Radiotherapy For Prostate Cancer Research Articles

Stereotactic body radiation therapy (SBRT) for prostate cancer: Improving treatment delivery efficiency and accuracy

Stereotactic body radiation therapy (SBRT) for prostate cancer: Improving treatment delivery efficiency and accuracy

Influence of Prostate Volume on the Incidence of Complications and Urinary Incontinence Following Thulium Fiber Laser Enucleation of the Prostate: Results from Multicenter, Real-world Experience of 2732 patients

BackgroundThe use of the new thulium fiber laser in enucleation of the prostate (ThuFLEP) has been introduced recently. ObjectiveTo evaluate complications and urinary incontinence (UI) after ThuFLEP in small and large prostate volume (PV). Design, setting, and participantsWe retrospectively reviewed patients who underwent ThuFLEP in six centers (from January 2020 to January 2023). The exclusion criteria were concomitant lower urinary tract surgery, previous prostate/urethral surgery, prostate cancer, and pelvic radiotherapy. Outcome measurements and statistical analysisPatients were divided into two groups: group 1: PV ≤80 ml; group 2: PV >80 ml. Univariable and multivariable logistic regression analyses were performed to evaluate the independent predictors of overall UI. Results and limitationsThere were 1458 patients in group 1 and 1274 in group 2. There was no significant difference in age. The median PV was 60 (61-72) ml in group 1 and 100 (90-122) ml in group 2. En bloc enucleation was employed more in group 1, while the early apical release technique was used more in group 2. The rate of prolonged irrigation for hematuria, urinary tract infection, and acute urinary retention did not differ significantly. Blood transfusion rate was significantly higher in group 2 (0.5% vs 2.0%, p = 0.001). There was no significant difference in the overall UI rate (12.3% in group 1 vs 14.7% in group 2, p = 0.08). A multivariable regression analysis showed that preoperative postvoiding urine residual (odds ratio 1.004, 95% confidence interval 1.002-1.007, p < 0.01) was the only factor significantly associated with higher odds of UI. A limitation of this study was its retrospective nature. ConclusionsComplications and UI rates following ThuFLEP were similar in patients with a PV up to or larger than 80 ml except for the blood transfusion rate that was higher in the latter. Patient summaryIn this study, we looked at outcomes after thulium fiber laser in enucleation of the prostate stratified by PV. We found that blood transfusion was higher in men with PV >80 ml, but urinary incontinence was similar.

Reply by Authors - Major Complications and Adverse Events Related to use of SpaceOAR Hydrogel for Prostate Cancer Radiotherapy

Reply by Authors - Major Complications and Adverse Events Related to use of SpaceOAR Hydrogel for Prostate Cancer Radiotherapy

Predictors of radiation-induced late rectal toxicity in prostate cancer treatment: a volumetric and dosimetric analysis

IntroductionProstate cancer (PCa) is a prevalent malignancy in European men, often treated with radiotherapy (RT) for localized disease. While modern RT achieves high success rates, concerns about late gastrointestinal (GI) toxicities persist. This retrospective study aims to identify predictors for late GI toxicities following definitive conventionally fractionated external beam RT (EBRT) for PCa, specifically exploring the dose to the rectal wall.Materials and methodsA cohort of 96 intermediate- to high-risk PCa patients underwent EBRT between 2008 and 2016. Rectum and rectum wall contours were delineated, and 3D dose matrices were extracted. Volumetric and dosimetric indices were computed, and statistical analyses were performed to identify predictors using the Mann–Whitney U-rank test, logistic regression, and recursive feature elimination.ResultsIn our cohort, 15 out of 96 patients experienced grade II late proctitis. Our analysis reveals distinct optimal predictors for rectum and rectum wall (RW) structures varying with α/β values (3.0 and 2.3 Gy) across prescribed doses of 68 to 76 Gy. Despite variability, RW predictors demonstrate greater consistency, notably V68Gy[%] to V74Gy[%] for α/β 3.0 Gy, and V68Gy[%] to V70Gy[%] for α/β 2.3 Gy. The model with α/β 2.3 Gy, featuring RW volume receiving 70 Gy (V70Gy[%]), stands out with a BIC value of 62.92, indicating its superior predictive effectiveness. Finally, focusing solely on the rectum structure, the V74Gy[%] emerges the best predictor for α/β 3.0 Gy, with a BIC value of 66.73.ConclusionThis investigation highlights the critical role of V70Gy[%] in the rectum wall as a robust predictor for grade II late gastrointestinal (GI) toxicity following external beam radiation therapy (EBRT) for prostate cancer (PCa). Furthermore, our findings suggest that focusing on the rectum wall specifically, rather than the entire rectum, may offer improved accuracy in assessing proctitis development. A V70Gy (in EQD2 with α/β 2.3 Gy) of ≤5% and if possible ≤1% for the rectal wall should be achieved to minimize the risk of late grade II proctitis.

