Tolerance of normal tissue to therapeutic irradiation

Dosimetric and radiobiological comparison of IMRT, VMAT, and helical tomotherapy planning techniques in hippocampal sparing whole brain radiotherapy with simultaneous integrated boost for multiple brain metastases

To compare treatment planning and dosimetric outcomes for hippocampal sparing whole brain radiotherapy (WBRT) with the simultaneous integrated boost (SIB) in brain metastasis (BM) patients using tumour control probability (TCP) and normal tissue complication probability (NTCP) formalism between IMRT, VMAT, and HT techniques. In this retrospective study, the treatment data of 20 BM patients who typically received whole brain radiation with SIB treatment were used. Prescription doses of 30 Gy and 36 Gy was delivered in 10 fractions for WBRT and SIB, respectively. Niemierko and LKB models were applied for calculating TCP and NTCP. All the plans were evaluated for the RTOG 0933 protocol criteria and found acceptable. Additionally, the homogeneity of the PTV boost is 0.07 ± 0.01, 0.1 ± 0.04, and 0.08 ± 0.02 for IMRT, VMAT, and HT, respectively (P < 0.05). The percentage of TCP for the PTV boost was 99.99 ± 0.003, 99.98 ± 0.004, and 99.99 ± 0.002 of IMRT, VMAT, and HT, respectively, (P < 0.005). The NTCP value of the lenses was higher with the VMAT plan as compared to IMRT and HT Plans. The hippocampal NTCP values are equal in all three planning proficiencies. The techniques like IMRT, VMAT, and HT can reduce the dose received by hippocampus to the dosimetric threshold during the delivery of WBRT with hippocampal sparing and can simultaneously boost multiple metastases. Overall, the high-quality dose distribution, TCP, and NTCP comparison between all three planning techniques show that the HT technique has better results when compared to the VMAT and IMRT techniques.

Proteomic changes in the hippocampus of large mammals after total-body low dose radiation

There is a growing interest in low dose radiation (LDR) to counteract neurodegeneration. However, LDR effects on normal brain have not been completely explored yet. Recent analyses showed that LDR exposure to normal brain tissue causes expression level changes of different proteins including neurodegeneration-associated proteins. We assessed the proteomic changes occurring in radiated vs. sham normal swine brains. Due to its involvement in various neurodegenerative processes, including those associated with cognitive changes after high dose radiation exposure, we focused on the hippocampus first. We observed significant proteomic changes in the hippocampus of radiated vs. sham swine after LDR (1.79Gy). Mass spectrometry results showed 190 up-regulated and 120 down-regulated proteins after LDR. Western blotting analyses confirmed increased levels of TPM1, TPM4, PCP4 and NPY (all proteins decreased in various neurodegenerative processes, with NPY and PCP4 known to be neuroprotective) in radiated vs. sham swine. These data support the use of LDR as a potential beneficial tool to interfere with neurodegenerative processes and perhaps other brain-related disorders, including behavioral disorders.

Risk adaptive planning with biology-based constraints may lead to higher tumor control probability in tumors of the canine brain: A planning study

BACKGROUND

Classical radiation protocols are guided by physical dose delivered homogeneously over the target. Protocols are chosen to keep normal tissue complication probability (NTCP) at an acceptable level. Organs at risk (OAR) adjacent to the target volume could lead to underdosage of the tumor and a decrease of tumor control probability (TCP). The intent of our study was to explore a biology-based dose escalation: by keeping NTCP for OAR constant, radiation dose was to be maximized, allowing to result in heterogeneous dose distributions.

METHODS

We used computed tomography datasets of 25 dogs with brain tumors, previously treated with 10x4 Gy (40 Gy to PTV D50). We generated 3 plans for each patient: A) original treatment plan with homogeneous dose distribution, B) heterogeneous dose distribution with strict adherence to the same NTCPs as in A), and C) heterogeneous dose distribution with adherence to NTCP <5%. For plan comparison, TCPs and TCP equivalent doses (homogenous target dose which results in the same TCP) were calculated. To enable the use of the generalized equivalent uniform dose (gEUD) metric of the tumor target in plan optimization, the calculated TCP values were used to obtain the volume effect parameter a.

RESULTS

As intended, NTCPs for all OARs did not differ from plan A) to B). In plan C), however, NTCPs were significantly higher for brain (mean 2.5% (SD±1.9, 95%CI: 1.7,3.3), p<0.001), optic chiasm (mean 2.0% (SD±2.2, 95%CI: 1.0,2.8), p=0.010) compared to plan A), but no significant increase was found for the brainstem. For 24 of 25 of the evaluated patients, the heterogenous plans B) and C) led to an increase in target dose and projected increase in TCP compared to the homogenous plan A). Furthermore, the distribution of the projected individual TCP values as a function of the dose was found to be in good agreement with the population TCP model.

CONCLUSION

Our study is a first step towards risk-adaptive radiation dose optimization. This strategy utilizes a biologic objective function based on TCP and NTCP instead of an objective function based on physical dose constraints.

Correlation between morphological parameters and dosimetric parameters of the heart and spinal cord in the intermediate- and advanced-stage esophageal cancer

BACKGROUND

Radiation therapy plays a pivotal role as the primary adjuvant treatment for esophageal cancer (EPC), emphasizing the critical importance of carefully balancing radiation doses to the target area and organs at risk in the radiotherapeutic management of esophageal cancer.

AIMS

This study aimed to explore the correlation between morphological parameters and dosimetric parameters of the heart and spinal cord in intermediate- and advanced-stage esophagus cancer to provide a reference for clinical treatment.

METHODS AND RESULTS

A total of 105 patients with intermediate- and advanced-stage EPC, who received treatment in our hospital from 2019 to 2021, were included. The morphological parameters were calculated by imaging. Intensity-modulated radiation therapy plan was executed at Raystation4.7. The PTV-G stood for the externally expanded planning target volume (PTV) of the gross tumor volume (GTV) and PTV-C for the externally expanded volume of the clinical target volume (CTV). The prescription dose of PTV-G and PTV-C was set as 60Gy/30F and 54Gy/30F, respectively. The linear regression model was used to analyze the correlation between morphologic parameters of EPC and dosimetric parameters of the heart and spinal cord. In 105 cases, the total lung length was correlated with the spinal cord maximum dose (D2 ). The heart mean doses (Dmean ) and heart V40 (the relative volume that receives 40 Gy or more) was correlated with PTV-G volume, PTV-G length; In middle- and upper-segment EPC cases, only the total lung volume was correlated with the spinal cord Dmean , spinal cord D2 , heart Dmean , and heart V40 ; In middle-stage EPC cases, the heart Dmean was correlated with the PTV-G volume, PTV-G length. The total lung length was correlated with the spinal cord D2 ; In middle- and lower-segment EPC, only the PTV-G volume and PTV-G length were correlated with the heart Dmean . All the aforementioned values were statistically significant.

CONCLUSIONS

Combined with the unsegmented tumor and different locations, the organ at risk dose was comprehensively considered.

Radiotheranostics in advanced prostate cancer: Current and future directions

The discovery of small molecules that target the extracellular domain of prostate-specific membrane antigen (PSMA) has led to advancements in diagnostic imaging and the development of precision radiopharmaceutical therapies. In this review, we present the available existing data and highlight the key ongoing clinical evaluations of PSMA-based imaging in the management of primary, biochemically recurrent, and metastatic prostate cancer. We also discuss clinical studies that explore the use of PSMA-based radiopharmaceutical therapy (RPT) in metastatic prostate cancer and forthcoming trials that investigate PSMA RPT in earlier disease states. Multidisciplinary collaboration in clinical trial design and therapeutic administration is critical to the continued progress of this evolving radiotheranostics field.

Pericardial effusion in oncological patients: current knowledge and principles of management

BACKGROUND

This article provides an up-to-date overview of pericardial effusion in oncological practice and a guidance on its management. Furthermore, it addresses the question of when malignancy should be suspected in case of newly diagnosed pericardial effusion.

MAIN BODY

Cancer-related pericardial effusion is commonly the result of localization of lung and breast cancer, melanoma, or lymphoma to the pericardium via direct invasion, lymphatic dissemination, or hematogenous spread. Several cancer therapies may also cause pericardial effusion, most often during or shortly after administration. Pericardial effusion following radiation therapy may instead develop after years. Other diseases, such as infections, and, rarely, primary tumors of the pericardium complete the spectrum of the possible etiologies of pericardial effusion in oncological patients. The diagnosis of cancer-related pericardial effusion is usually incidental, but cancer accounts for approximately one third of all cardiac tamponades. Drainage, which is mainly attained by pericardiocentesis, is needed when cancer or cancer treatment-related pericardial effusion leads to hemodynamic impairment. Placement of a pericardial catheter for 2-5 days is advised after pericardial fluid removal. In contrast, even a large pericardial effusion should be conservatively managed when the patient is stable, although the best frequency and timing of monitoring by echocardiography in this context are yet to be established. Pericardial effusion secondary to immune checkpoint inhibitors typically responds to corticosteroid therapy. Pericardiocentesis may also be considered to confirm the presence of neoplastic cells in the pericardial fluid, but the yield of cytological examination is low. In case of newly found pericardial effusion in individuals without active cancer and/or recent cancer treatment, a history of malignancy, unremitting or recurrent course, large effusion or presentation with cardiac tamponade, incomplete response to empirical therapy with nonsteroidal anti-inflammatory, and hemorrhagic fluid at pericardiocentesis suggest a neoplastic etiology.

