Guidelines for primary radiotherapy of patients with prostate cancer

Very high-energy electron therapy as light-particle alternative to transmission proton FLASH therapy - An evaluation of dosimetric performances

PURPOSE

Clinical translation of FLASH-radiotherapy (RT) to deep-seated tumours is still a technological challenge. One proposed solution consists of using ultra-high dose rate transmission proton (TP) beams of about 200-250 MeV to irradiate the tumour with the flat entrance of the proton depth-dose profile. This work evaluates the dosimetric performance of very high-energy electron (VHEE)-based RT (50-250 MeV) as a potential alternative to TP-based RT for the clinical transfer of the FLASH effect.

METHODS

Basic physics characteristics of VHEE and TP beams were compared utilizing Monte Carlo simulations in water. A VHEE-enabled research treatment planning system was used to evaluate the plan quality achievable with VHEE beams of different energies, compared to 250 MeV TP beams for a glioblastoma, an oesophagus, and a prostate cancer case.

RESULTS

Like TP, VHEE above 100 MeV can treat targets with roughly flat (within ± 20 %) depth-dose distributions. The achievable dosimetric target conformity and adjacent organs-at-risk (OAR) sparing is consequently driven for both modalities by their lateral beam penumbrae. Electron beams of 400[500] MeV match the penumbra of 200[250] MeV TP beams and penumbra is increased for lower electron energies. For the investigated patient cases, VHEE plans with energies of 150 MeV and above achieved a dosimetric plan quality comparable to that of 250 MeV TP plans. For the glioblastoma and the oesophagus case, although having a decreased conformity, even 100 MeV VHEE plans provided a similar target coverage and OAR sparing compared to TP.

CONCLUSIONS

VHEE-based FLASH-RT using sufficiently high beam energies may provide a lighter-particle alternative to TP-based FLASH-RT with comparable dosimetric plan quality.

Cost-effectiveness of hypofractionated versus conventional radiotherapy in patients with intermediate-risk prostate cancer: An ancillary study of the PROstate fractionated irradiation trial - PROFIT

PURPOSE

To evaluate the cost-effectiveness of moderate Hypofractionated Radiotherapy (H-RT) compared to Conventional Radiotherapy (C-RT) for intermediate-risk prostate caner (PCa).

METHODS

A prospective randomized clinical trial including 222 patients from six French cancer centers was conducted as an ancillary study of the international PROstate Fractionated Irradiation Trial (PROFIT). We carried-out a cost-effectiveness analysis (CEA) from the payer's perspective, with a time horizon of 48 months. Patients assigned to the H-RT arm received 6000 cGy in 20 fractions over 4 weeks, or 7800 cGy in 39 fractions over 7 to 8 weeks in the C-RT arm. Patients completed quality of life (QoL) questionnaire: Expanded Prostate Cancer Index Composite (EPIC) at baseline, 24 and 48 months, which were mapped to obtain a EuroQol five-dimensional questionnaire (EQ-5D) equivalent to generate Quality Adjusted Life Years (QALY). We assessed differences in QALYs and costs between the two arms with Generalized Linear Models (GLMs). Costs, estimated in euro (€) 2020, were combined with QALYs to estimate the Incremental Cost-effectiveness ratio (ICER) with non-parametric bootstrap.

RESULTS

Total costs per patien were lower in the H-RT arm compared to the C-RT arm €3,062 (95 % CI: 2,368 to 3,754) versus €4,285 (95 % CI: 3,355 to 5,215), (p < 0.05). QALY were marginally higher in the H-RT arm, however this difference was not significant: 0.044 (95 % CI: - 0.016 to 0.099).

CONCLUSIONS

Treating localized prostate cancer with moderate H-RT could reduce national health insurance spending. Adopting such a treatment with an updated reimbursement tariff would result in improving resource allocation in RT management.

Quality of life after definitive linear accelerator-based stereotactic radiotherapy for prostate cancer: a longitudinal study

BACKGROUND

Prostate cancer is the second most common malignancy worldwide, and the majority of patients are diagnosed with localized disease. We examined patients' quality of life after stereotactic body radiation therapy (SBRT) for prostate cancer.

METHODS

We included patients who were treated between 2016 and 2020. Inclusion criteria were adenocarcinoma of the prostate; class risk of low, intermediate, and high; and a World Health Organization performance status of 0-2. Quality of life was measured using the Functional Assessment of Cancer Therapy-Prostate (FACT-P).

RESULTS

A total of 439 patients were treated with SBRT, with a median age of 73 years old. The median follow-up period was 34 months. FACT-P Trial Outcome Index (p < 0.0001), FACT-General (p = 0.0003), and FACT-P-Total (p < 0.0001) scores declined at 1 month post-SBRT, then recovered and returned to the same level as before treatment at 3-4 months post-SBRT. The decrease in quality of life in the first month was particularly remarkable in patients who received long-term hormone injections (36%). One month after the end of SBRT, about 22% of patients experienced "quite a bit" or more troubling side effects.

CONCLUSIONS

This study showed longitudinal changes in quality of life by FACT-P after SBRT for prostate cancer. Overall, prostate SBRT was well tolerated.

Assessing the dose rate delivery of helical TomoTherapy prostate and head & neck treatments

The dose rate distributions delivered to 55 prostate and head & neck (H&N) cancer patients treated with a helical TomoTherapy (HT) system were resolved and assessed with regard to pitch and field width defined during treatment planning. Statistical analysis of the studied cases showed that the median treatment delivery time was 4.4 min and 6.3 min for the prostate and H&N cases, respectively. Dose rate volume histogram data for the studied cases showed that the 25% and 12% of the volume of the planning target volumes of the prostate and H&N cases are irradiated with a dose rate of greater or equal to 1 Gy min^-1. Quartile dose rate (QDR) data confirmed that in HT, where the target is irradiated in slices, most of the dose is delivered to each voxel of the target when it travels within the beam. Analysis of the planning data from all cases showed that this lasts for 68 s (median value). QDRs results showed that using the 2.5 cm field width, 75% of the prescribed dose is delivered to target voxels with a median dose rate of at least 3.2 Gy min^-1and 4.5 Gy min^-1, for the prostate and H&N cases, respectively. Systematically higher dose rates were observed for the H&N cases due to the shallower depths of the lesions in this anatomical site. Delivered dose rates were also found to increase with field width and pitch setting, due to the higher output of the system which, in general, results in accordingly decreased total treatment time. The biological effect of the dose rate findings of this work needs to be further investigated using in-vitro studies and clinical treatment data.

Single-Center Experience of Focal Thermo-Ablative Therapy After Pelvic Radiotherapy for In-Field Prostate Cancer Oligo-Recurrence

PURPOSE

In-field prostate cancer (PCa) oligo-recurrence after pelvic radiotherapy is a challenging situation for which metastasis-directed treatments may be beneficial, but options for focal therapies are scarce.

METHODS

We retrospectively reviewed data for patients with three or less in-field oligo-recurrent nodal, bone and/or locally recurrent (prostate, seminal vesicles, or prostatic bed) PCa lesions after radiation therapy, identified with molecular imaging (PET and/or MRI) and treated by focal ablative therapy (cryotherapy or radiofrequency) at the Institut Bergonié between 2012 and 2020. Chosen endpoints were the post-procedure PSA response (partially defined as a >50% reduction, complete as a PSA <0.05 ng/ml), progression-free survival (PFS) defined as either a biochemical relapse (defined as a rise >25% of the Nadir and above 2 ng/ml), radiological relapse (on any imaging technique), decision of treatment modification (hormonotherapy initiation or line change) or death, and tolerance.

RESULTS

Forty-three patients were included. Diagnostic imaging was mostly 18F-Choline positron emission tomography/computerized tomography (PET/CT) (75.0%), prostate specific membrane antigen (PSMA) PET/CT (9.1%) or a combination of pelvic magnetic resonance imaging (MRI), CT, and 99 mTc-bone scintigraphy (11.4%). PSA response was observed in 41.9% patients (partial in 30.3%, complete in 11.6%). In the hormone-sensitive exclusive focal ablation group (n = 31), partial and complete PSA responses were 32.3 and 12.9% respectively. Early local control (absence of visible residual active target) on the post-procedure imaging was achieved with 87.5% success. After a median follow-up of 30 months (IQR 13.3-56.8), the median PFS was 9 months overall (95% CI, 6-17), and 17 months (95% CI, 11-NA) for PSA responders. Complications occurred in 11.4% patients, with only one grade IIIb Dindo-Clavien event (uretral stenosis requiring endoscopic uretrotomy).

CONCLUSION

In PCa patients showing in-field oligo-recurrence after pelvic radiotherapy, focal ablative treatment is a feasible option, possibly delaying a systemic treatment initiation or modification. These invasive strategies should preferably be performed in expert centers and discussed along other available focal strategies in multi-disciplinary meetings.

Preoperative Prediction of Extracapsular Extension: Radiomics Signature Based on Magnetic Resonance Imaging to Stage Prostate Cancer

PURPOSE

To investigate and validate the potential role of a radiomics signature in predicting the side-specific probability of extracapsular extension (ECE) of prostate cancer (PCa).

