Radiotherapy For High-risk Prostate Cancer Research Articles

Overall survival benefit of androgen suppression in addition to dose-escalated external beam radiotherapy for high-risk prostate cancer: Nationwide real-world data indicates a shift in men that benefit

ObjectiveTo evaluate the real-world added value of androgen deprivation therapy (ADT) in addition to external beam radiotherapy (EBRT) in men with high-risk non-metastatic prostate cancer, in view of advances in radiotherapy and diagnostics. MethodsAll Dutch men diagnosed with high-risk non-metastatic prostate cancer (defined as: ≥cT2c-T3b N0M0, PSA ≥20–50 ng/ml, and/or Gleason score ≥8 (International Society of Urological Pathology [ISUP] grade ≥4)) from 2009 through 2019 and treated with EBRT with or without ADT were identified in the population-based Netherlands Cancer Registry.Propensity scores were used to match (1:1) men that received ADT to men that did not receive ADT. Subsequently, OS was compared. Analyses were also stratified by number of high-risk features, 1 (either ≥cT2c, PSA >20 ng/ml or Gleason score ≥8) versus ≥2 (out of ≥cT2c, PSA >20 ng/ml and Gleason score ≥8). ResultsA total of 14,773 men with high-risk non-metastatic prostate cancer were identified, 3,958 (27%) of which received EBRT alone. After matching, 3,427 men remained in both groups and baseline characteristics were well-balanced. After a median follow-up of 92 months, OS was better in men treated with EBRT and ADT compared to men treated with EBRT alone (10-year OS: 66.4% versus 61.8%; HR 0.88 [95%CI: 0.80–0.96]). There was no statistically significant difference in OS in the subgroup of men with only 1 high-risk feature (10-year OS 67.7% versus 64.9%; HR 0.95 [95%CI: 0.85–1.07]). ConclusionsIn a contemporary cohort of men treated for high-risk non-metastatic prostate cancer with EBRT, an OS benefit of adding ADT was only observed in men with at least 2 high-risk features. These results suggest that improvements in diagnostics and treatment in recent decades have resulted in a stage shift of men benefiting from the addition of ADT to EBRT.

Patterns of Failure After Prostate-Only Radiotherapy in High-Risk Prostate Cancer: Implications for Refining Pelvic Nodal Contouring Guidelines

PurposeTo study prostate specific membrane antigen – positron emission tomography (Ga68PSMA-PETCT) based patterns of relapse at biochemical failure (BCF) after prostate-only radiotherapy (PORT) in high-risk (HR) prostate cancer and its implications on pelvic contouring recommendations. Methods and materialsPatients with clinico-radiological high-risk node-negative prostate cancer treated with curative PORT and androgen deprivation therapy (ADT), either within the POP-RT randomised trial or off trial, who underwent a Ga68PSMA-PETCT upon BCF were included. Patterns of regional and distant recurrence on Ga68PSMA-PETCT were studied. Pelvic nodal recurrences were mapped with reference to the superior border of pubic symphysis. Pelvic lymph nodal caudal border (PLNcb) recommendations in the published contouring guidelines (RTOGcb, GETUGcb, PIVOTALcb, NRGcb, GFRUcb) were evaluated. ResultsOf the total 262 patients screened, 68 eligible patients were included (POP-RT trial 35 patients; off-trial 33 patients). Median follow-up was 91 months (IQR, 72–117) and median time to BCF was 65 months (IQR, 49–83). Regional and distant recurrence was seen in 31 (46%) and 31 (46%) patients, respectively. Of the nodal recurrences, nearly half (46%, 14/31) had no distant metastases and 64% (20/31) had a failure in the common iliac nodal region. The lower-most nodal recurrence was 20 mm cranial to the top of pubic symphysis (RTOGcb, GETUGcb, GFRUcb) and 10 mm cranial to the PIVOTALcb. The PLNcb recommended by NRG guideline (NRGcb) had an inter-patient variability of 32 mm, ranging from 16 mm above to 16 mm below the top of pubic symphysis, and the lower most nodal recurrence ranged from 4 mm to 36 mm cranial to NRGcb. ConclusionPelvic failures accounted for a major proportion of recurrences after prostate-only radiotherapy, with the caudal most nodal recurrence being 20 mm cranial to the top of pubic symphysis. This could have implications in defining the caudal border of contouring recommendations.

Treatment intensification strategies for men undergoing definitive radiotherapy for high-risk prostate cancer.

Treatment intensification of external beam radiotherapy (EBRT) plays a crucial role in the treatment of high-risk prostate cancer. We performed a critical narrative review of the relevant literature and present new developments in evidence-based treatment intensification strategies. For men with high-risk prostate cancer, there is strong evidence to support prolonging androgen deprivation therapy (ADT) to 18-36months and escalating the dose to the prostate using a brachytherapy boost. A potentially less toxic alternative to a brachytherapy boost is delivering a focal boost to dominant intraprostatic lesions using EBRT. In patients who meet STAMPEDE high-risk criteria, there is evidence to support adding a second-generation anti-androgen agent, such as abiraterone acetate, to long-term ADT. Elective pelvic lymph node irradiation may be beneficial in select patients, though more prospective data is needed to elucidate the group of patients who may benefit the most. Tumor genomic classifier (GC) testing and advanced molecular imaging will likely play a role in improving patient selection for treatment intensification as well as contribute to the evolution of treatment intensification strategies for future patients. Treatment intensification using a combination of EBRT, advanced hormonal therapies, and brachytherapy may improve patient outcomes and survival in men with high-risk prostate cancer. Shared decision-making between patients and multidisciplinary teams of radiation oncologists, urologists, and medical oncologists is essential for personalizing care in this setting and deciding which strategies make sense for individual patients.

