Robot-assisted biopsy sampling for online Raman spectroscopy cancer confirmation in the operating room

PURPOSE

Cancer confirmation in the operating room (OR) is crucial to improve local control in cancer therapies. Histopathological analysis remains the gold standard, but there is a lack of real-time in situ cancer confirmation to support margin confirmation or remnant tissue. Raman spectroscopy (RS), as a label-free optical technique, has proven its power in cancer detection and, when integrated into a robotic assistance system, can positively impact the efficiency of procedures and the quality of life of patients, avoiding potential recurrence.

METHODS

A workflow is proposed where a 6-DOF robotic system (optical camera + MECA500 robotic arm) assists the characterization of fresh tissue samples using RS. Three calibration methods are compared for the robot, and the temporal efficiency is compared with standard hand-held analysis. For healthy/cancerous tissue discrimination, a 1D-convolutional neural network is proposed and tested on three ex vivo datasets (brain, breast, and prostate) containing processed RS and histopathology ground truth.

RESULTS

The robot achieves a minimum error of 0.20 mm (0.12) on a set of 30 test landmarks and demonstrates significant time reduction in 4 of the 5 proposed tasks. The proposed classification model can identify brain, breast, and prostate cancer with an accuracy of 0.83 (0.02), 0.93 (0.01), and 0.71 (0.01), respectively.

CONCLUSION

Automated RS analysis with deep learning demonstrates promising classification performance compared to commonly used support vector machines. Robotic assistance in tissue characterization can contribute to highly accurate, rapid, and robust biopsy analysis in the OR. These two elements are an important step toward real-time cancer confirmation using RS and OR integration.

Repeat CyberKnife Radiosurgery for Trigeminal Neuralgia: Outcomes and Complications

BACKGROUND

CyberKnife radiosurgery (RS), as an initial first treatment, is recognized as an efficient and safe modality for trigeminal neuralgia (TN). However, knowledge on repeat CyberKnife RS in refractory cases is limited. The objective was to evaluate the clinical outcomes of repeat CyberKnife RS for TN.

METHODS

A retrospective review of 33 patients with refractory TN treated a second time with CyberKnife RS from 2009 to 2021. The median follow-up period after the second RS was 26.0 months (range 0.3-115.8). The median dose for the repeat RS was 60 Gy (range 60.0-70.0). Pain relief after the intervention was assessed using the Barrow Neurological Institute scale for pain (I-V). Scores I to IIIb were classified as an adequate pain relief and scores IV-V were classified as a treatment failure.

RESULTS

After the second RS, initial adequate pain relief was achieved in 87.9% of cases. The actuarial probabilities of maintaining an adequate pain relief at 6, 12, 24, and 36 months were 92.1%, 74.0%, 58.2%, and 58.2%, respectively. Regarding sustained pain relief, there was no significant difference between the first and the second RS. Sensory toxicity after the first RS was predictive of a better outcome following the second RS. The onset of hypesthesia rate was the same after the first or the second RS (21%).

CONCLUSION

Repeat RS is an effective and safe method for the treatment of refractory TN.

Role of 18F-choline and 18F-fluorodeoxyglucose positron emission tomography in combination with magnetic resonance imaging in brachytherapy planning for locally advanced cervical cancer: A pilot study

Background and purpose

This pilot study aims to describe the advantages of combining metabolic and anatomic imaging modalities in brachytherapy (BT) planning for locally advanced cervical cancer (LACC) and to evaluate the supplementary value of Fluoro(F)-Choline positron emission tomography/computed tomography (PET/CT) in comparison to 18F-fluorodeoxyglucose (FDG) in this setting.

Materials and methods

A prospective cohort of six patients with LACC was included in this study. Each patient underwent BT planning CT scan, magnetic resonance imaging (MRI), and both FDG and F-Choline PET/CT scans on the same day, with BT applicators in place. Patients were treated according to the standard of care. Metabolic target volumes (TV) were generated retrospectively and compared with the anatomic volumes using Dice coefficients and absolute volume comparison.

Results

The threshold at which the metabolic and anatomic volumes were the most concordant was found to be 35% maximum standardized uptake value (SUV max) for both PET/CT scans. Amongst the six patients in this cohort, three in the FDG cohort and four in the F-Choline cohort were found to have more than ten percent ratio of excess (increase) in their MRI gross tumor volumes (GTV) when incorporating the metabolic information from the PET/CT scans. However, no significant changes were needed in the high risk-clinical target volumes (CTVHR) for both PET tracers.

Conclusions

FDG and F-Choline PET/CT scans can substantially modify the BT GTV on MRI, without affecting the CTVHR. F-Choline is potentially more informative than FDG in assessing residual TV, particularly in cases with significant post-radiation inflammatory changes.

Phase 2 multicenter trial combining nivolumab and radiosurgery for NSCLC and RCC brain metastases

Background

Anti-PD-1 has activity in brain metastases (BM). This phase 2 open labeled non-randomized single arm trial examined the safety and efficacy of combining nivolumab with radiosurgery (SRS) in the treatment of patients with BM from non-small cell lung cancer (NSCLC) and renal cell carcinoma (RCC).

Methods

This was a multicenter trial (NCT02978404) in which patients diagnosed with NSCLC or RCC, having ≤ 10 cc of un-irradiated BM and no prior immunotherapy were eligible. Nivolumab (240mg or 480mg IV) was administered for up to 2 years until progression. SRS (15-21Gy) to all un-irradiated BM was delivered within 14 days after the first dose of nivolumab. The primary endpoint was intracranial progression free survival (iPFS).

Results

Twenty-six patients (22 NSCLC and 4 RCC) were enrolled between August 2017 and January 2020. A median of 3 (1-9) BM were treated with SRS. Median follow-up was 16.0 months (0.43-25.9 months). Two patients developed nivolumab and SRS related grade 3 fatigue. One-year iPFS and OS were 45.2% (95%CI 29.3-69.6%) and 61.3% (95%CI 45.1%-83.3%), respectively. Overall response (partial or complete) of SRS treated BM was attained in 14 out of the 20 patients with ≥1 evaluable follow-up MRI. Mean FACT-Br total scores were 90.2 at baseline and improved to 146.2 within 2-4 months (p = 0.0007).

Conclusions

The adverse event profile and FACT-Br assessments suggested that SRS during nivolumab was well tolerated. Upfront SRS with the initiation of anti-PD-1 prolonged the 1-year iPFS and achieved high intracranial control. This combined approach merits validation randomized studies.

PSMA-PET/CT-Guided Intensification of Radiation Therapy for Prostate Cancer (PSMAgRT): Findings of Detection Rate, Effect on Cancer Management, and Early Toxicity From a Phase 2 Randomized Controlled Trial

PURPOSE

Prostate-specific membrane antigen (PSMA) ligand positron emission tomography (PET) is increasingly integrated in prostate cancer management because of its diagnostic performance. We sought to evaluate the effect of PSMA-PET/computed tomography (CT)-guided intensification of radiation therapy (PSMAgRT) on patient outcomes. Here, we report secondary trial endpoints including the rate of new lesion detection, effect on prostate cancer management, and treatment-related toxicities.