PROCEDURES

The preoperative magnetic resonance imaging data of 238 prostatic samples from 119 enrolled PCa patients were retrospectively assessed. The samples with were randomized in a two-to-one ratio into training (n = 74) and validation (n = 45) datasets. The radiomics features were derived from T2-weighted images (T2WIs). The optimal radiomics features were identified from the least absolute shrinkage and selection operator (LASSO) logistic regression model and were used to construct a predictive radiomics signature via dimension reduction and selection approaches. The association between the radiomics signatures and pathological ECE status was explored. Receiver operating characteristic (ROC) analysis was used to assess the discriminatory ability of the signature. The calibration performance and clinical usefulness of the radiomics signature were subsequently assessed by calibration curve and decision curve analyses.

RESULTS

The proposed radiomics signature that incorporated 17 selected radiomics features was significantly associated with pathological ECE outcomes (P < 0.001) in both the training and validation datasets. The constructed model displayed good discrimination, with areas under the curve (AUC) of 0.906 (95 % confidence interval (CI), 0.847, 0.948) and 0.821 (95 % CI, 0.726, 0.894) for the training and validation datasets, respectively, and had a good calibration performance. The clinical utility of this model was confirmed through decision curve analysis.

CONCLUSIONS

The radiomics signature based on T2WIs showed the potential to predict the side-specific probability of pathological ECE status and can facilitate the preoperative individualized predictions for PCa patients.

Comparative dosimetrical analysis of intensity-modulated arc therapy, CyberKnife therapy and image-guided interstitial HDR and LDR brachytherapy of low risk prostate cancer

Background

The objective of the study was to dosimetrically compare the intensity-modulated-arc-therapy (IMAT), Cyber-Knife therapy (CK), single fraction interstitial high-dose-rate (HDR) and low-dose-rate (LDR) brachytherapy (BT) in low-risk prostate cancer.

Materials and methods

Treatment plans of ten patients treated with CK were selected and additional plans using IMAT, HDR and LDR BT were created on the same CT images. The prescribed dose was 2.5/70 Gy in IMAT, 8/40 Gy in CK, 21 Gy in HDR and 145 Gy in LDR BT to the prostate gland. EQD2 dose-volume parameters were calculated for each technique and compared.

Results

EQD2 total dose of the prostate was significantly lower with IMAT and CK than with HDR and LDR BT, D90 was 79.5 Gy, 116.4 Gy, 169.2 Gy and 157.9 Gy (p < 0.001). However, teletherapy plans were more conformal than BT, COIN was 0.84, 0.82, 0.76 and 0.76 (p < 0.001), respectively. The D₂ to the rectum and bladder were lower with HDR BT than with IMAT, CK and LDR BT, it was 66.7 Gy, 68.1 Gy, 36.0 Gy and 68.0 Gy (p = 0.0427), and 68.4 Gy, 78.9 Gy, 51.4 Gy and 70.3 Gy (p = 0.0091) in IMAT, CK, HDR and LDR BT plans, while D_0.1 to the urethra was lower with both IMAT and CK than with BTs: 79.9 Gy, 88.0 Gy, 132.7 Gy and 170.6 Gy (p < 0.001). D₂ to the hips was higher with IMAT and CK, than with BTs: 13.4 Gy, 20.7 Gy, 0.4 Gy and 1.5 Gy (p < 0.001), while D₂ to the sigmoid, bowel bag, testicles and penile bulb was higher with CK than with the other techniques.

Conclusions

HDR monotherapy yields the most advantageous dosimetrical plans, except for the dose to the urethra, where IMAT seems to be the optimal modality in the radiotherapy of low-risk prostate cancer.

Multicentre International Study for the Prevention with iAluRil of Radio-induced Cystitis (MISTIC): A Randomised Controlled Study

BACKGROUND

Radiation-induced cystitis is a common side effect of radiotherapy (RT) to the pelvic area. Hyaluronic acid (HA) and chondroitin sulfate (CS) are components of the urothelial mucosa and positive results have been obtained for intravesical HA/CS instillations for the treatment of urinary tract infections and bladder pain syndrome. HA/CS may also have a protective effect against RT bladder toxicity.

OBJECTIVE

To investigate whether HA and CS protect the urothelium during RT, alleviate lower urinary tract symptoms, and improve quality of life.

DESIGN SETTING AND PARTICIPANTS

This multicentre randomised controlled trial was conducted across seven centres in four countries. Male patients aged ≥18 yr scheduled to undergo primary intensity-modulated radiotherapy for localised prostate cancer were enrolled.

INTERVENTION

Patients were randomised to intravesical HA/CS plus an oral formulation of curcumin, quercetin, HA, and CS (group A) or no treatment (group B).

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

The primary endpoint was absolute changes from baseline to follow-up in urinary domain scores for the Expanded Prostate Cancer Index Composite (EPIC), the International Consultation on Incontinence Questionnaire-Male Lower Urinary Tract Symptoms (ICIQ-MLUTS), and the EuroQol Group EQ-5D-5L questionnaire. Data analysis for efficacy and safety outcomes was performed using an intention-to-treat (ITT) approach; the ITT population was defined as all randomised patients.

RESULTS AND LIMITATIONS

Of 57 patients screened, 49 were enrolled and randomly assigned to either active treatment (group A, n = 25) or the control (group B, n = 24). Three patients in the control group withdrew after randomisation. Changes from baseline to 12 mo were worse in the control group for subtotal scores for urinary symptoms and impact of symptoms on quality of life and for the total score (p =  0.05, p =  0.003, and p =  0.008, respectively). There was a significant time × group interaction in favour of active treatment for the incontinence symptom score (p =  0.011) and bother score (p =  0.017). The absence of a sham procedure and/or placebo is the main limitation.

CONCLUSIONS

Our results suggest that intravesical HA/CS in combination with an oral formulation may reduce urinary symptoms and improve QoL at short-term (1 yr) follow-up.

PATIENT SUMMARY

We investigated whether hyaluronic acid (HA) and chondroitin sulfate (CS) have a protective effect against the bladder toxicity of radiotherapy for prostate cancer. HA/CS used for weekly bladder irrigation for 6 wk and given orally with curcumin and quercetin for 12 wk reduced urinary incontinence symptoms and bother measured at 1-year follow-up. This may hold promise as a preventive treatment if the results are confirmed in further trials.

Analysis of prostate intensity- and volumetric-modulated arc radiation therapy planning quality with PlanIQTM

Purpose

The purpose of this study was to assess the quality of treatment planning using the PlanIQ^TM software and to investigate whether it is possible to improve the quality of treatment planning using the “Feasibility dose‐volume histogram (DVH)^TM” implemented in the PlanIQ^TM software.

Methods

Using the PlanIQ^TM software, we retrospectively analyzed the learning curve regarding the quality of the treatment plans for 148 patients of prostate intensity‐modulated radiation therapy and volumetric‐modulated radiation therapy performed at our institution over the past eight years. We also sought to examine the possibility of improving treatment planning quality by re‐planning in 47 patients where the quality of the target dose and the dose limits for organs at risk (OARs) were inadequate. The re‐planning treatment plans referred to the Feasibility DVH^TM implemented in the PlanIQ^TM software and modified the treatment planning system based on the target dose and OAR constraints.

Results

Analysis of the learning curve of the treatment plans quality using PlanIQ^TM software retrospectively showed a trend of improvement in the treatment plan quality from year to year. The improvement in the treatment plans quality was more influenced by dose reduction in the OARs than by target coverage.

In all cases where re‐planning was performed, the improvement in the treatment plan's quality resulted in a better treatment plan than the one adopted for delivery to patients in the clinical plan.

Conclusions

The PlanIQ^TM provided insights into the quality of the treatment plans at our institution and identified problems and areas for improvement in the treatment plans, allowing for the development of appropriate treatment plans for specific patients.

Radiomics and Prostate MRI: Current Role and Future Applications

Multiparametric prostate magnetic resonance imaging (mpMRI) is widely used as a triage test for men at a risk of prostate cancer. However, the traditional role of mpMRI was confined to prostate cancer staging. Radiomics is the quantitative extraction and analysis of minable data from medical images; it is emerging as a promising tool to detect and categorize prostate lesions. In this paper we review the role of radiomics applied to prostate mpMRI in detection and localization of prostate cancer, prediction of Gleason score and PI-RADS classification, prediction of extracapsular extension and of biochemical recurrence. We also provide a future perspective of artificial intelligence (machine learning and deep learning) applied to the field of prostate cancer.

Patterns of care for prostate cancer radiotherapy-results from a survey among German-speaking radiation oncologists

Background

Emerging moderately hypofractionated and ultra-hypofractionated schemes for radiotherapy (RT) of prostate cancer (PC) have resulted in various treatment options. The aim of this survey was to evaluate recent patterns of care of German-speaking radiation oncologists for RT of PC.

Methods

We developed an online survey which we distributed via e‑mail to all registered members of the German Society of Radiation Oncology (DEGRO). The survey was completed by 109 participants between March 3 and April 3, 2020. For evaluation of radiation dose, we used the equivalent dose at fractionation of 2 Gy with α/β = 1.5 Gy, equivalent dose (EQD2 [1.5 Gy]).

