If you ‘heart’ your ‘heart,’ a growing number of studies demonstrate that treating cancer with protons helps reduce the risk of heart disease due to radiation exposure. This is especially important for breast cancer patients, whose cardiovascular systems can suffer from conventional radiation spilling over into the heart and lungs.
The risk to breast cancer survivors has been realized for several years, as studies have shown that conventional radiation increases patients’ likelihood of contracting secondary cancer and heart disease significantly.
In 2013, JAMA Internal Medicine published a study showing an increased lifetime risk for heart attack or other “major heart event” of .5-3.5 percent. The highest risk, not surprisingly, was for women with cancer in their left breasts. Another large study of women in Europe first revealed the negative impacts of radiation for cancer treatment on the heart, showing that for every gray of radiation—a unit of radiation dose expressed in terms of absorbed energy per unit mass of tissue—increases a heart risk by 7.4 percent. A woman typically receives 45 to 60 gray units of radiation exposure (with a percentage if the total reaching the heart) in a conventional radiation regimen.
Proton therapy, on the other hand, provides more targeted doses of radiation, sparing these most sensitive organs and reducing the risk of heart disease and lung cancer later on.
A study out of Loma Linda University‘s Proton Treatment and Research Center showed a 97 percent five-year survival rate with minimal side effects to healthy breast, lung and heart tissue.
Loma Linda University’s Proton Treatment and Research Center conducted the clinical trial on patients with early stage invasive (non lobular) breast cancer. The 2014 study, “Partial Breast Radiation Therapy With Proton Beam: 5-Year Results With Cosmetic Outcomes,” represents the most solid data set to date on proton therapy and breast cancer outcomes.
The phase-two clinical trial followed 100 patients who received proton therapy and were monitored for an average of five years following treatment. Results show that the in-breast recurrence-free survival rate was 97 percent with minimal side effects to the breast, lungs and heart. The cosmetic results as assessed by patients and physicians were good to excellent in 90 percent of cases, which was maintained throughout the five years of follow-up. Other published series using photon radiation treatment has shown that good cosmetic results diminish over time, likely due to increased scarring of the breast that occurs as a result of increased exposure of normal breast tissues when conventional or photon radiation is used. In addition to being less toxic to the patient, the breast cancer treatment also reduced the duration of radiation treatment time from seven to two weeks.
Another study by the University of Florida was conducted to determine the dose of radiation to the heart and lungs received as a result of proton therapy. The study included left- and right-sided breast cancer patients who had received breast-conserving therapy or mastectomy and required radiation treatment that included the lymph node areas.
Results from the study demonstrated that, compared with the best conventional radiation therapy techniques available, proton therapy consistently resulted in decreased radiation delivered to the heart and lungs. In the case of left-sided breast cancer where the heart is in close proximity to the breast tissue, the heart dose was reduced and in some cases eliminated altogether to a degree not achievable with other radiation therapy techniques, including IMRT. For the high percentage of breast cancer patients who will be cured of their disease, the effect is an estimated 35 percent reduction in cardiac disease when compared to patients treated with conventional radiation therapy.
The study concluded that women with left- or right-sided breast cancer undergoing regional nodal irradiation, the use of proton therapy significantly decreases radiation dose to the heart and lungs as well as improving therapy coverage of the lymph node region. In addition, the treatment is feasible, technically robust and tolerated without excessive side effects.
The breast cancer clinical trial investigated the safety and efficacy of utilizing proton beam radiotherapy to deliver partial breast radiotherapy following lumpectomy for early stage breast cancer.
Initially, 50 patients who had invasive carcinoma and had undergone a lumpectomy were enrolled in the clinical trial, with 50 more being treated after initial analysis. The patients had invasive breast cancer with primary tumors that were three centimeters or less and the cancer had not metastasized. During treatment the patients were placed in a prone position in a patented, customized foam mold to improve the precision of the treatment. Proton treatment was given in 10 sessions over a two-week course. All showed excellent results.