METHODS AND MATERIALS

In this phase 2 cohort multiple randomized controlled trial across 2 institutions, men with prostate cancer planned for RT were randomly selected for PSMAgRT across 4 strata: oligometastatic, high risk (Cancer of the Prostate Risk Assessment ≥6 or cN1), salvage post-RT, and salvage postprostatectomy (RP). Primary endpoint was failure-free survival at 5 years, with analysis pending further follow-up. Secondary endpoints included new lesion detection yield of PSMA-PET/CT, acute and delayed toxicities, effect on prostate cancer management, and health-related quality-of-life outcomes. This trial is registered with ClinicalTrials.gov, identifier NCT03525288, companion to registry NCT03378856.

RESULTS

Between May 2018 and February 2021, 262 patients were enrolled and randomized. Nine patients were later excluded (5 control, 4 PSMAgRT), leaving 253 patients for analysis (23 oligometastatic, 86 high risk, 16 salvage post-RT, and 128 salvage post-RP). New lesions were detected in 45.5% of oligometastatic, 39.5% of high risk, 14.3% of salvage post-RT, and 51.6% of salvage post-RP. Overall, PSMA-PET/CT led to intensification of RT in over half of patients (52.0%), with minimal intensification of systemic therapy (4.0%). With a median follow-up of 12.9 months, this intensification was associated with 3 attributable grade 3+ events (2.5% of patients undergoing PSMAgRT) but no difference in the rate of grade 2+ events attributable to RT compared with controls (43%, both arms).

CONCLUSIONS

In this randomized trial, PSMA-PET/CT led to intensification of RT in more than half of patients. Longer follow-up is required to determine whether this intensification translates to effect on cancer control and long-term toxicity and health-related quality-of-life outcomes.

Effect of magnetic resonance imaging pre-processing on the performance of model-based prostate tumor probability mapping

Objective. Multi-parametric magnetic resonance imaging (mpMRI) has become an important tool for the detection of prostate cancer in the past two decades. Despite the high sensitivity of MRI for tissue characterization, it often suffers from a lack of specificity. Several well-established pre-processing tools are publicly available for improving image quality and removing both intra- and inter-patient variability in order to increase the diagnostic accuracy of MRI. To date, most of these pre-processing tools have largely been assessed individually. In this study we present a systematic evaluation of a multi-step mpMRI pre-processing pipeline to automate tumor localization within the prostate using a previously trained model.Approach. The study was conducted on 31 treatment-naïve prostate cancer patients with a PI-RADS-v2 compliant mpMRI examination. Multiple methods were compared for each pre-processing step: (1) bias field correction, (2) normalization, and (3) deformable multi-modal registration. Optimal parameter values were estimated for each step on the basis of relevant individual metrics. Tumor localization was then carried out via a model-based approach that takes both mpMRI and prior clinical knowledge features as input. A sequential optimization approach was adopted for determining the optimal parameters and techniques in each step of the pipeline.Main results. The application of bias field correction alone increased the accuracy of tumor localization (area under the curve (AUC) = 0.77;p-value = 0.004) over unprocessed data (AUC = 0.74). Adding normalization to the pre-processing pipeline further improved diagnostic accuracy of the model to an AUC of 0.85 (p-value = 0.000 12). Multi-modal registration of apparent diffusion coefficient images to T2-weighted images improved the alignment of tumor locations in all but one patient, resulting in a slight decrease in accuracy (AUC = 0.84;p-value = 0.30).Significance. Overall, our findings suggest that the combined effect of multiple pre-processing steps with optimal values has the ability to improve the quantitative classification of prostate cancer using mpMRI. Clinical trials: NCT03378856 and NCT03367702.

Focal HDR brachytherapy boost to stereotactic radiotherapy (fBTsRT) for prostate cancer: a phase II randomized controlled trial

BACKGROUND

For patients with a higher burden of localized prostate cancer, radiation dose escalation with brachytherapy boosts have improved cancer control outcomes at the cost of urinary toxicity. We hypothesize that a focal approach to brachytherapy boosts targeting only grossly visualized tumor volumes (GTV) combined with stereotactic radiotherapy will improve quality of life (QoL) outcomes without compromising cancer control.

METHODS

150 patients with intermediate or high-risk prostate cancer will be enrolled and randomized 1:1 in a cohort multiple randomized clinical trial phase 2 design. Patients are eligible if planned for standard-of-care (SOC) high dose rate (HDR) brachytherapy boost to radiotherapy (RT) with GTVs encompassing < 50% of the prostate gland. Those randomly selected will be offered the experimental treatment, consisting of focal HDR brachytherapy boost (fBT) of 13-15 Gy in 1 fraction followed by stereotactic radiotherapy (sRT) 36.25-40 Gy in 5 fractions to the prostate (+/- 25 Gy to the elective pelvis) delivered every other day. The primary endpoint is to determine if fBTsRT is superior to SOC by having fewer patients experience a minimally important decline (MID) in urinary function as measured by EPIC-26 at 1 and 2 years. Secondary endpoints include rates of toxicity measured by Common Terminology Criteria for Adverse Events (CTCAE), and failure-free survival outcomes.

DISCUSSION

This study will determine whether a novel approach for the treatment of localized prostate cancer, fBTsRT, improves QoL and merits further evaluation. Trial registration This trial was prospectively registered in ClinicalTrials.gov as NCT04100174 as a companion to registry NCT03378856 on September 24, 2019.

CyberKnife radiosurgery for trigeminal neuralgia: a retrospective review of 168 cases

OBJECTIVE

Gamma Knife radiosurgery is recognized as an efficient intervention for the treatment of refractory trigeminal neuralgia (TN). The CyberKnife, a more recent frameless and nonisocentric radiosurgery alternative, has not been studied as extensively for this condition. This study aims to evaluate the clinical outcomes of a first CyberKnife radiosurgery (CKRS) treatment in patients with medically refractory TN.

METHODS

A retrospective cohort study of 166 patients (168 procedures) with refractory TN treated from 2009 to 2021 at the Centre Hospitalier de l’Université de Montréal was conducted. The treatment was performed using a CyberKnife (model G4, VSI, or M6). The treatment median maximum dose was 80 (range 70.0–88.9) Gy.

RESULTS

Adequate pain relief, evaluated using Barrow Neurological Institute pain scale scores (I–IIIb), was achieved in 146 cases (86.9%). The median latency period before adequate pain relief was 35 (range 0–202) days. The median duration of pain relief for cases with a recurrence of pain was 8.3 (range 0.6–85.0) months. The actuarial rates of maintaining adequate pain relief at 12, 36, and 60 months from the treatment date were 77.0%, 62.5%, and 50.2%, respectively. There was new onset or aggravation of facial numbness in 44 cases (26.2%). This facial numbness was predictive of better maintenance of pain relief (p < 0.001). The maintenance of adequate pain relief was sustained longer in idiopathic cases compared with cases associated with multiple sclerosis (MS; p < 0.001).

CONCLUSIONS

In the authors’ experience, CKRS for refractory TN is efficient and safe. The onset or aggravation of facial hypoesthesia after treatment was predictive of a more sustained pain relief, and idiopathic cases had more sustained pain relief in comparison with MS-related cases.

