Illustration of proton beam therapy targeting a tumor while protecting surrounding organs.

Smarter Proton Therapy: Protecting Healthy Tissue While Targeting Cancer

Nico Varela in Health & Wellness November 2025 • 4 min read.

"A new range optimization technique balances tumor treatment with minimizing damage to surrounding organs at risk."

Proton beam therapy (PBT) is rapidly becoming a favored cancer treatment due to its unique ability to deliver radiation with pinpoint accuracy. Unlike traditional photon therapy, PBT deposits most of its energy at a specific depth, known as the Bragg peak, minimizing damage to surrounding healthy tissues. This targeted approach reduces overall radiation exposure, potentially leading to fewer side effects and improved quality of life for patients.

However, the effectiveness of PBT hinges on precise beam delivery. Changes in a patient's anatomy during treatment, such as tumor shrinkage or weight loss, can alter the proton beam's range, causing it to miss the target or irradiate unintended areas. This is especially critical when tumors are located near sensitive organs, known as organs at risk (OARs), like the small intestine, kidneys, or stomach.

To address these challenges, researchers have developed dynamic adaptive PBT techniques that incorporate image guidance and range optimization. This article explores a new range optimization method that aims to strike a delicate balance: maintaining optimal tumor dose coverage while minimizing radiation exposure to OARs.

The Innovation: Balancing Tumor Targeting and Organ Protection

Illustration of proton beam therapy targeting a tumor while protecting surrounding organs.

The study published in Physica Medica introduces a novel range optimization method called RO-TO (Range Optimization for Target and OARs). This approach builds upon existing range optimization techniques that focus solely on maximizing radiation dose to the tumor (RO-T). RO-TO, in contrast, considers both tumor dose coverage and the potential for radiation-induced damage to surrounding OARs.

To evaluate the effectiveness of RO-TO, researchers conducted a retrospective analysis of a patient who underwent PBT for abdominal lymph node metastases. They compared the original treatment plan (OP) with plans generated using bone-based registration (BR), tumor-based registration (TR) alone, TR with RO-T, and TR with RO-TO. Each approach was assessed based on its ability to:

Maintain target dose coverage (CTV D95%).
Ensure dose homogeneity within the tumor (CTV D5%-D95%).
Minimize radiation exposure to OARs, specifically the kidneys, small intestine, and stomach (Dmean and D2cc).

The results showed that both RO-T and RO-TO improved tumor dose coverage and homogeneity compared to BR and TR alone. However, RO-T led to increased radiation exposure to the small intestine and stomach, exceeding acceptable dose limits. RO-TO, on the other hand, achieved comparable or superior dose sparing for all OARs, demonstrating its ability to protect healthy tissues while effectively targeting the tumor.

Future Implications and the Path Forward

This study provides compelling evidence that RO-TO represents a significant advancement in dynamic adaptive PBT. By carefully balancing tumor targeting with OAR protection, this technique has the potential to improve treatment outcomes and reduce side effects for patients undergoing PBT.

The researchers acknowledge that this study is based on a single patient case and that further research is needed to validate these findings in a larger clinical dataset. They also highlight the need for more efficient optimization algorithms to reduce calculation times, making RO-TO more practical for routine clinical use.

Despite these limitations, this research paves the way for a new generation of PBT that is both more precise and more protective. As technology advances and optimization techniques improve, dynamic adaptive PBT promises to become an increasingly valuable tool in the fight against cancer.

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This article was crafted using a human-AI hybrid and collaborative approach. AI assisted our team with initial drafting, research insights, identifying key questions, and image generation. Our human editors guided topic selection, defined the angle, structured the content, ensured factual accuracy and relevance, refined the tone, and conducted thorough editing to deliver helpful, high-quality information.See our About page for more information.

This article is based on research published under:

DOI-LINK: 10.1016/j.ejmp.2018.11.010, Alternate LINK

Title: Range Optimization For Target And Organs At Risk In Dynamic Adaptive Passive Scattering Proton Beam Therapy – A Proof Of Concept

Subject: General Physics and Astronomy

Journal: Physica Medica

Publisher: Elsevier BV

Authors: Shunsuke Moriya, Hidenobu Tachibana, Kenji Hotta, Naoki Nakamura, Takeji Sakae, Tetsuo Akimoto

Published: 2018-12-01

Everything You Need To Know

What is Proton Beam Therapy?

Proton beam therapy (PBT) is a cancer treatment that uses protons instead of photons to deliver radiation. The primary advantage of PBT is its ability to precisely target tumors, minimizing damage to surrounding healthy tissues. This is achieved through the Bragg peak effect, where most of the proton's energy is deposited at a specific depth within the tumor. This targeted approach can reduce side effects and improve the quality of life for patients undergoing cancer treatment.

What is the range optimization method RO-TO?

The range optimization method, RO-TO (Range Optimization for Target and OARs), is a technique used in dynamic adaptive proton beam therapy. It aims to balance tumor treatment with minimizing radiation exposure to organs at risk (OARs). This method builds upon existing techniques like RO-T (Range Optimization for Target). RO-TO considers both tumor dose coverage and the potential for radiation-induced damage to surrounding OARs. RO-TO demonstrated superior dose sparing for all OARs.

What are Organs at Risk (OARs)?

Organs at Risk (OARs) are healthy tissues located near the tumor that can be unintentionally exposed to radiation during cancer treatment. In the context of PBT, OARs are a major concern because the goal is to minimize damage to these critical organs. Examples of OARs include the small intestine, kidneys, and stomach. Protecting OARs is crucial for reducing side effects and improving the overall patient outcome and is the key focus of the RO-TO optimization.

How does dynamic adaptive PBT work?

Dynamic adaptive PBT incorporates image guidance and range optimization to account for changes in a patient's anatomy during treatment. The tumor may shrink or the patient may lose weight which alters the proton beam's range. Dynamic adaptive PBT adapts to these changes, ensuring that the proton beam continues to accurately target the tumor while sparing surrounding healthy tissues. The RO-TO method is a component of dynamic adaptive PBT.

Why is RO-TO significant in cancer treatment?

RO-TO (Range Optimization for Target and OARs) is significant because it represents an advancement in dynamic adaptive PBT. By carefully balancing tumor targeting with OAR protection, this technique has the potential to improve treatment outcomes and reduce side effects for patients undergoing PBT. RO-TO's ability to spare OARs while maintaining tumor dose coverage is a critical improvement, offering the potential for better patient outcomes and quality of life compared to older techniques like RO-T.