Guidelines for radiotherapy of prostate cancer (2020 edition)

Significant interruptions in radiotherapy during curative treatment for prostate cancer are correlated with poorer oncological outcomes

PURPOSE

To investigate the effects of radical radiotherapy (RT) relevant interruptions (RRI), single (sRRI) or multiple (mRRI), on Biochemical Failure-Free Survival (BFFS), Metastases-Free Survival (MFS) and Overall Survival (OS) in prostate cancer (PCa) patients.

METHODS

We conducted a retrospective analysis involving 383 patients diagnosed with prostate cancer (PCa) who received radical RT between March 2013 and April 2021, with doses ranging from 60 to 80 Gy (median dose 76.0 Gy), either alone or in combination with androgen deprivation therapy. The study aimed to evaluate the effects of sRRI and mRRI radiation-related interruptions on BFFS, MFS, and OS using the Kaplan-Meier method. Additionally, we adjusted for relevant prognostic factors using three multivariate Cox regression proportional hazard models.

RESULTS

In the univariate analysis, it was observed that patients who experienced unexpected RRIs (50.1%: 35.5% sRRI and 14.6% mRRI), resulting in a median overall treatment time prolongation of five days, exhibited a higher incidence of biochemical failure (BF) and metastases (Met). However, no difference was observed in OS. In the multivariate analysis, it was found that RRIs were significantly associated with increased hazards of BF (sRRI, aHR: 4.61, 95% CI: 2.80-7.60; mRRIs, aHR: 9.92, 95% CI: 5.61-17.54), Met (sRRI, aHR: 4.20, 95% CI: 1.97-8.94; mRRI, aHR: 7.01, 95% CI: 2.94-6.71), and all-cause mortality (mRRI, aHR: 1.89, 95% CI: 1.18-3.03).

CONCLUSIONS

sRRIs were associated with both lower BFFS and MFS, while mRRIs with both BFFS, MFS and OS.

Evaluating the dosimetric impact of deep-learning-based auto-segmentation in prostate cancer radiotherapy: Insights into real-world clinical implementation and inter-observer variability

PURPOSE

This study aimed to investigate the dosimetric impact of deep-learning-based auto-contouring for clinical target volume (CTV) and organs at risk (OARs) delineation in prostate cancer radiotherapy planning. Additionally, we compared the geometric accuracy of auto-contouring system to the variability observed between human experts.

METHODS

We evaluated 28 planning CT volumes, each with three contour sets: reference original contours (OC), auto-segmented contours (AC), and expert-defined manual contours (EC). We generated 3D-CRT and intensity-modulated radiation therapy (IMRT) plans for each contour set and compared their dosimetric characteristics using dose-volume histograms (DVHs), homogeneity index (HI), conformity index (CI), and gamma pass rate (3%/3 mm).

RESULTS

The geometric differences between automated contours and both their original manual reference contours and a second set of manually generated contours are smaller than the differences between two manually contoured sets for bladder, right femoral head (RFH), and left femoral head (LFH) structures. Furthermore, dose distribution accuracy using planning target volumes (PTVs) derived from automatically contoured CTVs and auto-contoured OARs demonstrated consistency with plans based on reference contours across all evaluated cases for both 3D-CRT and IMRT plans. For example, in IMRT plans, the average D95 for PTVs was 77.71 ± 0.53 Gy for EC plans, 77.58 ± 0.69 Gy for OC plans, and 77.62 ± 0.38 Gy for AC plans. Automated contouring significantly reduced contouring time, averaging 0.53 ± 0.08 min compared to 24.9 ± 4.5 min for manual delineation.

CONCLUSION

Our automated contouring system can reduce inter-expert variability and achieve dosimetric accuracy comparable to gold standard reference contours, highlighting its potential for streamlining clinical workflows. The quantitative analysis revealed no consistent trend of increasing or decreasing PTVs derived from automatically contoured CTVs and OAR doses due to automated contours, indicating minimal impact on treatment outcomes. These findings support the clinical feasibility of utilizing our deep-learning-based auto-contouring model for prostate cancer radiotherapy planning.