Image-guided Raman spectroscopy navigation system to improve transperineal prostate cancer detection. Part 1: Raman spectroscopy fiber-optics system and in situ tissue characterization

SIGNIFICANCE

The diagnosis of prostate cancer (PCa) and focal treatment by brachytherapy are limited by the lack of precise intraoperative information to target tumors during biopsy collection and radiation seed placement. Image-guidance techniques could improve the safety and diagnostic yield of biopsy collection as well as increase the efficacy of radiotherapy.

AIM

To estimate the accuracy of PCa detection using in situ Raman spectroscopy (RS) in a pilot in-human clinical study and assess biochemical differences between in vivo and ex vivo measurements.

APPROACH

A new miniature RS fiber-optics system equipped with an electromagnetic (EM) tracker was guided by trans-rectal ultrasound-guided imaging, fused with preoperative magnetic resonance imaging to acquire 49 spectra in situ (in vivo) from 18 PCa patients. In addition, 179 spectra were acquired ex vivo in fresh prostate samples from 14 patients who underwent radical prostatectomy. Two machine-learning models were trained to discriminate cancer from normal prostate tissue from both in situ and ex vivo datasets.

RESULTS

A support vector machine (SVM) model was trained on the in situ dataset and its performance was evaluated using leave-one-patient-out cross validation from 28 normal prostate measurements and 21 in-tumor measurements. The model performed at 86% sensitivity and 72% specificity. Similarly, an SVM model was trained with the ex vivo dataset from 152 normal prostate measurements and 27 tumor measurements showing reduced cancer detection performance mostly attributable to spatial registration inaccuracies between probe measurements and histology assessment. A qualitative comparison between in situ and ex vivo measurements demonstrated a one-to-one correspondence and similar ratios between the main Raman bands (e.g., amide I-II bands, phenylalanine).

CONCLUSIONS

PCa detection can be achieved using RS and machine learning models for image-guidance applications using in situ measurements during prostate biopsy procedures.

Image-guided Raman spectroscopy navigation system to improve transperineal prostate cancer detection. Part 2: in-vivo tumor-targeting using a classification model combining spectral and MRI-radiomics features

SIGNIFICANCE

The diagnosis and treatment of prostate cancer (PCa) are limited by a lack of intraoperative information to accurately target tumors with needles for biopsy and brachytherapy. An innovative image-guidance technique using optical devices could improve the diagnostic yield of biopsy and efficacy of radiotherapy.

AIM

To evaluate the performance of multimodal PCa detection using biomolecular features from in-situ Raman spectroscopy (RS) combined with image-based (radiomics) features from multiparametric magnetic resonance images (mpMRI).

APPROACH

In a prospective pilot clinical study, 18 patients were recruited and underwent high-dose-rate brachytherapy. Multimodality image fusion (preoperative mpMRI with intraoperative transrectal ultrasound) combined with electromagnetic tracking was used to navigate an RS needle in the prostate prior to brachytherapy. This resulting dataset consisted of Raman spectra and co-located radiomics features from mpMRI. Feature selection was performed with the constraint that no more than 10 features were retained overall from a combination of inelastic scattering spectra and radiomics. These features were used to train support vector machine classifiers for PCa detection based on leave-one-patient-out cross-validation.

RESULTS

RS along with biopsy samples were acquired from 47 sites along the insertion trajectory of the fiber-optics needle: 26 were confirmed as benign or grade group = 1, and 21 as grade group &gt;1, according to histopathological reports. The combination of the fingerprint region of the RS and radiomics showed an accuracy of 83% (sensitivity = 81 % and a specificity = 85 % ), outperforming by more than 9% models trained with either spectroscopic or mpMRI data alone. An optimal number of features was identified between 6 and 8 features, which have good potential for discriminating grade group ≥1 / grade group &lt;1 (accuracy = 87 % ) or grade group &gt;1 / grade group ≤1 (accuracy = 91 % ).

CONCLUSIONS

In-situ Raman spectroscopy combined with mpMRI radiomics features can lead to highly accurate PCa detection for improved in-vivo targeting of biopsy sample collection and radiotherapy seed placement.

MRI-guided focal or integrated boost high dose rate brachytherapy for recurrent prostate cancer

Background and purpose

Locally recurrent prostate cancer after radiotherapy merits an effective salvage strategy that mitigates the risk of adverse events. We report outcomes of a cohort enrolled across two institutions investigating MRI-guided tumor-targeted salvage high dose rate brachytherapy (HDR-BT).

Materials and methods

Analysis of a prospective cohort of 88 patients treated across two institutions with MRI-guided salvage HDR-BT to visible local recurrence after radiotherapy (RT). Tumor target dose ranged from 22-26 Gy, using either an integrated boost (ibBT) or focal technique (fBT), delivered in two implants over a median of 7 days. Outcome metrics included cancer control and toxicity (CTCAE). Quality of life (QoL-EPIC) was analyzed in a subset.

Results

At a median follow-up of 35 months (6 -134), 3 and 5-year failure-free survival (FFS) outcomes were 67% and 49%, respectively. At 5 years, fBT was associated with a 17% cumulative incidence of local failure (LF) outside the GTV (vs. 7.8% ibBT, p=0.14), while LF within the GTV occurred in 13% (vs. 16% ibBT, p=0.81). Predictors of LF outside fBT volumes included pre-salvage PSA>7 ng/mL (p=0.03) and interval since RT less than 5 years (p=0.04). No attributable grade 3 events occurred, and ibBT was associated with a higher rate of grade 2 toxicity (p<0.001), and trend towards a larger reduction in QoL sexual domain score (p=0.07), compared to fBT.

Conclusion

A tumor-targeted HDR-BT salvage approach achieved favorable cancer control outcomes. While a fBT was associated with less toxicity, it may be best suited to a subgroup with lower PSA at later recurrence. Tumor targeted dose escalation may be warranted.

PSMA PET/CT guided intensification of therapy in patients at risk of advanced prostate cancer (PATRON): a pragmatic phase III randomized controlled trial

BACKGROUND

Positron emission tomography targeting the prostate specific membrane antigen (PSMA PET/CT) has demonstrated unparalleled performance as a staging examination for prostate cancer resulting in substantial changes in management. However, the impact of altered management on patient outcomes is largely unknown. This study aims to assess the impact of intensified radiotherapy or surgery guided by PSMA PET/CT in patients at risk of advanced prostate cancer.

METHODS

This pan-Canadian phase III randomized controlled trial will enroll 776 men with either untreated high risk prostate cancer (CAPRA score 6-10 or stage cN1) or biochemically recurrent prostate cancer post radical prostatectomy (PSA > 0.1 ng/mL). Patients will be randomized 1:1 to either receive conventional imaging or conventional plus PSMA PET imaging, with intensification of radiotherapy or surgery to newly identified disease sites. The primary endpoint is failure free survival at 5 years. Secondary endpoints include rates of adverse events, time to next-line therapy, as well as impact on health-related quality of life and cost effectiveness as measured by incremental cost per Quality Adjusted Life Years gained.

DISCUSSION

This study will help create level 1 evidence needed to demonstrate whether or not intensification of radiotherapy or surgery based on PSMA PET findings improves outcomes of patients at risk of advanced prostate cancer in a manner that is cost-effective.