Anatomy-based correction of kidney PVE on [Formula: see text] SPECT images

BACKGROUND

In peptide receptor radionuclide therapy (PRRT), accurate quantification of kidney activity on post-treatment SPECT images paves the way for patient-specific treatment. Due to the limited spatial resolution of SPECT images, the partial volume effect (PVE) is a significant source of quantitative bias. In this study, we aimed to evaluate the performance and robustness of anatomy-based partial volume correction (PVC) algorithms to recover the accurate activity concentration of realistic kidney geometries on [Formula: see text]Lu SPECT images recorded under clinical conditions.

METHODS

Based on the CT scan data from patients, three sets of fillable kidneys with surface-to-volume (S:V) ratios ranging from 1.5 to 2.8 cm-1, were 3D printed and attached in a IEC phantom. Quantitative [Formula: see text]Lu SPECT/CT acquisitions were performed on a GE Discovery NM CT 870 DR camera for the three modified IEC phantoms and for 6 different Target-To-Background ratios (TBRs: 2, 4, 6, 8, 10, 12). Two region-based (GTM and Labbé) and five voxel-based (GTM + MTC, Labbé + MTC, GTM + RBV, Labbé + RBV and IY) methods were evaluated with this data set. Additionally, the robustness of PVC methods to Point Spread Function (PSF) discrepancies, registration mismatches and background heterogeneity was evaluated.

RESULTS

Without PVC, the average kidney RCs across all TBRs ranged from 0.66 ± 0.05 (smallest kidney) to 0.80 ± 0.03 (largest kidney). For a TBR of 12, all anatomy-based method were able to recover the kidneys activity concentration with an error < 6%. All methods result in a comparable decline in RC restoration with decreasing TBR. The Labbé method was the most robust against PSF and registration mismatches but was also the most sensitive to background heterogeneity. Among the voxel-based methods, MTC images were less uniform than RBV and IY images at the outer edge of high uptake areas (kidneys and spheres).

CONCLUSION

Anatomy-based PVE correction allows for accurate SPECT quantification of the [Formula: see text]Lu activity concentration with realistic kidney geometries. Combined with recent progress in deep-learning algorithms for automatic anatomic segmentation of whole-body CT, these methods could be of particular interest for a fully automated OAR dosimetry pipeline with PVE correction.

A Meta-Analysis and Review of Radiation Dose Escalation in Definitive Radiation Therapy between Squamous Cell Carcinoma and Adenocarcinoma of Esophageal Cancer

Esophageal cancer, ranked as the eighth most prevalent cancer globally, is characterized by a low survival rate and poor prognosis. Concurrent chemoradiation therapy (CCRT) is the standard therapy in the non-surgical treatment of localized carcinoma of the esophagus. Nevertheless, the radiation doses employed in CCRT remain notably lower compared to the curative definite chemoradiation therapy utilized in the management of other carcinomas. In order to increase the local control rates and enhance the treatment outcomes, several clinical trials have used high-dose radiation to analyze the effect of dose escalation. Despite the integration of technically advanced RT schemes such as intensity-modulated radiation therapy (IMRT), the results of these trials have failed to demonstrate a significant improvement in overall survival or local progression-free survival. In this review, we investigated previous clinical trials to determine the ineffectiveness of radiation dose escalation in the context of CCRT for esophageal cancer. We aim to clarify the factors contributing to the limited efficacy of escalated radiation doses in improving patient outcomes. Furthermore, we delve into recent research endeavors, exploring prospective radiation dose modifications being altered based on the histological characteristics of the carcinoma. The exploration of these recent studies not only sheds light on potential refinements to the existing treatment protocols but also seeks to identify novel approaches that may pave the way for more efficacious and personalized therapeutic strategies for esophageal cancer management.

MIB Guides: Preclinical Radiopharmaceutical Dosimetry

Preclinical dosimetry is essential for guiding the design of animal radiopharmaceutical biodistribution, imaging, and therapy experiments, evaluating efficacy and/or toxicities in such experiments, ensuring compliance with ethical standards for animal research, and, perhaps most importantly, providing reasonable initial estimates of normal-organ doses in humans, required for clinical translation of new radiopharmaceuticals. This MIB Guide provides a basic protocol for obtaining preclinical dosimetry estimates with organ-level dosimetry software.

Radiation-Induced Myonecrosis: A Case Report of a Cervical Cancer Patient With a History of Systemic Lupus Erythematosus

Radiation-induced myonecrosis is a rare but serious complication of radiation therapy. We present a case of a 49-year-old woman with systemic lupus erythematosus who developed radiation-induced myonecrosis after concurrent chemoradiation for cervical cancer. She underwent external-beam radiation therapy, weekly cisplatin chemotherapy (40 mg/m2), and intracavitary brachytherapy. One month later, she received one cycle of nedaplatin (80 mg/m2) and irinotecan (60 mg/m2). Two months after treatment, she experienced pain in the left inguinal region. An MRI revealed a mass in the left obturator externus muscle and right pectineus muscle suggestive of myonecrosis. A biopsy confirmed the diagnosis. She received hyperbaric oxygen therapy, and her symptoms improved. The masses resolved completely.

Comparative Evaluation of Proton Therapy and Volumetric Modulated Arc Therapy for Brachial Plexus Sparing in the Comprehensive Reirradiation of High-Risk Recurrent Breast Cancer

Purpose

Recurrent or new primary breast cancer requiring comprehensive regional nodal irradiation after prior radiation therapy (RT) to the supraclavicular area and upper axilla is challenging due to cumulative brachial plexus (BP) dose tolerance. We assessed BP dose sparing achieved with pencil beam scanning proton therapy (PBS-PT) and photon volumetric modulated arc therapy (VMAT).

Methods and Materials

In an institutional review board-approved planning study, all patients with ipsilateral recurrent breast cancer treated with PBS-PT re-RT (PBT1) with at least partial BP overlap from prior photon RT were identified. Comparative VMAT plans (XRT1) using matched BP dose constraints were developed. A second pair of proton (PBT2) and VMAT (XRT2) plans using standardized target volumes were created, applying uniform prescription dose of 50.4 per 1.8 Gy and a maximum BP constraint <25 Gy. Incidence of brachial plexopathy was also assessed.

Results

Ten consecutive patients were identified. Median time between RT courses was 48 months (15-276). Median first, second, and cumulative RT doses were 50.4 Gy (range, 42.6-60.0), 50.4 Gy relative biologic effectiveness (RBE) (45.0-64.4), and 102.4 Gy (RBE) (95.0-120.0), respectively. Median follow-up was 15 months (5-33) and 18 months for living patients (11-33) Mean BP max was 37.5 Gy (RBE) for PBT1 and 36.9 Gy for XRT1. Target volume coverage of V85% (volume receiving 85% of prescription dose), V90%, and V95% were numerically lower for XRT1 versus PBT1. Similarly, axilla I-III and supraclavicular area coverage were significantly higher for PBT2 than XRT2 at dose levels of V55%, V65%, V75%, V85%, and V95%. Only axilla I V55% did not reach significance (P = .06) favoring PBS-PT. Two patients with high cumulative BPmax (95.2 Gy [RBE], 101.6 Gy [RBE]) developed brachial plexopathy symptoms with ulnar nerve distribution neuropathy without pain or weakness (1 of 2 had symptom resolution after 6 months without intervention).

Conclusions

PBS-PT improved BP sparing and target volume coverage versus VMAT. For patients requiring comprehensive re-RT for high-risk, nonmetastatic breast cancer recurrence with BP overlap and reasonable expectation for prolonged life expectancy, PBT may be the preferred treatment modality.

More than one way to skin a dose volume: the impact of dose-surface map calculation approach on study reproducibility

Objective.Dose-surface maps (DSMs) provide spatial representations of the radiation dose to organ surfaces during radiotherapy and are a valuable tool for identifying dose deposition patterns that are predictive of radiation toxicities. Over the years, many different DSM calculation approaches have been introduced and used in dose-outcome studies. However, little consideration has been given to how these calculation approaches may be impacting the reproducibility of studies in the field. Therefore, we conducted an investigation to determine the level of equivalence of DSMs calculated with different approaches and their subsequent impact on study results.Approach.Rectum and bladder DSMs were calculated for 20 prostate radiotherapy patients using combinations of the most common slice orientation and spacing styles in the literature. Equivalence of differently calculated DSMs was evaluated using pixel-wise comparisons and DSM features (rectum only). Finally, mock cohort comparison studies were conducted with DSMs calculated using each approach to determine the level of dosimetric study reproducibility between calculation approaches.Main results.We found that rectum DSMs calculated using the planar and non-coplanar orientation styles were non-equivalent in the posterior rectal region and that equivalence of DSMs calculated with different slice spacing styles was conditional on the choice of inter-slice distance used. DSM features were highly sensitive to choice of slice orientation style and DSM sampling resolution. Finally, while general result trends were consistent between the comparison studies performed using different DSMs, statisitically significant subregions and features could vary greatly in position and magnitude.Significance.We have determined that DSMs calculated with different calculation approaches are frequently non-equivalent and can lead to differing conclusions between studies performed using the same dataset. We recommend that the DSM research community work to establish consensus calculation approaches to ensure reproducibility within the field.

