ICRP Publication 127: Radiological Protection in Ion Beam Radiotherapy

A case of radiotherapy during pregnancy for oropharyngeal cancer: long term pediatric outcome evaluation and literature review

Oropharyngeal cancer (OphC) is extremely rare during pregnancy, although its incidence is expected to increase in the years to come. Any delay of treatment can heavily affect cancer control and survival. Information regarding radiotherapy during pregnancy and long-term pediatric outcome is lacking. In this article, we discuss a case of OphC in a pregnant woman, treated with surgery and radiotherapy, offering also an update review with respect to the limited current evidences of the feasibility and clinical results of radiotherapy during pregnancy. A 39-year-old pregnant woman (through assisted fertilization) with locally advanced OphC underwent surgery and subsequent radiotherapy. A special fetal shielding device and a modified planning optimization strategy were used to reduce the dose to the fetus as much as possible. Phantom and in-vivo dosimetry were performed to estimate the dose to the fetus and the related risks, according to ICRP90. Thanks to the actions taken, the mean dose to the fetus was estimated to be around 50 mSv. A healthy baby was born at 33 weeks of gestation + 6 days. After ten-year follow-up, the patient is in complete remission and her 16-year old daughter is healthy with good school performances. Adjuvant radiotherapy in OphC during pregnancy may be optimized to reduce the dose to the fetus and the measures taken represents a realistic option to ensure mother and baby health.

A Practical Primer on Particle Therapy

PURPOSE

Particle therapy is a promising treatment technique that is becoming more commonly used. Although proton beam therapy remains the most commonly used particle therapy, multiple other heavier ions have been used in the preclinical and clinical settings, each with its own unique properties. This practical review aims to summarize the differences between the studied particles, discussing their radiobiological and physical properties with additional review of the available clinical data.

METHODS AND MATERIALS

A search was carried out on the PubMed databases with search terms related to each particle. Relevant radiobiology, physics, and clinical studies were included. The articles were summarized to provide a practical resource for practicing clinicians.

RESULTS

A total of 113 articles and texts were included in our narrative review. Currently, proton beam therapy has the most data and is the most widely used, followed by carbon, helium, and neutrons. Although oxygen, neon, silicon, and argon have been used clinically, their future use will likely remain limited as monotherapy.

CONCLUSIONS

This review summarizes the properties of each of the clinically relevant particles. Protons, helium, and carbon will likely remain the most commonly used, although multi-ion therapy is an emerging technique.

A Systematic Review of LET-Guided Treatment Plan Optimisation in Proton Therapy: Identifying the Current State and Future Needs

The well-known clinical benefits of proton therapy are achieved through higher target-conformality and normal tissue sparing than conventional radiotherapy. However, there is an increased sensitivity to uncertainties in patient motion/setup, proton range and radiobiological effect. Although recent efforts have mitigated some uncertainties, radiobiological effect remains unresolved due to a lack of clinical data for relevant endpoints. Therefore, RBE optimisations may be currently unsuitable for clinical treatment planning. LET optimisation is a novel method that substitutes RBE with LET, shifting LET hotspots outside critical structures. This review outlines the current status of LET optimisation in proton therapy, highlighting knowledge gaps and possible future research. Following the PRISMA 2020 guidelines, a search of the MEDLINE® and Scopus databases was performed in July 2023, identifying 70 relevant articles. Generally, LET optimisation methods achieved their treatment objectives; however, clinical benefit is patient-dependent. Inconsistencies in the reported data suggest further testing is required to identify therapeutically favourable methods. We discuss the methods which are suitable for near-future clinical deployment, with fast computation times and compatibility with existing treatment protocols. Although there is some clinical evidence of a correlation between high LET and adverse effects, further developments are needed to inform future patient selection protocols for widespread application of LET optimisation in proton therapy.