TRIAL REGISTRATION

This trial was prospectively registered in ClinicalTrials.gov as NCT04557501 on September 21, 2020.

Performance of an integrated multimodality image guidance and dose-planning system supporting tumor-targeted HDR brachytherapy for prostate cancer

BACKGROUND AND PURPOSE

Advances in high-dose-rate brachytherapy to treat prostate cancer hinge on improved accuracy in navigation and targeting while optimizing a streamlined workflow. Multimodal image registration and electromagnetic (EM) tracking are two technologies integrated into a prototype system in the early phase of clinical evaluation. We aim to report on the system's accuracy and workflow performance in support of tumor-targeted procedures.

MATERIALS AND METHODS

In a prospective study, we evaluated the system in 43 consecutive procedures after clinical deployment. We measured workflow efficiency and EM catheter reconstruction accuracy. We also evaluated the system's MRI-TRUS registration accuracy with/without deformation, and with/without y-axis rotation for urethral alignment at initialization.

RESULTS

The cohort included 32 focal brachytherapy and 11 integrated boost whole-gland implants. Mean procedure time excluding dose delivery was 38 min (range: 21-83) for focal, and 56 min (range: 38-89) for whole-gland implants; stable over time. EM catheter reconstructions achieved a mean difference between computed and measured free-length of 0.8 mm (SD 0.8, no corrections performed), and mean axial manual corrections 1.3 mm (SD 0.7). EM also enabled the clinical use of a non or partially visible catheter in 21% of procedures. Registration accuracy improved with y-axis rotation for urethral alignment at initialization and with the elastic registration (mTRE 3.42 mm, SD 1.49).

CONCLUSION

The system supported tumor-targeting and was implemented with no demonstrable learning curve. EM reconstruction errors were small, correctable, and improved with calibration and control of external distortion sources; increasing confidence in the use of partially visible catheters. Image registration errors remained despite rotational alignment and deformation, and should be carefully considered.

Probabilistic target definition and planning in patients with prostate cancer

Intro.Current radiation therapy (RT) planning guidelines handle uncertainties in RT using geometric margins. This approach is simple to use but oversimplifies complex underlying processes and is cumbersome for non-homogeneous dose prescriptions. In this work, we characterize the performance of a novel probabilistic target definition and planning (PTP) approach, which uses voxel-level tumor likelihood information in treatment plan optimization.Methods.We expanded a treatment planning system with probabilistic therapy planning functionality that utilizes non-binary target maps (TM) as voxel-level input to dose plan optimization. Different dose plans were calculated and compared for twelve prostate cancer patients with multiparametric magnetic resonance imaging derived TMs. Dose plans were created using both classical and PTP approaches for uniform and integrated dose boost prescriptions. Dose performance between the different approaches was compared using dose benchmarks on target and organ-at-risk (OAR) volumes.Results.Over all dose metrics, PTP was shown to be comparable to classical planning. For plans of uniform dose prescription, the PTP approach created plans within 1 Gy of the classical planning approach across all dose metrics, with no significant differences (p > 0.2). For plans with the integrated dose boost, PTP plans exhibited higher dose heterogeneity, but still showed target doses comparable to the classical approach, without increasing doses to OAR.Conclusion.In this work we introduce direct incorporation of probabilistic target definition into treatment planning. This treatment planning approach can produce both uniform dose plans and plans with integrated dose boosts that are comparable to ones created using classical dose planning. PTP is a flexible way to optimize external beam radiotherapy, as it is not limited by the use of margins. PTP can produce dose plans equivalent to classical planning, while also allows for greater versatility in dose prescription and direct incorporation of patient target definition uncertainty into treatment planning.

PET/CT-Based Salvage Radiotherapy for Recurrent Prostate Cancer After Radical Prostatectomy: Impact on Treatment Management and Future Directions

Biochemical recurrence is a clinical situation experienced by 20 to 40% of prostate cancer patients treated with radical prostatectomy (RP). Prostate bed (PB) radiation therapy (RT) remains the mainstay salvage treatment, although it remains non-curative for up to 30% of patients developing further recurrence. Positron emission tomography with computed tomography (PET/CT) using prostate cancer-targeting radiotracers has emerged in the last decade as a new-generation imaging technique characterized by a better restaging accuracy compared to conventional imaging. By adapting targeting of recurrence sites and modulating treatment management, implementation in clinical practice of restaging PET/CT is challenging the established therapeutic standards born from randomized controlled trials. This article reviews the potential impact of restaging PET/CT on changes in the management of recurrent prostate cancer after RP. Based on PET/CT findings, it addresses potential adaptation of RT target volumes and doses, as well as use of androgen-deprivation therapy (ADT). However, the impact of such management changes on the oncological outcomes of PET/CT-based salvage RT strategies is as yet unknown.

A146 EVALUATION OF A COLONOSCOPY REFERRAL FORM IN QUEBEC: WHICH INDICATIONS CARRIES A HIGHER RISK OF ADVANCED NEOPLASIA?

Background

Patients referral for colonoscopy in the province of Quebec are organized through a standardized triage sheet that includes all indications categorized in 5 hierarchal scheduling priorities. In the context of a restricted access to colonoscopy, exacerbated by the COVID-19 pandemic, postponed elective endoscopies lead to potential diagnostic and therapeutic delays in patients with colorectal neoplasia. There is currently an important need to evaluate available tools to improve patients prioritization.

Aims

This study aims to determine CRC and advanced adenomas (AA) rates associated with indications of priority 3 (P3 fig.1). The secondary objective is to regroup and compare indications with higher and lower rate of CRC and AA.

Methods

This retrospective study included all adult patients who underwent a single diagnostic colonoscopy from March 2013 to March 2016 following a single FIT test in a tertiary teaching hospital. A literature review informed the adopted definition of higher-risk of CRC and AA according to P3 colonoscopy indications. These include: Positive FIT test (IN5), hematochezia in ≥ 40 years old patients (IN4), unexplained iron deficiency anemia (IN6) and symptoms suspicious of occult colorectal cancer (IN18). Lower risk P3 indications were defined as: suspicion of IBD (IN3), recent change in bowel habits (IN7), polyp viewed on imaging (IN17), inadequate bowel preparation (IN19), and diverticulitis follow-up (IN20). Higher and lower risk indications findings were analyzed.

Results

In our cohort of 2226 patients, indications for colonoscopy referral according to the standardized form were available for 1806 patients (10 P1, 69 P2, 1056 P3, 56 P4 and 615 P5). In our studied group of P3 indications, the mean age was 62.6±11.3 years, 54.1% were female and 173 (16.4%) patients had a significant finding of CRC or AA (table 1). Patients referred for higher risk indications had a significantly increased rate of CRC and AA (19.3% vs 5.1% p≤ 0.01) compared to patients referred for lower risk indications.

Conclusions

A standardized colonoscopy referral tool may be adapted to improve prioritization of patients at risk of advanced neoplasia. These findings are especially relevant in the context of limited access to colonoscopy like during a pandemic.