Hypofractionation Utilisation in Radiation Therapy: A Regional Department Evaluation

INTRODUCTION

There has been an uptake in hypofractionation radiotherapy schedules (> 2.45 Gy per fraction) worldwide over the last decade. The aim of this paper was to evaluate the change in fractionation schedules for patients undergoing radiotherapy in regional Queensland. The influence of treatment site, intent and patient social circumstances was assessed, identifying any current gaps in practice.

METHODS

This retrospective clinical audit, included patients who underwent radiotherapy in 2012, 2019 and 2022 at a large regional department. This allowed a 10-year analysis and an evaluation of any impact of COVID-19. Demographic data and treatment information was collected and analysed using descriptive statistics.

RESULTS

There was a notable trend favouring hypofractionation for patients treated for breast and prostate cancer. In 2012, 62.7% of breast cancer patients were treated with conventional fractionation and 37.3% were treated with hypofractionation, versus 2.4% and 92.1%, respectively, in 2022. Prostate cancer fractionation changed from 99.4% of patients treated with conventional fractionation and 0.6% with hypofractionation in 2012 to 23.2% and 74.1%, respectively, in 2022. The standard of care also shifted for palliative intent, with lung, brain and bone metastases in 2022 being treated with increased hypofractionated and ultra-hypofractionated radiotherapy (> 5 Gy per fraction). This coincides with more complex and modulated treatments being readily available, such as stereotactic radiotherapy and volumetric modulated arc therapy. Hypofractionated treatments, however, were not influenced by the social factors of patients, having no distinct relationship with Indigenous status, age and patients' distance to treatment.

CONCLUSION

This study has validated the increase in hypofractionated treatments over a range of cancer sites and treatment intents, with increased treatment complexity. This has a direct impact on both departmental resources and patient-centred care, offering value-based radiotherapy.

Prior-image-based low-dose CT reconstruction for adaptive radiation therapy

Objective. The study aims to reduce the imaging radiation dose in Adaptive Radiotherapy (ART) while maintaining high-quality CT images, critical for effective treatment planning and monitoring.Approach. We developed the Prior-aware Learned Primal-Dual Network (pLPD-UNet), which uses prior CT images to enhance reconstructions from low-dose scans. The network was separately trained on thorax and abdomen datasets to accommodate the unique imaging requirements of each anatomical region.Main results. The pLPD-UNet demonstrated improved reconstruction accuracy and robustness in handling sparse data compared to traditional methods. It effectively maintained image quality essential for precise organ delineation and dose calculation, while achieving a significant reduction in radiation exposure.Significance. This method offers a significant advancement in the practice of ART by integrating prior imaging data, potentially setting a new standard for balancing radiation safety with the need for high-resolution imaging in cancer treatment planning.

Comparison of online adaptive and non-adaptive magnetic resonance image-guided radiation therapy in prostate cancer using dose accumulation

Background and purpose

Conventional image-guided radiotherapy (conv-IGRT) is standard in prostate cancer (PC) but does not account for inter-fraction anatomical changes. Online-adaptive magnetic resonance-guided RT (OA-MRgRT) may improve organ-at-risk (OARs) sparing and clinical target volume (CTV) coverage. The aim of this study was to analyze accumulated OAR and target doses in PC after OA-MRgRT and conv-IGRT in comparison to pre-treatment reference planning (refPlan).