Long-Term Outcomes Following Fairly Brief Androgen Suppression and Stereotactic Radiation Therapy in High-Risk Prostate Cancer: Update from the FASTR/FASTR-2 Trials.

There has been emerging interest in the role of ultra-hypofractionated radiotherapy for high-risk prostate cancer, especially given its low α/β ratio. However, there is limited data on the long-term outcomes of this treatment strategy. The FASTR and FASTR-2 clinical trials were designed to assess the tolerability of stereotactic ablative body radiotherapy (SABR) in high-risk prostate cancer. FASTR was discontinued early due to unacceptable acute toxicity, whereas the acute toxicities in FASTR-2 were minimal. Herein, the long-term results from these trials are reported. Eligible patients had at least 1 high-risk feature as per the National Comprehensive Cancer Network criteria for high-risk prostate cancer, no evidence of metastatic disease, and either a score of 3+ on the Vulnerable Elderly Scale or declined standard therapy. A total of 19 patients from a single institution were enrolled on FASTR between 2011 and 2015. They received 40 Gy to the prostate and 25 Gy to the pelvic lymph nodes in 5 fractions delivered once weekly for 5 weeks, along with 1 year of androgen deprivation therapy (ADT). The excessive acute toxicity in FASTR prompted several modifications in FASTR-2, including the omission of nodal irradiation. A total of 30 patients from the same institution were enrolled on FASTR-2 between 2015 and 2017. They received 35 Gy to the prostate alone in 5 fractions delivered once weekly for 5 weeks, along with 18 months of ADT. A total of 44 patients were eligible for analysis, 16 from FASTR and 28 from FASTR-2. Most patients were >70 years old (77%). High-risk features included Gleason score ≥8 (46%), T3-T4 disease (27%) and baseline PSA >20 (50%). With a median follow-up of 6.4 years, the cumulative incidence of grade ≥3 genitourinary/gastrointestinal toxicity was 50% among FASTR patients and 7% among FASTR-2 patients. At 5 years, the combined rates of biochemical failure-free survival, freedom from distant metastases, prostate cancer-specific survival and overall survival were 72%, 90%, 92% and 83%, respectively. A total of 12 patients (27%) required further treatment. No significant differences in clinical outcomes were noted between the FASTR and FASTR-2 cohorts. SABR for high-risk prostate cancer is an attractive option for reducing treatment burden. Clinical outcomes and toxicity with the FASTR-2 protocol were comparable to conventionally-fractionated radiotherapy plus ADT. Larger prospective, randomized trials exploring the role of SABR with ADT in high-risk disease are necessary to better understand the efficacy and tolerability of this approach.

Late Urinary Toxicity and QoL with Curative Radiotherapy for High-Risk Prostate Cancer: Dose-Effect Relations in the POP-RT Randomized Phase III Trial

Whole pelvic radiotherapy (WPRT) showed better biochemical failure-free survival and metastasis-free survival than prostate-only radiotherapy (PORT) in the phase III randomized POP-RT trial for high and very high-risk prostate cancer, albeit with higher RTOG grade 2 late urinary toxicity. We report updated long term, symptom-wise comparison and dose-effect relations from this trial. Late urinary toxicity, and cumulative severity of each symptom over the follow-up period was graded using CTCAE v5.0. Grade 2+ toxicities were compared between the trial arms by chi square test. Bladder dosimetry in 5-Gy increments (V5, V10, V15...V65 Gy, V68 Gy) from the trial database of approved radiotherapy plans, was compared for each urinary symptom and overall late gr2+ toxicity by student t-test. Observed differences in dosimetric parameters were tested using multivariable logistic regression analysis, including age at diagnosis, known diabetes, tumor stage, trial arm, and prior transurethral resection of prostate (TURP). Urinary QOL scores were compared between arms using generalised linear mixed model. Combined late symptom-wise toxicity and dose-volume data were available for analysis for 193/224 patients. At a median follow-up of 75 months, cumulative CTCAE gr2+ late urinary toxicity remained higher with WPRT than PORT, though not statistically significant (36.5% vs 26.8%, p = 0.15). Grade 3 toxicity was low and similar in both arms. Symptom-wise cumulative rates showed no significant difference between arms (Table 1). Dosimetric comparison showed significantly higher bladder V5-V15 in patients with gr2+ toxicity over those with <gr2 urinary toxicity. On symptom-wise analysis, V5-V40 range was significantly higher for presence of dysuria, hematuria, and urgency. No significant differences were observed over higher dose range for any urinary symptom. On multivariable analysis, no significant association was identifiable between bladder dosimetry and urinary symptoms. Urinary QOL scores was similar between both the arms for all the symptoms. Compared to prostate-only radiotherapy, whole pelvic radiotherapy resulted similar Grade 3 urinary toxicity of about 5% with about 10% higher cumulative grade 2+ urinary toxicity over long term follow up. This difference was not reflected in patient-reported QOL. WPRT particularly increased urgency and hematuria. Larger bladder volume being irradiated with 5Gy to 15Gy dose range could contribute to increase in urinary symptoms.

