Extreme Hypofractionation with SBRT in Localized Prostate Cancer

Effect of Continuous Nutritionist-led Guidance on Bowel Preparation in Patients Undergoing Prostate Stereotactic Body Radiation Treatment With Endorectal Spacing: A Prospective Pilot Trial

OBJECTIVE

To evaluate the effect of a daily nutritionist consultation on rectal volume, gas, and prostate displacement during Stereotactic Body Radiation Treatment (SBRT) with an endorectal spacer.

METHODS

Twenty-six consecutive patients receiving 5 fraction SBRT with endorectal spacing were prospectively enrolled for an intensive daily nutritionist intervention utilizing biofeedback based on image guidance from each fraction. A retrospective control cohort receiving a standard bowel preparation was compared. Rectal volume, rectal gas, and prostate displacement were assessed by analysis of cone beam computed tomography. Data was analyzed using the SPSS statistics software.

RESULTS

Intense dietary intervention with biofeedback led to a consistently lower rectal gas score over 5 fractions ( P <0.001) and less variability in rectal volume during prostate SBRT indicating a nonsignificant trend for superior preparation in the intervention group compared with controls, particularly for the first 2 fractions. However, there was no significant impact on prostate displacement as measured by couch correction.

CONCLUSIONS

Intense dietary consultations effectively reduce rectal gas and variation of rectal volume during prostate SBRT with endorectal spacing. However, there was no advantage in reducing prostate displacement. Thus, labor-intensive daily nutritionist intervention with biofeedback is not cost-effective in reducing organ motion in patients with endorectal spacers compared with standard pretreatment dietary advice and is not recommended.

PSA reduction as predictor of biochemical relapse in low and favourable intermediate prostate cancer treated with radical radiotherapy

PURPOSE

Radiation therapy (RT) is standard treatment for localized prostate cancer (PCa). Prostate-specific antigen (PSA) kinetics, particularly PSA reduction (PSAr) after RT, are emerging as significant prognostic indicators for biochemical control. This retrospective multi-institutional study explores the correlation between PSAr and biochemical relapse-free survival (BRFS). This retrospective multi-institutional study explores the correlation between PSAr and biochemical relapse-free survival (BRFS).

METHODS

251 low-to-intermediate risk PCa patients treated with RT only were analyzed. Isoeffective RT schedules were: 39 fractions × 2 Gy, 28 × 2.55 Gy, 16 × 3.5 Gy, 5 × 7 Gy. Main objective was BRFS, defined as the time from PSA nadir (PSAn) to PSAn plus 2 ng/ml. PSAr was defined as the percentage of total PSA reduction from baseline. The optimal PSAr cut-off value was defined as 90%. Patients were stratified by PSAr, baseline PSA, Gleason Score (GS), and RT schedules.

RESULTS

GS was 3 + 3 in 120 (48%) patients and 3 + 4 in 131 (52%) patients. After a median follow-up of 36 months (30-48), 2 and 5-year BRFS were 97.3% and 95.2%, respectively, in patients with PSAr ≥ 90% and 89.5%, 61.5% in patients with PSAr < 90% (p = 0.00). In the responder population, median time to PSAr 90% was 24 months and the median time to PSAn was 28.7 months (20-38). At univariate and multivariate analyses, PSAr was the only significant predictor of BRFS [HR 6.519 (95% IC 1.9-22.2), p = 0.003].

CONCLUSIONS

PSAr could be a reliable prognostic factor for long-term biochemical control. This study underscores the potential of PSAr as a tool for risk stratification and personalized follow-up strategies in PCa management.

Does biodegradable peri-rectal spacer mitigate treatment toxicities in radiation therapy for localised prostate cancer-a systematic review and meta-analysis

INTRODUCTION

There is an increasing use of biodegradable peri-rectal spacer prior to radiation therapy for prostate cancer to reduce treatment-associated rectal toxicity. While data from individual trials and cohorts is maturing, there is a lack of an updated quantitative analysis that includes outcomes following peri-rectal spacer. We aim to delineate the clinical impact of peri-rectal spacer in localised prostate cancer patients treated with radiotherapy.

METHODS

In March 2024, a systematic search was performed on MEDLINE, Embase, and Cochrane Central Register of controlled trials for publications since the year 2010. Prospective and retrospective studies reporting comparative outcomes of patients with and without peri-rectal spacer prior to radiotherapy were considered. Outcomes are reported in binary fashion. Random effect meta-analysis with the use of weighted mean difference was adopted. Early (≤3 months) and late rectal toxicity stratified according to the Common Terminology Criteria for Adverse Events (CTCAE) criteria, early and late genitourinary toxicity, quality of life in bowel, sexual and urinary domains (in terms of minimal clinically important difference) were assessed.

RESULTS

The systematic review included 17 studies. There are 3 RCTs, 3 prospective cohorts, and 11 retrospective cohorts. Three thousand two hundred patients were included, with 1471 patients who received peri-rectal spacer and 1729 without. The use of spacer is associated with lower likelihood of late (1.62% vs. 9.35%, RR = 0.25, 95% CI = 0.15-0.42, P < 0.001) and early grade 2 or above late rectal toxicity (3.07% vs. 6.05%, RR = 0.53, 95% CI = 0.33-0.86, P < 0.001). No difference is observed in significant grade 3 or above GI (acute or late) events. There is no statistical difference in bowel-related bowel QoL (risk difference = -0.16, 95% CI = -0.38-0.06, P = 0.15). The perirectal spacer is not associated with negative impact to urinary or sexual domains of QoL either.