Salvage Reirradiation for Locally Recurrent Prostate Cancer: Results From a Prospective Study With 7.2 Years of Follow-Up.

There are no well-established re-treatment options for local recurrence after primary curative radiation therapy for prostate cancer (PCa), as prospective studies with long-term follow-up are lacking. Here, we present results from a prospective study on focal salvage reirradiation with external-beam radiation therapy with a median follow-up of 7.2 years. From 2013 to 2017, 38 patients with biopsy-proven locally recurrent PCa >2 years after previous treatment and absence of grade 2-3 toxicity from the first course of radiation were included. The treatment was 35 Gy in five fractions to the MRI-based target volume and 6 months of androgen-deprivation therapy starting 3 months before radiation. The Phoenix criteria defined biochemical recurrence-free survival (bRFS), and toxicity was scored according to Radiation Therapy Oncology Group criteria. Median age was 70 years, and median time from primary radiation to prostate-specific antigen (PSA) recurrence was 83 months. The actuarial 2-year and 5-year bRFS were 81% (95% CI, 69 to 94) and 58% (95% CI, 49 to 74), respectively. The actuarial 5-year local recurrence-free survival was 93% (95% CI, 82 to 100), metastasis-free survival was 82% (95% CI, 69 to 95), and overall survival was 87% (95% CI, 76 to 98). Two patients (5%) had durable grade 3 genitourinary toxicity, one combined with GI grade 3 toxicity. A PSA doubling time ≤6 months at salvage, a Gleason score >7, and a PSA nadir ≥0.1 ng/mL predicted a worse outcome. Reirradiation with EBRT for locally recurrent PCa after primary curative radiation therapy is clinically feasible and demonstrated a favorable outcome with acceptable toxicity in this prospective study with long-term follow-up.

Extreme hypofractionated stereotactic radiotherapy for localized prostate Cancer: Efficacy and late urinary toxicity according to transurethral resection of the prostate history

Background and purposeExtreme hypofractionated stereotactic body radiotherapy (SBRT) is a therapeutic alternative for localized low- or intermediate-risk prostate cancer. Despite the availability of several studies, the toxicity profile of SBRT has not been comprehensively described. This real-world evidence study assessed the efficacy and toxicities associated with this regimen, and potential prognosis factors for genitourinary toxicities. Materials and methodsThis retrospective study included 141 consecutive patients with localized prostatic adenocarcinoma treated with CyberKnife™ SBRT, as primary irradiation, at the Oscar Lambret Center between 2010 and 2020. The prescribed dose was 36.25 Gy in 5 fractions. Acute and late toxicities were graded according to the CTCAE (version 5.0). Biochemical recurrence-free survival (bRFS) and overall survival (OS) were estimated using the Kaplan–Meier method. The cumulative incidence of biochemical recurrence (cBR) was estimated using the Kalbfleisch–Prentice method. ResultsAmong the included patients, 13.5 % had a history of transurethral resection of the prostate (TURP). The median follow-up was 48 months. At 5 years, bRFS, cBR, and OS were 72 % (95 %CI: 61–81), 7 % (95 %CI: 3–14), and 82 % (95 %CI: 73–89), respectively. Twenty-nine patients experienced at least one late toxicity of grade ≥ 2; genitourinary (N = 29), including 3 cases of chronic hematuria, and/or gastrointestinal (N = 1). The cumulative incidence of late urinary toxicity of grade ≥ 2 was 20.6 % at 5 years (95 %CI: 13.9–28.1). Multivariate analysis revealed that a history of TURP was significantly associated with late urinary toxicity of grade ≥ 2, after adjusting for clinical target volume (Odds Ratio = 3.06; 95%CI: 1.05–8.86; P = 0.04). ConclusionExtreme hypofractionated SBRT is effective for localized prostate cancer with a low risk of late toxicity. A history of TURP is associated with a higher risk of late urinary toxicity. These findings may contribute to the optimal management of patients treated with this regimen, particularly those with a history of TURP.