Material and methods

Ten patients with PC, previously treated with OA-MRgRT at the 1.5 T MR-Linac (20x3Gy), were included. Accumulated OA-MRgRT doses were determined by deformably registering all fraction's MR-images. Conv-IGRT was simulated through rigid registration of the planning computed tomography with each fraction's MR-image for dose mapping/accumulation. Dose-volume parameters (DVPs), including CTV D50% and D98%, rectum, bladder, urethra, Dmax and V56Gy for OA-MRgRT, conv-IGRT and refPlan were compared using the Wilcoxon signed-rank test. Clinical relevance of accumulated dose differences was analyzed using a normal-tissue complication-probability model.

Results

CTV-DVPs were comparable, whereas OA-MRgRT yielded decreased median OAR-DVPs compared to conv-IGRT, except for bladder V56Gy. OA-MRgRT demonstrated significantly lower median rectum Dmax over conv-IGRT (59.1/59.9 Gy, p = 0.006) and refPlan (60.1 Gy, p = 0.012). Similarly, OA-MRgRT yielded reduced median bladder Dmax compared to conv-IGRT (60.0/60.4 Gy, p = 0.006), and refPlan (61.2 Gy, p = 0.002). Overall, accumulated dose differences were small and did not translate into clinically relevant effects.

Conclusion

Deformably accumulated OA-MRgRT using 20x3Gy in PC showed significant but small dosimetric differences comparted to conv-IGRT. Feasibility of a dose accumulation methodology was demonstrated, which may be relevant for evaluating future hypo-fractionated OA-MRgRT approaches.

Multidisciplinary real-world management of metastatic castration-sensitive prostate cancer: A French national study (PROFILE study)

While androgen deprivation therapy (ADT) has been the standard of care for patients with metastatic castration-sensitive prostate cancer (mCSPC), recent strategies like intensification of systemic treatment (Rozet et al., 2020) (i.e. adding another treatment to ADT) and radiotherapy have improved overall survival. PROFILE, a national retrospective multicentric real-world study, involved patients with mCSPC recruited by medical oncologists, urologists, and radiation oncologists, and who started treatment between November 2020 and May 2021. Patients by sites were included consecutively. Data were collected from medical records. Primary objectives were to: (1) describe retrospectively the characteristics of whole population of patients with mCSPC as well as subgroups defined by prognostic factors in France at diagnosis; (2) identify current practices for managing mCSPC in a real-life clinical setting. Among the 416 patients with mCSPC included in the PROFILE study, 315 (76%) were synchronous (metastasis at the initial diagnosis) and 101 (24%) were metachronous patients (metastasis diagnosed post-progression). A majority (83% of synchronous and 73% of metachronous patients) received an intensified systemic treatment (ADT plus ARSI [androgen-receptor signaling inhibitors]±chemotherapy±primary tumour radiotherapy±metastasis-directed therapy [MDT]), while only 40% of low-volume patients received prostate radiotherapy. This study depicts the standardization of new therapeutic strategies for patients with mCSPC in France with most of them receiving an intensified treatment, mainly with ADT+ARSI (64% of synchronous intensified patients and 76% of metachronous intensified patients). Most of patients were assessed using conventional imaging (CT scan and/or bone scan). Overall, PROFILE results are in line with French and European guidelines for diagnosis, management, and follow-up of such patients (Rozet et al., 2020; Cornford et al., 2021).

Radiotherapy Metastatic Prostate Cancer Cell Lines Treated with Gold Nanorods Modulate miRNA Signatures

MicroRNA (miRNA) modulation has been identified as a promising strategy for improving the response of human prostate cancer (PCa) to radiotherapy (RT). Studies have shown that mimics or inhibitors of miRNAs could modulate the sensitivity of PCa cells to RT. In addition, pegylated gold nanoparticles have been studied as a therapeutic approach to treat PCa cells and/or vehicles for carrying miRNAs to the inside of cells. Therefore, we evaluated the capacity of hypofractionated RT and pegylated gold nanorods (AuNPr-PEG) to modulate the miRNA signature on PCa cells. Thus, RT-qPCR was used to analyze miRNA-95, miRNA-106-5p, miRNA-145-5p, and miRNA-541-3p on three human metastatic prostate cell lines (PC3, DU145, and LNCaP) and one human prostate epithelial cell line (HprEpiC, a non-tumor cell line) with and without treatment. Our results showed that miRNA expression levels depend on cell type and the treatment combination applied using RT and AuNPr-PEG. In addition, cells pre-treated with AuNPr-PEG and submitted to 2.5 Gy per day for 3 days decreased the expression levels of miRNA-95, miRNA-106, miRNA-145, and miRNA-541-3p. In conclusion, PCa patients submitted to hypofractionated RT could receive personalized treatment based on their metastatic cellular miRNA signature, and AuNPr-PEG could be used to increase metastatic cell radiosensitivity.