Conventional vs. Hypo-Fractionated, Radiotherapy for High-Risk Prostate Cancer (PCS5), Randomized, Non-Inferiority, Phase 3 Trial: Posthoc Analysis of IMRT vs. 3D-CRT Radiation Therapy Associated Toxicities

The Prostate Cancer Study number 5 (PCS5), is a multi-centric non-inferiority, phase 3, randomized controlled trial of high-risk prostate cancer patients of treated with either conventionally fractionated radiotherapy (CFRT) or hypofractionated radiotherapy (HFRT). The 7 years' pre-planned analysis showed that HFRT (68 Gy in 25 fractions) was as effective and well tolerated as CFRT (76 Gy in 38 fractions). In this posthoc analysis we aim to report the genitourinary (GU) and gastrointestinal (GI) toxicities associated with radiation therapy techniques: intensity-modulated radiotherapy (IMRT) and 3D-conformal radiotherapy (3D-CRT). PCS5 randomized patients in a 1:1 ratio to receive either CFRT or HFRT. All patients received long term neoadjuvant, concurrent and adjuvant androgen suppression, with a median duration of 24 months. The toxicities were reported as per the Common Terminology Criteria for Adverse Events version 4. Acute toxicities were defined as presenting ≤ 180 days post-RT start and delayed > 180 days. The cumulative acute and delayed GI and GU toxicities were classified in grade groups: grade 1 or higher (G1+), G2+, and G3+. For each grade group, acute and delayed, we performed multivariable logistic regression analyses, adjusting for age, CTV volume, diabetes, fractionation (CRFT or HFRT), hypertension, and stage < T3b or ≥ T3b. For efficacy analyses cox-regression was utilized. A p-value < 0.05 was considered significant. Three hundred twenty of the 329 patients enrolled in the trial were included in this posthoc analyses. The mean age was 71.4 ± 6.1 years, and the mean CTV volume (n = 219) was 47.25 ± 19.9 cc. IMRT was used in 195 (60.6%) patients and 3D-CRT in 125 (39.1%) patients. Multivariable logistic regression showed a significant difference in favor of IMRT for GI G2+ acute toxicity (OR = 0.285 [0.14-0.59]; CI: 95%; p<0.001) and GI G2+ delayed toxicity (OR = 0.202 [0.60-0.69]; CI: 95%; p = 0.01). There were no differences in G3+ GI or GU toxicities and there were no grade 4 toxicities. There were no differences in efficacy at 7 years between the two treatment technics. Outcomes for IMRT vs. 3D-CRT respectively, overall survival (81.5% vs 79.2%; HR: 0.92 [0.55-1.53]; CI: 95%; p-value: 0.74), distant metastasis free survival (90,7% vs 92.8%; HR: 1.4 [0.63-3.1]; CI: 95%; p-value: 0.42), prostate cancer mortality (95.8% vs. 92.2%; HR: 0.93 [0.32-2.67]; CI: 95%; p-value: 0.89), and biochemical failure (85.1% vs 88%; HR: 1.35 [0.72-2.52]; CI: 95%; p-value: 0.35). This is the first phase 3 randomized controlled trial assessing the use of HFRT vs. CFRT, exclusively in high-risk prostate cancer patients. Given that our efficacy data at 7 years follow-up establishes moderate HFRT as a new standard of care and no difference between IMRT and 3D-CRT, we strongly recommend that patients who are treated with EBRT should receive IMRT, given the reduced acute and delayed grade 2 or higher GI toxicities.

10 Long-Term Outcomes Following Fairly Brief Androgen Suppression and Stereotactic Radiotherapy in High-Risk Prostate Cancer: Update From the FASTR/FASTR-2 Trials

10 Long-Term Outcomes Following Fairly Brief Androgen Suppression and Stereotactic Radiotherapy in High-Risk Prostate Cancer: Update From the FASTR/FASTR-2 Trials

Hypofractionated, Dose Escalation Radiation Therapy for High-Risk Prostate Cancer: The Safety Analysis of the Prostate Cancer Study-5, a Groupe de Radio-Oncologie Génito-Urinaire de Quebec Led Phase 3 Trial

