Hematologic Toxicity and Bone Marrow-Sparing Strategies in Chemoradiation for Locally Advanced Cervical Cancer: A Systematic Review

The standard treatment for locally advanced cervical cancer typically includes concomitant chemoradiation, a regimen known to induce severe hematologic toxicity (HT). Particularly, pelvic bone marrow dose exposure has been identified as a contributing factor to this hematologic toxicity. Chemotherapy further increases bone marrow suppression, often necessitating treatment interruptions or dose reductions. A systematic search for original articles published between 1 January 2006 and 7 January 2024 that reported on chemoradiotherapy for locally advanced cervical cancer and hematologic toxicities was conducted. Twenty-four articles comprising 1539 patients were included in the final analysis. HT of grade 2 and higher was observed across all studies and frequently exceeded 50%. When correlating active pelvic bone marrow and HT, significant correlations were found for volumes between 10 and 45 Gy and HT of grade 3 and higher. Several dose recommendations for pelvic bone and pelvic bone marrow sparing to reduce HT were established, including V10 < 90-95%, V20 < 65-86.6% and V40 < 22.8-40%. Applying dose constraints to the pelvic bone/bone marrow is a promising approach for reducing HT, and thus reliable implementation of therapy. However, prospective randomized controlled trials are needed to define precise dose constraints and optimize clinical strategies.

Feasibility of Achieving Dose Constraints for Dysphagia Aspiration-Related Structures and Its Clinical Significance in Intensity-Modulated Radiotherapy Planning of Head and Neck Cancer

Introduction Dysphagia is commonly seen in patients with head and neck cancers after undergoing chemoradiotherapy and is often under-reported and also not given clinical importance. The quality of life of the patients can be significantly improved if the required dose constraints to the dysphagia aspiration-related structures (DARS) are achieved. The present study was conducted in order to determine the feasibility of achieving the dose constraints to DARS between the standard intensity-modulated radiotherapy (st-IMRT) arm and the dysphagia-optimized IMRT (do-IMRT) arm. Material and methods Sixty patients with head and neck cancer were recruited and randomized into two groups: In one group called the st-IMRT, constraints were not given to DARS, and in the other group called the do-IMRT, constraints were given to DARS. Treatment was given in the form of chemoradiation with a dose of 70 Gy in 35 fractions by IMRT technique, over seven weeks, 2 Gy per fraction along with weekly concurrent Cisplatin (35 mg/m2) in both the groups. Step and shoot IMRT setup was used for planning, and the system used for planning was Eclipse 13.6 (Varian Medical System, Inc., Palo Alto, CA, US); progressive resolution optimizer algorithm was used for optimization, and Anisotropic Analytical Algorithm algorithm was used for dose calculation. Truebeam was used for treatment delivery. DARS dosimetric parameters assessed were Dmean, V30, V50, V60, V70, D50, and D80. Radiation-induced toxicities to the skin, mucosa, larynx, salivary gland, and dysphagia and hematological toxicities were assessed in between both the groups during and after radiotherapy up to six months based on Common Terminology Criteria for Adverse Effects v5.0. p-values were calculated using the unpaired T-test. Results In the cohort of 60 patients with head and neck cancers, 95% were males. Dosimetric parameters of the planning target volume (PTV) were compared but were not found to be significant. In the dosimetry of the organs at risk, a p-value of some structures was found to be significant although the doses received were well within the tolerable limits in both arms. DARS dosimetry V60 and V70 of the inferior constrictor muscle was found to be statistically significant (p=0.01 and 0.008, respectively). V60 and V70 of larynx were also statistically significant (p=0.009 and 0.000, respectively). V70 and D50 of cricopharyngeus were found to be statistically significant (p=0.01 and 0.03, respectively), V30 and V60 for combined pharyngeal constrictor muscles were found to be statistically significant (p=0.02 and 0.01), and lastly, V60 for combined DARS was also significant (p=0.004). Post-treatment 33.3% of patients in the st-IMRT arm required Ryle's tube placement. No grade 4 toxicities were seen in either arm regarding hematological toxicities, acute or chronic radiation-induced toxicities. In site-wise comparison of doses, the p-value was not found to be significant in patients with oropharyngeal and oral cavity carcinomas but was found to be statistically significant in the larynx and hypopharynx subsites. Conclusion The feasibility of achieving dose constraints to the DARS was seen in cases of laryngeal and hypopharyngeal cancers where the constrictor muscles were at a distance from the PTV. Further, the feasibility of achieving dose constraints may be seen in lower-dose prescriptions either in postoperative cases or in low-risk clinical target volume nodal volumes.

