Radiation therapy for breast cancer has become far more precise. But one question still matters: how can doctors treat the cancer effectively while limiting radiation to nearby healthy organs?
It comes up most with left-sided breast cancer, chest wall treatment, or when regional lymph nodes need treatment, because the heart and lungs sit close to the treatment area. Proton therapy is one approach that can help reduce radiation exposure to these organs in appropriately selected patients.
Why Do the Heart and Lungs Matter?
Because they lie close to the breast and chest wall, the heart and lungs can receive some radiation during treatment. How much depends on which side the cancer is on, the size and location of the treatment area, whether lymph nodes (including the internal mammary nodes) need treating, your anatomy, and the technique used.
How Can Proton Therapy Help?
Conventional radiation uses photon beams, which release radiation along their path and continue past the target. Protons behave differently. With careful planning, they deliver most of their dose within the intended area and then drop off rapidly, known as the Bragg peak. This can allow radiation oncologists to reduce radiation exposure to tissues beyond the target, such as the heart, the left anterior descending (LAD) coronary artery, the left ventricle, the lung on the treated side and the opposite breast.
So the potential benefit isn’t simply about using a different type of radiation. It’s about finding the right balance between covering the target and sparing normal tissue.
What Does the Research Show?
Several studies have looked at proton therapy’s ability to lower heart and lung doses, and Indian data are available too.
A 2023 study by Sapna Nangia and colleagues looked at 20 breast cancer patients treated with intensity-modulated proton therapy (IMPT) in India. Eleven had breast-conserving surgery and nine had a mastectomy, with regional nodal irradiation used where appropriate. The researchers reported adequate target coverage with low doses to the heart and its substructures. The mean heart dose was 0.78 GyE overall and 0.87 GyE in left-sided patients. The team also assessed the LAD and left ventricle separately, since different parts of the heart can receive quite different doses.
These findings demonstrate the potential for low cardiac and surrounding normal-tissue doses with proton therapy in selected breast cancer patients.
It’s worth remembering that this was a small, single-centre series with a median follow-up of 12.5 months and no photon comparison group, so it describes the doses achieved rather than clinical outcomes. A lower dose doesn’t automatically mean long-term heart complications are eliminated, and long-term outcomes are still being studied.
Proton vs Photon Therapy
Proton therapy isn’t automatically better than photon therapy for every patient. Modern photon techniques, including deep inspiration breath hold (DIBH), can also deliver excellent target coverage with good heart and lung sparing.
The useful question is which plan treats the cancer adequately while keeping exposure to healthy tissue as low as reasonably possible. For some patients, that’s a photon plan. For others, particularly when the heart or lungs would receive higher doses with photons, proton therapy may offer a meaningful dosimetric advantage. Comparing individual treatment plans is how the team decides.
Does Proton Therapy Prevent Heart and Lung Problems?
No. It shouldn’t be described as eliminating the risk of heart or lung complications. Its potential advantage is the ability to reduce radiation dose to nearby normal tissues in appropriately selected treatment plans. A lower dose is a treatment-planning result, while fewer long-term complications can only be confirmed through clinical follow-up over time.
Who May Be Considered for Proton Therapy?
The heart sits closer to the left breast, and the internal mammary lymph nodes lie close to both the heart and lungs. That is why exposure to these organs becomes an important planning consideration.
Proton therapy may be considered for selected patients when reducing radiation to nearby organs is clinically important, for example with left-sided breast cancer, lymph node involvement (including internal mammary nodes), plans where the heart or lungs would receive significant exposure, or anatomy that makes sparing more challenging. The decision should rest on your disease, your anatomy and a comparison of treatment plans, not on the side of the cancer alone.
Proton therapy is also being used to reduce long-term radiation effects in lymphoma and childhood cancers.
The Goal: Treat the Cancer While Sparing Healthy Tissue
For appropriately selected patients, proton therapy may be an option for reducing radiation exposure to the heart and lungs. As research continues, it is being evaluated not only through dose reductions in treatment plans but also through longer-term patient outcomes.
If you’re being considered for radiation therapy, talk with your radiation oncologist about the available techniques and whether a proton therapy plan could lower the dose to your heart and lungs in your individual case.
Frequently Asked Questions
Is proton therapy suitable for left-sided breast cancer?
It can be considered in selected patients, particularly when reducing cardiac exposure is an important planning goal.
Can proton therapy reduce heart and lung dose?
Studies have shown it can reduce dose to the heart, cardiac substructures and the lung on the treated side in selected plans, though the degree of benefit varies with anatomy and technique. Indian data from Nangia et al. also showed low cardiac doses with IMPT.
Is proton therapy better than photon therapy?
Not necessarily for every patient. It depends on the individual treatment plan and the doses nearby organs receive.
Does proton therapy eliminate cardiac risk?
No. It can reduce cardiac radiation exposure, but it does not eliminate the possibility of long-term cardiac effects.
Disclaimer: This article is for general information only and is not a substitute for advice from your treating doctor.