Results

Median EQD2(1.5 Gy) for definitive RT of the prostate is 77.60 Gy (range: 64.49–84.00) with median single doses (SD) of 2.00 Gy (range: 1.80–3.00), while for postoperative RT of the prostate bed, median EQD2(1.5 Gy) is 66.00 Gy (range: 60.00–74.00) with median SD of 2.00 Gy (range: 1.80–2.00). For definitive RT, the pelvic lymph nodes (LNs) are treated in case of suspect findings in imaging (82.6%) and/or according to risk formulas/tables (78.0%). In the postoperative setting, 78.9% use imaging and 78.0% use the postoperative tumor stage for LN irradiation. In the definitive and postoperative situation, LNs are irradiated with a median EQD2(1.5 Gy) of 47.52 Gy with a range of 42.43–66.00 and 41.76–62.79, respectively.

Conclusion

German-speaking radiation oncologists’ patterns of care for patients with PC are mainly in line with the published data and treatment recommendation guidelines. However, dose prescription is highly heterogenous for RT of the prostate/prostate bed, while the dose to the pelvic LNs is mainly consistent.

Supplementary Information

The online version of this article (10.1007/s00066-020-01738-1) contains supplementary material, which is available to authorized users.

Dosimetric Impact of the Positional Imaging Frequency for Hypofractionated Prostate Radiotherapy - A Voxel-by-Voxel Analysis

Background

To investigate deviations between planned and applied treatment doses for hypofractionated prostate radiotherapy and to quantify dosimetric accuracy in dependence of the image guidance frequency.

Methods

Daily diagnostic in-room CTs were carried out in 10 patients in treatment position as image guidance for hypofractionated prostate radiotherapy. Fraction doses were mapped to the planning CTs and recalculated, and applied doses were accumulated voxel-wise using deformable registration. Non-daily imaging schedules were simulated by deriving position correction vectors from individual scans and used to rigidly register the following scans until the next repositioning before dose recalculation and accumulation. Planned and applied doses were compared regarding dose-volume indices and TCP and NTCP values in dependence of the imaging and repositioning frequency.

Results

Daily image-guided repositioning was associated with only negligible deviations of analyzed dose-volume parameters and conformity/homogeneity indices for the prostate, bladder and rectum. Average CTV T did not significantly deviate from the plan values, and rectum NTCPs were highly comparable, while bladder NTCPs were reduced. For non-daily image-guided repositioning, there were significant deviations in the high-dose range from the planned values. Similarly, CTV dose conformity and homogeneity were reduced. While TCPs and rectal NTCPs did not significantly deteriorate for non-daily repositioning, bladder NTCPs appeared falsely diminished in dependence of the imaging frequency.

Conclusion

Using voxel-by-voxel dose accumulation, we showed for the first time that daily image-guided repositioning resulted in only negligible dosimetric deviations for hypofractionated prostate radiotherapy. Regarding dosimetric aberrations for non-daily imaging, daily imaging is required to adequately deliver treatment.

A-blockers for the management of lower urinary tract symptoms in patients with prostate cancer treated with external beam radiotherapy: a randomized controlled study

BACKGROUND

This is a prospective study aiming to assess the efficacy of α-blockers in treating radiotherapy-induced symptoms of the lower urinary tract and its possible prophylactic role on acute urinary retention (AUR) in patients undergoing radical external beam radiotherapy (EBRT) for localized prostate cancer (PCa).

METHODS

Overall, 108 patients with localized PCa were recruited and randomly assigned in to two groups; 54 patients of Group 1 received tamsulosin 0.4 mg once daily with the initiation of EBRT and for 6 months and 54 patients of Group 2 served as the control group. All patients received radical EBRT and had post-void volume (Vres) assessment. The International Prostate Symptom Score (IPSS) questionnaire and evaluation of episodes of AUR were performed after the end of radiotherapy, at 3 and at 6 months.

RESULTS

The incidence of AUR was significantly (p = 0.027) lower in group 1 compared to group 2. No independent predictive factors for AUR were identified in regression analysis. The IPSS changes in univariate and multivariate analysis at 3 months showed significant correlation with α-blockers only, while at 6 months showed significant correlation with Vres assessments (at 3 and 6 months) and with α-blockers. Side effects due to medication were mild and none of the patients discontinued the treatment.

CONCLUSIONS

The selective use of α-blocker appears to prevent AUR in EBRT-treated patients. Although the administration of α-blockers might relieve patient-reported symptoms, there are no established independent predictive factors to distinguish patients who may benefit.

Optimal PSA Threshold for Androgen-Deprivation Therapy in Patients with Prostate Cancer following Radical Prostatectomy and Adjuvant Radiation Therapy

PURPOSE

The benefits of early administration of androgen-deprivation therapy (ADT) in patients with prostate-specific antigen (PSA)-only recurrent prostate cancer (PCa) following radical prostatectomy (RP) are controversial. We investigated the impact of early versus delayed ADT on survival outcomes in patients with non-metastatic, localized or locally advanced PCa who received radiation therapy (RT) following RP and later developed distant metastasis.

MATERIALS AND METHODS

A retrospective analysis was performed on 69 patients with non-metastatic, localized or locally advanced PCa who received RT following RP and later developed distant metastasis between January 2006 and December 2012. Patients were stratified according to the level of PSA at which ADT was administered (<2 ng/mL vs. ≥2 ng/mL). Study endpoints were progression to castration-resistant prostate cancer (CRPC)-free survival and cancer-specific survival (CSS).

RESULTS

Patients were stratified according to the criteria of 2 ng/mL of PSA at which ADT was administered, based on the Youden sensitivity analysis. Delayed ADT at PSA ≥2 ng/mL was an independent prognosticator of cancer-specific mortality (p=0.047), and a marginally significant prognosticator of progression to CRPC (p=0.051). During the median follow-up of 81.0 (interquartile range 54.2-115.7) months, patients who received early ADT at PSA <2 ng/mL had significantly higher CSS rates compared to patients who received delayed ADT at PSA ≥2 ng/mL (p=0.002). Progression to CRPC-free survival was comparable between the two groups (p=0.331).

CONCLUSION

Early ADT at the PSA level of less than 2 ng/mL confers CSS benefits in patients with localized or locally advanced PCa who were previously treated with RP.

Biological dose summation of intensity-modulated arc therapy and image-guided high-dose-rate interstitial brachytherapy in intermediate- and high-risk prostate cancer

Purpose

To present an alternative method for summing biologically effective doses of intensity-modulated arc therapy (IMAT) as teletherapy (TT), with interstitial high-dose-rate (HDR) brachytherapy (BT) boost in prostate cancer. Total doses using IMAT boost was compared with BT boost using our method.

Material and methods

Initially, 25 IMAT TT plus interstitial HDR-BT plans were included, and additional plans using IMAT TT boost were created. The prescribed dose was 2/44 Gy to the whole pelvis, 2/60 Gy to the prostate and seminal vesicles, and 1 × 10 Gy BT or 2/18 Gy IMAT TT to the prostate. Teletherapy computed tomography (CT) was registered with ultrasound (US) of BT, and the most exposed volume of critical organs in BT were identified on these CT images. The minimal dose of these from IMAT TT was summed with their BT dose, and these EQD₂ doses were compared using BT vs. IMAT TT boost. This method was compared with uniform dose conception (UDC).

Results

D₉₀ of the prostate was significantly higher with BT than with IMAT TT boost: 99.3 Gy vs. 77.9 Gy, p = 0.0034. The D₂ to rectum, bladder, and hips were 50.3 Gy vs. 76.8 Gy (p = 0.0117), 64.7 Gy vs. 78.3 Gy (p = 0.0117), and 41.9 Gy vs. 50.6 Gy (p = 0.0044), while D_0.1 to urethra was 96.1 Gy vs. 79.3 Gy (p = 0.0180), respectively. UDC overestimated D₂ (rectum) by 37% (p = 0.0117), D₂ (bladder) by 5% (p = 0.0214), and underestimated D_0.1 (urethra) by 1% (p = 0.0277).

Conclusions

Based on our biological dose summation method, the total dose of prostate is higher using BT boost than the IMAT. BT boost yields lower rectum, bladder, and hips doses, but higher dose to urethra. UDC overestimates rectum and bladder dose and underestimates the dose to urethra.