Preliminary study on diagnostic reference levels of whole-body PET-CT examinations in Jiangsu Province, China

To survey the whole-body positron emission tomography/computed tomography (PET-CT) examinations in Jiangsu Province and establish the diagnostic reference levels (DRL). A total of nine hospitals in southern, central and northern Jiangsu Provinces were selected. Activity duration product (ADP), activity per body weight (AW), dose-length product (DLP) and total effective dose (ET) were choosen to establish DRLs for whole-body PET-CT examinations. DRL and achievable dose (AD) were calculated according to International Commission on Radiological Protection report. The conversion coefficient method was used to calculate the ET induced by PET-CT whole-body imaging. DRLs of whole-body PET-CT examinations in Jiangsu Province were set to be 922 mGy·cm (DLP), 4453 MBq.min (ADP), 5.22 MBq.kg-1(AW), 19.8 mSv (ET). The ET for whole-body PET-CT examinations is higher than other countries. The effective dose from radionuclides (EF) in female patients is lower than that in male patients. Effective doses from CT(ECT), ET and ECT/ET in female patients are higher than that in male patients (P < 0.01). Provincial DRLs are established for four radiation metrics in whole-body PET-CT examinations. DRL of AW in whole-body PET-CT examinations is at the medium level, and DLP is higher than that reported in most literature, which has the potential to be further reduced.

Epigenetic modifications in radiation-induced non-targeted effects and their clinical significance

BACKGROUND

Ionizing radiation (IR) plays an important role in the diagnosis and treatment of cancer. Besides the targeted effects, the non-targeted effects, which cause damage to non-irradiated cells and genomic instability in normal tissues, also play a role in the side effects of radiotherapy and have been shown to involve both alterations in DNA sequence and regulation of epigenetic modifications.

SCOPE OF REVIEW

We summarize the recent findings regarding epigenetic modifications that are involved in radiation-induced non-targeted effects as well as their clinical significance in radiotherapy and radioprotection.

MAJOR CONCLUSIONS

Epigenetic modifications play an important role in both the realization and modulation of radiobiological effects. However, the molecular mechanisms underlying non-targeted effects still need to be clarified.

GENERAL SIGNIFICANCE

A better understanding of the epigenetic mechanisms related to radiation-induced non-targeted effects will guide both individualized clinical radiotherapy and individualized precise radioprotection.

Mathematical Model for Evaluation of Tumor Response in Targeted Radionuclide Therapy with 211At Using Implanted Mouse Tumor

Recent introduction of alpha-emitting radionuclides in targeted radionuclide therapy has stimulated the development of new radiopharmaceuticals. Preclinical evaluation using an animal experiment with an implanted tumor model is frequently used to examine the efficiency of the treatment method and to predict the treatment response before clinical trials. Here, we propose a mathematical model for evaluation of the tumor response in an implanted tumor model and apply it to the data obtained from the previous experiment of ²¹¹At treatment in a thyroid cancer mouse model. The proposed model is based on the set of differential equations, describing the kinetics of radiopharmaceuticals, the tumor growth, and the treatment response. First, the tumor growth rate was estimated from the control data without injection of ²¹¹At. The kinetic behavior of the injected radionuclide was used to estimate the radiation dose profile to the target tumor, which can suppress the tumor growth in a dose-dependent manner. An additional two factors, including the time delay for the reduction of tumor volume and the impaired recovery of tumor regrowth after the treatment, were needed to simulate the temporal changes of tumor size after treatment. Finally, the parameters obtained from the simulated tumor growth curve were able to predict the tumor response in other experimental settings. The model can provide valuable information for planning the administration dose of radiopharmaceuticals in clinical trials, especially to determine the starting dose at which efficacy can be expected with a sufficient safety margin.

Sensitivity and latency of ionising radiation-induced cataract

When managed with appropriate radiation protection procedures, ionising radiation is of great benefit to society. Opacification of the lens, and vision impairing cataract, have recently been recognised at potential effects of relatively low dose radiation exposure, on the order of 1 Gy or below. Within the last 10 years, understanding of the effects of low dose ionising radiation on the lens has increased, particularly in terms of DNA damage and responses, and how multiple radiation or other events in the lens might contribute to the overall risk of cataract. However, gaps remain, not least in the understanding of how radiation interacts with other risk factors such as aging, as well as the relative radiosensitivity of the lens compared to tissues of the body. This paper reviews the current literature in the field of low dose radiation cataract, with a particular focus on sensitivity and latency.