Funding Agencies

None

Canadian Urological Association best practice report: Prostate-specific membrane antigen positron emission tomography/computed tomography (PSMA PET/CT) and PET/magnetic resonance (MR) in prostate cancer

Prostate-specific membrane antigen (PSMA)-targeted positron emission tomography (PET) is increasingly being used worldwide as part of the clinical workup for men with prostate cancer. With high overall accuracy for the detection of prostate cancer, PSMA-targeted PET has an increasingly established role in the setting of biochemical failure after primary therapy and an evolving role in the setting of initial disease staging; its utility for guiding management in the setting of metastatic disease is less clear. Although the specificity is high, familiarization with potential pitfalls in the interpretation of PSMA-targeted PET, including knowledge of the causes for false-positive and negative examinations, is critical. The aim of this best practice report is to provide an illustrative discussion of the current and evolving clinical indications for PSMA-targeted PET, as well as a review of physiological radiopharmaceutical biodistribution and potential imaging pitfalls.

Current topics in radiotherapy for genitourinary cancers: Consensus statements of the Genitourinary Radiation Oncologists of Canada

INTRODUCTION

The biennial meeting of the Genitourinary Radiation Oncologists of Canada (GUROC) took place November 22-23, 2019. A consensus-building session was held during the meeting addressing topics of emerging interest or controversy in the management of genitourinary malignancies.

METHODS

Draft statements were debated among all meeting attendees in an open forum with anonymous live voting. Statements for which there was at least 75% agreement among attendees were adopted as GUROC consensus.

RESULTS

Four evidence-based consensus statements were developed. First, the use of prostate radiotherapy is recommended in the setting of de novo low-volume metastatic hormone-sensitive prostate cancer to improve overall survival. Second, the support of ongoing randomized trials evaluating metastasis-directed ablative local therapy in oligometastatic prostate cancer is recommended; where such trials are available, off-trial use of oligometastasis-directed ablative radiotherapy at this time is strongly discouraged. Third, routine use of prostate-rectal hydrogel spacer devices in patients with localized prostate cancer planned to receive external beam radiotherapy is not recommended; instead, selective use in patients at highest risk of rectal toxicity may be considered. Finally, multidisciplinary consultation is recommended for all patients with newly diagnosed localized muscle-invasive bladder cancer.

CONCLUSIONS

The GUROC consensus statements provide practical guidance to clinicians in areas of current controversy in the management of prostate and bladder cancer, and it is hoped that their implementation will contribute to improved outcomes in real-world practice and greater support of clinical trials.

Image guidance in radiation therapy for better cure of cancer

The key goal and main challenge of radiation therapy is the elimination of tumors without any concurring damages of the surrounding healthy tissues and organs. Radiation doses required to achieve sufficient cancer‐cell kill exceed in most clinical situations the dose that can be tolerated by the healthy tissues, especially when large parts of the affected organ are irradiated. High‐precision radiation oncology aims at optimizing tumor coverage, while sparing normal tissues. Medical imaging during the preparation phase, as well as in the treatment room for localization of the tumor and directing the beam, referred to as image‐guided radiotherapy (IGRT), is the cornerstone of precision radiation oncology. Sophisticated high‐resolution real‐time IGRT using X‐rays, computer tomography, magnetic resonance imaging, or ultrasound, enables delivery of high radiation doses to tumors without significant damage of healthy organs. IGRT is the most convincing success story of radiation oncology over the last decades, and it remains a major driving force of innovation, contributing to the development of personalized oncology, for example, through the use of real‐time imaging biomarkers for individualized dose delivery.

A1 COLONOSCOPY FINDINGS FOLLOWING A FECAL IMMUNOCHEMICAL TEST: A RETROSPECTIVE STUDY ASSESSING THE SCREENING TEST PERFORMANCE

Background

Fecal Immunochemical Testing (FIT) is the preferred test for colorectal cancer screening in the average risk population in Canada.

Aims

This study aims to assess colonoscopy findings in patients who have undergone a FIT within the previous 2 years.

Methods

This retrospective study included all adult patients that have undergone a single diagnostic colonoscopy from March 2013 to March 2016 following a single FIT test at the CIUSSS de l’Estrie, a tertiary hospital. The primary outcome was to evaluate rates of clinically significant lesion when comparing FIT positive (FIT+) to FIT negative (FIT-) colonoscopy, using Quebec’s current threshold of 175 ng/ml of hemoglobin. Secondary outcomes included all other type of lesions, delays between FIT testing and colonoscopy, procedural time, caecal intubation rates and withdrawal time.

Results

Overall, 2230 patients were included, aged 62.0±10.5 years, 55.0% were female and 26.1% had a positive FIT. Patients with a positive FIT had a significantly higher polypectomy rate (62.4% vs 41.3%, p&lt;0.01) and higher number of polyps per patient (2.9±2.5 vs 2.1±1.5, p&lt;0.01). FIT+ had significantly higher rates of adenocarcinoma (3.4% vs 0.7%, p&lt;0.01) with 11 out of 31 patients bearing a negative FIT with the current threshold. No difference was found for sessile serrated polyps (7.8% vs 6.0%, p=0.13). Patients with a FIT+ had significantly higher advanced adenomas (24.0% vs 5.6%, p&lt;0.01), proximal polyps (33.6% vs 22.4%, p&lt;0.01), distal polyps (52.8% vs 28.2%, p&lt;0.01), non-advanced adenomas (38.5% vs 23.9%, p&lt;0.01) and benign polyps (25.1% vs 17.2%, p&lt;0.01). Patients with FIT+ received their colonoscopy 7.5 months earlier than FIT- patients (3.3±2.2 vs 10.8±8.3 months, p&lt;0.01). FIT+ also yielded a significant longer procedural time (28.5±14.1 vs 25.5±12.1, p&lt;0.01) but no difference was noted for caecal intubation rates and withdrawal time (93.3% vs 94.0%, p=0.55 and 14.0±8.4 vs 12.0±7.7, p=0.20 respectively). Results were similar when lowering the threshold to 150, 100, 75 and even 50 ng/ml. 8 patients with an adenocarcinoma had a FIT level lower than 50 ng/ml.

Conclusions

Patients with a colonoscopy and a positive FIT have higher rates of significant findings. Although commonly used for colorectal cancer screening, FIT still failed to detect almost 30% of adenomas and adenocarcinomas found during colonoscopy. It also does not perform very well for serrated polyps. Our data also fails to show an improved yield of the FIT when lowering the its threshold from 175 to 50. There is still a great need for a more sensitive non-invasive colon cancer screening test.