Comparison of Survival Between Hypofractionated and Conventional Radiotherapy in Clinically Localized Prostate Cancer: A Single-Center Retrospective Cohort

Background: Prostate cancer (pCa) is the most frequently diagnosed visceral cancer among men. The main role of radical prostatectomy and external-beam radiation therapy (EBRT) in the management of patients with localized pCa has been established. Objectives: This study aims at comparing the clinical outcomes of hypofractionated versus conventional EBRT in the definitive management of patients with localized pCa. Methods: From 2013 to 2019, a consecutive series of patients with localized pCa was treated with conventional (74 Gy at 2 Gy fractions) or hypofractionated (70.2 Gy at 2.7 Gy fractions) radiotherapy schedules, using 3-dimensional conformal radiation therapy (3D-CRT) and intensity-modulated radiation therapy (IMRT), respectively. The impact of the fractionation schedule on biochemical or clinical relapse-free survival (bc-RFS) and overall survival (OS) was assessed. Results: The median follow-up was 42 months (range: 8 - 81 months). Among 170 patients, 81 were treated with conventional and 89 with the hypofractionated schedule. The patient characteristics between groups were comparable. The mean bc-RFS of patients in conventional and hypofractionated groups was 34.9 and 35.4 months, respectively (confidence interval (CI) 95%: 34.5 - 35.7, P = 0.25). Accordingly, the mean OS of patients in conventional and hypofractionated groups was 34.6 and 38.6 months, respectively (CI 95%: 37.3 - 38.6, P = 0.04). The sub-analysis showed that the OS benefit of hypofractionated schedule was limited to intermediate- and high-risk groups with a trend toward significance (CI 95%: 0.02 - 1.46, P = 0.054). Conclusions: Hypofractionation had OS benefit over the conventional schedule for definitive radiotherapy of localized pCa. This benefit was limited to patients with intermediate- and high-risk pCa.

Diagnostic performance of a nomogram incorporating cribriform morphology for the prediction of adverse pathology in prostate cancer at radical prostatectomy

The aim of the present study was to develop a novel nomogram that incorporated clinical factors, imaging parameters and biopsy pathological factors (including cribriform morphology) to predict adverse pathology in prostate cancer (PCa). A total of 223 patients with PCa, who had undergone preoperative multi-parametric magnetic resonance imaging and had a biopsy of Gleason pattern (GP) 4, absence of GP 5 and pure Grade Group (GG) 3 [Gleason score (GS) 3+4, GS 4+3, GS 4+4], were retrospectively enrolled onto the study. The contribution of GG to the biopsy and Prostate Imaging Reporting and Data System (PI-RADS) score for PCa harboring adverse pathology were analyzed. Univariate and multivariate logistic regression analyses were performed to determine significant pathology predictors of adverse pathology for nomogram development. The nomogram was internally validated using bootstrapping with 1,000 iterations. The diagnostic performance of the nomogram was analyzed by receiver operating characteristics (ROC) analysis and decision curve analysis (DCA). A higher biopsy GG and PI-RADS score were associated with an increased likelihood of adverse pathology. Prostate specific antigen density (PSAD), biopsy GG, cribriform morphology on biopsy and PI-RADS score were significant predictors and were included in the nomogram. The ROC area under the curve of the nomogram was 0.88 (95% confidence interval, 0.84-0.91), with a high specificity (0.91) and moderate sensitivity (0.72). The novel nomogram was shown to have a higher net benefit for the prediction of adverse pathology in PCa, compared with any individual factors determined by DCA. Overall, a novel nomogram incorporating PSAD, PI-RADS score, biopsy GG and cribriform morphology on biopsy was shown to perform well in the prediction of PCa harboring adverse pathology at the time of radical prostatectomy.

J. Kotte AN, Bol GH, T. van den Berg CA. Clinical implementation of MRI-based organs-at-risk auto-segmentation with convolutional networks for prostate radiotherapy

BACKGROUND

Structure delineation is a necessary, yet time-consuming manual procedure in radiotherapy. Recently, convolutional neural networks have been proposed to speed-up and automatise this procedure, obtaining promising results. With the advent of magnetic resonance imaging (MRI)-guided radiotherapy, MR-based segmentation is becoming increasingly relevant. However, the majority of the studies investigated automatic contouring based on computed tomography (CT).

PURPOSE

In this study, we investigate the feasibility of clinical use of deep learning-based automatic OARs delineation on MRI.

MATERIALS AND METHODS

We included 150 patients diagnosed with prostate cancer who underwent MR-only radiotherapy. A three-dimensional (3D) T1-weighted dual spoiled gradient-recalled echo sequence was acquired with 3T MRI for the generation of the synthetic-CT. The first 48 patients were included in a feasibility study training two 3D convolutional networks called DeepMedic and dense V-net (dV-net) to segment bladder, rectum and femurs. A research version of an atlas-based software was considered for comparison. Dice similarity coefficient, 95% Hausdorff distances (HD95), and mean distances were calculated against clinical delineations. For eight patients, an expert RTT scored the quality of the contouring for all the three methods. A choice among the three approaches was made, and the chosen approach was retrained on 97 patients and implemented for automatic use in the clinical workflow. For the successive 53 patients, Dice, HD95 and mean distances were calculated against the clinically used delineations.

RESULTS

DeepMedic, dV-net and the atlas-based software generated contours in 60 s, 4 s and 10-15 min, respectively. Performances were higher for both the networks compared to the atlas-based software. The qualitative analysis demonstrated that delineation from DeepMedic required fewer adaptations, followed by dV-net and the atlas-based software. DeepMedic was clinically implemented. After retraining DeepMedic and testing on the successive patients, the performances slightly improved.

CONCLUSION

High conformality for OARs delineation was achieved with two in-house trained networks, obtaining a significant speed-up of the delineation procedure. Comparison of different approaches has been performed leading to the succesful adoption of one of the neural networks, DeepMedic, in the clinical workflow. DeepMedic maintained in a clinical setting the accuracy obtained in the feasibility study.

Template-based automation of treatment planning in advanced radiotherapy: a comprehensive dosimetric and clinical evaluation

Despite the recent advanced developments in radiation therapy planning, treatment planning for head-neck and pelvic cancers remains challenging due to large concave target volumes, multiple dose prescriptions and numerous organs at risk close to targets. Inter-institutional studies highlighted that plan quality strongly depends on planner experience and skills. Automated optimization of planning procedure may improve plan quality and best practice. We performed a comprehensive dosimetric and clinical evaluation of the Pinnacle3 AutoPlanning engine, comparing automatically generated plans (AP) with the historically clinically accepted manually-generated ones (MP). Thirty-six patients (12 for each of the following anatomical sites: head-neck, high-risk prostate and endometrial cancer) were re-planned with the AutoPlanning engine. Planning and optimization workflow was developed to automatically generate "dual-arc" VMAT plans with simultaneously integrated boost. Various dose and dose-volume parameters were used to build three metrics able to supply a global Plan Quality Index evaluation in terms of dose conformity indexes, targets coverage and sparing of critical organs. All plans were scored in a blinded clinical evaluation by two senior radiation oncologists. Dose accuracy was validated using the PTW Octavius-4D phantom together with the 1500 2D-array. Autoplanning was able to produce high-quality clinically acceptable plans in all cases. The main benefit of Autoplanning strategy was the improvement of overall treatment quality due to significant increased dose conformity and reduction of integral dose by 6-10%, keeping similar targets coverage. Overall planning time was reduced to 60-80 minutes, about a third of time needed for manual planning. In 94% of clinical evaluations, the AP plans scored equal or better to MP plans. Despite the increased fluence modulation, dose measurements reported an optimal agreement with dose calculations with a γ-pass-rate greater than 95% for 3%(global)-2 mm criteria. Autoplanning engine is an effective device enabling the generation of VMAT high quality treatment plans according to institutional specific planning protocols.

Efficacy of a hydrogel spacer in three-dimensional conformal radiation therapy for prostate cancer

Objectives

We aimed to compare the dose constraints fulfillment rate of the three-dimensional conformal radiotherapy treatment plan before and after a hydrogel spacer insertion.

Methods

The planning computed tomography scans of 39 patients who received stereotactic body radiotherapy for prostate cancer were used. All patients inserted a hydrogel spacer and underwent computed tomography scans before and after spacer insertion. The three-dimensional conformal radiotherapy plans according to NCCN classification, low-, intermediate- and high-risk, were made for each patient. Clinical target volume included prostate and seminal vesicle 2 cm for high risk, prostate and seminal vesicle 1 cm for intermediate risk and prostate only for low risk. Three-dimensional conformal radiotherapy including a seven-field conformal technique with 76 Gy in 38 fractions. Dose constraints for rectum and bladder were V70 Gy ≤ 15%, V65 Gy ≤ 30% and V40 Gy ≤ 60%.

Results

Among 39 patients, 35 (90%), 19 (49%) and 13 (33%) and 38 (97%), 38 (97%) and 34 (87%) patients before and after the spacer insertion fulfilled rectum dose constraints for low-, intermediate- and high-risk plans, respectively. A hydrogel spacer significantly reduced rectum dose and improved the rectum dose constraints fulfillment rate in intermediate (P &lt; 0.01) and high (P &lt; 0.01), but no difference was found in low-risk plan (P = 0.25). On multivariate analysis, spacer use was associated with the higher rectum dose constraints fulfillment rate.

Conclusions

A hydrogel spacer reduced rectum dose and improved the dose constraints fulfillment rate in three-dimensional conformal radiotherapy plan. Although IMRT is the standard treatment, 3D-CRT using a hydrogel spacer may be a treatment option.

Dosimetric Impact of Interfractional Variations in Prostate Cancer Radiotherapy-Implications for Imaging Frequency and Treatment Adaptation

Background and purpose: To analyze deviations of the applied from the planned doses on a voxel-by-voxel basis for definitive prostate cancer radiotherapy depending on anatomic variations and imaging frequency.

