The spotlight recently shone on proton therapy by the International Journal of Radiation Oncology-Biology-Physics, known as the Red Journal, marks a milestone in its recognition as an established treatment for cancer.
It also holds good news for patients considering their treatment options.
Several articles offer new insight into the effectiveness of proton therapy for treatment of different tumor types. Here’s our breakdown of the most important results.
Although proton therapy has been effectively used for treatment of this most common of male cancers, its limited availability has resulted in few studies in order to compare efficacy with other methods such as surgery or radiation therapy. Dr. Curtis Bryant and colleagues at the University of Florida authored a study demonstrating that approximately 1,300 patients receiving proton therapy, 99 percent of low-risk, 94 percent of intermediate-risk and 74 percent of high-risk patients were free from further progression of the disease five years after treatment. Metastases to organs located at a distance from the prostate was nearly nonexistent for all the groups.
Additionally, among all patients, average International Prostate Symptom Scores—which measures symptoms and side effects of the disease—were in the “mild” category and the same after treatment as before.
“The University of Florida Health Proton Therapy Institute study confirms the positive results previously published by the Loma Linda University Proton Center,” said Scott Warwick, chair of the National Association of Proton Therapy and Provision vice president for strategic initiatives and program development. “Additionally, the results from the study are better than any previously published data supporting the use of IMRT (conventional radiation) for prostate cancer.”
Another study submitted by the University of Florida, an a much smaller group of patients, 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 achieveable 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.
A study of 92 patients at Memorial Sloan Kettering Cancer Center looked at the results of patients treated with proton therapy who had already undergone conventional radiation therapy in prior years for their disease. The study demonstrated that proton therapy is an effective means by which to treat head and neck tumors that recur after initial conventional irradiation.
“Because the physical properties of (proton therapy) allow the delivery of higher radiation doses to the tumor while minimizing the dose to the previously irradiated normal tissues, we have been able to achieve adequate disease control and survival with reasonably low rates of acute and, to date, late toxicity,” wrote the authors.
A study of 69 patients with hepatocellular carcinoma at Loma Linda University Medical Center compared transarterial chemoembolization, a catheter procedure that administers chemotherapy drugs and embolizes blood vessels feeding the tumor, to proton therapy.
While the two-year survival rate was the same for both treatment groups, proton therapy recipients achieved better local control of the tumor and progression-free survival. Additionally, the patients experienced “significantly fewer hospitalization days after proton treatment, which may indicate reduced toxicity with proton beam therapy,” the article noted.