Optimal planning target margin for prostate radiotherapy based on interfractional and intrafractional variability assessment during 1.5T MRI-guided radiotherapy

Introduction

We analyzed daily pre-treatment- (PRE) and real-time motion monitoring- (MM) MRI scans of patients receiving definitive prostate radiotherapy (RT) with 1.5 T MRI guidance to assess interfractional and intrafractional variability of the prostate and suggest optimal planning target volume (PTV) margin.

Materials and methods

Rigid registration between PRE-MRI and planning CT images based on the pelvic bone and prostate anatomy were performed. Interfractional setup margin (SM) and interobserver variability (IO) were assessed by comparing the centroid values of prostate contours delineated on PRE-MRIs. MM-MRIs were used for internal margin (IM) assessment, and PTV margin was calculated using the van Herk formula.

Results

We delineated 400 prostate contours on PRE-MRI images. SM was 0.57 ± 0.42, 2.45 ± 1.98, and 2.28 ± 2.08 mm in the left-right (LR), anterior-posterior (AP), and superior-inferior (SI) directions, respectively, after bone localization and 0.76 ± 0.57, 1.89 ± 1.60, and 2.02 ± 1.79 mm in the LR, AP, and SI directions, respectively, after prostate localization. IO was 1.06 ± 0.58, 2.32 ± 1.08, and 3.30 ± 1.85 mm in the LR, AP, and SI directions, respectively, after bone localization and 1.11 ± 0.55, 2.13 ± 1.07, and 3.53 ± 1.65 mm in the LR, AP, and SI directions, respectively, after prostate localization. Average IM was 2.12 ± 0.86, 2.24 ± 1.07, and 2.84 ± 0.88 mm in the LR, AP, and SI directions, respectively. Calculated PTV margin was 2.21, 5.16, and 5.40 mm in the LR, AP, and SI directions, respectively.

Conclusions

Movements in the SI direction were the largest source of variability in definitive prostate RT, and interobserver variability was a non-negligible source of margin. The optimal PTV margin should also consider the internal margin.

Advances in high-risk localized prostate cancer: Staging and management

Nearly 15% of individuals with localized prostate cancer are identified as high risk for recurrence and progression of the disease, which is why the correct staging is vital for the definition of correct treatment-also developing novel therapeutic strategies to find a balance between getting better outcomes without sacrificing the quality of life (QoL). In this narrative review, we introduced the current standards of staging and primary treatment of high-risk localized prostate cancer (PCa), based on international guidelines and arguments in the debate, under the light of the most recent literature. It brings essential tools such as PSMA PET/CT and different nomograms (Briganti. MSKCC, Gandaglia) for accurate staging and selecting wisely the definitive therapy. Even though there is a broad discussion over the best local treatment in curative-intent treatment, it looks more important to define which patient profile would adapt correctly to every different treatment, highlighting the benefits and superior outcomes with multimodal treatment.

Pelvic radiation-induced urinary strictures: etiology and management of a challenging disease

Radiation is a common treatment modality for pelvic malignancies. While it can be effective at cancer control, downstream effects can manifest months to years after treatment, leaving patients with significant morbidity. Within urology, a particularly difficult post-radiation consequence is urinary tract stricture, either of the urethra, bladder neck, or ureter. In this review, we will discuss the mechanism of radiation damage and treatment options for these potentially devastating urinary sequelae.