The Challenge of Single-Photon Emission Computed Tomography Image Segmentation in the Internal Dosimetry of 177Lu Molecular Therapies

The aim of this article is to review the single photon emission computed tomography (SPECT) segmentation methods used in patient-specific dosimetry of 177Lu molecular therapy. Notably, 177Lu-labelled radiopharmaceuticals are currently used in molecular therapy of metastatic neuroendocrine tumours (ligands for somatostatin receptors) and metastatic prostate adenocarcinomas (PSMA ligands). The proper segmentation of the organs at risk and tumours in targeted radionuclide therapy is an important part of the optimisation process of internal patient dosimetry in this kind of therapy. Because this is the first step in dosimetry assessments, on which further dose calculations are based, it is important to know the level of uncertainty that is associated with this part of the analysis. However, the robust quantification of SPECT images, which would ensure accurate dosimetry assessments, is very hard to achieve due to the intrinsic features of this device. In this article, papers on this topic were collected and reviewed to weigh up the advantages and disadvantages of the segmentation methods used in clinical practice. Degrading factors of SPECT images were also studied to assess their impact on the quantification of 177Lu therapy images. Our review of the recent literature gives an insight into this important topic. However, based on the PubMed and IEEE databases, only a few papers investigating segmentation methods in 177Lumolecular therapy were found. Although segmentation is an important step in internal dose calculations, this subject has been relatively lightly investigated for SPECT systems. This is mostly due to the inner features of SPECT. What is more, even when studies are conducted, they usually utilise the diagnostic radionuclide 99mTc and not a therapeutic one like 177Lu, which could be of concern regarding SPECT camera performance and its overall outcome on dosimetry.

Small Bowel Dose Constraints in Radiation Therapy—Where Omics-Driven Biomarkers and Bioinformatics Can Take Us in the Future

Radiation-induced gastrointestinal (GI) dose constraints are still a matter of concern with the ongoing evolution of patient outcomes and treatment-related toxicity in the era of image-guided intensity-modulated radiation therapy (IMRT), stereotactic ablative radiotherapy (SABR), and novel systemic agents. Small bowel (SB) dose constraints in pelvic radiotherapy (RT) are a critical aspect of treatment planning, and prospective data to support them are scarce. Previous and current guidelines are based on retrospective data and experts’ opinions. Patient-related factors, including genetic, biological, and clinical features and systemic management, modulate toxicity. Omic and microbiome alterations between patients receiving RT to the SB may aid in the identification of patients at risk and real-time identification of acute and late toxicity. Actionable biomarkers may represent a pragmatic approach to translating findings into personalized treatment with biologically optimized dose escalation, given the mitigation of the understood risk. Biomarkers grounded in the genome, transcriptome, proteome, and microbiome should undergo analysis in trials that employ, R.T. Bioinformatic templates will be needed to help advance data collection, aggregation, and analysis, and eventually, decision making with respect to dose constraints in the modern RT era.

Understanding radiation-generated electronic traps in radiation dosimeters based on organic field-effect transistors

Organic dosimeters offer unique advantages over traditional technologies, and they can be used to expand the capabilities of current radiation detection systems. In-depth knowledge of the mechanisms underlying the interaction between radiation and organic materials is essential for their widespread adoption. Here, we identified and quantitatively characterized the electronic traps generated during the operation of radiation dosimeters based on organic field-effect transistors. Spectral analysis of the trap density of states, along with optical and structural studies, revealed the origin of trap states as local structural disorder within the crystalline films. Our results provide new insights into the radiation-induced defects in organic dosimeters, and pave the way for the development of more efficient and reliable radiation detection devices.

212Pb-Pretargeted Theranostics for Pancreatic Cancer

Although pancreatic ductal adenocarcinoma (PDAC) is associated with limited treatment options and poor patient outcomes, targeted α-particle therapy (TAT) represents a promising development in the field. TAT shows potential in treating metastatic cancers, including those that have become resistant to conventional treatments. Among the most auspicious radionuclides stands the in vivo α-generator 212Pb. Combined with the imaging-compatible radionuclide 203Pb, this theranostic match is a promising modality rapidly translating into the clinic. Methods: Using the pretargeting approach between a radiolabeled 1,2,4,5-tetrazine (Tz) tracer and a trans-cyclooctene (TCO) modified antibody, imaging and therapy with radiolead were performed on a PDAC tumor xenograft mouse model. For therapy, 3 cohorts received a single administration of 1.1, 2.2, or 3.7 MBq of the pretargeting agent, [212Pb]Pb-DO3A-PEG7-Tz, whereby administered activity levels were guided by dosimetric analysis. Results: The treated mice were holistically evaluated; minimal-to-mild renal tubular necrosis was observed. At the same time, median survival doubled for the highest-dose cohort (10.7 wk) compared with the control cohort (5.1 wk). Conclusion: This foundational study demonstrated the feasibility and safety of pretargeted TAT with 212Pb in PDAC while considering dose limitations and potential adverse effects.

Long-Term Nephrotoxicity of 177Lu-PSMA Radioligand Therapy

β-emitting 177Lu targeting prostate-specific membrane antigen (PSMA) is an approved treatment option for metastatic castration-resistant prostate cancer. Data on its long-term nephrotoxicity are sparse. This study aimed to retrospectively evaluate post-177Lu-PSMA estimated glomerular filtration rate (eGFR) dynamics for at least 12 mo in a cohort of metastatic castration-resistant prostate cancer patients. Methods: The institutional databases of 3 German tertiary referral centers identified 106 patients who underwent at least 4 cycles of 177Lu-PSMA and had at least 12 mo of eGFR follow-up data. eGFR (by the Chronic Kidney Disease Epidemiology Collaboration formula) at 3, 6, and 12 mo after 177Lu-PSMA radioligand therapy was estimated using monoexponentially fitted curves through available eGFR data. eGFR changes were grouped (≥15%-<30%, moderate; ≥30%-<40%, severe; and ≥40%, very severe). Associations between eGFR changes (%) and nephrotoxic risk factors, prior treatment lines, and number of 177Lu-PSMA cycles were analyzed using multivariable linear regression. Results: At least moderate eGFR decreases were present in 45% (48/106) of patients; of those, nearly half (23/48) had a severe or very severe eGFR decrease. A higher number of risk factors at baseline (-4.51, P = 0.03) was associated with a greater eGFR decrease. Limitations of the study were the retrospective design, lack of a control group, and limited number of patients with a follow-up longer than 1 y. Conclusion: A considerable proportion of patients may experience moderate or severe decreases in eGFR 1 y from initiation of 177Lu-PSMA. A higher number of risk factors at baseline seems to aggravate loss of renal function. Further prospective trials are warranted to estimate the nephrotoxic potential of 177Lu-PSMA.

Renal and Multiorgan Safety of 177Lu-PSMA-617 in Patients with Metastatic Castration-Resistant Prostate Cancer in the VISION Dosimetry Substudy

In the VISION trial, [177Lu]Lu-PSMA-617 (177Lu-PSMA-617) plus protocol-permitted standard of care significantly improved overall survival and radiographic progression-free survival compared with standard of care alone in patients with prostate-specific membrane antigen-positive metastatic castration-resistant prostate cancer. This VISION dosimetry substudy quantified absorbed doses of 177Lu-PSMA-617 in the kidneys and other organs. Methods: Participants were a separate cohort of 30 nonrandomized patients receiving standard of care plus 177Lu-PSMA-617 at 7.4 GBq per cycle for up to 6 cycles. Blood samples, whole-body conjugate planar image scintigraphy, and abdominal SPECT/CT images were collected. SPECT/CT images were collected at 2, 24, 48, and 168 h after administration in cycle 1 and at a single time point 48 h after administration in cycles 2-6. Outcomes were absorbed dose per unit activity per cycle and cumulative absorbed dose over all cycles. Cumulative absorbed doses were predicted by extrapolation from cycle 1, and calculation of observed values was based on measurements of cycle 1 and cycles 2-6. Safety was also assessed. Results: Mean (±SD) absorbed doses per cycle in the kidneys were 0.43 ± 0.16 Gy/GBq in cycle 1 and 0.44 ± 0.21 Gy/GBq in cycles 2-6. The observed and predicted 6-cycle cumulative absorbed doses in the kidneys were 15 ± 6 and 19 ± 7 Gy, respectively. Observed and predicted cumulative absorbed doses were similar in other at-risk organs. Safety findings were consistent with those in the VISION study; no patients experienced renal treatment-emergent adverse events of a grade higher than 3. Conclusion: The renal cumulative absorbed 177Lu-PSMA-617 dose was below the established limit. 177Lu-PSMA-617 had a good overall safety profile, and low renal radiotoxicity was not a safety concern. Cumulative absorbed doses in at-risk organs over multiple cycles can be predicted by extrapolation from cycle 1 data in patients with metastatic castration-resistant prostate cancer receiving 177Lu-PSMA-617.

Essentials of Theranostics: A Guide for Physicians and Medical Physicists

Radiopharmaceutical therapies (RPTs) are gaining increased interest with the recent emergence of novel safe and effective theranostic agents, improving outcomes for thousands of patients. The term theranostics refers to the use of diagnostic and therapeutic agents that share the same molecular target; a major step toward precision medicine, especially for oncologic applications. The authors dissect the fundamentals of theranostics in nuclear medicine. First, they explain the radioactive decay schemes and the characteristics of emitted electromagnetic radiation used for imaging, as well as particles used for therapeutic purposes, followed by the interaction of the different types of radiation with tissue. These concepts directly apply to clinical RPTs and play a major role in the efficacy and toxicity profile of different radiopharmaceutical agents. Personalized dosimetry is a powerful tool that can help estimate patient-specific absorbed doses, in tumors as well as normal organs. Dosimetry in RPT is an area of active investigation, as most of what we know about the relationship between delivered dose and tissue damage is extrapolated from external-beam radiation therapy; more research is needed to understand this relationship as it pertains to RPTs. Tumor heterogeneity is increasingly recognized as an important prognostic factor. Novel molecular imaging agents, often in combination with fluorine 18-fluorodeoxyglucose, are crucial for assessment of target expression in the tumor and potential hypermetabolic disease that may lack the molecular target expression. ©RSNA, 2023 Test Your Knowledge questions are available in the supplemental material.