Funding Agencies

None

Phantom Validation of DCE-MRI Magnitude and Phase-Based Vascular Input Function Measurements

Accurate, patient-specific measurement of arterial input functions (AIF) may improve model-based analysis of vascular permeability. This study investigated factors affecting AIF measurements from magnetic resonance imaging (MRI) magnitude (AIF_MAGN) and phase (AIF_PHA) signals, and compared them against computed tomography (CT) (AIF_CT), under controlled conditions relevant to clinical protocols using a multimodality flow phantom. The flow phantom was applied at flip angles of 20° and 30°, flow rates (3-7.5 mL/s), and peak bolus concentrations (0.5-10 mM), for in-plane and through-plane flow. Spatial 3D-FLASH signal and variable flip angle T1 profiles were measured to investigate in-flow and radiofrequency-related biases, and magnitude- and phase-derived Gd-DTPA concentrations were compared. MRI AIF performance was tested against AIF_CT via Pearson correlation analysis. AIF_MAGN was sensitive to imaging orientation, spatial location, flip angle, and flow rate, and it grossly underestimated AIF_CT peak concentrations. Conversion to Gd-DTPA concentration using T1 taken at the same orientation and flow rate as the dynamic contrast-enhanced acquisition improved AIF_MAGN accuracy; yet, AIF_MAGN metrics remained variable and significantly reduced from AIF_CT at concentrations above 2.5 mM. AIF_PHA performed equivalently within 1 mM to AIF_CT across all tested conditions. AIF_PHA, but not AIF_MAGN, reported equivalent measurements to AIF_CT across the range of tested conditions. AIF_PHA showed superior robustness.

Quantitative Determination of Paralytic Shellfish Poisoning Toxins in Shellfish Using Prechromatographic Oxidation and Liquid Chromatography with Fluorescence Detection: Collaborative Study

A collaborative study was conducted for the determination of paralytic shellfish poisoning (PSP) toxins in shellfish. The method used liquid chromatography with fluorescence detection after prechromatographic oxidation of the toxins with hydrogen peroxide and periodate. The PSP toxins studied were saxitoxin (STX), neosaxitoxin (NEO), gonyautoxins 2 and 3 (GTX2,3; together), gonyautoxins 1 and 4 (GTX1,4; together), decarbamoyl saxitoxin (dcSTX), B-1 (GTX5), C-1 and C-2 (C1,2; together), and C-3 and C-4 (C3,4; together). B-2 (GTX6) toxin was also included, but for qualitative identification only. Mussels, both blank and naturally contaminated, were mixed and homogenized to provide a variety of PSP toxin mixtures and concentration levels. The same procedure was followed with clams, oysters, and scallops. Twenty-one test samples in total were sent to 21 collaborators who agreed to participate in the study. Results were obtained from 18 laboratories representing 14 different countries. It is recommended that the method be adopted First Action by AOAC INTERNATIONAL.

Diagnostic Reliability of Leptomeningeal Disease Using Magnetic Resonance Imaging

Brain metastases are seen in 20%-50% of patients with metastatic solid tumors. On the other hand, leptomeningeal disease (LMD) occurs more rarely. The gold standard for the diagnosis of LMD is serial cerebrospinal fluid (CSF) analyses, although in daily practice, the diagnosis of LMD is often made by neuroimaging. Leptomeningeal metastases (LM) have been a relative contra-indication to radiosurgery. It can be noted that focal LMD can be difficult to distinguish from a superficially located/cortical-based brain metastasis which is not a contra-indication for radiosurgery. Hence, justifying the need of a reliable diagnosis method.

The goal of this study was to determine the inter-observer reliability of contrast-enhanced magnetic resonance imaging (gdMRI) in the differentiation of focal cortical-based metastases from leptomeningeal spread.

This is a retrospective review of a prospectively collected database of patients with brain metastases. A total of 42 cases with superficial lesions were selected for review. Additionally, eight control cases demonstrating deep and/or white-matter based lesions were included in the study.

Three neuroradiologists and three radiation oncologists were asked to review each study and score the presence of LM. Inter-observer agreement was calculated using group-derived agreement coefficients (Gwet’s AC1 and Gwet's AC2). Pair-wise inter-observer agreement coefficients never reached substantial values for trichotomized outcomes (LMD, non-LMD or indeterminate) but did reach a substantial value in a minority of cases for dichotomised outcomes (LMD or non-LMD). The control subgroup analysis revealed substantial agreement between most pairs for both trichotomized and dichotomised outcomes.

We observed low inter-observer agreement amongst specialists for the diagnosis of focal LMD by gdMRI. Neuroimaging should not be relied upon to make treatment decisions, notably to deny patients radiosurgery.

Changes in apparent diffusion coefficient radiomics features during dose-painted radiotherapy and high dose rate brachytherapy for prostate cancer

Background and purpose

Dose escalation has improved cancer outcomes for patients with localized prostate cancer. Targeting subprostatic tumor regions for dose intensification may further improve outcomes. Apparent Diffusion Coefficient (ADC) maps may enable early radiation response assessment and dose adaptation. This study was a proof-of-principle investigation of early changes in ADC radiomics features for patients undergoing radiotherapy with dose escalation to the gross tumor volume (GTV).

Materials and methods

Fifty-nine patients were enrolled on a prospective tumor dose-escalation trial. Multi-parametric MRI was performed at baseline and week six, corresponding to the time of peak ADC change. GTV and prostate contours were deformably registered between baseline and week six T2-weighted images, and applied to ADC maps, to account for diminished image contrast post-EBRT and possible differences in prostate gland volume, shape, and orientation. A total of 101 radiomics features were tested for significant change post-EBRT using two-tailed Student's t-test. All ADC features of the prostate and GTV volumes were correlated using Pearson's coefficient (p < 0.00008, based on Bonferroni correction).

Results

ADC feature extraction was insensitive to b = 0 s/mm² exclusion, and to gradient non-linearity bias. GTV presented predominant changes in first-order features, particularly 10Percentile, and prostate volumes presented predominant changes in second-order features. Changes in both first and second-order features of GTV and prostate ROIs were strongly correlated.

Conclusions

Our data confirmed significant changes in numerous GTV and prostate features assessed from ADC and T2-weighted images during radiotherapy; all of which may be potential biomarkers of early radiation response.

Simplified and robust one-step radiosynthesis of [18 F]DCFPyL via direct radiofluorination and cartridge-based purification

[18 F]DCFPyL is a clinical-stage PET radiotracer used to image prostate cancer. This report details the efficient production of [18 F]DCFPyL using single-step direct radiofluorination, without the use of carboxylic acid-protecting groups. Radiolabeling reaction optimization studies revealed an inverse correlation between the amount of precursor used and the radiochemical yield. This simplified approach enabled automated preparation of [18 F]DCFPyL within 28 minutes using HPLC purification (26% ± 6%, at EOS, n = 4), which was then scaled up for large-batch production to generate 1.46 ± 0.23 Ci of [18 F]DCFPyL at EOS (n = 7) in high molar activity (37 933 ± 4158 mCi/μmol, 1403 ± 153 GBq/μmol, at EOS, n = 7). Further, this work enabled the development of [18 F]DCFPyL production in 21 minutes using an easy cartridge-based purification (25% ± 9% radiochemical yield, at EOS, n = 3).

Procarbazine, lomustine and vincristine toxicity in low-grade gliomas

Background

Procarbazine, lomustine, and vincristine (pcv) significantly improve survival outcomes in lgg (low-grade gliomas). Administration of pcv to lgg patients increased tremendously over the past years as it went from 2 patients per year between 2005 and 2012 to 23 patients in 2015 only in our centre. However, serious hematological and non-hematological adverse events may occur. The purpose of this study was to evaluate the toxicity of pcv and its clinical relevance in our practice.

Methods

We retrospectively reviewed the charts of 57 patients with lgg who received pcv at the Centre hospitalier de l'Université de Montréal between 1 January 2005 and 27 July 2016.