In Curative Stereotactic Body Radiation Therapy for Prostate Cancer, There Is a High Possibility That 45 Gy in Five Fractions Will Not Be Tolerated without a Hydrogel Spacer.

The purpose of this study was to determine the maximum tolerated dose (MTD) for stereotactic body radiation therapy (SBRT) in the treatment of non-metastatic prostate cancer. This study was a phase 1 dose escalation trial conducted in Japan. Patients with histologically proven prostate cancer without lymph nodes or distant metastases were enrolled. The prescribed doses were 42.5, 45, or 47.5 Gy in five fractions. Dose-limiting toxicity (DLT) was defined as grade (G) 3+ gastrointestinal or genitourinary toxicity within 180 days after SBRT completion, and a 6 plus 6 design was used as the method of dose escalation. A total of 16 patients were enrolled, with 6 in the 42.5 Gy group and 10 in the 45 Gy group. No DLT was observed in the 42.5 Gy group. In the 45 Gy group, one patient experienced G3 rectal hemorrhage, and another had G4 rectal perforation, leading to the determination of 42.5 Gy as the MTD. None of the patients experienced biochemical recurrence or death during the follow-up period. We concluded that SBRT for non-metastatic prostate cancer at 42.5 Gy in five fractions could be safely performed, but a total dose of 45 Gy increased severe toxicity.

A commentary on "assessment of treatment outcomes: cytoreductive surgery compared to radiotherapy in oligometastatic prostate cancer - an in-depth quantitative evaluation and retrospective cohort analysis".

A commentary on "assessment of treatment outcomes: cytoreductive surgery compared to radiotherapy in oligometastatic prostate cancer - an in-depth quantitative evaluation and retrospective cohort analysis".

Hormonal therapy and radiation therapy in prostate cancer: 5-year outcomes from a trial evaluating combined androgen blockade with 5-alpha reductase inhibitors as an alternative to gonadotropin releasing hormone agonists

BackgroundWe previously reported that for men undergoing combined androgen deprivation therapy (ADT) and radiation therapy (RT) for prostate cancer, substitution of LHRH-agonists with 5-α- reductase inhibitors (5-ARIs) led to improved preservation of 6-month hormonal quality of life (hQOL). With longer term follow-up, we evaluated disease control. MethodsIn this non-randomized trial, men with unfavorable intermediate or high-risk prostate cancer, aged ≥70 years or with Charlson Comorbidity Index ≥2, were treated with RT (78-79.2 Gy in 39-44 fractions) and either oral ADT (oADT; 5-ARI with antiandrogen) or standard of care ADT (SOC; leuprolide with antiandrogen) for up to 28 months. The primary endpoint was EPIC hQOL; secondary endpoints included biochemical control and survival as well as changes in cholesterol and hemoglobin levels. ResultsBetween 2011-2018, 70 men were enrolled (40 in oADT; 30 in SOC). Median follow-up was 65 months [IQR 36-94]. Five-year freedom from biochemical failure for oADT and SOC was 89% versus 86%, disease free survival was 62% versus 69%, cancer-specific survival was 100% versus 96%, and overall survival was 70% versus 81% (all P>0.1). Testosterone (2 mo through 3 yr) and hemoglobin levels (2 mo through 2 yr) were higher, and cholesterol levels (1 yr) were lower in the oADT groups (all P<0.05). ConclusionsIn this non-randomized study, men treated with combined RT and oADT had better preservation of hQOL and comparable 5-year disease outcomes to men treated with SOC. Eugonadal testosterone with this approach may yield measurable benefits in cholesterol and hemoglobin levels. MicroabstractWe investigated the role of 5α-reductase inhibitors (5-ARIs) as an alternative to LHRH-agonists in this non-randomized trial of men with unfavorable intermediate/high-risk prostate cancer. Men treated with 5-ARIs had better preservation of hormonal quality of life with no obvious detriment in biochemical outcomes with 5 years of follow-up. This approach may be beneficial in men at high risk of toxicities.