A multi-centre stereotactic radiosurgery planning study of multiple brain metastases using isocentric linear accelerators with 5 and 2.5 mm width multi-leaf collimators, CyberKnife and Gamma Knife

Objectives

This study compared plans of high definition (HD), 2.5 mm width multi-leaf collimator (MLC), to standard, 5 mm width, isocentric linear accelerator (linacs), CyberKnife (CK), and Gamma Knife (GK) for stereotactic radiosurgery (SRS) techniques on multiple brain metastases.

Methods

Eleven patients undergoing SRS for multiple brain metastases were chosen. Targets and organs at risk (OARs) were delineated and optimized SRS plans were generated and compared.

Results

The linacs delivered similar conformity index (CI) values, but the gradient index (GI) for HD MLCs was significantly lower (P-value <.001). Half the OARs received significantly lower dose using HD MLCs. CK delivered a significantly lower CI than HD MLC linac (P-value <.001), but a significantly higher GI (P-value <.001). CI was significantly improved with the HD MLC linac compared to GK (P-value = 4.591 × 10-3), however, GK delivered a significantly lower GI (P-value <.001). OAR dose sparing was similar for the HD MLC TL, CK, and GK.

Conclusions

Comparing linacs for SRS, the preferred choice is HD MLCs. Similar results were achieved with the HD MLC linac, CK, or GK, with each delivering significant improvements in different aspects of plan quality.

Advances in knowledge

This article is the first to compare HD and standard width MLC linac plans using a combination of single isocentre volumetric modulated arc therapy and multi-isocentric dynamic conformal arc plans as required, which is a more clinically relevant assessment. Furthermore, it compares these plans with CK and GK, assessing the relative merits of each technique.

Analysis of safety and efficacy of proton radiotherapy for optic nerve sheath meningioma

Background

Primary optic nerve sheath meningiomas (ONSMs) represent a group of benign tumors originating from the optic nerve sheath, typically causing painless, gradual onset monocular visual loss, which can result in blindness if left untreated. Radiation therapy represents an important treatment option for patients with ONSM, allowing for preservation and potential improvement in visual function. In particular, proton radiotherapy may enable a reduction of the side effects due to its physical advantage of an inverted dose profile with a steep dose gradient. The study investigates the visual acuity, local tumor control, and treatment-related toxicities following proton beam radiotherapy with a single institutional cohort comprising 32 patients treated for ONSM.

Methods

Patients with primary ONSM, either histologically (16/32) or radiologically confirmed (16/32), which were treated at the Department of Radiation Oncology at the University Hospital Heidelberg (Germany) were assessed in regard to their visual outcomes, treatment toxicity, and local tumor control following radiotherapy according to response assessment in neuro-oncology criteria.

Results

After a median follow-up time of 39.5 months, the 5-year local progression-free survival was estimated at 100%, with 84.4% of patients reporting improvement or stability in visual acuity during their last follow-up. Radiation-induced optic neuropathy (RION) was encountered in 9.4%.

Conclusions

Our study demonstrates proton beam therapy as a safe and effective treatment alternative in the therapeutic management of ONSMs. RION represents a rare but dreaded complication after treatment. Future head-to-head comparisons with photon radiotherapy in a prospective setting are required to demonstrate a potential, additional clinical benefit.

The contest between internal and external-beam dosimetry: The Zeno's paradox of Achilles and the tortoise

Radionuclide therapy, also called molecular radiotherapy (MRT), has come of age, with several novel radiopharmaceuticals being approved for clinical use or under development in the last decade. External beam radiotherapy (EBRT) is a well-established treatment modality, with about half of all oncologic patients expected to receive at least one external radiation treatment over their disease course. The efficacy and the toxicity of both types of treatment rely on the interaction of radiation with biological tissues. Dosimetry played a fundamental role in the scientific and technological evolution of EBRT, and absorbed doses to the target and to the organs at risk are calculated on a routine basis. In contrast, in MRT the usefulness of internal dosimetry has long been questioned, and a structured path to include absorbed dose calculation is missing. However, following a similar route of development as EBRT, MRT treatments could probably be optimized in a significant proportion of patients, likely based on dosimetry and radiobiology. In the present paper we describe the differences and the similarities between internal and external-beam dosimetry in the context of radiation treatments, and we retrace the main stages of their development over the last decades.

Radiotherapy-associated Sensorineural Hearing Loss in Pediatric Oncology Patients

During the radiotherapeutic treatment of pediatric oncology patients, they would be at a latent risk of developing ionizing radiation-induced ototoxicity when the cochlea or auditory nerve is located within the radiation field. Sensorineural hearing loss (SNHL) is an irreversible late complication of radiotherapy, and its incidence depends on various factors such as the patient's hearing sensitivity, total radiation dose to the cochlea, radiotherapy fractionation regimen, age and chemoradiation. Importantly, this complication exhibits serious challenges to adult survivors of childhood cancer, as it has been linked to impairments in academic achievement, psychosocial development, independent living skills, and employment in the survivor population. Therefore, early detection and proper management can alleviate academic, speech, language, social, and psychological morbidity arising from hearing deficits. In the present review, we have addressed issues such as underlying mechanisms of radiation-induced SNHL, audiometric findings of pediatric cancer patients treated with radiotherapy, and management and protection measures against radiation-induced ototoxicity.

The impact of fluorine-18-fluoroethyltyrosine positron emission tomography scan timing on radiotherapy planning in newly diagnosed patients with glioblastoma

Background and purpose

Glioblastoma is one of the most common and aggressive primary brain tumours in adults. Though radiation therapy (RT) techniques have progressed significantly in recent decades, patient survival has seen little improvement. However, an area of promise is the use of fluorine-18-fluoroethyltyrosine positron-emission-tomography (18F-FET PET) imaging to assist in RT target delineation. This retrospective study aims to assess the impact of 18F-FET PET scan timing on the resultant RT target volumes and subsequent RT plans in post-operative glioblastoma patients.

Materials and Methods

The imaging and RT treatment data of eight patients diagnosed with glioblastoma and treated at a single institution were analysed. Before starting RT, each patient had two 18F-FET-PET scans acquired within seven days of each other. The information from these 18F-FET-PET scans aided in the creation of two novel target volume sets. The new volumes and plans were compared with each other and the originals.

Results

The median clinical target volume (CTV) 1 was statistically smaller than CTV 2. The median Dice score for the CTV1/CTV2 was 0.98 and, of the voxels that differ (median 6.5 cc), 99.7% were covered with a 5 mm expansion. Overall organs at risk (OAR) and target dosimetry were similar in the PTV1 and PTV2 plans.

Conclusion

Provided the 18F-FET PET scan is acquired within two weeks of the RT planning and a comprehensive approach is taken to CTV delineation, the timing of scan acquisition has minimal impact on the resulting RT plan.

Quantitative imaging for 177Lu-PSMA treatment response monitoring and dosimetry

PSMA-targeted radiopharmaceutical therapy is an established treatment option for metastatic castration-resistant prostate cancer (mCRPC). However, response rates and duration using 177Lu-PSMA-617 vary considerably between patients. Quantitative 177Lu SPECT imaging is one approach that may be leveraged to more closely monitor inter-cycle response, as well as patient-specific absorbed doses. In this work, we describe our experience implementing quantitative imaging throughout the course of 177Lu-PSMA treatment, including serial SPECT imaging to monitor response and for individualized dosimetry. We also describe our imaging protocols and dose calculation workflows for 3D voxelized patient-specific organ and tumor dosimetry, including a review of the current landscape and efforts towards harmonized dosimetry.

Analysis of dose distribution reproducibility based on a fluence map of in vivo transit dose using an electronic portal imaging device

Morphological changes can affect distribution of dose in patients. Determination of the dose distribution changes for each fraction radiotherapy can be done by relativein vivodosimetry (IVD). This study analysed the distribution of doses per fraction based on the fluence map recorded by the electronic portal imaging device (EPID) of the patient's transit dose. This research examined cases involving the cervix, breast, and nasopharynx. Transit dose analysis was performed by calculating the gamma index (GI) with composite and field-by-field methods. The gamma passing rate (GPR) value was assessed for its correlation with the subject's body weight. In the case of the nasopharynx, breast, and cervix, the GPR value decreased as the fraction increased. In the case of the nasopharynx, the correlation between the GPR and fraction radiotherapy showed no difference when using either composite or field-by-field methods. However, in cases involving the cervix and breast, there was a difference in the correlation values between the composite and field-by-field methods, where the subject had a significant correlation (p< 0.05) when it was done using a field-by-field method. In addition, the nasopharynx had the highest number of subjects with significant correlation (p< 0.05) between GPR and body weight, followed by the cervix and breast. In the nasopharynx, breast, and cervix, the reproducibility of the dose distribution decreased. This decreased reproducibility was associated with changes in body weight.