Results

Procarbazine, lomustine, and vincristine were associated with severe hematological toxicity as clinically significant grade 3 anemia, neutropenia, and thrombocytopenia occurred in 7%, 10%, and 28% of patients, respectively. Other frequent adverse events such as the increase of liver enzymes, cutaneous rash, neurotoxicity, and vomiting occurred in 65%, 26%, 60%, and 40% of patients, respectively. Patients with prophylactic trimethoprim/sulfamethoxazole had more grade 3 hematological toxicity with pcv, especially anemia (p = 0.040) and thrombocytopenia (p = 0.003) but we found no increase in pcv toxicity in patients on concurrent anticonvulsants. Patients with grade 3 neutropenia had a significantly lower survival (median survival 44.0 months vs. 114.0 months, p = 0.001). Patients who were given pcv at diagnosis had more grade 3 anemia than those who received it at subsequent lines of treatment (p = 0.042).

Conclusion

Procarbazine, lomustine, and vincristine increase survival in lgg but were also associated with major hematologic, hepatic, neurologic, and cutaneous toxicity. Anti-Pneumocystis jiroveci pneumonia (pjp) prophylaxis, but not anticonvulsants, enhances hematologic toxicity.

Validation of MRI to TRUS registration for high-dose-rate prostate brachytherapy

PURPOSE

The objective of this study was to develop and validate an open-source module for MRI to transrectal ultrasound (TRUS) registration to support tumor-targeted prostate brachytherapy.

METHODS AND MATERIALS

In this study, 15 patients with prostate cancer lesions visible on multiparametric MRI were selected for the validation. T2-weighted images with 1-mm isotropic voxel size and diffusion weighted images were acquired on a 1.5T Siemens imager. Three-dimensional (3D) TRUS images with 0.5-mm slice thickness were acquired. The investigated registration module was incorporated in the open-source 3D Slicer platform, which can compute rigid and deformable transformations. An extension of 3D Slicer, SlicerRT, allows import of and export to DICOM-RT formats. For validation, similarity indices, prostate volumes, and centroid positions were determined in addition to registration errors for common 3D points identified by an experienced radiation oncologist.

RESULTS

The average time to compute the registration was 35 ± 3 s. For the rigid and deformable registration, respectively, Dice similarity coefficients were 0.87 ± 0.05 and 0.93 ± 0.01 while the 95% Hausdorff distances were 4.2 ± 1.0 and 2.2 ± 0.3 mm. MRI volumes obtained after the rigid and deformable registration were not statistically different (p > 0.05) from reference TRUS volumes. For the rigid and deformable registration, respectively, 3D distance errors between reference and registered centroid positions were 2.1 ± 1.0 and 0.4 ± 0.1 mm while registration errors between common points were 3.5 ± 3.2 and 2.3 ± 1.1 mm. Deformable registration was found significantly better (p < 0.05) than rigid registration for all parameters.

CONCLUSIONS

An open-source MRI to TRUS registration platform was validated for integration in the brachytherapy workflow.

A comparison of early prostate-specific antigen decline between prostate brachytherapy and different fractionation of external beam radiation-Impact on biochemical failure

PURPOSE

The aim of this study was to compare early prostate-specific antigen (PSA) decline patterns and PSA nadirs between low-dose-rate seed prostate brachytherapy (LDR-PB) and different fractionations of external beam radiotherapy (EBRT) and their predictive importance for biochemical failure (bF).

METHODS AND MATERIALS

Patients with D'Amico low- or intermediate-risk prostate cancer who underwent a single-modality treatment without androgen deprivation were included in this study. Three different treatment groups were compared: (1) normofractionation EBRT up to 70.2-79.2 Gy/1.8-2.0 Gy, (2) LDR-PB, and (3) EBRT with hypofractionation 60 Gy/3 Gy daily or 5-7.25 Gy once a week over 9-5 weeks, to a total dose of 45-36.25 Gy, respectively. The log-rank test, Cox regression analysis, and nonparametric tests were used.

RESULTS

We analyzed 892 patients: the median followup for patients without bF was 84 months (interquartile range 60-102 months), with 12% of patients experiencing bF. The PSA decline within the first 15 months was generally exponential. LDR-PB showed a faster early exponential decline compared with EBRT treatments, but whether decline was fast or slow had no influence on recurrence. The only factors that were positive predictive factors in univariate and multivariate analyses were the time to nadir >48 months (median), PSA nadir <0.5 ng/mL, and <0.2 ng/mL (all p < 0.001).

CONCLUSIONS

Although there are significant differences in early exponential PSA decline between different treatments, only the PSA nadir and longer time to nadir were predictive factors for bF.

MR elastography to measure the effects of cancer and pathology fixation on prostate biomechanics, and comparison with T 1, T 2 and ADC

MRI is under evaluation for image-guided intervention for prostate cancer. The sensitivity and specificity of MRI parameters is determined via correlation with the gold-standard of histopathology. Whole-mount histopathology of prostatectomy specimens can be digitally registered to in vivo imaging for correlation. When biomechanical-based deformable registration is employed to account for deformation during histopathology processing, the ex vivo biomechanical properties are required. However, these properties are altered by pathology fixation, and vary with disease. Hence, this study employs magnetic resonance elastography (MRE) to measure ex vivo prostate biomechanical properties before and after fixation. A quasi-static MRE method was employed to measure high resolution maps of Young's modulus (E) before and after fixation of canine prostate and prostatectomy specimens (n  =  4) from prostate cancer patients who had previously received radiation therapy. For comparison, T ₁, T ₂ and apparent diffusion coefficient (ADC) were measured in parallel. E (kPa) varied across clinical anatomy and for histopathology-identified tumor: peripheral zone: 99(±22), central gland: 48(±37), tumor: 85(±53), and increased consistently with fixation (factor of 11  ±  5; p  <  0.02). T ₂ decreased consistently with fixation, while changes in T ₁ and ADC were more complex and inconsistent. The biomechanics of the clinical prostate specimens varied greatly with fixation, and to a lesser extent with disease and anatomy. The data obtained will improve the precision of prostate pathology correlation, leading to more accurate disease detection and targeting.

Dosimetric impact of intrafraction changes in MR-guided high-dose-rate (HDR) brachytherapy for prostate cancer

PURPOSE

To assess changes in implant and treatment volumes through the course of a prostate high-dose-rate brachytherapy procedure and their impact on plan quality metrics.

METHODS AND MATERIALS

Sixteen MRI-guided high-dose-rate procedures included a post-treatment MR (ptMR) immediately after treatment delivery (135 min between MR scans). Target and organs at risk (OARs) were contoured, and catheters were reconstructed. The delivered treatment plan was applied to the ptMR image set. Volumes and dosimetric parameters in the ptMR were evaluated and compared with the delivered plan using a paired two-tailed t-test with p < 0.05 considered statistically significant.