Rectum and Bladder Toxicity in Postoperative Prostate Bed Irradiation: Dose-Volume Parameters Analysis

Although prostate cancer treatment is increasingly effective, its toxicities pose a major concern. The aim of our study was to assess the rate of adverse events (AEs) and the prognostic value of dose-volume histogram (DVH) parameters for the occurrence of treatment toxicity in patients treated with post-prostatectomy prostate bed radiotherapy (RT). The AEs were scored according to the CTCAE v.5.0. The rectum and bladder were contoured according to the RTOG Guidelines. The DVH parameters were assessed using data exported from the ECLIPSE treatment-planning system. Genitourinary (GU) and gastrointestinal (GI) toxicity were analysed using consecutive dose thresholds for the percentage of an organ at risk (OAR) receiving a given dose and the QUANTEC dose constraints. A total of 213 patients were included in the final analysis. Acute grade 2 or higher (≥G2) GU AEs occurred in 18.7% and late in 21.3% of patients. Acute ≥G2 GI toxicity occurred in 11.7% and late ≥G2 in 11.2% of the patients. Five patients experienced grade 4 AEs. The most common adverse effects were diarrhoea, proctitis, cystitis, and dysuria. The most significant predictors of acute ≥G2 GI toxicity were rectum V47 and V46 (p < 0.001 and p < 0.001) and rectum wall V46 (p = 0.001), whereas the most significant predictors of late ≥G2 GI AEs were rectum wall V47 and V48 (p = 0.019 and p = 0.021). None of the bladder or bladder wall parameters was significantly associated with the risk of acute toxicity. The minimum doses to bladder wall (p = 0.004) and bladder (p = 0.005) were the most significant predictors of late ≥G2 GU toxicity. Postoperative radiotherapy is associated with a clinically relevant risk of AEs, which is associated with DVH parameters, and remains even in patients who fulfil commonly accepted dose constraints. Considering the lack of survival benefit of postoperative adjuvant RT, our results support delaying treatment through an early salvage approach to avoid or defer toxicity.

Dose-Volume Histogram Parameters and Quality of Life in Patients with Prostate Cancer Treated with Surgery and High-Dose Volumetric-Intensity-Modulated Arc Therapy to the Prostate Bed

INTRODUCTION

Prostate bed radiotherapy (RT) is a major affecter of patients' long-term quality of life (QoL). To ensure the best possible outcome of these patients, dose constraints are key for optimal RT planning and delivery. However, establishing refined dose constraints requires access to patient-level data. Therefore, we aimed to provide such data on the relationship between OAR and gastrointestinal (GI) as well as genitourinary (GU) QoL outcomes of a homogenous patient cohort who received dose-intensified post-operative RT to the prostate bed. Furthermore, we aimed to conduct an exploratory analysis of the resulting data.

METHODS

Patients who were treated with prostate bed RT between 2010 and 2020 were inquired about their QoL based on the Expanded Prostate Cancer Index Composite (EPIC). Those (n = 99) who received volumetric arc therapy (VMAT) of at least 70 Gy to the prostate bed were included. Dose-volume histogram (DVH) parameters were gathered and correlated with the EPIC scores.