The low α\β ratio of 1.2 to 2 for prostate cancer (PCa) suggests high radiation-fraction sensitivity and predicts a therapeutic advantage of hypofractionated (HF) radiation therapy (RT). To date, no phase 3 randomized clinical trial has compared moderately HF RT with standard fractionation (SF) exclusively in high-risk PCa patients. We are reporting the safety of moderate HF RT in high-risk PCa in an initially noninferiority-designed phase 3 clinical trial. From February 2012 to March 2015, 329 high-risk PCa patients were randomized to receive either SF or HF RT. All patients received neoadjuvant, concurrent, and long-term adjuvant androgen deprivation therapy. Standard fractionation RT consisted of 76 Gy in 2 Gy per fraction to the prostate, where 46 Gy was delivered to the pelvic lymph nodes. Hypofractionated RT included concomitant dose escalation of 68 Gy in 2.72 Gy per fraction to the prostate and 45 Gy in 1.8 Gy per fraction to the pelvic lymph nodes. The coprimary endpoints were acute and delayed toxicity at 6 and 24 months, respectively. The trial was originally designed as a noninferiority with a 5% absolute margin. Given the lower-than-expected toxicities in both arms, the noninferiority analysis was completely dropped. Of the 329 patients, 164 were randomized to the HF and 165 to the SF arms. In total, there were more grade 1 or worse acute gastrointestinal (GI) events in the HF arm, 102 versus 83 events in the HF and SF arm, respectively (P=.016). This did not remain significant at 8 weeks of follow-up. There were no differences in grade 1 or worse acute GU events in the 2 arms, 105 versus 99 events in the HF and SF arm, respectively (P=.3). At 24 months, 12 patients in the SF arm and 15 patients in the HF arm had grade 2 or worse delayed GI-related adverse events (hazard ratio, 1.32; 95% CI, 0.62-2.83; P=.482). There were 11 patients in the SF arm and 3 patients in the HF arm with grade 2 or higher delayed genitourinary (GU) toxicities (hazard ratio, 0.26; 95% CI, 0.07-0.94; P=.037). There were 3 grade 3 GI and one grade 3 GU delayed toxicities in the HF arm and 3 grade 3 GU and no grade 3 GI toxicities in the SF arm. No grade 4-toxicities were reported. This is the first study of moderate HF dose-escalated RT in exclusively high-risk patients with prostate cancer treated with long-term androgen deprivation therapy and pelvic RT. Although our data were not analyzed as a noninferiority, our results demonstrate that moderately HF RT is well-tolerated, similar to SF RT at 2 years, and could be considered an alternative to SF RT.

Variability of radiotherapy volume delineation: PSMA PET/MRI and MRI based clinical target volume and lymph node target volume for high-risk prostate cancer

PurposeA comparative retrospective study to assess the impact of PSMA Ligand PET/MRI ([68 Ga]-Ga-PSMA-11 and [18F]-F-PSMA-1007 PET/MRI) as a new method of target delineation compared to conventional imaging on whole-pelvis radiotherapy for high-risk prostate cancer (PCa).Patients and methodsForty-nine patients with primary high-risk PCa completed the whole-pelvis radiotherapy plan based on PSMA PET/MRI and MRI. The primary endpoint compared the size and overlap of clinical target volume (CTV) and nodal gross tumour volume (GTVn) based on PSMA PET/MRI and MRI. The diagnostic performance of two methods for pelvic lymph node metastasis (PLNM) was evaluated.ResultsIn the radiotherapy planning for high-risk PCa patients, there was a significant correlation between MRI-CTV and PET/MRI-CTV (P = 0.005), as well as between MRI-GTVn and PET/MRI-GTVn (P < 0.001). There are non-significant differences in the CTV and GTVn based on MRI and PET/MRI images (P = 0.660, P = 0.650, respectively). The conformity index (CI), lesion coverage factor (LCF) and Dice similarity coefficient (DSC) of CTVs were 0.999, 0.953 and 0.954. The CI, LCF and DSC of GTVns were 0.927, 0.284, and 0.32. Based on pathological lymph node analysis of 463 lymph nodes from 37 patients, the sensitivity, specificity of PET/MRI in the diagnosis of PLNM were 77.78% and 99.76%, respectively, which were higher than those of MRI (P = 0.011). Eight high-risk PCa patients who finished PSMA PET/MRI changed their N or M stage.ConclusionThe CTV delineated based on PET/MRI and MRI differ little. The GTVn delineated based on PET/MRI encompasses metastatic pelvic lymph nodes more accurately than MRI and avoids covering pelvic lymph nodes without metastasis. We emphasize the utility of PET/MRI fusion images in GTVn delineation in whole pelvic radiotherapy for PCa. The use of PSMA PET/MRI aids in the realization of more individual and precise radiotherapy for PCa.

Predictors for late genitourinary toxicity in men receiving radiotherapy for high-risk prostate cancer using planned and accumulated dose

Significant deviations between bladder dose planned (DP) and dose accumulated (DA) have been reported in patients receiving radiotherapy for prostate cancer. This study aimed to construct multivariate analysis (MVA) models to predict the risk of late genitourinary (GU) toxicity with clinical and DP or DA as dose-volume (DV) variables. Bladder DA obtained from 150 patients were compared with DP. MVA models were built from significant clinical and DV variables (p<0.05) at univariate analysis. Previously developed dose-based-region-of-interest (DB-ROI) metrics using expanded ring structures from the prostate were included. Goodness-of-fit test and calibration plots were generated to determine model performance. Internal validation was accomplished using Bootstrapping. Intermediate-high DA (V30-65 Gy and DB-ROI-20-50mm) for bladder increased compared to DP. However, at the very high dose region, DA (D0.003 cc, V75 Gy, and DB-ROI-5-10mm) were significantly lower. In MVA, single variable models were generated with odds ratio (OR)<1. DB-ROI-50mm was predictive of Grade≥1 GU toxicity for DA and DP (DA and DP; OR: 0.96, p: 0.04) and achieved an area under the receiver operating curve (AUC) of>0.6. Prostate volume (OR: 0.87, p: 0.01) was significant in predicting Grade 2 GU toxicity with a high AUC of 0.81. Higher DA (V30-65 Gy) received by the bladder were not translated to higher late GU toxicity. DB-ROIs demonstrated higher predictive power than standard DV metrics in associating Grade≥1 toxicity. Smaller prostate volumes have a minor protective effect on late Grade 2 GU toxicity.