RESULTS

An average increase of 8.9% in prostate volume was observed for whole-gland treatments, resulting in reduction in coverage for both prostate and planning target volume, reflected in decreased V₁₀₀ (mean 3.3% and 4.6%, respectively, p < 0.05), and D₉₀ (mean 7.1% and 7.6%, respectively, of prescription dose, p < 0.05). There was no significant change in doses to OARs. For partial-gland treatments, there was an increase in planning target volume (9.1%), resulting in reduced coverage and D₉₀ (mean 3.6% and 12.4%, respectively, p < 0.05). A decrease in D_0.5cc for bladder (3%, p < 0.05) was observed, with no significant changes in dose to other OARs.

CONCLUSIONS

Volumetric changes were observed during the time between planning MR and ptMR. Nonetheless, treatment plans for both whole- and partial-gland therapies remained clinically acceptable. These results apply to clinical settings in which patients remain in the same position and under anesthesia during the entire treatment process.

Improved outcomes with dose escalation in localized prostate cancer treated with precision image-guided radiotherapy

BACKGROUND AND PURPOSE

Dose-escalated radiotherapy (DE) improves outcomes in localized prostate cancer (PCa). The impact of DE in the context of image-guided radiotherapy (IGRT) remains unknown. Herein, we determined outcomes of three sequential cohorts treated with progressive DE-IGRT.

MATERIALS AND METHODS

We analyzed data from 1998 to 2012. Patients treated with radical radiotherapy were included, with three sequential institutional schedules: (A) 75.6Gy, (B) 79.8Gy, (C) 78Gy, with 1.8, 1.9 and 2Gy/fraction, respectively. IGRT consisted of fiducial markers and daily EPID (A, B) or CBCT (C).

RESULTS

961 patients were included, with median follow-up of 6.1y. 30.5%, 32.6% and 36.9% were treated in A, B and C, respectively. Risk category distribution was 179 (18.6%) low-, 653 (67.9%) intermediate- and 129 (13.5%) high-risk. PSA, T-category, androgen deprivation use and risk distribution were similar among groups. BCR (biochemical recurrence) was different (p<0.001) between A, B and C with 5-year rates of 23%, 17% and 9%, respectively (HR 2.68 [95% CI 1.87-3.85] and 1.92 [95% CI 1.33-2.78] for A and B compared to C, respectively). Findings were most significant in the intermediate-risk category. Metastasis, cause-specific-death and toxicities were not different between cohorts.

CONCLUSION

Our findings suggest continuous BCR improvement with progressive DE-IGRT. Prospective validation considering further DE with IGRT seems warranted.

The utilization of magnetic resonance imaging in the operating room

Online image guidance in the operating room using ultrasound imaging led to the resurgence of prostate brachytherapy in the 1980s. Here we describe the evolution of integrating MRI technology in the brachytherapy suite or operating room. Given the complexity, cost, and inherent safety issues associated with MRI system integration, first steps focused on the computational integration of images rather than systems. This approach has broad appeal given minimal infrastructure costs and efficiencies comparable with standard care workflows. However, many concerns remain regarding accuracy of registration through the course of a brachytherapy procedure. In selected academic institutions, MRI systems have been integrated in or near the brachytherapy suite in varied configurations to improve the precision and quality of treatments. Navigation toolsets specifically adapted to prostate brachytherapy are in development and are reviewed.

Advancements in brachytherapy

Brachytherapy is a radiotherapy modality associated with a highly focal dose distribution. Brachytherapy treats the cancer tissue from the inside, and the radiation does not travel through healthy tissue to reach the target as with external beam radiotherapy techniques. The nature of brachytherapy makes it attractive for boosting limited size target volumes to very high doses while sparing normal tissues. Significant developments over the last decades have increased the use of 3D image guided procedures with the utilization of CT, MRI, US and PET. This has taken brachytherapy to a new level in terms of controlling dose and demonstrating excellent clinical outcome. Interests in focal, hypofractionated and adaptive treatments are increasing, and brachytherapy has significant potential to develop further in these directions with current and new treatment indications.

Technical Note: Method to correlate whole-specimen histopathology of radical prostatectomy with diagnostic MR imaging

PURPOSE

Validation of MRI-guided tumor boundary delineation for targeted prostate cancer therapy is achieved via correlation with gold-standard histopathology of radical prostatectomy specimens. Challenges to accurate correlation include matching the pathology sectioning plane with the in vivo imaging slice plane and correction for the deformation that occurs between in vivo imaging and histology. A methodology is presented for matching of the histological sectioning angle and position to the in vivo imaging slices.

METHODS

Patients (n = 4) with biochemical failure following external beam radiotherapy underwent diagnostic MRI to confirm localized recurrence of prostate cancer, followed by salvage radical prostatectomy. High-resolution 3-D MRI of the ex vivo specimens was acquired to determine the pathology sectioning angle that best matched the in vivo imaging slice plane, using matching anatomical features and implanted fiducials. A novel sectioning device was developed to guide sectioning at the correct angle, and to assist the insertion of reference dye marks to aid in histopathology reconstruction.

RESULTS

The percentage difference in the positioning of the urethra in the ex vivo pathology sections compared to the positioning in in vivo images was reduced from 34% to 7% through slicing at the best match angle. Reference dye marks were generated, which were visible in ex vivo imaging, in the tissue sections before and after processing, and in histology sections.

CONCLUSIONS

The method achieved an almost fivefold reduction in the slice-matching error and is readily implementable in combination with standard MRI technology. The technique will be employed to generate datasets for correlation of whole-specimen prostate histopathology with in vivo diagnostic MRI using 3-D deformable registration, allowing assessment of the sensitivity and specificity of MRI parameters for prostate cancer. Although developed specifically for prostate, the method is readily adaptable to other types of whole tissue specimen, such as mastectomy or liver resection.

Dosimetric feasibility of ablative dose escalated focal monotherapy with MRI-guided high-dose-rate (HDR) brachytherapy for prostate cancer

PURPOSE

To determine the dosimetric feasibility of dose-escalated MRI-guided high-dose-rate brachytherapy (HDR-BT) focal monotherapy for prostate cancer (PCa).

METHODS

In all patients, GTV was defined with mpMRI, and deformably registered onto post-catheter insertion planning MRI. PTV included the GTV plus 9mm craniocaudal and 5mm in every other direction. In discovery-cohort, plans were obtained for each PTV independently aiming to deliver ⩾16.5Gy/fraction (two fraction schedule) while respecting predefined organs-at-risk (OAR) constraints or halted when achieved equivalent single-dose plan (24Gy). Dosimetric results of original and focal HDR-BT plans were evaluated to develop a planning protocol for the validation-cohort.

RESULTS

In discovery-cohort (20-patients, 32-GTVs): PTV D95% ⩾16.5Gy could not be reached in a single plan (3%) and was accomplished (range 16.5-23.8Gy) in 15 GTVs (47%). Single-dose schedule was feasible in 16 (50%) plans. In the validation-cohort (10-patients, 10-GTVs, two separate implants each): plans met acceptable and ideal criteria in 100% and 43-100% respectively. Migration to single-dose treatment schedule was feasible in 7 implants (35%), without relaxing OAR's constraints or increasing the dose (D100% and D35%) to mpMRI-normal prostate (p>0.05).

CONCLUSION

Focal ablative dose-escalated radiation is feasible with the proposed protocol. Prospective studies are warranted to determine the clinical outcomes.