In General

Proton therapy is an advanced form of radiation treatment.

In the treatment of cancer, radiation therapy works by attacking a cancer cell’s DNA, inhibiting growth and reproduction. While advancements in targeting have made the delivery of photon radiation more exact, it can damage nearby healthy tissue and organs. X-rays deposit their energy on the way to, and then beyond its target, necessitating administration of entry and exit doses.[1] This additional exposure can cause substantial side effects for patients.

Figure 1: Traditional radiation treatment has a relatively high entrance dose and exit dose. Proton therapy has a lower entrance dose and no exit dose.

proton therapy exit dose

Proton therapy, conversely, leaves healthy tissue undisturbed.[2] This distinct advantage comes from the unique behavior of protons as they move through the body. Demonstrated on the Bragg Curve, protons reach a peak near the end of their path. The absorbed dose of radiation increases very gradually with greater depth, rising to its peak when the protons are stopped. Highly-charged protons deliver a treatment dose more directly into targeted tissue and tumors than X-rays. In clinical applications, proton therapy can be administered to a precise depth within a patient’s body, to a site as small as a few millimeters in diameter – leaving healthy cells unaffected.[3]

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[1] W.D. Newhauser, R. Zhang. The physics of proton therapy. Physics in Medicine and Biology. 60(8) (2015). doi:10.1088/0031-9155/60/8/r155

[2] X. Zhang, Y. Li, X. Pan, et. al. Intensity-Modulated Proton Therapy Reduces the Dose to Normal Tissue Compared With Intensity-Modulated Radiation Therapy or Passive Scattering Proton Therapy and Enables Individualized Radical Radiotherapy for Extensive Stage IIIB Non-Small-Cell Lung Cancer: A Virtual Clinical Study. Int J Radiat Oncol Biol Phys. 77(2):357-66 (June 12010). doi:10.1016/j.ijrobp.2009.04.028.

[3] T.P. Diwanji, P. Mohindra, M. Vyfhuis, et. al. Advances in radiotherapy techniques and delivery for non-small cell lung cancer: benefits of intensity-modulated radiation therapy, proton therapy, and stereotactic body radiation therapy. Translational Lung Cancer Research. 6(2), 131-147 (2017). doi:10.21037/tlcr.2017.04.04