Materials and methods: Daily in-room CT imaging was performed in treatment position for 10 patients with prostate cancer undergoing intensity-modulated radiotherapy (340 fraction CTs). Applied fraction doses were recalculated on daily images, and voxel-wise dose accumulation was performed using a deformable registration algorithm. For weekly imaging, weekly position correction vectors were derived and used to rigidly register daily scans of that week to the planning CT scan prior to dose accumulation. Applied and prescribed doses were compared in dependence of the imaging frequency, and derived TCP and NTCP values were calculated.

Results: Daily CT-based repositioning resulted in non-significant deviations of all analyzed dose-volume, conformity and uniformity parameters to the CTV, bladder and rectum irrespective of anatomic changes. Derived average TCP values were comparable, and NTCP values for the applied doses to the bladder and rectum did not significantly deviate from the planned values. For weekly imaging, the applied D₂ to the CTV, rectum and bladder significantly varied from the planned doses, and the CTV conformity index and D₉₈ decreased. While TCP values were comparable, the NTCP for the bladder erroneously appeared reduced for weekly repositioning.

Conclusions: Based on daily diagnostic quality CT imaging and voxel-wise dose accumulation, we demonstrated for the first time that daily, but not weekly imaging resulted in only negligible deviations of the applied from the planned doses for prostate intensity-modulated radiotherapy. Therefore, weekly imaging may not be adequately reliable for adaptive treatment delivery techniques for prostate. This work will contribute to devising adaptive re-planning strategies for prostate radiotherapy.

A treatment planning study comparing IMRT techniques and cyber knife for stereotactic body radiotherapy of low-risk prostate carcinoma

Purpose

Comparing radiation treatment plans by using the same safety margins and dose objectives for all techniques, to ascertain the optimal radiation technique for the stereotactic body radiotherapy (SBRT) of low-risk prostate cancer.

Material and methods

Treatment plans for 27 randomly selected patients were compared using intensity-modulated (IMRT) techniques as Sliding Window (SW), volumetric modulated arc therapy (VMAT), and helical tomotherapy (HT), as well as Cyber Knife (CK) system. The target dose was calculated to 36.25 Gy delivered in five fractions over 1 week. Dosimetric indices for target volume and organs at risk (OAR) as well as normal tissue complication probability (NTCP) of late rectal and urinary bladder toxicities were analyzed.

Results

The CK provided lower homogeneity in the target volume, but higher values for most of the conformity indices compared to the IMRT approaches. The SW demonstrated superior rectum sparing at medium-to-high dose range (V18 Gy - V32.6 Gy) compared to other techniques (p < 0.05). The whole urinary bladder experienced the best shielding by SW and VMAT at the medium dose (V18 Gy, p < 0.05 versus CK), however we obtained no relevant differences between techniques at the high dose. Generally, the CK demonstrated significantly superior rectum and bladder exposure at V18 Gy as compared to HT, SW, and VMAT. For the rectum, mean NTCP values were significantly superior for HT (NTCP = 2.3%, p < 0.05), and for urinary bladder, the NTCP showed no significant advantages for any technique.

Conclusion

No absolute dosimetric advantage was revealed to choose between CK or IMRT techniques for the SBRT of low-grade prostate cancer. Using the same safety margins and dose objectives, IMRT techniques demonstrated superior sparing of the rectum and bladder at a medium dose compared to CK. Comparing different IMRT approaches SW displayed superior rectum sparing at a medium-to-high dose range, whereas both SW and RA revealed superior bladder sparing compared to HT. HT demonstrated a significantly lower NTCP outcome compared to CK or IMRT techniques regarding the rectum. Radiation plans can be optimized further by an individual modification of dose objectives independent of the treatment plan strategy.

Electronic supplementary material

The online version of this article (10.1186/s13014-019-1353-6) contains supplementary material, which is available to authorized users.

Robust contour propagation using deep learning and image registration for online adaptive proton therapy of prostate cancer

Purpose

To develop and validate a robust and accurate registration pipeline for automatic contour propagation for online adaptive Intensity‐Modulated Proton Therapy (IMPT) of prostate cancer using elastix software and deep learning.

Methods

A three‐dimensional (3D) Convolutional Neural Network was trained for automatic bladder segmentation of the computed tomography (CT) scans. The automatic bladder segmentation alongside the computed tomography (CT) scan is jointly optimized to add explicit knowledge about the underlying anatomy to the registration algorithm. We included three datasets from different institutes and CT manufacturers. The first was used for training and testing the ConvNet, where the second and the third were used for evaluation of the proposed pipeline. The system performance was quantified geometrically using the dice similarity coefficient (DSC), the mean surface distance (MSD), and the 95% Hausdorff distance (HD). The propagated contours were validated clinically through generating the associated IMPT plans and compare it with the IMPT plans based on the manual delineations. Propagated contours were considered clinically acceptable if their treatment plans met the dosimetric coverage constraints on the manual contours.

Results

The bladder segmentation network achieved a DSC of 88% and 82% on the test datasets. The proposed registration pipeline achieved a MSD of 1.29 ± 0.39, 1.48 ± 1.16, and 1.49 ± 0.44 mm for the prostate, seminal vesicles, and lymph nodes, respectively, on the second dataset and a MSD of 2.31 ± 1.92 and 1.76 ± 1.39 mm for the prostate and seminal vesicles on the third dataset. The automatically propagated contours met the dose coverage constraints in 86%, 91%, and 99% of the cases for the prostate, seminal vesicles, and lymph nodes, respectively. A Conservative Success Rate (CSR) of 80% was obtained, compared to 65% when only using intensity‐based registration.

Conclusion

The proposed registration pipeline obtained highly promising results for generating treatment plans adapted to the daily anatomy. With 80% of the automatically generated treatment plans directly usable without manual correction, a substantial improvement in system robustness was reached compared to a previous approach. The proposed method therefore facilitates more precise proton therapy of prostate cancer, potentially leading to fewer treatment‐related adverse side effects.

Multiparametric MRI - local staging of prostate cancer and beyond

Background Accurate local staging is critical for treatment planning and prognosis in patients with prostate cancer (PCa). The primary aim is to differentiate between organ-confined and locally advanced disease with the latter carrying a worse clinical prognosis. Multiparametric MRI (mpMRI) is the imaging modality of choice for the local staging of PCa and has an incremental value in assessing pelvic nodal disease and bone involvement. It has shown superior performance compared to traditional staging based on clinical nomograms, and provides additional information on the site and extent of disease. MRI has a high specificity for diagnosing extracapsular extension (ECE), seminal vesicle invasion (SVI) and lymph node (LN) metastases, however, sensitivity remains poor. As a result, extended pelvic LN dissection remains the gold standard for assessing pelvic nodal involvement, and there has been recent progress in developing advanced imaging techniques for more distal staging. Conclusions T2W-weighted imaging is the cornerstone for local staging of PCa. Imaging at 3T and incorporating both diffusion weighted and dynamic contrast enhanced imaging can further increase accuracy. "Next generation" imaging including whole body MRI and PET-MRI imaging using prostate specific membrane antigen (68Ga-PSMA), has shown promising for assessment of LN and bone involvement as compared to the traditional work-up using bone scintigraphy and body CT.

Definition of fields margins for the optimized 2D radiotherapy of prostate carcinoma

Prostate cancer (PCa) is one of the most common malignancies in men both in western and developing countries. Radiotherapy (RT) is an important therapeutic option. New technologies (including 3D, intensity modulated RT, image-guided RT and, volumetric modulated arc therapy) have been introduced in the last few decades with progressive improvement of clinical outcomes. However, in many developing countries, the only treatment option is the traditional two-dimensional (2D) technique based on standard simulation. The guidelines for 2D field definition are still based on expert's opinions. The aim of the present study was to propose new practical guidelines for 2D fields definition based on 3D simulation in PCa. A total of 20 patients were enrolled. Computed tomography-simulation and pelvic magnetic resonance images were merged to define the prostate volumes. Clinical Target Volume (CTV) was defined using the European Organisation for Research and Treatment of Cancer guidelines in consideration of the four risk categories: Low, intermediate, and high risk with or without seminal vesicles involvement, respectively. Planning Target Volume (PTV) was defined by adding 10 mm to the CTV. For each category, two treatment plans were calculated using a cobalt source or 10 MV photons. Progressive optimization was achieved by evaluating 3D dose distribution. Finally, the optimal distances between field margins and radiological landmarks (bones and rectum with contrast medium) were defined. The results were reported in tabular form. Both field margins (PTV D_98% >95%) needed to adequately irradiate all patients and to achieve a similar result in 95% of the enrolled patients are reported. Using a group of patients with PCa and based on a 3D planning analysis, we propose new practical guidelines for PCa 2D-RT based on current criteria for risk category and CTV, and PTV definition.

Real-time adaptive planning method for radiotherapy treatment delivery for prostate cancer patients, based on a library of plans accounting for possible anatomy configuration changes

BACKGROUND AND PURPOSE

In prostate cancer treatment with external beam radiation therapy (EBRT), prostate motion and internal changes in tissue distribution can lead to a decrease in plan quality. In most currently used planning methods, the uncertainties due to prostate motion are compensated by irradiating a larger treatment volume. However, this could cause underdosage of the treatment volume and overdosage of the organs at risk (OARs). To reduce this problem, in this proof of principle study we developed and evaluated a novel adaptive planning method. The strategy proposed corrects the dose delivered by each beam according to the actual position of the target in order to produce a final dose distribution dosimetrically as similar as possible to the prescribed one.