Obtaining organ-specific radiobiological parameters from clinical data for radiation therapy planning of head and neck cancers

Objective.Different radiation therapy (RT) strategies, e.g. conventional fractionation RT (CFRT), hypofractionation RT (HFRT), stereotactic body RT (SBRT), adaptive RT, and re-irradiation are often used to treat head and neck (HN) cancers. Combining and/or comparing these strategies requires calculating biological effective dose (BED). The purpose of this study is to develop a practical process to estimate organ-specific radiobiologic model parameters that may be used for BED calculations in individualized RT planning for HN cancers.Approach.Clinical dose constraint data for CFRT, HFRT and SBRT for 5 organs at risk (OARs) namely spinal cord, brainstem, brachial plexus, optic pathway, and esophagus obtained from literature were analyzed. These clinical data correspond to a particular endpoint. The linear-quadratic (LQ) and linear-quadratic-linear (LQ-L) models were used to fit these clinical data and extract relevant model parameters (alpha/beta ratio, gamma/alpha,dTand BED) from the iso-effective curve. The dose constraints in terms of equivalent physical dose in 2 Gy-fraction (EQD2) were calculated using the obtained parameters.Main results.The LQ-L and LQ models fitted clinical data well from the CFRT to SBRT with the LQ-L representing a better fit for most of the OARs. The alpha/beta values for LQ-L (LQ) were found to be 2.72 (2.11) Gy, 0.55 (0.30) Gy, 2.82 (2.90) Gy, 6.57 (3.86) Gy, 5.38 (4.71) Gy, and the dose constraint EQD2 were 55.91 (54.90) Gy, 57.35 (56.79) Gy, 57.54 (56.35) Gy, 60.13 (59.72) Gy and 65.66 (64.50) Gy for spinal cord, optic pathway, brainstem, brachial plexus, and esophagus, respectively. Additional two LQ-L parametersdTwere 5.24 Gy, 5.09 Gy, 7.00 Gy, 5.23 Gy, and 6.16 Gy, and gamma/alpha were 7.91, 34.02, 8.67, 5.62 and 4.95.Significance.A practical process was developed to extract organ-specific radiobiological model parameters from clinical data. The obtained parameters can be used for biologically based radiation planning such as calculating dose constraints of different fractionation regimens.

Stereotactic intensity-modulated radiotherapy for skull base meningioma using the HybridArc with Novalis STx system

Background

Skull base meningiomas are often difficult to remove completely with preserved nerve function and may require radiation therapy. However, the Gamma Knife is unsuitable for large tumor volume or the optic nerve, which is difficult to identify on imaging. We report the results of stereotactic radiotherapy with HybridArc using Novalis STx for skull base meningiomas.

Methods

We retrospectively examined 28 patients with skull base meningioma who underwent stereotactic radiotherapy (54 Gy/30 fractions) with HybridArc.

Results

The 28 patients, nine males and 19 females, were aged 31-83 years (mean 58.4 years), and the tumor volume was 2.6-97.1 mL (mean 29.7 mL). HybridArc irradiation was performed with D95 54 Gy/30 fractions for all patients with a median follow-up period of 36.0 months (range: 12-78 months). Tumor control rates at 1, 2, and 5 years after radiotherapy were 92.6%, 89.1%, and 82.8%, respectively. Only one non-atypical meningioma remained uncontrolled; thus, the tumor control rate for non-atypical meningioma at 1, 2, and 5 years was 94.1%. Tumor control rates for atypical meningioma at 1, 2, and 5 years were 85.7%, 71.4%, and 53.6%, respectively, significantly worse than for non-atypical meningiomas (P = 0.0395). Radiation injury was observed in two cases (7.1%). Visual field defects were observed in 16 patients, and diplopia in 6. Visual field and diplopia improvements were achieved in 5 and 2 patients, respectively (with overlap).

Conclusion

Stereotactic radiotherapy (54 Gy/30 fractions) with HybridArc using Novalis STx is a safe and effective approach for relatively large skull base meningiomas.

Impact of Modern Low Dose Involved Site Radiation Therapy on Normal Tissue Toxicity in Cervicothoracic Non-Hodgkin Lymphomas: A Biophysical Study

This biophysical study aimed to determine fitting parameters for the Lyman-Kutcher-Burman (LKB) dose-response model for normal tissue complication probability (NTCP) calculations of acute side effects and to investigate the impact of reduced radiation doses on the probability of their occurrence in supradiaphragmatic non-Hodgkin lymphoma (NHL) irradiation. A cohort of 114 patients with NHL in the cervicothoracic region, treated between 2015 and 2021 at the University Hospitals of Münster, Hamburg, and Essen, with involved site radiation therapy (ISRT), were included. Among them, 68 patients with aggressive NHL (a-NHL) received consolidative radiation therapy with 24-54 Gy following (R-)CHOP chemotherapy. Additionally, 46 patients with indolent NHL (i-NHL) underwent radiotherapy with 22.5-45.0 Gy. Two treatment plans were prospectively created for each patient (a-NHL: 30.0/40.0 Gy; i-NHL: 24.0/30.0 Gy). NTCP were then calculated using the optimized LKB model. The adapted dose-response models properly predicted the patient's probability of developing acute side effects when receiving doses ≤ 50 Gy. In addition, it was shown that reduced radiation doses can influence the NTCP of acute side effects depending on the aggressiveness of NHL significantly. This study provided a foundation to prospectively assess the probability of adverse side effects among today's reduced radiation doses in the treatment of NHL.

NTCP modelling of xerostomia after radiotherapy for oropharyngeal cancer using the PRO-CTCAE and CTCAE scoring systems at different time-points post-RT

PURPOSE

This study aims at determining the parameter values of three normal tissue complication probability (NTCP) models for the contralateral parotid gland, contralateral submandibular gland (SMG) and contralateral salivary glands regarding the endpoint of xerostomia 6-24 months after radiotherapy for oropharynx cancer.

METHODS

The treatment and outcome data of 231 patients with favorable risk, HPV-associated oropharyngeal squamous cell carcinoma are analyzed. 60 Gy intensity modulated radiotherapy was delivered to all the patients. The presence and severity of xerostomia was recorded (pre- and post- radiotherapy) by the PRO-CTCAE and the CTCAE scoring systems. In both scoring systems, patients with a change in symptom severity (from baseline) of ≥ 2 were considered responders.

RESULTS

Xerostomia was observed in 61.3 %, 39.2 %, 28.6 % and 27.0 % of the patients based on the PRO-CTCAE scoring system at 6-, 12-, 18- and 24-months post-RT, respectively. The AUCs of the contralateral salivary glands ranged between 0.58-0.64 in the LKB model with the gEUD ranging between 20.3 Gy and 24.7 Gy.

CONCLUSIONS

Based on the PRO-CTCAE scores, mean dose < 22 Gy, V50 < 10 % for the contralateral salivary glands and mean dose < 18 Gy, V45 < 10 % for the contralateral parotid were found to significantly reduce by a factor of 2-3 the risk for radiation induced xerostomia that is observed at 6-24 months post-RT, respectively. Also, gEUD < 22 Gy to the contralateral salivary glands and < 18 Gy to the contralateral parotid was found to significantly reduce the risk for radiation induced xerostomia that is observed at 6-24 months post-RT by 2.0-2.3 times.

A systematic review of the normal tissue complication probability models and parameters: Head and neck cancers treated with conformal radiotherapy

This systematic review study aims to provide comprehensive data on different radiobiological models, parameters, and endpoints used for calculating the normal tissue complication probability (NTCP) based on clinical data from head and neck cancer patients treated with conformal radiotherapy. A systematic literature search was carried out according to the PRISMA guideline for the identification of relevant publications in six electronic databases of Embase, PubMed, Scopus, and Google Scholar to July 2022 using specific keywords in the paper's title and abstract. The initial search resulted in 1368 articles for all organs for the review article about the NTCP parameters. One hundred and seventy-eight articles were accepted for all organs with complete parameters for the mentioned models and finally, 20 head and neck cancer articles were accepted for review. Analysis of the studies shows that the Lyman-Kutcher-Burman (LKB) model properly links the NTCP curve parameters to the postradiotherapy endpoints. In the LKB model for esophagus, the minimum, and maximum corresponding parameters were reported as TD50  = 2.61 Gy with grade ≥3 radiation-induced esophagitis endpoints as the minimum TD50 and TD50  = 68 Gy as the maximum ones. nmin  = 0.06, nmax  = 1.04, mmin  = 0.1, and mmax  = 0.65, respectively. Unfortunately, there was not a wide range of published articles on other organs at risk like ear or cauda equina except Burman et al. (Fitting of normal tissue tolerance data to an analytic function. Int J Radiat Oncol Biol Phys Ther. 1991;21:123-135). Findings suggest that the validation of different radiobiological models and their corresponding parameters need to be investigated in vivo and in vitro for developing a more accurate NTCP model to be used for radiotherapy treatment planning optimization.

Quality assessment of automatically planned O-Ring linac SBRT plans for pelvic lymph node metastases, finding the optimal minimum target size by comparison with robotic SBRT

PURPOSE

The purpose of this study is to assess the quality of automatic planned O-Ring Halcyon linac SBRT plans for pelvic lymph node metastases and to establish an absolute PTV volume threshold as a plan quality prediction criterion. Compliance of the plans to institutional SBRT plan evaluation criteria and differences in plan quality and treatment delivery times between Halcyon Linac and CyberKnife robotic SBRT were evaluated.

