A Beam of Protons for Lymphoma

A Beam of Protons to Deliver Radiation Precisely

External beam RT with photons is most common, but proton therapy may also an option for some patients with lymphoma.

Radiation therapy is important in treating many different types of cancer. Radiation comes in different forms, and most commonly, photons (x-rays) are used to target malignant tissue. But some cancer centers have built radiation machines that use proton beams. Proton beams are a stream of positively charged particles that deliver energy within a short distance. In theory, protons may reach tumors deep within the body with less harm to nearby tissues.

According to the National Comprehensive Cancer Network, or NCCN, however, proton therapy is not recommended for routine use at this time.

Many Lymphomas Occur in the Chest Near Critical Structures

For patients with lymphoma, proton therapy might be preferred to photons in certain cases and for a variety of reasons. Although effective, chemotherapy used to treat lymphomas can have some toxicity to both heart and lungs, which are sensitive to both the effects of chemotherapy and radiation.

Chemotherapy and radiation are often planned together, but they are administered separately, and often, one will follow the other in the treatment of lymphoma. Proton therapy reduces exposure to healthy tissues, which may reduce subsequent side effects.

Many patients with lymphoma are younger when diagnosed and live long lives after treatment, so they are at risk for late emerging, long-term side effects associated with standard therapies.

Based on what is known about proton therapy, many believe side effects will be reduced compared to conventional therapy. Doctors and researchers are also working on the chemotherapy side of the equation, exploring the use of newer agents with fewer side effects, looking to any impact on long-term outcomes and late side effects.

Why Proton Therapy for Hodgkin Lymphoma (HL)?

Patients with Hodgkin lymphoma, in particular, have high cure rates, but they also tend to develop treatment side effects from the chemotherapy and radiation. In fact, childhood HL survivors are one of the groups at most risk for severe or life-threatening chronic health conditions, such as a second cancer or heart disease.

These increased risks are believed due at least in part to the late effects from chemotherapy and from radiotherapy.  

Because proton therapy is more precise in delivering radiation, the hope is that less heart disease and fewer second cancers will develop. So far, in one study, the incidence of second cancers among those treated with proton versus photon radiation appeared to be similar, but data are limited and more research is needed.

Oncologists Cite Balancing Act

Oncologists who support the use of proton therapy for HL have pointed to the “balancing act” between relapse due to inadequate therapy and severe late toxicities from overly aggressive treatment. Some say that if you increased the chemotherapy to offset for not having radiation therapy, you would likely not make any gains in terms of long-term toxicities; they also highlight the importance of ‘freedom from a second relapse’ as an outcome measure.

According to Hoppe and colleagues, proton therapy provides lower overall radiation doses to the heart, lungs, breasts, esophagus, and other structures for the vast majority of HL patients. Only time will tell if proton therapy will become increasingly routine.

Background and Sources on Proton Therapy for Lymphoma:

Proton Therapy for Lymphoma. http://www.mdanderson.org/patient-and-cancer-information/proton-therapy-center/conditions-we-treat/lymphomas/index.html Accessed November 2014.

Proton Therapy for Hodgkin Lymphoma. http://www.floridaproton.org/cancers-treated/hodgkin-lymphoma Accessed November 2014.

Proton therapy for Lymphoma. http://www.scripps.org/services/cancer-care__proton-therapy/conditions-treated__proton-therapy-for-lymphoma Accessed November 2014

Miralbell R, Lomax A, Cella L, Schneider U. Potential reduction of the incidence of radiation-induced second cancers by using proton beams in the treatment of pediatric tumors. Int J Radiat Oncol Biol Phys. 2002;54(3):824-829.

Chung CS, Yock TI, Nelson K, Xu Y, Keating NL, Tarbell NJ. Incidence of second malignancies among patients treated with proton versus photon radiation. Int J Radiat Oncol Biol Phys. 2013;87(1):46-52.

Protons: Moving Therapy for Hodgkin Lymphoma in a Positive Direction. http://www.cancernetwork.com/articles/protons-moving-therapy-hodgkin-lymphoma-positive-direction Accessed November 2014.

Continue Reading