MATERIAL AND METHODS

Our adaptive planning method was tested on a phantom case and on a clinical case. For the first, a pilot study was performed on an in-silico pelvic phantom. A "library" of intensity modulated RT (IMRT) plans corresponding to possible positions of the prostate during a treatment fraction was generated at planning stage. Then a 3D random walk model was used to simulate possible displacements of the prostate during the treatment fraction. At treatment stage, at the end of each beam, based on the current position of the target, the beam from the library of plans, which could reproduce the best approximation of the prescribed dose distribution, was selected and delivered. In the clinical case, the same approach was used on two prostate cancer patients: for the first a tissue deformation was simulated in-silico and for the second a cone beam CT (CBCT) taken during the treatment was used to simulate an intra-fraction change. Then, dosimetric comparisons with the standard treatment plan and, for the second patient, also with an isocenter shift correction, were performed.

RESULTS

For the phantom case, the plan generated using the adaptive planning method was able to meet all the dosimetric requirements and to correct for a misdosage of 13% of the dose prescription on the prostate. For the first clinical case, the standard planning method caused underdosage of the seminal vesicles, respectively by 5% and 4% of the prescribed dose, when the position changes for the target were correctly taken into account. The proposed adaptive planning method corrected any possible missed target coverage, reducing at the same time the dose on the OARs. For the second clinical case, both with the standard planning strategy and with the isocenter shift correction target coverage was significantly worsened (in particular uniformity) and some organs exceeded some toxicity objectives. While with our approach, the most uniform coverage for the target was produced and systematically the lowest toxicity values for the organs at risk were achieved.

CONCLUSIONS

In our proof of principle study, the adaptive planning method performed better than the standard planning and the isocenter shift methods for prostate EBRT. It improved the coverage of the treatment volumes and lowered the dose to the OARs. This planning method is particularly promising for hypofractionated IMRT treatments in which a higher precision and control on dose deposition are needed. Further studies will be performed to test more extensively the proposed adaptive planning method and to evaluate it at a full clinical level.

Comparison of volumetric-modulated arc therapy and intensity-modulated radiation therapy prostate cancer plans accounting for cold spots

This study compared dosimetric indices of volumetric-modulated arc therapy (VMAT) with intensity-modulated radiation therapy (IMRT) accounting for cold spots in prostate cancer plans. IMRT plans were retrospectively generated from 30 prostate cancer patients with ten cases for each risk group, who received VMAT plans. The mean, maximum, and minimum doses, and conformity and homogeneity indexes were evaluated for planning target volume (PTV) and the mean dose and V20-V70 for organs at risk (OAR) including the rectum, bladder, right and left femoral heads, and rectum overlapped with PTV (ROP) regions. The numbers and volume percentages of cold spots within PTVs and ROP regions were measured using in-house software. Three-dimensional probabilistic distributions of the probability and distributions of cold spots were generated using a centroid matching technique for visualization and analysis. There was a statistically better dose conformity in the PTV, rectum, and bladder dose-sparing in VMAT compared to that in the IMRT plans, whereas VMAT had statistically worse target dose homogeneity, and right and left femoral head dose-sparing than those of the IMRT plans. The average volume percentage of cold spots per PTV for the VMAT was 4.37 ± 2.68%, which was smaller than the 5.72 ± 1.84% observed for IMRT plans (P = 0.007). The volume percentage of cold spots per ROP for the VMAT did not significantly differ from those for the IMRT plans. Compared with IMRT, the VMAT plans achieved better PTV dose conformity, OAR dose-sparing, and smaller cold spots in the treatment of prostate cancer.

ESTRO ACROP consensus guideline on CT- and MRI-based target volume delineation for primary radiation therapy of localized prostate cancer

BACKGROUND AND PURPOSE

Delineation of clinical target volumes (CTVs) remains a weak link in radiation therapy (RT), and large inter-observer variation is seen. Guidelines for target and organs at risk delineation for prostate cancer in the primary setting are scarce. The aim was to develop a delineation guideline obtained by consensus between a broad European group of radiation oncologists.

MATERIAL AND METHODS

An ESTRO contouring consensus panel consisting of leading radiation oncologists and one radiologist with known subspecialty expertise in prostate cancer was asked to delineate the prostate, seminal vesicles and rectum on co-registered CT and MRI scans. After evaluation of the different contours, literature review and multiple informal discussions by electronic mail a CTV definition was defined and a guide for contouring the CTV of the prostate and the rectum was developed.

RESULTS

The panel achieved consensus CTV contouring definitions to be used as guideline for primary RT of localized prostate cancer.

CONCLUSION

The ESTRO consensus on CT/MRI based CTV delineation for primary RT of localized prostate cancer, endorsed by a broad base of the radiation oncology community, is presented to improve consistency and reliability.

How Histopathologic Tumor Extent and Patterns of Recurrence Data Inform the Development of Radiation Therapy Treatment Volumes in Solid Malignancies

The ability to deliver highly conformal radiation therapy using intensity-modulated radiation therapy and particle therapy provides for new opportunities to improve patient outcomes by reducing treatment-related morbidities following radiation therapy. By reducing the volume of normal tissue exposed to radiation therapy (RT), while also allowing for the opportunity to escalate the dose of RT delivered to the tumor, use of conformal RT delivery should also provide the possibility of expanding the therapeutic index of radiotherapy. However, the ability to safely and confidently deliver conformal RT is largely dependent on our ability to clearly define the clinical target volume for radiation therapy, which requires an in-depth knowledge of histopathologic extent of different tumor types, as well as patterns of recurrence data. In this article, we provide a comprehensive review of the histopathologic and radiographic data that provide the basis for evidence-based guidelines for clinical tumor volume delineation.

Added Value of Multiparametric Magnetic Resonance Imaging to Clinical Nomograms for Predicting Adverse Pathology in Prostate Cancer

PURPOSE

We examined the additional value of preoperative prostate multiparametric magnetic resonance imaging and transrectal ultrasound/multiparametric magnetic resonance imaging fusion guided targeted biopsy when performed in combination with clinical nomograms to predict adverse pathology at radical prostatectomy.

MATERIALS AND METHODS

We identified all patients who underwent 3 Tesla multiparametric magnetic resonance imaging prior to fusion biopsy and radical prostatectomy. The Partin and the MSKCC (Memorial Sloan Kettering Cancer Center) preradical prostatectomy nomograms were applied to estimate the probability of organ confined disease, extraprostatic extension, seminal vesicle invasion and lymph node involvement using transrectal ultrasound guided systematic biopsy and transrectal ultrasound/multiparametric magnetic resonance imaging fusion guided targeted biopsy Gleason scores. With radical prostatectomy pathology as the gold standard we developed multivariable logistic regression models based on these nomograms before and after adding multiparametric magnetic resonance imaging to assess any additional predictive ability.

RESULTS

A total of 532 patients were included in study. When multiparametric magnetic resonance imaging findings were added to the systematic biopsy based MSKCC nomogram, the AUC increased by 0.10 for organ confined disease (p <0.001), 0.10 for extraprostatic extension (p = 0.003), 0.09 for seminal vesicle invasion (p = 0.011) and 0.06 for lymph node involvement (p = 0.120). Using Gleason scores derived from targeted biopsy compared to systematic biopsy provided an additional predictive value of organ confined disease (Δ AUC 0.07, p = 0.003) and extraprostatic extension (Δ AUC 0.07, p = 0.048) at radical prostatectomy with the MSKCC nomogram. Similar results were obtained using the Partin nomogram.

CONCLUSIONS

Magnetic resonance imaging alone or in addition to standard clinical nomograms provides significant additional predictive ability of adverse pathology at the time of radical prostatectomy. This information can be greatly beneficial to urologists for preoperative planning and for counseling patients regarding the risks of future therapy.

Dosimetric effect of limited aperture multileaf collimator on VMAT plan quality: A study of prostate and head-and-neck cancers

AIM

The aim of study was to evaluate the dosimetric effect of collimator-rotation on VMAT plan quality, when using limited aperture multileaf collimator of Elekta Beam Modulator™ providing a maximum aperture of 21 cm × 16 cm.

BACKGROUND

The increased use of VMAT technique to deliver IMRT from conventional to very specialized treatments present a challenge in plan optimization. In this study VMAT plans were optimized for prostate and head and neck cancers using Elekta Beam-Modulator^TM, whereas previous studies were reported for conventional Linac aperture.

MATERIALS AND METHODS

VMAT plans for nine of each prostate and head-and-neck cancer patients were produced using the 6 MV photon beam for Elekta-SynergyS^® Linac using Pinnacle³ treatment planning system. Single arc, dual arc and two combined independent-single arcs were optimized for collimator angles (C) 0°, 90° and 0°-90° (0°-90°; i.e. the first-arc was assigned C0° and second-arc was assigned C90°). A treatment plan comparison was performed among C0°, C90° and C(0°-90°) for single-arc dual-arc and two independent-single-arcs VMAT techniques to evaluate the influence of extreme collimator rotations (C0° and 90°) on VMAT plan quality. Plan evaluation criteria included the target coverage, conformity index, homogeneity index and doses to organs at risk. A 'two-sided student t-test' (p ≤ 0.05) was used to determine if there was a significant difference in dose volume indices of plans.