Conventional vs. Hypofractionated, Radiotherapy for High-Risk Prostate Cancer: 7-Year Outcomes of the Randomized, Non-Inferiority, Phase 3 PCS5 Trial

<h3>Purpose/Objective(s)</h3> The low α\β ratio of prostate cancer (PCa), 1.5-2, suggests high radiation-fraction sensitivity and predicts a therapeutic advantage of hypofractionated radiation treatment (HFRT). Most available data of moderate HFRT have focused on low, intermediate and/or mixed risk groups. We therefore conducted the first randomized trial of moderately HFRT in high-risk PCa patients only, and present the pre-planned analysis of efficacy at seven years (Prostate Cancer Study number 5: PCS5) <h3>Materials/Methods</h3> PCS5 is a Canadian multi-centric, non-inferiority phase III trial of intensity-modulated conventionally fractionated radiation therapy (CFRT) vs. HFRT in men with high-risk PCa as per NCCN definition. From Feb. 2012 to Mar. 2015, 329 patients were randomized in a 1:1 ratio to receive either CFRT or HFRT. All patients received neo-adjuvant, concurrent and adjuvant androgen suppression, with a median duration of 24 months. CFRT consisted of 76 Gy in 2 Gy per fraction to the prostate where 46 Gy was delivered to the pelvic lymph nodes. HFRT consisted of concomitant dose escalation of 68 Gy in 2.72 Gy per fraction to the prostate and 45 Gy, in 1.8Gy per fraction to the pelvic lymph nodes. Participants were analyzed as per intention-to-treat. <h3>Results</h3> Of the 329 patients, 164 were randomized to HFRT and 165 to CFRT. Of these, 159 men in the hypofractionation arm and 160 in the standard arm were included in survival analyses. At 7 years of follow up there were no significant differences in survival between HFRT and CFRT for overall mortality (81.7% vs. 82%; HR 0.92 [0.56-1.53]; CI:95%; p=0.76), prostate cancer specific mortality (94.9% vs. 96.4%; HR 1.31 [0.46-3.78]; CI:95%; p=0.61), biochemical recurrence (87.4% vs. 85.1%; HR 0.89 [0.49-1.60]; CI:95%; p=0.69), distant metastatic recurrence (91.5% vs. 91.8%; HR 0.89 [0.41-1.90]; CI:95%; p=0.76), or disease free survival, respectively (either biochemical or distant recurrence) (86.5% vs. 83.4%; HR 0.82 [0.47-1.46]; CI:95%; p=0.50). The Relative Risks were close to 1.00 for all outcomes at 3-, 5-, and 7-years after treatment, with very tight bootstrapped confidence intervals, suggesting equivalent risks for all outcomes in both study arms. There were no significant differences in grade 3 or higher acute and delayed genitourinary (GU) and gastrointestinal (GI) toxicities at 2 years and no new toxicities emerged thereafter. There were no grade 4 toxicities in either arm. <h3>Conclusion</h3> This is the first hypofractionated radiotherapy study in high-risk PCa patients treated with contemporary radiation and androgen suppression. Hypofractionated radiotherapy using 68 Gy in 25 fractions is non-inferior to conventional fractionation using 76Gy in 38 fractions and can be considered as a new standard of care for external-beam radiotherapy of high-risk prostate cancer.

A Prospective Study of Stereotactic Body Radiotherapy (SBRT) with Concomitant Whole-Pelvic Radiotherapy (WPRT) for High-Risk Localized Prostate Cancer Patients Using 1.5 Tesla Magnetic Resonance Guidance: The Preliminary Clinical Outcome.

