Proton versus Photon Breath-Hold Radiation for Left-Sided Breast Cancer after Breast-Conserving Surgery: A Dosimetric Comparison

Proton Reirradiation for High-Risk Recurrent or New Primary Breast Cancer

Radiotherapy is an integral component of multidisciplinary breast cancer care. Given how commonly radiotherapy is used in the treatment of breast cancer, many patients with recurrences have received previous radiotherapy. Patients with new primary breast cancer may also have received previous radiotherapy to the thoracic region. Curative doses and comprehensive field photon reirradiation (reRT) have often been avoided in these patients due to concerns for severe toxicities to organs-at-risk (OARs), such as the heart, lungs, brachial plexus, and soft tissue. However, many patients may benefit from definitive-intent reRT, such as patients with high-risk disease features such as lymph node involvement and dermal/epidermal invasion. Proton therapy is a potentially advantageous treatment option for delivery of reRT due to its lack of exit dose and greater conformality that allow for enhanced non-target tissue sparing of previously irradiated tissues. In this review, we discuss the clinical applications of proton therapy for patients with breast cancer requiring reRT, the currently available literature and how it compares to historical photon reRT outcomes, treatment planning considerations, and questions in this area warranting further study. Given the dosimetric advantages of protons and the data reported to date, proton therapy is a promising option for patients who would benefit from the added locoregional disease control provided by reRT for recurrent or new primary breast cancer.

Recent advances progress in radiotherapy for breast cancer after breast-conserving surgery: a review

Adjuvant radiotherapy after breast-conserving surgery has become an integral part of the treatment of breast cancer. In recent years, the development of radiotherapy technology has made great progress in this field, including the comparison of the curative effects of various radiotherapy techniques and the performance of the segmentation times. The choice of radiotherapy technology needs to be co-determined by clinical evidence practice and evaluated for each individual patient to achieve precision radiotherapy. This article discusses the treatment effects of different radiotherapy, techniques, the risk of second cancers and short-range radiation therapy techniques after breast-conserving surgery such as hypo fractionated whole breast irradiation and accelerated partial breast irradiation. The choice of radiotherapy regimen needs to be based on the individual condition of the patient, and the general principle is to focus on the target area and reduce the irradiation of the normal tissues and organs. Short-range radiotherapy and hypofractionated are superior to conventional radiotherapy and are expected to become the mainstream treatment after breast-conserving surgery.

Heart Sparing Radiotherapy Techniques in Breast Cancer: A Focus on Deep Inspiration Breath Hold

Adjuvant radiation therapy is a critical component of breast cancer management. However, when breast cancer patients receive incidental radiation to the heart, there is an increased risk of cardiac disease and mortality. This is most common for patients with left-sided breast cancers and those receiving nodal irradiation as part of treatment. The overall risk of cardiac toxicity increases 4–16% with each Gray increase in mean heart radiation dose, with data suggesting that no lower limit exists which would eliminate cardiac risk entirely. Radiation techniques have improved over time, leading to lower cardiac radiation exposure than in the past. This decline is expected to reduce the incidence of radiation-induced heart dysfunction in patients. Deep inspiration breath hold (DIBH) is one such technique that was developed to reduce the risk of cardiac death and coronary events. DIBH is a non-invasive approach that capitalizes on the natural physiology of the respiratory cycle to increase the distance between the heart and the therapeutic target throughout the course of radiation therapy. DIBH has been shown to decrease the mean incidental radiation doses to the heart and left anterior descending coronary artery by approximately 20–70%. In this review, we summarize different techniques for DIBH and discuss recent data on this technique.

Management of Motion and Anatomical Variations in Charged Particle Therapy: Past, Present, and Into the Future

The major aim of radiation therapy is to provide curative or palliative treatment to cancerous malignancies while minimizing damage to healthy tissues. Charged particle radiotherapy utilizing carbon ions or protons is uniquely suited for this task due to its ability to achieve highly conformal dose distributions around the tumor volume. For these treatment modalities, uncertainties in the localization of patient anatomy due to inter- and intra-fractional motion present a heightened risk of undesired dose delivery. A diverse range of mitigation strategies have been developed and clinically implemented in various disease sites to monitor and correct for patient motion, but much work remains. This review provides an overview of current clinical practices for inter and intra-fractional motion management in charged particle therapy, including motion control, current imaging and motion tracking modalities, as well as treatment planning and delivery techniques. We also cover progress to date on emerging technologies including particle-based radiography imaging, novel treatment delivery methods such as tumor tracking and FLASH, and artificial intelligence and discuss their potential impact towards improving or increasing the challenge of motion mitigation in charged particle therapy.

Target motion management in breast cancer radiation therapy

Background

Over the last two decades, breast cancer remains the main cause of cancer deaths in women. To treat this type of cancer, radiation therapy (RT) has proved to be efficient. RT for breast cancer is, however, challenged by intrafractional motion caused by respiration. The problem is more severe for the left-sided breast cancer due to the proximity to the heart as an organ-at-risk. While particle therapy results in superior dose characteristics than conventional RT, due to the physics of particle interactions in the body, particle therapy is more sensitive to target motion.

Conclusions

This review highlights current and emerging strategies for the management of intrafractional target motion in breast cancer treatment with an emphasis on particle therapy, as a modern RT technique. There are major challenges associated with transferring real-time motion monitoring technologies from photon to particles beams. Surface imaging would be the dominant imaging modality for real-time intrafractional motion monitoring for breast cancer. The magnetic resonance imaging (MRI) guidance and ultra high dose rate (FLASH)-RT seem to be state-of-the-art approaches to deal with 4D RT for breast cancer.