RESULTS

For both prostate and head-and-neck, plan quality at collimator angles C0° and C(0°-90°) was clinically acceptable for all VMAT-techniques, except SA for head-and-neck. Poorer target coverage, higher normal tissue doses and significant p-values were observed for collimator angle 90° when compared with C0° and C(0°-90°).

CONCLUSIONS

A collimator rotation of 0° provided significantly better target coverage and sparing of organs-at-risk than a collimator rotation of 90° for all VMAT techniques.

Dual-timing PSA as a biomarker for patients with salvage intensity modulated radiation therapy for biochemical failure after radical prostatectomy

We investigated the outcomes and the associated clinical-pathological factors in patients with prostate cancer (PCa) undergoing salvage intensity modulated radiation therapy (IMRT) for post-radical-prostatectomy (RP) biochemical failure. We report clinical outcomes of post-RP salvage IMRT, and describe chronic toxicity in these patients.Fifty patients with PCa underwent post-RP salvage IMRT. The median dose of IMRT was 70 Gy to the prostatic and seminal vesicle bed. Clinical-pathological and toxicity information were collected. The prostate cancer-specific survival (PCSS), disease-free survival (DFS), and biochemical-failure-free survival (BFFS) were calculated. Prognostic factors were analyzed for their association with disease control.The median follow-up time was 74 months. The 5-year PCSS, DFS, and BFFS after salvage IMRT were 95%, 88%, and 60%, respectively. Two patients (4%) experienced late gastrointestinal toxicity ≥ grade 3, and 5 patients (10%) had late genitourinary toxicity ≥ grade 3. On multivariate analysis, post-RP prostate-specific antigen (PSA) nadir ≤0.1 ng/ml (P=0.018) and PSA ≤0.5 ng/ml at salvage IMRT (P=0.016) were independent factors predicting better BFFS. Patients with both post-RP PSA nadir ≤0.1 ng/ml and PSA ≤0.5 ng/ml at salvage IMRT had a 5-year BFFS of 83% as compared with 43% in other patients (P=0.001).In conclusion, with hormonal therapy in most PCa patients, the addition of salvage IMRT for post-RP biochemical failure can achieve a good outcome with low toxicity. Patients with a post-RP PSA nadir ≤0.1 ng/ml and PSA ≤0.5 ng/ml at salvage IMRT could benefit the most from salvage IMRT.

High-Dose 3D-CRT in the Radical and Postoperative Setting for Prostate Cancer. Analysis of Survival and Late Rectal and Urinary Toxicity

Purpose

The aim of the study was to retrospectively compare outcome and complications of prostate cancer patients treated with a curative and postoperative intent using a pretreatment defined NCCN classification.

Material and methods

A total of 103 patients was treated curatively (RAD) and 94 postoperatively (POST-OP). The mean age was higher in the RAD group (72.6 years; range, 56.4–85.1) than in the POST-OP group (65.4 years; range, 43.9–77) (P <0.0001). According to the NCCN prognostic classification, 13 (12%) patients were at low risk, 48 (47%) at intermediate risk and 42 (41%) at high risk in the RAD group. In the POST-OP group, 13 (14%) patients were low risk, 37 (40%) at intermediate risk and 44 (46%) at high risk. Hormone therapy was used in 98 patients (95%) in the RAD group and 45 patients (47.8%) in the POST-OP group. Patients were treated with three-dimensional conformal radiotherapy. The prescription dose was 80 Gy in 2-Gy fractions in the RAD group and 70 Gy in 2-Gy fractions in the POST-OP.

Results

No biochemical, clinical relapse was found in low-risk patients in the RAD group and 1 relapse was found in the POST-OP group. The largest number of relapses occurred (39%) and (33%) in intermediate-high risk in RAD and POST-OP groups, respectively. In the cause-specific survival analysis, no significant differences were found in the high-risk group between RAD and POST-OP groups (P = 0.9). In the analysis of 5-year biochemical relapse-free survival, no significant differences were found in the high-risk group between RAD and POST-OP groups (P = 0.1020).

Conclusions

Radiotherapy in the RAD low-risk group was an excellent treatment. RAD and POST-OP radiotherapy were well tolerated with very low toxicity. The cause-specific survival at 5 years was 95% and 97% for the two treatment groups, RAD and POST-OP, respectively (logrank test, P = 0.2908).

Seminal vesicle invasion on multi-parametric magnetic resonance imaging: Correlation with histopathology

OBJECTIVES

The pre-treatment risk of seminal vesicle (SV) invasion (SVI) from prostate cancer is currently based on nomograms which include clinical stage (cT), Gleason score (GS) and prostate-specific antigen (PSA). The aim of our study was to evaluate the staging accuracy of 3T (3T) multi-parametric (mp) Magnetic Resonance Imaging (MRI) by comparing the imaging report of SVI with the tissue histopathology. The additional value in the existing prediction models and the role of radiologists' experience were also examined.

METHODS

After obtaining institutional review board approval, we retrospectively reviewed clinico-pathological data from 527 patients who underwent a robot-assisted radical prostatectomy (RARP) between January 2012 and March 2015. Preoperative prostate imaging with an endorectal 3T-mp-MRI was performed in all patients. Sequences consisted of an axial pre-contrast T1 sequence, three orthogonally-oriented T2 sequences, axial diffusion weighted and dynamic contrast-enhanced sequences. We considered SVI in case of low-signal intensity in the SV on T2-weighted sequences or apparent mass while diffusion-weighted and DCE sequences were used to confirm findings on T2. Whole-mount section pathology was performed in all patients. The sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of MRI (index test) for the prediction of histological SVI (reference standard) were calculated. We developed logistic multivariable regression models including: clinical variables (PSA, cT, percentage of involved cores/total cores, primary GS 4-5) and Partin table estimates. MRI results (negative/positive exam) were then added in the models and the multivariate modeling was reassessed. In order to assess the extent of SVI and the reason for mismatch with pathology an MRI-review from an expert genitourinary radiologist was performed in a subgroup of 379 patients.

RESULTS

A total of 54 patients (10%) were found to have SVI on RARP-histopathology. In the overall cohort sensitivity, specificity, PPV and NPV for SVI detection on MRI were 75.9%, 94.7%, 62% and 97% respectively. Based on our sub-analysis, the radiologist's expertise improved the accuracy demonstrating a sensitivity, specificity, PPV and NPV of 85.4%, 95.6%, 70.0% and 98.2%, respectively. In the multivariate analysis PSA (odds ratio [OR] 1.07, p=0.008), primary GS 4 or 5 (OR 3.671, p=0.007) and Partin estimates (OR 1.07, p=0.023) were significant predictors of SVI. When MRI results were added to the analysis, a highly significant prediction of SVI was observed (OR 45.9, p<0.0001). Comparing Partin, MRI and Partin with MRI predictive models, the areas under the curve were 0.837, 0.884 and 0.929, respectively.

CONCLUSIONS

MRI had high diagnostic accuracy for SVI on histopathology. It provided added diagnostic value to clinical/Partin based SVI-prediction models alone. A key factor is radiologist's experience, though no inter-observer variability could be examined due to the availability of a single expert radiologist.

Intraprostatic Fiducials Compared with Bony Anatomy and Skin Marks for Image-Guided Radiation Therapy of Prostate Cancer

Purpose

Prostate motion occurs during radiotherapy for localized prostate cancer. We evaluated the input of intraprostatic fiducials for image-guided radiation therapy and compared it with bony anatomy and skin marks.

Methods

Eleven patients were implanted with three fiducial markers in the prostate. Daily sets of orthogonal kV-kV images were compared with digitally reconstructed radiography. Data were recorded for skin marks, bony anatomy, and fiducial markers. The variations were analyzed along three principal axes (left-right: LR, superoinferior: SI, and anteroposterior: AP).

Results

A total of 2,417 measures were recorded over 38 fractions of radiotherapy (76 Gy). Fiducial marker movements from bony anatomy were ≤ 5 mm for 84.2% (confidence interval: CI 95%±1.5), 91.3% (CI 95%±1.1), and 99.5% (CI 95%±0.4) of the measures along the AP, SI, and LR axes, respectively. Ninety-five percent of the shifts between a fiducial marker and the bony anatomy were < 8 mm in the AP and SI axes, and < 3 mm in the LR axis. Fiducial marker movements from skin marks were ≤ 5 mm for 64.8% (CI 95%±1.9), 79.2% (CI 95%±1.6), and 87.2% (CI 95%±1.3) of the measures along the AP, SI, and LR axes, respectively. Bony anatomy movements from skin marks were ≤ 5 mm for 84% (CI 95%±1.4), 92% (CI 95%±1.1), and 87% (CI 95%±1.3) of the measurements along the AP, SI, and LR axes, respectively.

Conclusion

Using fiducial markers provides better accuracy of repositioning of the prostate than using bony anatomy and skin marks for image-guided radiotherapy of prostate cancer.