Simple SummaryMagnetic resonance (MR)-guided stereotactic body radiotherapy (MRgSBRT) with concomitant whole-pelvic nodal radiotherapy (WPRT) represents a novel radiotherapy paradigm for high-risk prostate cancer (HR-PC), potentially improving online image guidance and clinical outcomes. This is the first prospective study aims to report the preliminary clinical experiences and treatment outcome of 1.5 Tesla adaptive MRgSBRT with concomitant WPRT in HR-PC patients (72.5 ± 6.8 years). Forty-two consecutive localized HR-PC patients were treated by online adaptive MRgSBRT (8 Gy(prostate)/5 Gy(WPRT) × 5 fractions) combined with androgen deprivation therapy (ADT) and followed up (median: 251 days, range: 20–609 days). The maximum cumulative acute gastrointestinal (GI)/ genitourinary (GU) grade 1 and 2 toxicity rates were 19.0%/81.0% and 2.4%/7.1%, respectively. The subacute (>30 days) GI/GU grade 1 and 2 toxicity rates were 21.4%/64.3% and 2.4%/2.4%, respectively. No grade 3 toxicities were reported. Patient-reported quality of life (QoL) showed insignificant changes in urinary, bowel, sexual, and hormonal domain scores during the follow-up period. All patients had early post-MRgSBRT biochemical responses, while biochemical recurrence (prostate-specific antigen nadir + 2 ng/mL) occurred in one patient at month 18. The early results suggested favorable treatment-related toxicities and encouraging patient-reported QoLs, but long-term follow-up is still needed. Background: Conventionally fractionated whole-pelvic nodal radiotherapy (WPRT) improves clinical outcome compared to prostate-only RT in high-risk prostate cancer (HR-PC). MR-guided stereotactic body radiotherapy (MRgSBRT) with concomitant WPRT represents a novel radiotherapy (RT) paradigm for HR-PC, potentially improving online image guidance and clinical outcomes. This study aims to report the preliminary clinical experiences and treatment outcome of 1.5 Tesla adaptive MRgSBRT with concomitant WPRT in HR-PC patients. Materials and methods: Forty-two consecutive HR-PC patients (72.5 ± 6.8 years) were prospectively enrolled, treated by online adaptive MRgSBRT (8 Gy(prostate)/5 Gy(WPRT) × 5 fractions) combined with androgen deprivation therapy (ADT) and followed up (median: 251 days, range: 20–609 days). Clinical outcomes were measured by gastrointestinal (GI) and genitourinary (GU) toxicities according to the Common Terminology Criteria for Adverse Events (CTCAE) Scale v. 5.0, patient-reported quality of life (QoL) with EPIC (Expanded Prostate Cancer Index Composite) questionnaire, and prostate-specific antigen (PSA) responses. Results: All MRgSBRT fractions achieved planning objectives and dose specifications of the targets and organs at risk, and they were successfully delivered. The maximum cumulative acute GI/GU grade 1 and 2 toxicity rates were 19.0%/81.0% and 2.4%/7.1%, respectively. The subacute (>30 days) GI/GU grade 1 and 2 toxicity rates were 21.4%/64.3% and 2.4%/2.4%, respectively. No grade 3 toxicities were reported. QoL showed insignificant changes in urinary, bowel, sexual, and hormonal domain scores during the follow-up period. All patients had early post-MRgSBRT biochemical responses, while biochemical recurrence (PSA nadir + 2 ng/mL) occurred in one patient at month 18. Conclusions: To our knowledge, this is the first prospective study that showed the clinical outcomes of MRgSBRT with concomitant WPRT in HR-PC patients. The early results suggested favorable treatment-related toxicities and encouraging patient-reported QoLs, but long-term follow-up is needed to confirm our early results.

Dose-volume analysis of planned versus accumulated dose as a predictor for late gastrointestinal toxicity in men receiving radiotherapy for high-risk prostate cancer.

Significant dose deviations have been reported between planned (DP) and accumulated (DA) dose in prostate radiotherapy. This study aimed to develop multivariate analysis (MVA) models associating Grade 1 and 2 gastrointestinal (GI) toxicity with clinical and DP or DA dosimetric variables separately. Dose volume (DV) metrics were compared between DA and DP for 150 high-risk prostate cancer patients. MV models were generated from significant clinical and dosimetric variables (p<0.05) at univariate level. Dose-based-region of interest (DB-ROI) metrics were included. Model performance was measured, and additional subgroup analysis were performed. Rectal DA demonstrated a higher intermediate-high dose (V30-65 Gy and DB-ROI at 15-50mm) compared to DP. Conversely, at the very high dose region, rectal DA (V75 Gy and DB-ROI at 5-10mm) were significantly lower. In MVA, rectal DB-ROI at 10mm was predictive for Grade≥1 GI toxicity for DA and DP. Age, rectal DA for D0.03 cc, and rectal DP for DB-ROI 10mm were predictors for Grade 2 GI toxicity. Subgroup analysis revealed that patients≥72years old and a rectal DA of≥78.2Gy were highly predictive of Grade 2 GI toxicity. The dosimetric impact of a higher dose rectal dose in DA due to volumetric changes was minimal and was not predictive of detrimental clinical toxicity apart from rectal D0.03 cc≥78.2Gy for Grade 2 GI toxicity. The use of the DB-ROI method can provide equivalent predictive power as the DV method in toxicity prediction.

Local failure, distant metastasis, and survival after definitive radiotherapy for intermediate- and high-risk prostate cancer: An individual patient-level meta-analysis of 18 randomized trials.