METHODS

Twenty-one CyberKnife treatment plans were replanned for Halcyon. Prescription doses range was 26-40 Gy in mean three fractions. The mean/median planning target volume was 4.0/3.6 cm3 . Institutional criteria for the plan evaluation were: New Conformity Index (NCI), Conformity Index (CI), Modified Gradient Index (MGI), selectivity index reciprocal (PIV/TVPIV ), and the target coverage by prescription isodose (%PIV). Statistical analysis based on the receiver operating characteristic (ROC) curve was used to determine a plan quality predictor threshold of the PTV volume. Comparative analysis of normal tissue complication probabilities (NTCP) was used to assess the risk of toxicity in healthy tissues.

RESULTS

Seventy-one percent (n = 15)/95% (n = 20) of Halcyon and 81% (n = 17)/100% (n = 21) of CK plans fulfilled all ideal/tolerance criteria. For PTVs above a found optimal threshold of 2.6 cm3 (71%, n = 15), no statistically significant difference was observed between the CI, NCI, PIV/TVPIV , and MGI indexes of both groups, while the coverage (%PIV) was statistically but not clinically significantly different between cohorts. Significantly shorter delivery times are expected with Halcyon. No significant differences in NTCP were observed.

CONCLUSION

All but one automatically optimized Halcyon treatment plans demonstrated ideal or acceptable performance. PTV threshold of 2.6 cm3 can be used as decision criteria in clinical settings. The results of our study demonstrated the promising performance of the Halcyon for pelvic SBRT, although plan-specific QA is required to verify machine performance during plan delivery.

Systemic Therapy for Melanoma Brain and Leptomeningeal Metastases

OPINION STATEMENT

Melanoma has a high propensity to metastasize to the brain which portends a poorer prognosis. With advanced radiation techniques and targeted therapies, outcomes however are improving. Melanoma brain metastases are best managed in a multi-disciplinary approach, including medical oncologists, neuro-oncologists, radiation oncologists, and neurosurgeons. The sequence of therapies is dependent on the number and size of brain metastases, status of systemic disease control, prior therapies, performance status, and neurological symptoms. The goal of treatment is to minimize neurologic morbidity and prolong both progression free and overall survival while maximizing quality of life. Surgery should be considered for solitary metastases, or large and/or symptomatic metastases with edema. Stereotactic radiosurgery offers a benefit over whole-brain radiation attributed to the relative radioresistance of melanoma and reduction in neurotoxicity. Thus far, data supports a more durable response with systemic therapy using combination immunotherapy of ipilimumab and nivolumab, though targeting the presence of BRAF mutations can also be utilized. BRAF inhibitor therapy is often used after immunotherapy failure, unless a more rapid initial response is needed and then can be done prior to initiating immunotherapy. Further trials are needed, particularly for leptomeningeal metastases which currently require the multi-disciplinary approach to determine best treatment plan.

Focused ultrasound combined with radiotherapy for malignant brain tumor: a preclinical and clinical study

INTRODUCTION

Blood-brain barrier (BBB) remains to be the major obstacle to conquer in treating patients with malignant brain tumors. Radiation therapy (RT), despite being the mainstay adjuvant modality regardless of BBB, the effect of radiation induced cell death is hindered by the hypoxic microenvironment. Focused ultrasound (FUS) combined with systemic microbubbles has been shown not only to open BBB but also potentially increased regional perfusion. However, no clinical study has investigated the combination of RT with FUS-BBB opening (RT-FUS).

METHODS

We aimed to provide preclinical evidence of RT-FUS combination in GBM animal model, and to report an interim analysis of an ongoing single arm, prospective, pilot study (NCT01628406) of combining RT-FUS for recurrent malignant high grade glioma patients, of whom re-RT was considered for disease control. In both preclinical and clinical studies, FUS-BBB opening was conducted within 2 h before RT. Treatment responses were evaluated by objective response rate (ORR) using magnetic resonance imaging, progression free survival, and overall survival, and adverse events (AE) in clinical study. Survival analysis was performed in preclinical study and descriptive analysis was performed in clinical study.

RESULTS

In mouse GBM model, the survival analysis showed RT-FUS (2 Gy) group was significantly longer than RT (2 Gy) group and control, but not RT (5 Gy) group. In the pilot clinical trial, an interim analysis of six recurrent malignant high grade glioma patients underwent a total of 24 RT-FUS treatments was presented. Three patients had rapid disease progression at a mean of 33 days after RT-FUS, while another three patients had at least stable disease (mean 323 days) after RT-FUS with or without salvage chemotherapy or target therapy. One patient had partial response after RT-FUS, making the ORR of 16.7%. There was no FUS-related AEs, but one (16.7%) re-RT-related grade three radiation necrosis.

CONCLUSION

Reirradiation is becoming an option after disease recurrence for both primary and secondary malignant brain tumors since systemic therapy significantly prolongs survival in cancer patients. The mechanism behind the synergistic effect of RT-FUS in preclinical model needs further study. The clinical evidence from the interim analysis of an ongoing clinical trial (NCT01628406) showed a combination of RT-FUS was safe (no FUS-related adverse effect). A comprehensive analysis of radiation dosimetry and FUS energy distribution is expected after completing the final recruitment.

Dosimetric and radiobiological analyses of a de-escalation strategy for elective nodal regions in human papillomavirus-associated oropharyngeal cancer

Introduction

In this simulation study, we examined the effects of a de-escalation strategy with a reduced dose to subclinical nodal regions in patients with human papillomavirus (HPV)-associated oropharyngeal carcinoma (OPC).

Methods

We created two patterns of intensity-modulated radiotherapy for 16 patients with HPV-associated OPC. In the standard and de-escalation plans, the initial field including elective nodal regions received 46 and 30 Gy, followed by 20 and 36 Gy to the cutdown field, respectively. Comparison metrics were set for each organ at risk (OAR). We compared these metric values and the probability of adverse effects based on the normal tissue complication probability (NTCP) model between the two plans.

Results

Both plans generally met the dose constraints for the targets and all OAR. Among the comparison metrics, the mean doses to the brain, pharyngeal constrictor muscle, thyroid, and skin and the dose to a 1 % volume of the skin were higher in the standard plan than in the de-escalation plan (P = 0.031, 0.007, < 0.001, < 0.001, and 0.006, respectively). NTCP analyses revealed that the probability of adverse effects in the ipsilateral parotid gland and thyroid was higher in the standard plan than in the de-escalation plan (standard vs. de-escalation plans: ipsilateral parotid gland, 6.4 % vs. 5.0 %, P = 0.016; thyroid, 3.3 % vs. 0.5 %, P < 0.001).

Conclusions

A de-escalation strategy with elective nodal regions is a promising treatment to prevent a decline in the quality of life in patients with HPV-associated OPC, particularly xerostomia, dysphagia, and hypothyroidism.

Radiation and Immune Checkpoint Inhibitors: Combination Therapy for Treatment of Hepatocellular Carcinoma

The liver tumor immune microenvironment has been thought to possess a critical role in the development and progression of hepatocellular carcinoma (HCC). Despite the approval of immune checkpoint inhibitors (ICIs), such as programmed cell death receptor 1 (PD-1)/programmed cell death ligand 1 (PD-L1) and cytotoxic T lymphocyte associated protein 4 (CTLA-4) inhibitors, for several types of cancers, including HCC, liver metastases have shown evidence of resistance or poor response to immunotherapies. Radiation therapy (RT) has displayed evidence of immunosuppressive effects through the upregulation of immune checkpoint molecules post-treatment. However, it was revealed that the limitations of ICIs can be overcome through the use of RT, as it can reshape the liver immune microenvironment. Moreover, ICIs are able to overcome the RT-induced inhibitory signals, effectively restoring anti-tumor activity. Owing to the synergetic effect believed to arise from the combination of ICIs with RT, several clinical trials are currently ongoing to assess the efficacy and safety of this treatment for patients with HCC.

Incidence risk assessment of secondary cancer due to radiotherapy of women with rectal cancer using BEIR VII, EPA, and ICRP models

Background

Radiotherapy has a significant side effect known as radiation-induced secondary cancer. This study aims to evaluate the dose and secondary cancer risk for women with rectal cancer treated with three-dimensional conformal radiation therapy (3D-CRT) to the organs at risk (OARs) and some sensitive organs using different types of radiation-induced cancer risk prediction models, including Biological Effects of Ionizing Radiation (BEIRVII), Environmental Protection Agency (EPA) and International Commission on Radiological Protection (ICRP), and compare the results of the different models for same organs.

Materials and methods

Thirty female patients with rectal cancer were considered and dose calculations were based on the PCRT-3D treatment planning system, while the radiotherapy of the patients had been performed using Shinva linear accelerator with a total dose of 45 Gy at 25 fractions. Planning target volume (PTV), OARs, and some sensitive organs were contoured, three models were used to evaluate secondary cancer risk (SCR) using the excess relative risk (ERR) and excess absolute risk (EAR).

Results

The bladder presents the highest risk, in terms of ERR, and the femur head and uterus in terms of EAR from the three models (BEIR VII, EPA, and ICRP).

Conclusion

Based on the obtained results, radiotherapy of rectal cancer is relatively higher for the bladder and femur head, compared to the risk for other organs, the kidney risk is significantly lower. It was observed that the SCR from the ICRP model was higher compared to BEIR VII and EPA models.