Volumetric-modulated arc therapy and intensity-modulated radiation therapy treatment planning for prostate cancer with flattened beam and flattening filter free linear accelerators

This study on patients with localized prostate cancer was set up to investigate valuable differences using flattened beam (FB) and flattening filter free (FFF) mode in the application of intensity-modulated radiotherapy (IMRT) and volumetric-modulated arc therapy (VMAT). For ten patients, four different plans were calculated with Oncentra planning system of Elekta, using Synergy machines: IMRT and VMAT, with and without flattening filter. Homogeneity and conformity indexes, dose to the organs at risk, and measurements of peripheral dose and dosimetric plan verification including record of the delivery times were analyzed and statistically evaluated. The indexes for homogeneity and conformity (CTV and PTV) are either advantageous or not significantly different for FFF compared to FB with one minor exception. Regarding the doses to the organs at risk and the measured peripheral dose, equivalent or lower doses were delivered for FFF than with FB. Furthermore, the delivery times were significantly shorter for FFF. VMAT compared to IMRT reveals benefits or at least equivalent values. VMAT-FFF combines the most advantageous plan quality parameters with the shortest delivery times and reduced peripheral dose and is therefore recommended for the given equipment and cancer localization.

Validation of the relative insensitivity of volumetric-modulated arc therapy (VMAT) plan quality to gantry space resolution

Volumetric-modulated arc therapy (VMAT) is an efficient form of radiotherapy used to deliver intensity-modulated radiotherapy beams. The aim of this study was to investigate the relative insensitivity of VMAT plan quality to gantry angle spacing (GS). Most previous VMAT planning and dosimetric work for GS resolution has been conducted for single arc VMAT. In this work, a quantitative comparison of dose-volume indices (DIs) was made for partial-, single- and double-arc VMAT plans optimized at 2°, 3° and 4° GS, representing a large variation in deliverable multileaf collimator segments. VMAT plans of six prostate cancer and six head-and-neck cancer patients were simulated for an Elekta SynergyS® Linac (Elekta Ltd, Crawley, UK), using the SmartArc™ module of Pinnacle³ TPS, (version 9.2, Philips Healthcare). All optimization techniques generated clinically acceptable VMAT plans, except for the single-arc for the head-and-neck cancer patients. Plan quality was assessed by comparing the DIs for the planning target volume, organs at risk and normal tissue. A GS of 2°, with finest resolution and consequently highest intensity modulation, was considered to be the reference, and this was compared with GS 3° and 4°. The differences between the majority of reference DIs and compared DIs were <2%. The metrics, such as treatment plan optimization time and pretreatment (phantom) dosimetric calculation time, supported the use of a GS of 4°. The ArcCHECK™ phantom-measured dosimetric agreement verifications resulted in a >95.0% passing rate, using the criteria for γ (3%, 3 mm). In conclusion, a GS of 4° is an optimal choice for minimal usage of planning resources without compromise of plan quality.

Cancer-Specific Mortality Among Korean Men with Localized or Locally Advanced Prostate Cancer Treated with Radical Prostatectomy Versus Radiotherapy: A Multi-Center Study Using Propensity Scoring and Competing Risk Regression Analyses

Purpose

Studies comparing radical prostatectomy (RP) outcomes with those of radiotherapy with or without androgen deprivation therapy (RT±ADT) for prostate cancer (PCa) have yielded conflicting results. Therefore, we used propensity score-matched analysis and competing risk regression analysis to compare cancer-specific mortality (CSM) and other-cause mortality (OCM) between these two treatments.

Materials and Methods

The multi-center, Severance Urological Oncology Group registry was utilized to identify 3,028 patients with clinically localized or locally advanced PCa treated by RP (n=2,521) or RT±ADT (n=507) between 2000 and 2016. RT±ADT cases (n=339) were matched with an equal number of RP cases by propensity scoring based on age, preoperative prostate-specific antigen, clinical tumor stage, biopsy Gleason score, and Charlson Comorbidity Index (CCI). CSM and OCM were co-primary endpoints.

Results

Median follow-up was 65.0 months. Five-year overall survival rates for patients treated with RP and RT±ADT were 94.7% and 92.0%, respectively (p=0.105). Cumulative incidence estimates revealed comparable CSM rates following both treatments within all National Comprehensive Cancer Network risk groups. Gleason score ≥ 8 was associated with higher risk of CSM (p=0.009). OCM rates were comparable between both groups in the low- and intermediate-risk categories (p=0.354 and p=0.643, respectively). For high-risk patients, RT±ADT resulted in higher OCM rates than RP (p=0.011). Predictors of OCM were age ≥ 75 years (p=0.002) and CCI ≥ 2 (p < 0.001).

Conclusion

RP and RT±ADT provide comparable CSM outcomes in patients with localized or locally advanced PCa. The risk of OCM may be higher for older high-risk patients with significant comorbidities.

Prostate magnetic resonance imaging for brachytherapists: Diagnosis, imaging pitfalls, and post-therapy assessment

Optimal integration of multiparametric MRI (mp MRI) into prostate brachytherapy practice necessitates an understanding of imaging findings pertinent to prostate cancer detection and staging. This review will summarize prostate cancer imaging findings and tumor staging on mp MRI, including an overview of the Prostate Imaging Reporting and Data System (PIRADS)-structured reporting schema, mp MRI findings observed in the post-therapy setting including cases of post-treatment recurrence, and MRI concepts integral to successful salvage brachytherapy.

Harmonization of the Volume of Interest Delineation among All Eleven Radiotherapy Centers in the North of France

Background

Inter-observer delineation variation has been detailed for many years in almost every tumor location. Inadequate delineation can impair the chance of cure and/or increase toxicity. The aim of our original work was to prospectively improve the homogeneity of delineation among all of the senior radiation oncologists in the Nord-Pas de Calais region, irrespective of the conditions of practice.

Methods

All 11 centers were involved. The first studied cancer was prostate cancer. Three clinical cases were studied: a low-risk prostate cancer case (case 1), a high-risk prostate cancer case (pelvic nodes, case 2) and a case of post-operative biochemical elevated PSA (case 3). All of the involved physicians delineated characteristically the clinical target volume (CTV) and organs at risk. The volumes were compared using validated indexes: the volume ratio (VR), common and additional volumes (CV and AV), volume overlap (VO) and Dice similarity coefficient (DSC). A second delineation of the same three cases was performed after discussion of the slice results and the choice of shared guidelines to evaluate homogenization. A comparative analysis of the indexes before and after discussion was conducted using the Wilcoxon test for paired samples. A p-value less than 0.05 was considered to indicate statistical significance.

Results

The indexes were not improved in case 1, for which the inter-observer agreement was considered good after the first comparison (DSC = 0.83±0.06). In case 2, the second comparison showed homogenization of the CTV delineation with a significant improvement in CV (81.4±11.7 vs. 88.6±10.26, respectively, p = 0.048), VO (0.41±0.09 vs. 0.47±0.07, respectively; p = 0.009) and DSC (0.58±0.09 vs. 0.63±0.07, respectively; p = 0.0098). In case 3, VR and AV were significantly improved: VR: 1.71(±0.6) vs. 1.34(±0.46), respectively, p = 0.0034; AV: 46.58(±14.50) vs. 38.08(±15.10), respectively, p = 0.0024. DSC was not improved, but it was already superior to 0.6 in the first comparison.

Conclusion

Our prospective work showed that a collaborative discussion about clinical cases and the choice of shared guidelines within an established framework improved the homogeneity of CTV delineation among the senior radiation oncologists in our region.

Does Radiotherapy for the Primary Tumor Benefit Prostate Cancer Patients with Distant Metastasis at Initial Diagnosis?

PURPOSE/OBJECTIVES

Treatment of the primary tumor reportedly improves survival in several types of metastatic cancer. We herein evaluated the efficacy and toxicity of radiotherapy for the primary tumor in prostate cancer with metastasis.

MATERIALS/METHODS

The study cohort included 140 men with metastatic prostate cancer at initial diagnosis. Metastatic sites were divided into 4 groups as follows: solitary bone, 2-4 bones, ≥5 bones, and visceral organs. Patient, tumor, and treatment characteristics, and clinical outcomes were compared between patients treated with (prostate radiotherapy [PRT] group) or without radiotherapy to the primary tumor.

RESULTS

Patients in PRT group presented with a statistically significantly younger age (p = .02), whereas other characteristics showed no significant difference. Overall survival (OS) and biochemical failure-free survival (BCFFS) were improved in PRT patients (3-year OS: 69% vs. 43%, p = 0.004; 3-year BCFFS: 52% vs. 16%, p = 0.002). Multivariate analysis identified PRT as a significant predictor of both OS (hazard ratio [HR] = 0.43, p = 0.015). None of the 38 PRT patients experienced severe (grade ≥3) genitourinary or gastrointestinal toxicity.

CONCLUSIONS

Our data suggest that radiotherapy to the primary tumor was associated with improved OS and BCFFS in metastatic prostate cancer. The results of this study warrant prospective controlled clinical trials of this approach in stage IV prostate cancer patients with limited extent of bone metastasis and good performance status.