RESULTS

The median age at the time of prostate bed RT was 68.9 years, and patients were inquired about their QoL in the median 2.3 years after RT. The median pre-RT prostate-specific antigen (PSA) serum level was 0.35 ng/mL. The median duration between surgery and RT was 1.5 years. The median prescribed dose to the prostate bed was 72 Gy. A total of 61.6% received prostate bed RT only. For the bladder, the highest level of statistical correlation (p < 0.01) was seen for V10-20Gy, Dmean and Dmedian with urinary QoL. For bladder wall, the highest level of statistically significant correlation (p < 0.01) was seen for V5-25Gy, Dmean and Dmedian with urinary QoL. Penile bulb V70Gy was statistically significantly correlated with sexual QoL (p < 0.05). A larger rectal volume was significantly correlated with improved bowel QoL (p < 0.05). Sigmoid and urethral DVH parameters as well as the surgical approach were not statistically significantly correlated with QoL.

CONCLUSION

Specific dose constraints for bladder volumes receiving low doses seem desirable for the further optimization of prostate bed RT. This may be particularly relevant in the context of the aspiration of establishing focal RT of prostate cancer and its local recurrences. Our comprehensive dataset may aid future researchers in achieving these goals.

Doses, fractionations, constraints for stereotactic radiotherapy

This paper describes how to select the most appropriate stereotactic radiotherapy (SRT ) dose and fractionation scheme according to lesion size and site, organs at risk (OARs) proximity and the biological effective dose. In single-dose SRT, 15-34 Gy are generally used while in fractionated SRT 30 and 75 Gy in 2-5 fractions are administered. The ICRU Report No. 91, which is specifically dedicated to SRT treatments, provided indications for dose prescription (with its definition and essential steps), dose delivery and optimal coverage which was defined as the best planning target volume coverage that can be obtained in the irradiated district. Calculation algorithms and OAR s dose constraints are provided as well as treatment planning system characteristics, suggested beam energy and multileaf collimator leaf size. Finally, parameters for irradiation geometry and plan quality are also reported.

Right Atrial Dose Is Associated with Worse Outcome in Patients Undergoing Definitive Stereotactic Body Radiation Therapy for Central Lung Tumors

Simple Summary

The clinical consequences of irradiating the cardiac substructures during stereotactic body radiation therapy (SBRT) remains unclear. We evaluated 83 lung cancer patients who underwent SBRT for early stage lung cancer. Using specialized software, we generated structures for fourteen cardiac substructures and evaluated radiation dose parameters for each. Among these parameters, the dose to 45% (D45%) of either the right atria or ventricle was associated with worse non-cancer associated survival with an identified cutoff value of 890 cGy and 564 cGy for each, respectively. Via these cutoffs, the D45% to the right atria, not the right ventricle, was associated with worse non-cancer associated and overall survival. Based on these findings, reducing the dose to the right atria during SBRT may improve patient outcomes in at risk patients.

Abstract

The consequence of cardiac substructure irradiation in patients receiving stereotactic body radiation therapy (SBRT) is not well characterized. We reviewed the charts of patients with central lung tumors managed by definitive SBRT from June 2010–April 2019. All patients were treated with five fractions, typically either 5000 cGy (44.6%) or 5500 cGy (42.2%). Via a multi-patient atlas, fourteen cardiac substructures were autosegmented, manually reviewed and analyzed using dosimetric parameters. A total of 83 patients were included with a median follow up of 33.4 months. Univariate Cox regression analysis identified a D45% dose to the right atria and ventricle for further study. Sequential log-rank testing evaluating an association between non-cancer associated survival and D45% dose to the right atria or ventricle and association was employed, identifying candidate cutoff values of 890.3 cGy and 564.4 cGy, respectively. Kaplan–Meier analysis using the reported cutoff values found the D45% right atria constraint to be significantly associated with non-cancer associated (p ≤ 0.001) and overall survival (p ≤ 0.001) but not the right ventricle constraint. Within a multivariate model, the proposed right atria D45% cutoff remained significantly correlated with non-cancer associated survival (Hazard’s Ratio (HR) ≤ 8.5, 95% confidence interval (CI) 1.1–64.5, p ≤ 0.04) and OS (HR ≤ 6.1, 95% CI 1.0–36.8, p ≤ 0.04). In conclusion, a dose to D45% of the right atria significantly correlated with outcome and the candidate constraint of 890 cGy stratified non-cancer associated and OS. The inclusion of these findings with previously characterized relationships between proximal airway constraints and survival enhances our understanding of why centrally located tumors are high risk and potentially identifies key constraints in organ at risk prioritization.