277 Background: The prognostic importance of local failure (LF) after definitive radiotherapy (RT) in patients with NCCN intermediate- (IRPCa) and high-risk prostate cancer (HRPCa) remains unclear, particularly given the likelihood that occult distant metastases (DMs) at presentation may be the true driver of natural history. Here, we leverage individual patient data (IPD) from 18 randomized control trials (RCTs) to evaluate the prognostic impact of LF and the kinetics of DM after RT. Methods: IPD for 18 RCTs were obtained from the Meta-Analysis of Randomized trials in Cancer of the Prostate (MARCAP) Consortium, comprising a total of 12533 patients (6288 HRPCa &amp; 6245 IRPCa). Multivariable Cox proportional hazards (PH) models were developed to evaluate the relationship between overall survival (OS), PCa-specific survival (PCSS), DM-free survival (DMFS) &amp; LF as a time-dependent covariate, adjusted for clinicodemographic parameters. Markov PH models, defined via transitions between 4 states, were developed to evaluate the aforementioned relationship. Proportional hazards assumption was imposed and examined for both models. Time is from randomization. Results: Median follow-up was 9.1 years. There were 795 (13%) LF &amp; 1288 (21%) DM events for patients with HRPCa; these numbers were 449 (7%) &amp; 451 (7%) for IRPCa. For HRPCa &amp; IRPCa, 81% and 81% of DMs developed from a clinically relapse-free state (cRFS), with a median time of 46 and 60 months, respectively (p &lt; 0.0001). 39% &amp; 13% of DM events occurred within 2 years after RT for HRPCa &amp; IRPCa, respectively. At later time points, DM events were more likely to emerge after an LF event for both HRPCa (9% vs. 34% between 0-2 vs. 8-10 years post-RT, p = 0.001) and IRPCa (10% vs. 34% between 0-2 vs. 8-10 years post-RT, p = 0.008). LF was significantly associated with OS (hazard ratio [HR] 1.17, 95% confidence interval [CI] 1.06–1.30), PCSS (HR 2.02, 95% CI 1.75-2.33) &amp; DMFS (HR 1.94, 95% CI 1.75–2.15) (p &lt; 0.01 for all) in patients with HRPCa. LF was also significantly associated with DMFS (HR 1.57, 95% CI 1.36–1.81) but not OS in patients with IRPCa. Patients who had not transitioned to the LF state had a significantly lower HR of transitioning to a PCa-specific death state than those who transitioned to the LF state (HR 0.32, 95% CI 0.21–0.50, p &lt; 0.001). Conclusions: LF is an independent prognosticator of OS, PCSS &amp; DMFS in HRPCa and of DMFS in IRPCa. The predominant mode of DM development is from the cRFS state, underscoring the importance of accurate upfront staging &amp; systemic therapy. However, particularly at late time points, an increasing proportion of DM events originated after diagnosis of a LF, constituting a “second wave” of DM events. This suggests that optimizing local control is also important, though the majority of DM events appear prior to a clinically-detected LF.

Online adaptive radiotherapy potentially reduces toxicity for high-risk prostate cancer treatment

Background and purposeWith daily, MR-guided online adapted radiotherapy (MRgART) it may be possible to reduce the PTV in pelvic RT. This study investigated the potential reduction in normal tissue complication probability (NTCP) of MRgART compared to standard radiotherapy for high-risk prostate cancer. Materials and methodsTwenty patients treated with 78 Gy to the prostate and 56 Gy to elective pelvic lymph nodes were included. VMAT plans were generated with standard clinical PTV margins. Additionally to the planning MR, patients had three MRI scans during treatment to simulate an MRgART. A reference plan with PTV margins determined for MRgART was created per patient and adapted to each of the following MRs. Adapted plans were warped to the planning MR for dose accumulation. The standard plan was rigidly registered to each adaptation MR before it was warped to the planning MR for dose accumulation. Dosimetric impact was compared by DVH analysis and potential clinical effects were assessed by NTCP modeling. ResultsMRgART yielded statistically significant lower doses for the bladder wall, rectum and peritoneal cavity, compared to the standard RT, which translated into reduced median risks of urine incontinence (ΔNTCP 2.8%), urine voiding pain (ΔNTCP 2.8%) and acute gastrointestinal toxicity (ΔNTCP 17.4%). Mean population accumulated doses were as good or better for all investigated OAR when planned for MRgART as standard RT. ConclusionOnline adapted radiotherapy may reduce the dose to organs at risk in high-risk prostate cancer patients, due to reduced PTV margins. This potentially translates to significant reductions in the risks of acute and late adverse effects.

P054 - Dosimetric and clinical results of the toxicity of image-guided radiotherapy for high-risk prostate cancer in western Algeria

P054 - Dosimetric and clinical results of the toxicity of image-guided radiotherapy for high-risk prostate cancer in western Algeria

151: Prostate SBRT Boost Radiotherapy (PBS Trial): A Randomized Phase II Trial of SBRT Versus Conventionally-Fractionated Radiotherapy Boost Following Pelvic Radiotherapy in High-Risk Prostate Cancer

151: Prostate SBRT Boost Radiotherapy (PBS Trial): A Randomized Phase II Trial of SBRT Versus Conventionally-Fractionated Radiotherapy Boost Following Pelvic Radiotherapy in High-Risk Prostate Cancer

Comparison of radical prostatectomy and external beam radiotherapy in high-risk prostate cancer.

PurposeWe evaluated clinical outcomes of high-risk prostate cancer patients receiving external beam radiotherapy (EBRT) or radical prostatectomy (RP).Materials and MethodsPatients were classified as high-risk prostate cancer and received definitive treatment between 2005 and 2015. Patients with previous pelvic radiotherapy, positive lymph node or distant metastasis were excluded. The primary outcomes were prostate cancer-specific survival (PCSS) and distant metastasis-free survival (DMFS). ResultsOf 583 patients met the inclusion criteria (77 EBRT and 506 RP), the estimated 10-year PCSS was 97.0% in the RP and 95.9% in the EBRT (p = 0.770). No significant difference was seen in the DMFS (p = 0.540), whereas there was a trend in favor of RP over EBRT in overall survival (OS) (p = 0.068). Propensity score matching analysis with confounding variables was done, with 183 patients (66 EBRT and 117 RP) were included. No significant difference in DMFS, PCSS or OS was found. ConclusionOur data demonstrated similar oncologic PCSS, OS, and DMFS outcomes between EBRT and RP patients.