10-yr Results of Moderately Hypofractionated Postoperative Radiotherapy for Prostate Cancer Focused on Treatment Related Toxicity

IntroductionTo retrospectively report long term outcomes following postoperative hypofractionated radiotherapy (RT) for prostate cancer, emphasizing treatment related toxicity. Material and MethodsPatients for whom adjuvant or salvage RT was indicated after prostatectomy were treated with a course of moderate hypofractionation consisting in the delivery of 62.5 Gy in 25 fractions (2.5 Gy per fraction) on the prostate bed in five consecutive weeks (EQD21.5 = 70 Gy) by means of 3D-CRT in most of them. Androgen deprivation therapy (ADT) was allowed at physician's discretion. Patients were evaluated for urinary and rectal complications according to the Common Terminology Criteria for Adverse Events v4 (CTCAE v.4). Overall survival (OS), biochemical recurrence free survival (bRFS), and metastasis-free survival (MFS) were estimated using the Kaplan–Meier method. ResultsOne hundred and ten patients with a median age of 67 years (range 51-78) were enrolled. The majority of them (82%) had adverse pathologic features only, while 31 (28%) had early biochemical relapse. Median PSA level before RT was 0.12 ng/ml (range 0-9 ng/ml). Median time from surgery was 4 months (range 1-136 months). Twenty-eight patients (25.4%) also received ADT. At a median follow up of 103 months (range 19-138 months), late Grade 3 and Grade 4 rectal toxicity were 0.9% (one case of hematochezia) and 0.9% (one case of fistula), respectively, while late Grade 3 GU side effects (urethral stenosis) occurred in 9 cases (8%). No late Grade 4 events were observed, respectively. Ten-year OS, b-RFS and MFS were 77.3% (95% C.I.: 82.1% - 72.5%), 53.3% (95% C.I.: 59.9% - 47.6%), and 76.7% (95% C.I.: 81.2% - 72.2%), respectively. ConclusionOur study provides long term data that a shortened course of postoperative RT is as safe and effective as a long course of conventionally fractionated RT and would improve patients’ convenience and significantly reduce RT department workloads. Micro-AbstractThis retrospective study on postoperative hypofractionated RT for prostate cancer (110 patients, 103-month follow-up) reveals low rates of severe toxicities. Ten-year survival rates are encouraging (77.3% overall, 53.3% biochemical recurrence-free, 76.7% metastasis-free). These results suggest that hypofractionated RT is a safe and effective alternative, offering convenience and reduced workload compared to conventional RT.

166 Radiation Therapy and IRreversible Electroporation (RTIRE) for Intermediate Risk Prostate Cancer

OBJECTIVES/GOALS: Prostate cancer treatment is associated with significant genitourinary side effects. There is a critical need for treatment with decreased morbidity. We report the development of a novel treatment paradigm combining irreversible electroporation and lower dose radiation to provide prostate cancer patients with a less morbid treatment. METHODS/STUDY POPULATION: Intermediate risk prostate cancer patients will undergo focal irreversible electroporation followed by low dose, whole gland radiation therapy. The primary endpoint is freedom from clinically significant cancer on biopsy at 12-month follow up. Secondary endpoints include safety profile, oncologic efficacy, effectiveness of RT and need for secondary treatment. This trial (NCT05345444) and currently actively recruiting patients after initial feasibility trial. Sample size is calculated to detect an increase in the proportion of patients who are cancer free at 1-year, from 0.80 to 0.95. An exact binomial test with a 10% one-sided significance level will have 94.3% power to detect the difference between the null and alternative hypothesis when the sample size is 42. RESULTS/ANTICIPATED RESULTS: This is a clinical trial in progress. DISCUSSION/SIGNIFICANCE: Combined irreversible electroporation (IRE) and a lower dose radiotherapy (RTIRE) may provide prostate cancer patients a treatment with minimal side effects.

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.