Exceeding Radiation Dose to Volume Parameters for the Proximal Airways with Stereotactic Body Radiation Therapy Is More Likely for Ultracentral Lung Tumors and Associated with Worse Outcome

Simple Summary

The optimal way to treat central (CLT) and ultracentral (UCLT) lung tumors with curative radiation is unclear. We evaluated 83 patients with CLT and UCLT who underwent a curative radiotherapy technique called stereotactic body radiation therapy (SBRT). On statistical analysis, patients with UCLT had worse overall survival. Using a cohort of patients matched for relevant variables such as gender and performance status, we evaluated radiation doses to critical central structures such as the airway and heart. In this group, patients with UCLT were more likely to exceed dose constraints as compared CLT, particularly constraints regarding the airway. Additionally, patients had worse non-cancer associated survival when radiation doses were higher than 18 Gy to 4cc’s of either the trachea or proximal bronchial tree. Based on these findings, patients with UCLT have worse outcomes which could be secondary to higher radiation doses to the trachea and proximal bronchial tree.

Abstract

The preferred radiotherapeutic approach for central (CLT) and ultracentral (UCLT) lung tumors is unclear. We assessed the toxicity and outcomes of patients with CLT and UCLT who underwent definitive five-fraction stereotactic body radiation therapy (SBRT). We reviewed the charts of patients with either CLT or UCLT managed with SBRT from June 2010–April 2019. CLT were defined as gross tumor volume (GTV) within 2 cm of either the proximal bronchial tree, trachea, mediastinum, aorta, or spinal cord. UCLT were defined as GTV abutting any of these structures. Propensity score matching was performed for gender, performance status, and history of prior lung cancer. Within this cohort of 83 patients, 43 (51.8%) patients had UCLT. The median patient age was 73.1 years with a median follow up of 29.9 months. The two most common dose fractionation schemes were 5000 cGy (44.6%) and 5500 cGy (42.2%) in five fractions. Multivariate analysis revealed UCLT to be associated with worse overall survival (OS) (HR = 1.9, p = 0.02) but not time to progression (TTP). Using propensity score match pairing, UCLT correlated with reduced non-cancer associated survival (p = 0.049) and OS (p = 0.03), but not TTP. Within the matched cohort, dosimetric study found exceeding a D4cc of 18 Gy to either the proximal bronchus (HR = 3.9, p = 0.007) or trachea (HR = 4.0, p = 0.02) was correlated with worse non-cancer associated survival. In patients undergoing five fraction SBRT, UCLT location was associated with worse non-cancer associated survival and OS, which could be secondary to excessive D4cc dose to the proximal airways.

Carbon Ion Dose Constraints in the Head and Neck and Skull Base: Review of MedAustron Institutional Protocols

Background

Dose constraints are of paramount importance for the outcome of any radiotherapy treatment. In this article, we report dose-volume constraints as well as currently used fractionation schedules for carbon ion radiotherapy as applied in MedAustron (Wiener Neustadt, Austria).

Materials and Methods

For fractionation schedules, both German and Japanese regimes were used. From the clinical experience of National Institute of Radiological Sciences (Chiba, Japan) and Heidelberg Ion Therapy (Heidelberg, Germany; formerly GSI Helmholtzzentrum für Schwerionenforschung, Darmstadt, Germany) and the work by colleagues in Centro Nazionale Adroterapia Oncologica (Pavia, Italy) recalculating the dose from the microdosimetric kinetic model to the local effect model, we have set the dose constraints for critical organs of the head and neck area. Where no clinical data was available, an educated guess was made, based on data available from photon and proton series.