Biomedical advances and future prospects of high-precision three-dimensional radiotherapy and four-dimensional radiotherapy

Biomedical advances of external-beam radiotherapy (EBRT) with improvements in physical accuracy are reviewed. High-precision (±1 mm) three-dimensional radiotherapy (3DRT) can utilize respective therapeutic open doors in the tumor control probability curve and in the normal tissue complication probability curve instead of the one single therapeutic window in two-dimensional EBRT. High-precision 3DRT achieved higher tumor control and probable survival rates for patients with small peripheral lung and liver cancers. Four-dimensional radiotherapy (4DRT), which can reduce uncertainties in 3DRT due to organ motion by real-time (every 0.1-1 s) tumor-tracking and immediate (0.1-1 s) irradiation, have achieved reduced adverse effects for prostate and pancreatic tumors near the digestive tract and with similar or better tumor control. Particle beam therapy improved tumor control and probable survival for patients with large liver tumors. The clinical outcomes of locally advanced or multiple tumors located near serial-type organs can theoretically be improved further by integrating the 4DRT concept with particle beams.

Dosimetric comparison in sparing normal tissue dosage by using auto-SBRT planning in oligo liver tumors

Purpose

The study aimed to compare the dosimetric distribution of VMAT plans by increasing the number of half arcs in liver SBRT and investigate the effect by using automatic plan software in plan optimization.

Method

Thirty-one patients with oligo liver tumors were randomly selected. VMAT treatment plans with different numbers of coplanar half arcs were generated.

Result

Adding arcs significantly increased the PTV, D2%, D50%, and CI, but sacrificed the plan homogeneity. It also decreased the maximum dose of normal tissues such as the stomach, duodenum, and spinal cord and reduced Dmean, D500cc, and D700cc for the liver. Nevertheless, the diminishing effect gradually decayed into three arcs. Meanwhile, the addition of arcs substantially extended the beam-on time.

Conclusion

In the context of SBRT for oligo liver tumors, increasing the number of coplanar half arcs will improve PTV conformity and offer better protection for OARs, albeit at the expense of increased treatment duration. Considering the trade-off between plan quality and treatment efficiency, a three-arc plan may be more suitable for clinical implementation.

Proton versus photon therapy for high-risk prostate cancer with dose escalation of dominant intraprostatic lesions: a preliminary planning study

Background and purpose

This study aimed to investigate the feasibility of safe-dose escalation to dominant intraprostatic lesions (DILs) and assess the clinical impact using dose-volume (DV) and biological metrics in photon and proton therapy. Biological parameters defined as late grade ≥ 2 gastrointestinal (GI) and genitourinary (GU) derived from planned (D P) and accumulated dose (D A) were utilized.

Materials and methods

In total, 10 patients with high-risk prostate cancer with multiparametric MRI-defined DILs were investigated. Each patient had two plans with a focal boost to the DILs using intensity-modulated proton therapy (IMPT) and volumetric-modulated arc therapy (VMAT). Plans were optimized to obtain DIL coverage while respecting the mandatory organ-at-risk constraints. For the planning evaluation, DV metrics, tumor control probability (TCP) for the DILs and whole prostate excluding the DILs (prostate-DILs), and normal tissue complication probability (NTCP) for the rectum and bladder were calculated. Wilcoxon signed-rank test was used for analyzing TCP and NTCP data.

Results

IMPT achieved a higher Dmean for the DILs compared to VMAT (IMPT: 68.1 GyRBE vs. VMAT: 66.6 Gy, p < 0.05). Intermediate-high rectal and bladder doses were lower for IMPT (p < 0.05), while the high-dose region (V60 Gy) remained comparable. IMPT-TCP for prostate-DIL were higher compared to VMAT (IMPT: 86%; α/β = 3, 94.3%; α/β = 1.5 vs. VMAT: 84.7%; α/β = 3, 93.9%; α/β = 1.5, p < 0.05). Likewise, IMPT obtained a moderately higher DIL TCP (IMPT: 97%; α/β = 3, 99.3%; α/β = 1.5 vs. VMAT: 95.9%; α/β = 3, 98.9%; α/β = 1.5, p < 0.05). Rectal D A-NTCP displayed the highest GI toxicity risk at 5.6%, and IMPT has a lower GI toxicity risk compared to VMAT-predicted Quantec-NTCP (p < 0.05). Bladder D P-NTCP projected a higher GU toxicity than D A-NTCP, with VMAT having the highest risk (p < 0.05).

Conclusion

Dose escalation using IMPT is able to achieve a high TCP for the DILs, with the lowest rectal and bladder DV doses at the intermediate-high-dose range. The reduction in physical dose was translated into a lower NTCP (p < 0.05) for the bladder, although rectal toxicity remained equivalent.

Neoadjuvant radiochemotherapy with cisplatin/5-flourouracil or carboplatin/paclitaxel in patients with resectable cancer of the esophagus and the gastroesophageal junction - comparison of postoperative mortality and complications, toxicity, and pathological tumor response

PURPOSE

In 2012, the CROSS trial implemented a new neoadjuvant radiochemotherapy protocol for patients with locally advanced, resectable cancer of the esophagus prior to scheduled surgery. There are only limited studies comparing the CROSS protocol with a PF-based (cisplatin/5-fluorouracil) nRCT protocol.

METHODS

In this retrospective, monocentric analysis, 134 patients suffering from esophageal cancer were included. Those patients received either PF-based nRCT (PF group) or nRCT according to the CROSS protocol (CROSS group) prior to elective en bloc esophagectomy. Perioperative mortality and morbidity, nRCT-related toxicity, and complete pathological regression were compared between both groups. Logistic regression analysis was performed in order to identify independent factors for pathological complete response (pCR).

RESULTS

Thirty-day/hospital mortality showed no significant differences between both groups. Postoperative complications ≥ grade 3 according to Clavien-Dindo classification were experienced in 58.8% (PF group) and 47.6% (CROSS group) (p = 0.2) respectively. nRCT-associated toxicity ≥ grade 3 was 30.8% (PF group) and 37.2% (CROSS group) (p = 0.6). There was no significant difference regarding the pCR rate between both groups (23.5% vs. 30.5%; p = 0.6). In multivariate analysis, SCC (OR 7.7; p < 0.01) and an initial grading of G1/G2 (OR 2.8; p = 0.03) were shown to be independent risk factors for higher rates of pCR.

CONCLUSION

We conclude that both nRCT protocols are effective and safe. There were no significant differences regarding toxicity, pathological tumor response, and postoperative morbidity and mortality between both groups. Squamous cell carcinoma (SCC) and favorable preoperative tumor grading (G1 and G2) are independent predictors for higher pCR rate in multivariate analysis.

A Phase 1, Open-label, Dose-Ascending Study to Evaluate the Safety and Tolerability of the Therapeutic Radiopharmaceutical 131I-MIP-1095 for the Treatment of Metastatic Castration-Resistant Prostate Cancer

PURPOSE

131I-MIP-1095 is a targeted radiotherapeutic that contains 131I, a β-particle emitter, and MIP-1095, a urea-based ligand for prostate-specific membrane antigen. We report the first phase 1, dose-escalation study of 131I-MIP-1095 in patients with metastatic castration-resistant prostate cancer (mCRPC).

METHODS

This study enrolled men with mCRPC refractory to second-generation antiandrogen(s) and taxane chemotherapy. Dosimetry/biodistribution assessments were performed. Safety and tolerability were determined in subjects who qualified for therapeutic administration of 131I-MIP-1095 with maximum tolerated activity examined in a dose-ascending manner (3 + 3 design methodology). Disease outcomes including prostate-specific antigen (PSA) change, tumor response, survival, and circulating tumor cell concentration were assessed.

RESULTS

A total of 9 subjects with mCRPC were included in this study. On the basis of dosimetry results, 5 of 9 patients were treated: 3 in cohort 1 (50 mCi) and 2 in cohort 2 (75 mCi). Accrual stopped at the cohort 2 activity level in response to the US Food and Drug Administration mandate for 131I-MIP-1095 manufacturing concerns. Parotid/salivary glands (3.5 Gy/Bq), liver (2.2 Gy/Bq), kidneys (1.3 Gy/Bq), and spleen (0.7 Gy/Bq) demonstrated the greatest extent of 131I-MIP-1095 exposure. There were no deaths, serious adverse events, or drug discontinuations due to treatment-emergent adverse events. Grade 1-2 thrombocytopenia, anemia, leukopenia, and dry mouth most commonly occurred. One subject (33.3%) exhibited maximum decline for the PSA response of 50% or greater.

CONCLUSION

131I-MIP-1095 demonstrated favorable dosimetry, biodistribution, and safety, as well as a modest PSA response supporting further investigation for treatment of men with mCRPC.Clinical Trial Registration: ClinicalTrials.gov identifier: NCT03030885, Registered January 25, 2017 (https://clinicaltrials.gov/ct2/show/NCT03030885).

Comparison of Acute Gastrointestinal Toxicity of Intensity-Modulated Radiotherapy Versus Three-Dimensional Conformal Radiotherapy in Patients of Carcinoma Cervix

Introduction Cervical cancer is the most common gynaecological malignancy worldwide, with a higher prevalence in middle- and low-income countries. Chemoradiotherapy, followed by intracavitary brachytherapy, is the treatment of choice in locally advanced cervical cancer. The most common acute side effect of external beam radiotherapy (EBRT) is bowel toxicity in the form of diarrhoea and abdominal cramps. The treatment techniques of EBRT were revolutionised with the advent of intensity modulation. This study aims to prospectively analyse whether the dosimetric advantage of intensity-modulated radiotherapy (IMRT) over three-dimensional conformal radiotherapy (3DCRT) is translated clinically into a decrease in acute toxicity. Method Twenty-four patients were randomised into two groups: the 3DCRT and the IMRT. Acute gastrointestinal (GI) toxicity was assessed during treatment using radiation therapy oncology group grading. The factors under consideration were age, stage of the disease, treatment technique, chemotherapy, and the intention of therapy (radical or adjuvant). The mean bowel bag dose of the two techniques was analysed. Result Among the factors under consideration, it was found that the treatment technique was the only factor that had a significant association with acute bowel toxicity in both univariate (p = 0.036) and multivariate analyses (p = 0.028). The mean V25 (the volume receiving 25 Gy), V45, and V50 of the bowel bag in the IMRT arm were significantly less than the 3DCRT arm. Grades 2 and 3 acute bowel toxicities were also higher in the 3DCRT arm. Conclusion The treatment technique is essential to determining acute GI toxicity during pelvic radiotherapy. With IMRT, the dose to the bowel bag and, in turn, the acute bowel toxicity can be reduced.