Incidence and Management of Radiation Cystitis After Pelvic Radiotherapy for Prostate Cancer: Analysis from a National Database

ObjectivesTo determine the incidence of radiation cystitis on Prostate Cancer (PCa) patients undergoing pelvic radiotherapy (RT), evaluating the most used management strategies, and identifying potential risk factors associated with the development of this condition. MethodsA retrospective analysis was conducted using the PearlDiver™ Mariner database, containing patient records compiled between 2011 and 2022. International Classification of Diseases (ICD) and Current Procedural Terminology (CPT) codes were employed to identify population and outcomes. We evaluated patients who underwent RT for PCa and subsequently developed radiation cystitis. Primary objective was to determine the overall incidence of radiation cystitis. Furthermore, we investigated its associated risk factors and management. ResultsA total of 274,865 PCa patients underwent RT during the study period. Of these, 48,713 (17.7%) experienced hematuria following RT, while 7,721 (2.8%) were diagnosed with radiation cystitis. After the diagnosis, 2,307 patients (29.9%) received diagnostic or therapeutic endoscopic interventions. Only 59 patients (0.76%) underwent endovascular embolization, while 151 patients (1.95%) required cystectomy. Hyperbaric oxygen therapy, administered to 1,287 patients (16.67%), was the only treatment that displayed a significant upward trend. Multivariate logistic regression identified obesity (OR 1.29; 95% C.I. 1.23 — 1.35), smoking (OR 1.27; 95% C.I. 1.22 — 1.33), and diabetes (OR 1.32; 95% C.I. 1.26 — 1.39), as significant risk factors for radiation cystitis (all p-values < 0.001). ConclusionsRadiation cystitis represents a rare complication after pelvic RT with significant clinical impact. Its incidence has remained stable throughout the study period. The identified risk factors corroborate the pathophysiology of radiation cystitis. Hyperbaric oxygen therapy was the only treatment to show an upward trend during the study period.

Ultra-hypofractionated radiotherapy for prostate cancer including seminal vesicles in the target volume: a treatment-planning study based on the HYPO-RT-PC fractionation schedule

PurposeUltra-hypofractionated (UHF) radiation therapy (RT) has become a treatment alternative for patients with localized prostate cancer. In more advanced cases, seminal vesicles (SV) are routinely included in the target volume. The Scandinavian HYPO-RT-PC trial, which compared 42.7Gy in 7 fractions (fr) to conventional fractionation (CF), did not include SV in the CTV. The primary objective of the present work is to implement a UHF simultaneous integrated boost (SIB) for prostate cancer RT, incorporating SV into the target volume based on this fractionation schedule. A secondary objective is to analyze the unintentional dose coverage of SV from state-of-the-art VMAT treatments to the prostate gland only. Material and MethodsTwo different equi-effective UHF-SIB treatment schedules to SV were derived based on the CF clinical schedule (50.0Gy/25fr to elective SV and 70.0Gy/35fr to verified SV-invasion (SVI)) using the linear quadric model with α/β=2Gy and 3Gy. The dose to the prostate was 42.7Gy/7fr in both schedules with 31.2Gy/37.8Gy (α/β=2Gy) and 32.7Gy/40.1Gy (α/β=3Gy) to elective SV/verified SVI. VMAT plans to the proximal 10mm and 20mm were optimized and dose-volume-metrics for target volumes and organs at risk (OAR) evaluated. ResultsDose metrics were overall lower for UHF-SIB compared to CF. QUANTEC based volume-criteria are 2-7% lower for rectum and 2-4% lower for bladder in the UHF-SIB. D98% to elective SV were 7-12Gy3 lower with UHF-SIB and the corresponding data for verified SVI were about 2-3Gy3. The SV(10mm) V90%/(29.5Gy) for prostate only treatments (42.7Gy) were in median (IQR) 99% (87-100)/ 78% (58-99) for CTV/PTV. ConclusionUHF RT, based on the HYPO-RT-PC fractionation schedule, with a SIB technique to the prostate and the base of the SV can be planned with lower doses (EQD2) to OARs compared to CF. Unintentional dose to the proximal parts of SV in prostate only treatment can be substantial.

Lonidamine Induced Selective Acidification and De-Energization of Prostate Cancer Xenografts: Enhanced Tumor Response to Radiation Therapy.

