Proton Therapy

Proton Therapy

Proton therapy is a form of particle therapy utilized in the treatment of cancer, employing a beam of protons to irradiate diseased tissue. Its primary advantage lies in its ability to precisely target the radiation dosage compared to other forms of external beam radiotherapy.

During proton therapy, a particle accelerator directs a beam of protons to target the tumor. These charged particles damage the DNA of cells, ultimately leading to cell death or interference with their ability to replicate. Cancer cells, with their heightened rate of division and impaired DNA repair mechanisms, are particularly susceptible to this type of attack.

Due to their substantial mass, protons exhibit minimal lateral scattering in tissue, maintaining focus on the tumor and minimizing radiation exposure to surrounding tissues. Each proton has a designated range within tissue, with few protons penetrating beyond that distance. Moreover, the maximum dose is delivered just beyond the tumor's boundary, known as the Bragg peak.

To treat deeper tumors, the proton accelerator must produce a beam with higher energy, typically measured in electron volts (eV). Tumors closer to the body's surface are treated with lower-energy protons. Accelerators typically generate protons with energies ranging from 70 to 250 Mega electron Volts (MeV). By adjusting proton energy during treatment, cell damage is maximized within the tumor while minimizing radiation exposure to nearby tissues. Tissues deeper within the body receive minimal radiation exposure due to the limited penetration of protons.

Treatment typically involves applying protons of varying energies to cover the entire tumor, with each energy level corresponding to a specific depth (illustrated by blue lines). The cumulative radiation dosage is referred to as the Spread-Out Bragg Peak (SOBP), depicted as a red line. It's crucial to note that tissues behind or deeper than the tumor receive no radiation from proton therapy, while those in front or shallower than the tumor receive radiation based on the SOBP.

Proton therapy finds applications in two main categories of treatments. Firstly, it's used in diseases requiring higher radiation doses for optimal efficacy, leading to improved local control. Examples include uveal melanoma, skull base tumors, and sarcomas. Secondly, it's employed to minimize side effects by precisely targeting tumors, particularly in pediatric neoplasms and prostate cancer.

While the effectiveness of proton therapy in prostate cancer treatment remains debated, its usage continues to grow, especially considering the high prevalence of prostate cancer diagnoses. Additionally, proton therapy offers advantages in treating ocular tumors, where its low energy requirement allows for sophisticated alignment methods to protect sensitive tissues like the optic nerve and preserve vision.