Dose color wash comparison of proton versus photon in axial, sagittal, and coronal planes. Dose distribution to lung, heart, and esophagus are significantly lower in the proton plan.
Proton therapy is an alternative to photons in challenging thoracic cancers, particularly in cases where radiotherapy dose to critical organs such as lung or heart must be minimized. Proton beam therapy allows for the safe treatment of appropriately selected thoracic tumors with minimal side effects. Modern proton beam therapy incorporates use of pencil beam scanning technique and on- treatment cone-beam CT imaging, which facilitates accurate and successful treatment of complex thoracic tumors.
A 59-year-old male was diagnosed with a stage IIIB adenocarcinoma of the left lower lobe of the lung, with adenopathy in the contralateral mediastinal and supraclavicular regions. Given the large volume of his disease, he was not able to receive upfront chemoradiation given risk of treatment-related side effects. He started with 4 cycles of chemotherapy with excellent response. Despite the reduction in size his tumor, treatment with traditional photon intensity-modulated radiotherapy (IMRT) did not meet acceptable safe standards. In addition, the doses delivered to esophagus and heart
in the proposed photon radiotherapy were at levels known to cause a significant increase in the risk for esophageal and cardiac side effects.
Given that safety could not be achieved with standard photon radiotherapy, the patient then received evaluation for intensity modulated proton therapy (IMPT). Treatment planning with pencil beam scanning proton therapy resulted in a marked reduction in lung, heart, and esophagus doses.The overall proton plan achieved was considered safe while still effectively treating the areas containing cancer. He completed curative-intent chemoradiation with protons and tolerated treatment with minimal side effects.
To refer a patient or find out more about the Johns Hopkins Proton Therapy Center, visit hopkinsproton.org.