Results

We report the constraints for the optic nerve and chiasm, brainstem, spinal cord, cochlea, brain parenchyma, salivary gland, eye and adnexa, and mandibular/maxillary bone; constraints are grouped based on a fractionation scheme (German versus Japanese) and the risk of toxicity (safe, low to middle, and middle to high).

Conclusion

We think validation of dose constraints should present a relevant part of the activity of any carbon ion radiotherapy facility, and we anticipate future multicentric, joint evaluations.

Dosimetric feasibility of computed tomography-based image-guided brachytherapy in locally advanced cervical cancer: a Japanese prospective multi-institutional study

The aim of this study was to assess the feasibility of planning dose-volume histogram (DVH) parameters in computed tomography-based 3D image-guided brachytherapy for locally advanced cervical cancer. In a prospective multi-institutional study, 60 patients with stage IIA2-IVA cervical cancer from eight institutions were treated with external beam radiotherapy using central shielding and intracavitary or hybrid (combined intracavitary/interstitial) brachytherapy (HBT). The dose constraints were set as a cumulative linear quadratic equivalent dose (EQD2) of at least 60 Gy for high-risk clinical target volume (HR-CTV) D90, D2cc ≤ 75 Gy for rectum, D2cc ≤ 90 Gy for bladder and D2cc ≤ 75 Gy for sigmoid. The median HR-CTV D90 was 70.0 Gy (range, 62.8-83.7 Gy) in EQD2. The median D2cc of rectum, bladder and sigmoid was 57.1 Gy (range, 39.8-72.1 Gy), 68.9 Gy (range, 46.5-84.9 Gy) and 57.2 Gy (range, 39.2-71.2 Gy) in EQD2, respectively. In 76 of 233 sessions (33%), 23 patients underwent HBT, and the median number of interstitial needles was 2 (range, 1-5). HBT for a bulky HR-CTV (≥40 cm3) significantly improved the HR-CTV D90 compared with intracavitary brachytherapy alone (P = 0.010). All patients fulfilled the dose constrains for target and at risk organs by undergoing HBT in one-third of sessions. We conclude that the planning DVH parameters used in our protocol are clinically feasible.

Hippocampal radiotherapy dose constraints for predicting long-term neurocognitive outcomes: mature data from a prospective trial in young patients with brain tumors

BACKGROUND

Hippocampus is considered to be the seat for neurocognitive functions. Avoidance of hippocampus during radiotherapy to brain may serve to preserve various domains of neurocognition. We aimed to derive radiotherapy dose constraints to hippocampi for preserving neurocognition in young patients with brain tumors by measuring various neurocognitive parameters.

METHODS

Forty-eight patients with residual/progressive benign or low-grade brain tumors treated with stereotactic conformal radiotherapy (SCRT) to a dose of 54 Gy in 30 fractions underwent prospective neuropsychological assessments at baseline before SCRT and at 6 months and 2, 3, 4, and 5 years. Hippocampi were drawn as per the Radiation Therapy Oncology Group atlas. Longitudinal change in intelligence quotient scores was correlated with hippocampal doses.

RESULTS

Mean volume of bilateral hippocampi was 4.35 cc (range: 2.12-8.41 cc). Craniopharyngioma was the commonest histologic subtype. A drop of >10% in mean full-scale intelligence quotient (FSIQ) scores at 3 and 5 years post SCRT was observed in patients in whom left hippocampus received a mean dose of 30.7 Gy (P = 0.04) and 31 Gy (P = 0.04), respectively. Mean performance quotient (PQ) scores dropped > 10% at 5 years when the left hippocampus received a dose of > 32 Gy (P = 0.03). There was no significant correlation of radiotherapy doses with verbal quotient, or with doses received by the right hippocampus. Multivariate analysis revealed young age (<13 y) and left hippocampus dose predicted for clinically relevant decline in certain neurocognitive domains.

CONCLUSIONS

A mean dose of ≤30 Gy to the left hippocampus as a dose constraint for preserving intelligence quotient is suggested.