Oberley-Deegan R. CT vs. bioluminescence: A comparison of imaging techniques for orthotopic prostate tumors in mice

Prostate cancer is one of the most diagnosed cancers in men in the United States. In mouse models, orthotopic tumors are favored for their biological relevance and simulation of growth in a microenvironment akin to that found in humans. However, to monitor the disease course, animal models require consistent and noninvasive surveillance. In vivo bioluminescent imaging has become a mainstay imaging modality due to its flexibility and ease of use. However, with some orthotopic prostate tumor models, bioluminescence fails to describe disease progression due to optical scattering and signal attenuation. CT scanning, in addition to its utility in human cancer diagnosis and surveillance, can be applied to mouse models with improved results. However, CT imaging has poor definition when imaging soft tissues and is not routinely used in prostate cancer models. Using an orthotopic prostate cancer model, our results demonstrate that, when compared to bioluminescent imaging, CT imaging correlates more closely to orthotopic prostate tumor growth in mice. Based on the data from this study, we conclude that CT imaging can be used as an alternative to the more commonly used bioluminescent imaging for measuring orthotopic prostate cancer growth over time.

Biological Response of Human Cancer Cells to Ionizing Radiation in Combination with Gold Nanoparticles

Simple Summary

Various types of metallic nanoparticles and especially gold nanoparticles (AuNPs) have been utilized in radiation studies to enhance the radiosensitization of cancer cells while minimizing detrimental effects in normal tissue. The aim of our study was to investigate the biological responses of various human cancer cells to gold-nanoparticle-induced radiosensitization. This was accomplished by using different AuNPs and several techniques in order to provide valuable insights regarding the multiple adverse biological effects, following ionizing radiation (IR) in combination with AuNPs. Insightful methodologies such as transmission electron microscopy were employed to identify comprehensively the complexity of the biological damage occurrence. Our findings confirm that AuNP radiosensitization may occur due to extensive and/or complex DNA damage, cell death, or cellular senescence. This multiparameter study aims to further elucidate the biological mechanisms and at the same time provide new information regarding the use of AuNPs as radiosensitizers in cancer treatment.

Abstract

In the context of improving radiation therapy, high-atomic number (Z) metallic nanoparticles and, more importantly, gold-based nanostructures are developed as radiation enhancers/radiosensitizers. Due to the diversity of cell lines, nanoparticles, as well as radiation types or doses, the resulting biological effects may differ and remain obscure. In this multiparameter study, we aim to shed light on these effects and investigate them further by employing X-irradiation and three human cancer cell lines (PC3, A549, and U2OS cells) treated by multiple techniques. TEM experiments on PC3 cells showed that citrate-capped AuNPs were found to be located mostly in membranous structures/vesicles or autophagosomes, but also, in the case of PEG-capped AuNPs, inside the nucleus as well. The colony-forming capability of cancer cells radiosensitized by AuNPs decreased significantly and the DNA damage detected by cytogenetics, γH2AX immunostaining, and by single (γH2AX) or double (γH2AX and OGG1) immunolocalization via transmission electron microscopy (TEM) was in many cases higher and/or persistent after combination with AuNPs than upon individual exposure to ionizing radiation (IR). Moreover, different cell cycle distribution was evident in PC3 but not A549 cells after treatment with AuNPs and/or irradiation. Finally, cellular senescence was investigated by using a newly established staining procedure for lipofuscin, based on a Sudan Black-B analogue (GL13) which showed that based on the AuNPs’ concentration, an increased number of senescent cells might be observed after exposure to IR. Even though different cell lines or different types and concentrations of AuNPs may alter the levels of radiosensitization, our results imply that the complexity of damage might also be an important factor of AuNP-induced radiosensitization.