Multidisciplinary consensus on cancer management during pregnancy

Cancer during pregnancy is a challenge for multi- and interdisciplinary collaboration due to the diagnostic, prognostic and therapeutic implications, the need for an integrated harmonization of medical action for the pregnant patient and the embryo or foetus and the characteristics of each gestational period, which will determine the protocol to be proposed and its limitations. For this reason, a group of experts appointed by participating scientific societies, which includes the Spanish Society of Medical Oncology (Sociedad Española de Oncología Médica—SEOM), the Spanish Association of Surgeons (Asociación Española de Cirujanos—AEC), the Spanish Society of Gynaecology and Obstetrics (Sociedad Española de Ginecología y Obstetricia—SEGO), the Spanish Society of Nuclear Medicine and Molecular Imaging (Sociedad Española de Medicina Nuclear e Imagen Molecular—SEMNIM), the Spanish Society of Oncological Radiotherapy (Sociedad Española de Oncología Radioterápica—SEOR) and the Spanish Society of Medical Radiology (Sociedad Española de Radiología Médica—SERAM), have worked together to establish consensus recommendations that allow the harmonization of management and ultimately the optimization of the healthcare of pregnant patients with cancer. When cancer is detected in a pregnant woman, the week of gestation in which the diagnosis is made must be considered, as well as the characteristics of the tumour. It is strongly recommended that a multidisciplinary team assesses the situation and guides the patient and her family during the informing, diagnosis and treatment process. Likewise, the foetus should be monitored and managed by specialized obstetricians who are part of a multidisciplinary cancer committee.

Is there any benefit to particles over photon radiotherapy?

Particle, essentially, proton radiotherapy (RT) could provide some benefits over photon RT, especially in reducing the side effects of RT. We performed a systematic review to identify the performed randomised clinical trials (RCTs) and ongoing RCTs comparing particle RT with photon therapy. So far, there are no results available from phase 3 RCTs comparing particle RT with photon therapy. Furthermore, the results on side effects comparing proton and carbon ion beam RT with photon RT do vary. The introduction of new techniques in photon RT, such as image-guided RT (IGRT), intensity-modulated RT (IMRT), volumetric arc therapy (VMAT) and stereotactic body RT (SBRT) was already effective in reducing side effects. At present, the lack of evidence limits the indications for proton and carbon ion beam RTs and makes the particle RT still experimental.

Modern radiotherapy in cancer treatment during pregnancy

Breast cancer, gynecological malignancies and lymphomas are the most frequently diagnosed tumors in pregnant women. The feasibility of radiotherapy during pregnancy remains a subject of debate and clinicians continue to hesitate on this approach, trying to avoid radiotherapy in most cases. Since the 1990s, several technological advances, including intensity modulated and image guided radiation delivery, have been implemented in radiation oncology to improve the radiation treatment in terms of effectiveness and tolerability. It remains uncertain which short- and long-term health effects the radiation exposure of the fetus may have through advanced radiotherapy techniques. The present systematic literature review aims to summarize the limited current evidences of the feasibility and clinical results of "modern" radiotherapy procedures for the treatment of the most frequently diagnosed tumors in pregnant women.

Risk of second cancer after ion beam radiotherapy: insights from animal carcinogenesis studies

Purpose: To review recent studies to better understand the risk of second cancer after ion beam radiotherapy and to clarify the importance of animal radiobiology therein. Results: Risk of developing second cancer after radiotherapy is a concern, particularly for survivors of childhood tumors. Ion beam radiotherapy is expected to reduce the risk of second cancer by reducing exposure of normal tissues to radiation. Large uncertainty lies, however, in the choice of relative biological effectiveness (RBE) of high linear energy transfer (LET) radiation (e.g. carbon ions and neutrons) in cancer induction, especially for children. Studies have attempted to predict the risk of second cancer after ion beam radiotherapy based on an assessment of radiation dose, the risk of low LET radiation, and assumptions about RBE. Animal experiments have yielded RBE values for selected tissues, radiation types, and age at the time of irradiation; the results indicate potentially variable RBE which depends on tissues, ages, and dose levels. Animal studies have also attempted to identify genetic alterations in tumors induced by high LET radiation. Conclusions: Estimating the RBE value for cancer induction is important for understanding the risk of second cancer after ion beam radiotherapy. More comprehensive animal radiobiology studies are needed.