KEY POINTS

1. Children and young adults with benign and low-grade gliomas survive long after therapy.2. Higher dose to the hippocampi may result in long-term neurocognitive impairment.3. Mean dose of <30 Gy to left hippocampus could be used as a pragmatic dose constraint to prevent long-term neurocognitive decline.

Brainstem NTCP and Dose Constraints for Carbon Ion RT-Application and Translation From Japanese to European RBE-Weighted Dose

Background and Purpose

The Italian National Center of Oncological Hadrontherapy (CNAO) has applied dose constraints for carbon ion RT (CIRT) as defined by Japan’s National Institute of Radiological Sciences (NIRS). However, these institutions use different models to predict the relative biological effectiveness (RBE). CNAO applies the Local Effect Model I (LEM I), which in most clinical situations predicts higher RBE than NIRS’s Microdosimetric Kinetic Model (MKM). Equal constraints therefore become more restrictive at CNAO. Tolerance doses for the brainstem have not been validated for LEM I-weighted dose (D_{LEM I}). However, brainstem constraints and a Normal Tissue Complication Probability (NTCP) model were recently reported for MKM-weighted dose (D_MKM), showing that a constraint relaxation to D_{MKM|0.7 cm³} <30 Gy (RBE) and D_{MKM|0.1 cm³} <40 Gy (RBE) was feasible. The aim of this work was to evaluate the brainstem NTCP associated with CNAO’s current clinical practice and to propose new brainstem constraints for LEM I-optimized CIRT at CNAO.

Material and Methods

We reproduced the absorbed dose of 30 representative patient treatment plans from CNAO. Subsequently, we calculated both D_{LEM I} and D_MKM, and the relationship between D_MKM and D_{LEM I} for various brainstem dose metrics was analyzed. Furthermore, the NTCP model developed for D_MKM was applied to estimate the NTCPs of the delivered plans.

Results

The translation of CNAO treatment plans to D_MKM confirmed that the former CNAO constraints were conservative compared with D_MKM constraints. Estimated NTCPs were 0% for all but one case, in which the NTCP was 2%. The relationship D_MKM/D_{LEM I} could be described by a quadratic regression model which revealed that the validated D_MKM constraints corresponded to D_{LEM I|0.7 cm³} <41 Gy (RBE) (95% CI, 38–44 Gy (RBE)) and D_{LEM I|0.1 cm³} <49 Gy (RBE) (95% CI, 46–52 Gy (RBE)).

Conclusion

Our study demonstrates that RBE-weighted dose translation is of crucial importance in order to exchange experience and thus harmonize CIRT treatments globally. To mitigate uncertainties involved, we propose to use the lower bound of the 95% CI of the translation estimates, i.e., D_{LEM I|0.7 cm³} <38 Gy (RBE) and D_{LEM I|0.1 cm³} <46 Gy (RBE) as brainstem dose constraints for 16 fraction CIRT treatments optimized with LEM I.

Radiotherapy dose limit for uterus fertility sparing in curative chemoradiotherapy for rectal cancer

AIMS

Curative sphincter sparing radiotherapy is a treatment option for early rectal cancer. There are many methods developed for fertility preservation in young patients treated with pelvic radiotherapy. Pregnancy rates after radiotherapy are dependent on the radiation dose to ovaries and uterus. Data on outcomes of total body irradiation suggest a pregnancy is possible following 12-14 Gy TBI, despite elevated rates of preterm deliveries and other complications.

METHODS

We report a case of full-term delivery of twins after curative chemoradiotherapy for anorectal adenocarcinoma T2 N0 M0 with the total dose 58.6 Gy. The patient underwent laparoscopic laterocranial ovarian transposition before radiotherapy.

RESULTS

Long term complete remission was achieved after treatment. Although a spontaneous conception was not successful, the patient underwent an in vitro fertilisation procedure with donor eggs and conceived twins 10 years after the radiotherapy treatment. The mean dose to the uterus was 16 Gy and to the uterine cervix 35 Gy. She reached a full-term pregnancy and delivered two healthy babies by caesarean section at a gestational age of 38 weeks, weighing 2420 g and 2220 g.