Prostate cancer is a multi-focal disease that can be treated using surgery, radiation, androgen deprivation, and chemotherapy, depending on its presentation. Standard dose-escalated radiation therapy (RT) in the range of 70-80 Gray (GY) is a standard treatment option for prostate cancer. It could be used at different phases of the disease (e.g., as the only primary treatment when the cancer is confined to the prostate gland, combined with other therapies, or as an adjuvant treatment after surgery). Unfortunately, RT for prostate cancer is associated with gastro-intestinal and genitourinary toxicity. We have previously reported that the metabolic modulator lonidamine (LND) produces cancer sensitization through tumor acidification and de-energization in diverse neoplasms. We hypothesized that LND could allow lower RT doses by producing the same effect in prostate cancer, thus reducing the detrimental side effects associated with RT. Using the Seahorse XFe96 and YSI 2300 Stat Plus analyzers, we corroborated the expected LND-induced intracellular acidification and de-energization of isolated human prostate cancer cells using the PC3 cell line. These results were substantiated by non-invasive 31P magnetic resonance spectroscopy (MRS), studying PC3 prostate cancer xenografts treated with LND (100 mg/kg, i.p.). In addition, we found that LND significantly increased tumor lactate levels in the xenografts using 1H MRS non-invasively. Subsequently, LND was combined with radiation therapy in a growth delay experiment, where we found that 150 µM LND followed by 4 GY RT produced a significant growth delay in PC3 prostate cancer xenografts, compared to either control, LND, or RT alone. We conclude that the metabolic modulator LND radio-sensitizes experimental prostate cancer models, allowing the use of lower radiation doses and diminishing the potential side effects of RT. These results suggest the possible clinical translation of LND as a radio-sensitizer in patients with prostate cancer.

Preventing Rectal Toxicity in Prostate Cancer: Diet and Supplement Alternative to Enemas or Rectal Spacer

Background: Rectal toxicity is an important side effect of prostate cancer irradiation affecting 25% of patients. The role of dosimetric variables has a set of dose-volume constraints and curves to estimate the risk of rectal damage. The rectum position at the time of CT planning is different from the position during radiotherapy. Three methods are available to achieve optimal rectum position: enema; prostate cancer spacer; fiber-/fat-free diet. Methods: A 70.2 Gray radiation divided into 26 hypo-fractions was administered to 115 patients with prostate cancer by VMAT referred to a single center in Italy. To empty the rectum, all patients were administered a fiber-/fat-free diet and those with Eating Disorders (ED) were also added with activated charcoal (2 tablets/day) and a macrogol-based medical device (2 sachets/day). During treatment, the volumetric amount of rectum in the target was measured by comparing control-CT with simulation-CT, and acute toxicity was also checked. Results: The rectum position during control-CT in diet-only patients (29) predicted toxicity recorded during treatment, while in the ED group rectum position was adherent to position during simulations. Rectal volume target &gt; 0.25 cc receiving a dose &gt; V70 caused acute G3 toxicity that attenuated or worsened with rectal displacement. Acute rectal toxicity occurred in 6/29 (20.68%) patients (1 G3, 5 G1) in the diet-only group, while only in 1/86 (1.16%) patients (G1) in the ED group. No chronic toxicity was recorded in either group. Conclusion: Prostate cancer patients treated with VMAT, diet, charcoal, and macrogol emptied the rectum optimally and reduced incidence and severity of acute rectal toxicity, also with benefit on late toxicity.

Second primary cancers following radiotherapy for prostate cancer: How many are actually due to the radiotherapy?

Second primary cancers following radiotherapy for prostate cancer: How many are actually due to the radiotherapy?

Abstract 1353: Potentiating salvage radiotherapy in radiorecurrent prostate cancer through anti-CTLA4 therapy: Implications from a syngeneic model