Long-term nephrotoxicity in irradiated pediatric kidney tumor survivors: A systematic review

OBJECTIVE

Nephrotoxicity can occur as a side effect after treatment for kidney tumor in childhood. The use of radiotherapy (RT) has a potential additional effect.

METHODS

A systematic electronic literature search that combined childhood kidney cancer with different treatments and nephrotoxicity terms was performed in EMBASE. Studies were included based on the reporting of nephrotoxicity occurrence after treatment for kidney tumor during pediatric age, with 75% of participants being under the age of 25 years at the time of diagnosis, and having been treated with any type of kidney surgery, chemotherapy, and/or RT.

RESULTS

A pooled analysis did not show significant difference in estimated glomerular filtration rate between the group of patients who received RT compared with the group treated without RT (SMD -0.11 [95% CI -1.07-0.84] p = .733).

CONCLUSION

The current literature suggests that the use of RT does not have a significant impact on the decline of kidney function as independent factor.

Hypoglossal nerve delineation in nasopharyngeal carcinoma patients may reduce the radiation dose and damage to the nerve

This study aims to establish a delineation guideline for the contouring of the hypoglossal nerve by dividing the nerve into different segments, and to test the possibility of a radiation dose reduction to the hypoglossal nerve in NPC patients receiving radiotherapy. Twenty NPC patients were selected arbitrarily. The hypoglossal nerves were delineated using anatomic landmarks and divided into the cisternal, intracanalicular, carotid, and transverse segments. The tumor coverage by radiation and dose-volume parameters of the nerve with and without various dose constraints to the hypoglossal nerve were compared. The hypoglossal nerve, which is invisible on CT images, can be delineated accurately with the assistance of several anatomic landmarks. Without a dose constraint to the hypoglossal nerve, the carotid space, intracanalicular, and transverse segments had high radiation dose-volumes. The dose-volume to the nerve, however, can be reduced when the nerve was defined and a dose constraint was given. The delineation of the hypoglossal nerve with its different segments is feasible. The carotid space, intracanalicular, and transverse segments received the highest dose, where the nerve damage was most likely located. The dose to the nerve can be reduced to less than 70 Gy using the intensity-modulated radiotherapy technique.

A Comprehensive Primer on Radiation Oncology for Non-Radiation Oncologists

Background: Multidisciplinary management is crucial in cancer diagnosis and treatment. Multidisciplinary teams include specialists in surgery, medical therapies, and radiation therapy (RT), each playing unique roles in oncology care. One significant aspect is RT, guided by radiation oncologists (ROs). This paper serves as a detailed primer for non-oncologists, medical students, or non-clinical investigators, educating them on contemporary RT practices. Methods: This report follows the process of RT planning and execution. Starting from the decision-making in multidisciplinary teams to the completion of RT and subsequent patient follow-up, it aims to offer non-oncologists an understanding of the RO's work in a comprehensive manner. Results: The first step in RT is a planning session that includes obtaining a CT scan of the area to be treated, known as the CT simulation. The patients are imaged in the exact position in which they will receive treatment. The second step, which is the primary source of uncertainty, involves the delineation of treatment targets and organs at risk (OAR). The objective is to ensure precise irradiation of the target volume while sparing the OARs as much as possible. Various radiation modalities, such as external beam therapy with electrons, photons, or particles (including protons and carbon ions), as well as brachytherapy, are utilized. Within these modalities, several techniques, such as three-dimensional conformal RT, intensity-modulated RT, volumetric modulated arc therapy, scattering beam proton therapy, and intensity-modulated proton therapy, are employed to achieve optimal treatment outcomes. The RT plan development is an iterative process involving medical physicists, dosimetrists, and ROs. The complexity and time required vary, ranging from an hour to a week. Once approved, RT begins, with image-guided RT being standard practice for patient alignment. The RO manages acute toxicities during treatment and prepares a summary upon completion. There is a considerable variance in practices, with some ROs offering lifelong follow-up and managing potential late effects of treatment. Conclusions: Comprehension of RT clinical effects by non-oncologists providers significantly elevates long-term patient care quality. Hence, educating non-oncologists enhances care for RT patients, underlining this report's importance.

Model development of dose and volume predictors for esophagitis induced during chemoradiotherapy for lung cancer as a step towards radiobiological treatment planning

BACKGROUND

Currently, radiation therapy treatment planning system intends biological optimization that relies heavily upon plan metrics from tumor control probability (TCP) and normal tissue complication probability (NTCP) modeling. Implementation and expansion of TCP and NTCP models with alternative data is an important step towards reliable radiobiological treatment planning. In this retrospective single institution study, the treatment charts of 139 lung cancer patients treated with chemo-radiotherapy were reviewed and correlated dosimetric predictors with the incidence of esophagitis and established NTCP model of esophagitis grade 1 and 2 for lung cancer patients.

METHODS

Esophagus is an organ at risk (OAR) in lung cancer radiotherapy (RT). Esophagitis is a common toxicity induced by RT. In this study, dose volume parameters Vx (Vx: percentage esophageal volume receiving ≥ x Gy) and mean esophagus dose (MED) as quantitative dose-volume metrics, the esophagitis grade 1 and 2 as endpoints, were reviewed and derived from the treatment planning system and the electronic medical record system. Statistical analysis of binary logistic regression and probit were performed to have correlated the probability of grade 1 and 2 esophagitis to MED and Vx. IBM SPSS software version 24 at 5% significant level (α = 0.05) was used in the statistical analysis.

RESULTS

The probabilities of incidence of grade 1 and 2 esophagitis proportionally increased with increasing the values of Vx and MED. V20, V30, V40, V50 and MED are statistically significant good dosimetric predictors of esophagitis grade 1. 50% incidence probability (TD50) of MED for grade 1 and 2 esophagitis were determined. Lyman Kutcher Burman model parameters, such as, n, m and TD50, were fitted and compared with other published findings. Furthermore, the sigmoid shaped dose responding curve between probability of esophagitis grade 1 and MED were generated respecting to races, gender, age and smoking status.

CONCLUSIONS

V20, V30, V40 and V50 were added onto Quantitative Analysis of Normal Tissue Effects in the clinic, or QUANTEC group's dose constrains of V35, V50, V70 and MED. Our findings may be useful as both validation of 3-Dimensional planning era models and also additional clinical guidelines in treatment planning and plan evaluation using radiobiology optimization.

Novel hybrid treatment planning approach for irradiation a pediatric craniospinal axis

This study presents a new treatment planning approach merging 3D-CRT and VMAT fields into a hybrid treatment plan (HybTP), in order to achieve an optimum dose coverage of the planning target volume (PTV) and protection of OAR. Craniospinal axis irradiation (CSI) treated with 3D conformal radiotherapy (3D-CRT) is associated with high doses to the heart and eye lenses but provides better sparing of lungs and kidneys compared to volumetric modulated arc therapy (VMAT). VMAT treatment spares eye lenses and the heart, but lungs and kidneys are not as effective as 3D-CRT. Thus, a combination of both techniques (HybTP) may be optimal in sparing all these organs at risk (OAR). The results of HybTP are compared with helical tomotherapy (HT), intensity modulated radio therapy (IMRT), VMAT, and 3D-CRT plans. Hybrid, HT, VMAT, IMRT, and 3D-CRT treatment plans for a male child (age 6 years) with medulloblastoma were created and compared. A total dose of 35.2 Gy (PTV) with a dose per fraction of 1.6 Gy was prescribed. The following dose acceptance criteria were defined: The plans were compared regarding dose homogeneity index (HI) and conformity index (CI), PTV coverage, (particularly at cribriform plate) and doses at OARs. Best conformity was achieved with HT (CI = 0.98) followed by VMAT (CI = 0.96), IMRT (CI = 0.91), HybTP (CI = 0.86), and 3D-CRT (CI = 0.83). The homogeneity index varied marginally. For both HT and IMRT the HI was 0.07, and for 3D-CRT, VMAT and HybTP the HI was between 0.13 and 0.15. The cribriform plate was sufficiently covered by HybTP, VMAT, and 3D-CRT. The dose acceptance criteria for OARs were met by HT and HybTP. VMAT did not meet the criteria for lung (Dmean = right 10.4 Gy/left 10.2 Gy), 3D-CRT did not meet the criteria for eye lenses (Dmax = right 32.3 Gy/left 33.1), and heart (V25≈44%) and IMRT did not meet the criteria for lung (Dmean = right 11.1 Gy/left 11.2 Gy) and eye lenses (Dmax = right 12.2 Gy/left 13.1). HybTP meets all defined acceptance criteria and has proved to be a reasonable alternative for CSI. With HybTP that combines VMAT at the brain and heart with 3D-CRT posterior spinal fields (to spare lungs and kidneys), both appropriate coverage of the PTV and sparing of OAR can be achieved.