% of all breast cancers diagnosed in the United States. For the past 20 years, the standard of care for this type of cancer has included chemotherapy and a targeted antibody, trastuzumab. Although remarkably effective, this treatment also has the potential to cause damage to the heart.
“Trastuzumab has been a game-changer for the treatment of HER-2 positive breast cancer, which was once considered very aggressive and deadly,” says Dr. Zeidan. “Women diagnosed with this cancer today have a much better chance of surviving than 20 years ago.”
Trastuzumab: “A double-edged sword”
While this trend is worth celebrating, Dr. Zeidan notes that it’s tempered by the fact that chemotherapy and trastuzumab have the potential to damage heart muscle, which can increase the risk of heart failure. Therefore, these patients should be closely monitored for years after treatment to ensure that their heart function is not impaired in any way.
“These systemic therapies have revolutionized the management of breast cancer and are extremely effective in killing cancer cells,” says Dr. Zeidan. “But they are a double-edged sword, as they pose significant risks of cardiotoxicity.” And since today’s patients live much longer after treatment, he says, it’s up to the radiation oncologist to ensure that treatment doesn’t compromise their future health and quality of life.
Because RT is commonly used for patients with HER-2 positive breast cancer, Dr. Zeidan says RT has, by association, developed a stigma over the years. “We wanted to see, once and for all, the cardiotoxicity attributed to systemic therapies and/or RT in this patient population,” he says.
Dr. Zeidan, along with his co-investigators in Belgium, Philip Poortmans, MD, and Evandro de Azambuja, MD, undertook the analysis of 3,321 patients with HER-2 positive breast cancer across Europe, the UK, Australia and Canada who had been treated with trastuzumab, with or without RT. “Each patient’s cardiac function was closely monitored over a median follow-up period of 11 years,” notes Dr. Zeidan.
Patients in the new study were divided into three groups: those who received trastuzumab alone (no RT), those who were treated with trastuzumab plus RT in the left breast, and those who received trastuzumab plus RT in the left breast. right.
“No additional effect on the heart of RT”
According to Dr. Zeidan, every patient has the right to know what health risks they may face years after their treatment, whether they are undergoing chemotherapy or RT or a combination of both. “They need to know exactly where their risk is coming from and what each contributes in terms of overall cardiotoxicity,” says Dr. Zeidan.
The team’s research found that, over a period of 10 years after treatment, the incidence of a cardiovascular event such as a heart attack was minimal (only 0.6 to 1.0%). “In all three groups,” points out Dr. Zeidan. “We were surprised that the incremental toxicity of RT was so extremely low. It really had no additional effect on the heart beyond the cardiotoxicity they had already experienced on their baseline chemotherapy.
If the same study had been done 10 or 20 years ago, Dr Zeidan says it’s unlikely the numbers would have been as good. “Technology has improved so much over the past three decades – RT is much safer now,” he says. “Before, with older technologies, the cardiac dose for breast cancer patients was too high.”
The study results should be a relief for patients worried about receiving both chemotherapy and radiation therapy, says Dr. Zeidan. “For HER-2 positive patients receiving systemic therapy, adding RT using modern techniques can reduce cardiac toxicity to a bare minimum,” he says. “Additionally, for breast cancer patients with baseline cardiovascular risks, their cardiologist can rest assured that RT will not pose any additional risk beyond chemotherapy.”
Protecting the heart during RT
Dr. Zeidan says that when using RT to treat breast cancer, it’s critical that it is delivered in a way that protects the heart, says Dr. Zeidan. “At the Lynn Cancer Institute, we spend hours perfecting the radiation therapy plan to get to the lowest possible dose,” he says. “It’s especially important for a young woman in her 40s or 50s who still has many years ahead of her.”
Dr. Zeidan says the Lynn Cancer Institute also has state-of-the-art technology that allows them to see exactly how much radiation is being delivered to the heart, allowing them to deliver the lowest possible dose to the organ while administering breast RT.
Another approach to protect the heart is to use the Deep Inspiration Breath Hold (DIBH) technique during treatment, in which patients hold their breath during a deep inhalation. “This provides additional protection by creating an air pocket between the chest and the heart, which helps shield the heart while the radiation is delivered,” says Dr. Zeidan.
Dr. Zeidan warns that continued surveillance of patients with HER-2 positive breast cancer is needed to study the late effects of new treatments for breast cancer patients. “We also need to explore ways to reduce cardiotoxicity for patients receiving chemotherapy and new targeted therapies,” he adds.
For now, however, Dr. Zeidan says he hopes the study results can help support and advance care protocols for HER-2 positive breast cancer. “This is the largest study to date to answer this specific question, and the data should provide peace of mind for both patient and physician.”