Abstract Background: Advanced prostate cancer (PCa) is a leading cause in cancer death and can elicit significant morbidity and mortality. A common treatment modality for advanced PCa is radiation therapy (RT). Currently, salvage of local disease recurrence after RT is a major clinical problem. Emerging evidence indicates the importance of the immune system in governing RT response. In support of this, immune checkpoint inhibitors (ICIs), which enhance immune activation, have demonstrated clinical therapeutic promise in combination with RT in certain advanced cancers. Irradiation (IR) combined with ICIs may prime the immune system to recognize and target recurrent cancer. Purpose: Investigate the therapeutic efficacy of ICIs in combination with RT for radiorecurrent PCa in a syngeneic pre-clinical model. Methods: TRAMP-C2 cells were treated with 10 Gy of radiation over 5 fractions (similar to clinical hypofractionated (HF) schedule) to generate TRAMP-C2 HF cells. Immune-competent mice were transplanted subcutaneously with TRAMP-C2 HF cells. Once tumors reached palpable size, mice were administered either ICIs (anti-PDL1 or anti-CTLA4) alone or in combination with RT. Tumor volume was monitored to determine the treatment effect. Correlative studies on excised tumors and secondary lymphoid organs included flow cytometry and NanoString gene expression panel to evaluate immunological mechanisms that contribute to anti-tumor effects. Results: TRAMP-C2 HF cells were validated for radiation resistance and exhibited a more aggressive phenotype (reduction in senescence, increase in clonogenicity) similar to clinically recurrent PCa. Radiation resistance of TRAMP-C2 HF tumors was validated in vivo. Administration of anti-PDL1 and anti-CTLA4 as monotherapy or in combination did not achieve significant tumor growth delay compared to control. IR alone produced an observable tumor growth delay compared to ICIs alone. The combination of anti-PDL1 and IR did not yield additional growth delay compared to IR alone. Strikingly, significant tumor growth delay was seen with the combination of IR and anti-CTLA4 compared to IR alone, while also resulting in complete cure in a third of the mice. mice. Lymph nodes and tumors from mice treated with IR and anti-CTLA4 vs. IR and isotype control demonstrated differential expression of genes in T cell functions and enrichment in both CD4+ and CD8+ T cell populations. Conclusion: We generated the first syngeneic radiorecurrent PCa model and demonstrated that combining anti-CTLA4 and IR results in synergistic tumor response. Combined therapy resulted in augmented immune response, most notably enhancement of CD8 T cell activity. Significance: These findings contribute to our understanding of immunological events associated with RT and ICIs in the context of radiorecurrent PCa and support new avenues for salvage therapy in clinical trials. Citation Format: Hanzhi Wang, Linsey Gong, Xiaoyong Huang, Stephanie D. White, Hanz T. Chung, Danny Vesprini, Tera N. Petchiny, Emmanouil Fokas, Hansen He, Robert S. Kerbel, Stanley K. Liu. Potentiating salvage radiotherapy in radiorecurrent prostate cancer through anti-CTLA4 therapy: Implications from a syngeneic model [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 1353.

Radiation-induced lumbosacral plexopathy and pelvic insufficiency fracture: A case report of unique coexistence of complications after radiotherapy for prostate cancer

Radiation-induced lumbosacral plexopathy and pelvic insufficiency fracture: A case report of unique coexistence of complications after radiotherapy for prostate cancer

Updated Analysis of Comparative Toxicity of Proton and Photon Radiation for Prostate Cancer.

Previous comparative effectiveness studies have not demonstrated a benefit of proton beam therapy (PBT) compared with intensity-modulated radiation therapy (IMRT) for prostate cancer. An updated comparison of GI and genitourinary (GU) toxicity is needed. We investigated the SEER-Medicare linked database, identifying patients with localized prostate cancer diagnosed from 2010 to 2017. Procedure and diagnosis codes indicative of treatment-related toxicity were identified. As a sensitivity analysis, we also identified toxicity based only on procedure codes. Patients who underwent IMRT and PBT were matched 2:1 on the basis of clinical and sociodemographic characteristics. We then compared GI and GU toxicity at 6, 12, and 24 months after treatment. The final sample included 772 PBT patients matched to 1,544 IMRT patients. The frequency of GI toxicity for IMRT versus PBT was 3.5% versus 2.5% at 6 months (P = .18), 9.5% versus 10.2% at 12 months (P = .18), and 20.5% versus 23.4% at 24 months (P = .11). The frequency of only procedure codes indicative of GI toxicity for IMRT versus PBT was too low to be reported and not significantly different. The frequency of GU toxicity for IMRT versus PBT was 6.8% versus 5.7% (P = .30), 14.3% versus 12.2% (P = .13), and 28.2% versus 25.8% (P = .21) at 6, 12, and 24 months, respectively. When looking only at procedure codes, the frequency of GU toxicity for IMRT was 1.0% at 6 months, whereas it was too infrequent to report for PBT (P = .64). GU toxicity for IMRT versus PBT was 3.3% versus 2.1% (P = .10), and 8.7% versus 6.7% (P = .10) at 12 and 24 months, respectively. In this observational study, there were no statistically significant differences between PBT and IMRT in terms of GI or GU toxicity.