Stereotactic Body Radiotherapy for High-Risk Prostate Cancer: A Systematic Review.

Simple SummaryStereotactic body radiotherapy, i.e., high-precision radiotherapy delivering high doses within a few treatment sessions, is a very convenient treatment option, which has been shown to be effective and well tolerated in prostate cancer patients with low- or intermediate-risk profiles. This review summarizes the available data and analyzes, whether this modern treatment may routinely be offered to prostate cancer patients with a high-risk profile.Background: Radiotherapy (RT) is an established, potentially curative treatment option for all risk constellations of localized prostate cancer (PCA). Androgen deprivation therapy (ADT) and dose-escalated RT can further improve outcome in high-risk (HR) PCA. In recent years, shorter RT schedules based on hypofractionated RT have shown equal outcome. Stereotactic body radiotherapy (SBRT) is a highly conformal RT technique enabling ultra-hypofractionation which has been shown to be safe and efficient in patients with low- and intermediate-risk PCA. There is a paucity of data on the role of SBRT in HR PCA. In particular, the need for pelvic elective nodal irradiation (ENI) needs to be addressed. Therefore, we conducted a systematic review to analyze the available data on observed toxicities, ADT prescription practice, and oncological outcome to shed more light on the value of SBRT in HR PCA. Methods: We searched the PubMed and Embase electronic databases for the terms “prostate cancer” AND “stereotactic” AND “radiotherapy” in June 2020. We adhered to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) recommendations. Results: After a rigorous selection process, we identified 18 individual studies meeting all selection criteria for further analyses. Five additional studies were included because their content was judged as relevant. Three trials have reported on prostate SBRT including pelvic nodes; 2 with ENI and 1 with positive pelvic nodes only. The remaining studies investigated SBRT of the prostate only. Grade 2+ acute genitourinary (GU) toxicity was between 12% and 46.7% in the studies investigating pelvic nodes irradiation and ranged from 0% to 89% in the prostate only studies. Grade 2+ chronic GU toxicity was between 7% and 60% vs. 2% and 56.7%. Acute gastrointestinal (GI) grade 2+ toxicity was between 0% to 4% and 0% to 18% for studies with and without pelvic nodes irradiation, respectively. Chronic GI grade 2+ toxicity rates were between 4% and 50.1% vs. 0% and 40%. SBRT of prostate and positive pelvic nodes only showed similar toxicity rates as SBRT for the prostate only. Among the trials that reported on ADT use, the majority of HR PCA patients underwent ADT for at least 2 months; mostly neoadjuvant and concurrent. Biochemical control rates ranged from 82% to 100% after 2 years and 56% to 100% after 3 years. Only a few studies reported longer follow-up data. Conclusion: At this point, SBRT with or without pelvic ENI cannot be considered the standard of care in HR PCA, due to missing level 1 evidence. Treatment may be offered to selected patients at specialized centers with access to high-precision RT. While concomitant ADT is the current standard of care, the necessary duration of ADT in combination with SBRT remains unclear. Ideally, all eligible patients should be enrolled in clinical trials.

Observation with or without late radiotherapy is equivalent to early radiotherapy in high-risk prostate cancer after radical prostatectomy: A SEER-Medicare analysis on trends, survival outcomes, and complications.

BackgroundWe aimed to illustrate national trends of post-radical prostatectomy (RP) radiotherapy (RT) and compare outcomes and toxicities in patients receiving eRT versus observation with or without late radiotherapy (lRT).MethodsUtilizing the Surveillance, Epidemiology, and End Results (SEER)-Medicare data from 2001 to 2011, we identified 7557 patients with high-risk pathologic features after RP (≥pT3N0 and/or positive surgical margins). Our study cohort consisted of patients receiving RT within 6 months of surgery (eRT), those receiving RT after 6 months (lRT), and those never receiving RT (observation). Another subcohort, delayed RT (dRT), encompassed both lRT and observation. Trends of post-RP RT were compared using the Cochran–Armitage trend test. Cox regression models identified factors predictive of worse survival outcomes. Kaplan–Meier analyses compared the eRT and the dRT groups.ResultsAmong those with pathologically confirmed high-risk prostate cancer (PCa) after RP, 12.7% (n = 959), 13.2% (n = 1710), and 74.1% (n = 4888) underwent eRT, lRT, and observation without RT, respectively. Of these strategies, the proportion of men on observation without RT increased significantly over time (p = 0.004). The multivariable Cox regression model demonstrated similar outcomes between the eRT and the dRT groups. At a median follow-up of 5.9 years, five-year overall and cancer-specific survival outcomes were more favorable in the dRT group, when compared to the eRT group.ConclusionsA blanket adoption of the eRT in high-risk PCa based on clinical trials with limited follow-up may result in overtreatment of a significant number of men and expose them to unnecessary radiation toxicity.