CONCLUSION

This is the first case report of the successful pregnancy following sphincter sparing curative pelvic radiotherapy for rectal cancer. Furthermore it allows us to propose an increased limit dose to the uterus enabling fertility sparing beyond the limits achieved from total body irradiation series with 12-14 Gy and accept 16 Gy as uterine body (35 Gy for uterine cervix) limit for IMRT treatment planning in young patients asking for maintaining fertility potential.

Dose-Limiting Organs at Risk in Carbon Ion Re-Irradiation of Head and Neck Malignancies: An Individual Risk-Benefit Tradeoff

Background: Carbon ion re-irradiation (CIR) was evaluated to investigate treatment planning and the consequences of individual risk-benefit evaluations concerning dose-limiting organs at risk (OAR). Methods: A total of 115 consecutive patients with recurrent head and neck cancer (HNC) were analyzed after initial radiotherapy and CIR at the same anatomical site. Toxicities were evaluated in line with the Common Terminology Criteria for Adverse Events 4.03. Results: The median maximum cumulative equivalent doses applied in fractions of 2 Gy (EQD2) to the brainstem, optic chiasm, ipsilateral optic nerve, and spinal cord were 56.8 Gy (range 0.94-103.9), 51.4 Gy (range 0-120.3 Gy), 63.6 Gy (range 0-146.1 Gy), and 28.8 Gy (range 0.2-87.7 Gy). The median follow up after CIR was 24.0 months (range 2.5-72.0 months). The cumulative rates of acute and late severe (≥grade III) side effects after CIR were 1.8% and 14.3%. Conclusion: In recurrent HNC, an individual risk-benefit tradeoff is frequently inevitable due to unfavorable location of tumors in close proximity to vital OAR. There are uncertainties about the dose tolerance of OAR after CIR, which warrant increased awareness about the potential treatment toxicity and further studies on heavy ion re-irradiation.

Dosimetric benefits of placing dose constraints on the brachial plexus in patients with nasopharyngeal carcinoma receiving intensity-modulated radiation therapy: a comparative study

This study aimed to evaluate whether placing dose constraints on the brachial plexus (BP) could provide dosimetric benefits in patients with nasopharyngeal carcinoma (NPC) undergoing intensity-modulated radiation therapy (IMRT). Planning CT images for 30 patients with NPC treated with definitive IMRT were retrospectively reviewed. Target volumes, the BP and other critical structures were delineated; two separate IMRT plans were designed for each patient: one set no restrictions for the BP; the other considered the BP as a critical structure for which a maximum dose limit of ≤66 Gy was set. No significant differences between the two plans were observed in the conformity index, homogeneity index, maximum dose to the planning target volumes (PTVs), minimum dose to the PTVs, percentages of the volume of the PTVnx and PTVnd receiving more than 110% of the prescribed dose, or percentages of the volume of the PTVs receiving 95% and > 93% of the prescribed dose. Dose constraints significantly reduced the maximum dose, mean dose, V45, V50, V54, V60, V66 and V70 to the BP. Dose constraints significantly reduced the maximum dose to the BP, V45, V60 and V66 in both N0-1 and N2-3 disease; however, the magnitude of the dosimetric gain for each parameter between N0-1 and N2-3 disease was not significantly different, except for the V60 and V66. In conclusion, placing dose constraints on the BP can significantly decrease the irradiated volume and dose, without compromising adequate dose delivery to the target volume.

Technical aspects of radiation therapy for anal cancer

Historically treated with surgery, current practice recommends anal carcinoma to be treated with a combination of chemotherapy and radiation. This review will examine the anatomy, modes of disease spread and recurrence, and evaluate the existing evidence for treatment options for these tumors. An in-depth examination of specific radiation therapy (RT) techniques-such as conventional 3D-conformal RT and intensity-modulated RT-will be discussed along with modern dose constraints. RT field arrangement, patient setup, and recommended gross and clinical target volume (CTV) contours will be considered. Areas in need of further investigation, such as the role in treatment for positron emission tomography (PET) will be explored.