CONCLUSION

In localised prostate cancer patients treated with radiation therapy, the use of peri-rectal spacer is associated with reduced rectal toxicities.

Stereotactic body radiotherapy (SBRT) as a treatment for localized prostate cancer: a retrospective analysis

BACKGROUND

External beam radiotherapy (EBRT) is a standard treatment for localized prostate cancer, with recent advancements favoring a reduced number of treatment sessions. Stereotactic body radiotherapy (SBRT) is a form of radiotherapy that delivers higher doses per fraction, typically in five or fewer sessions. This retrospective study aims to evaluate the implementation of the PACE-SBRT protocol for localized prostate cancer at our center by assessing the incidence and severity of toxicity, as well as biochemical relapse-free survival.

METHODS

We conducted a retrospective analysis of patients with localized prostate cancer treated with SBRT at the Iridium Network in Antwerp, Belgium, who were treated between January 1, 2020, and December 31, 2022. Data were extracted from electronic medical records and included descriptive information on patient outcomes. Acute and late genitourinary (GU) and gastrointestinal (GI) toxicities were graded according to the Common Terminology Criteria for Adverse Events (CTCAE) version 4.0. Acute toxicity was defined as events occurring within 90 days post-SBRT, whereas late toxicity was evaluated at 6 months, 1 year, 2 years, and 3 years post treatment. Biochemical recurrence was defined via the Phoenix criteria, as a rise in PSA levels of 2 ng/mL or more above the post treatment nadir.

RESULTS

A total of 267 patients met the eligibility criteria for this study. In total, 9% of patients were low risk, 51% were intermediate risk, and 40% were high risk. The cumulative incidence of Grade 2 or higher GU toxicity was 27%, and for GI toxicity, it was 2%. At 24 months, 11.5% (20/175) of patients experienced CTCAE grade 2 or higher GU toxicity, and 1.7% (3/175) experienced grade 2 or higher GI toxicity. Biochemical relapse occurred in 1.5% (4/267) of patients, leading to a 2-year biochemical relapse-free survival rate of 98.5%.

CONCLUSION

SBRT for localized prostate cancer has favorable oncological outcomes with a low incidence of Grade 2 or higher toxicity. The results of this study are consistent with findings from prospective trials, suggesting that SBRT is an effective treatment modality. Trial registration Retrospectively registered.

Reduction of Postradiation Therapy Urinary Toxicity Via Intrafractional Megavoltage-Kilovoltage Prostate Location Monitoring

PURPOSE

We hypothesized that an in-house developed system using megavoltage and kilovoltage image guidance (MKIG) to ensure correct prostate positioning during stereotactic body radiation therapy (SBRT) could potentially avoid unwanted doses to nontarget tissues, leading to reduced toxicities.

METHODS AND MATERIALS

We built a 3-dimensional MKIG platform that accurately tracks prostate implanted fiducials in real time and clinically translated the system to replace a commercial approach, intrafraction motion review (IMR), which only tracks fiducials in the 2-dimensional kilovoltage views. From 2017 to 2019, 150 patients with prostate cancer were treated with SBRT and monitored using MKIG. The motion trace of the fiducials alerts therapists to interrupt and reposition the prostate when displacement exceeds a 1.5 mm threshold. A comparison cohort of 121 patients was treated with the same dose regimen and treatment technique but managed by IMR. Statistics of intrafractional patient shifts and delivery time were collected to evaluate the workflow efficacy. The incidence of grade ≥2 urinary toxicities was analyzed to assess clinical complications. The median follow-up time was 3.7 years (0.2-8.2 years).

RESULTS

MKIG treatments had more treatment shifts (1.09 vs 0.28) and a longer average delivery time per fraction (579 ± 205 seconds vs 357 ± 117 seconds) than IMR treatments. Three-quarters (75%) of shifts resulting from MKIG were ≤3 mm, versus 51% in IMR, indicating that MKIG detected and corrected smaller deviations. The incidence of grade ≥2 urinary toxicity was lower in the MKIG than the IMR cohort: 10.7% versus 19.8% (P = .047). On multivariate analysis of late urinary toxicity, only high (>7) preradiation therapy international prostate symptom score (P < .043) and the use of MKIG were selected (P < .029).

CONCLUSIONS

Automated and quantitative MKIG introduced minimal workflow impact and was superior to IMR in localizing the prostate during SBRT, which correlated with a clinically significant reduction in late urinary toxicity. Further clinical testing using randomized trials will be required to validate the impact on outcomes.

The Proteogenomics of Prostate Cancer Radioresistance

Prostate cancer is frequently treated with radiotherapy. Unfortunately, aggressive radioresistant relapses can arise, and the molecular underpinnings of radioresistance are unknown. Modern clinical radiotherapy is evolving to deliver higher doses of radiation in fewer fractions (hypofractionation). We therefore analyzed genomic, transcriptomic, and proteomic data to characterize prostate cancer radioresistance in cells treated with both conventionally fractionated and hypofractionated radiotherapy. Independent of fractionation schedule, resistance to radiotherapy involved massive genomic instability and abrogation of DNA mismatch repair. Specific prostate cancer driver genes were modulated at the RNA and protein levels, with distinct protein subcellular responses to radiotherapy. Conventional fractionation led to a far more aggressive biomolecular response than hypofractionation. Testing preclinical candidates identified in cell lines, we revealed POLQ (DNA Polymerase Theta) as a radiosensitizer. POLQ-modulated radioresistance in model systems and was predictive of it in large patient cohorts. The molecular response to radiation is highly multimodal and sheds light on prostate cancer lethality.

SIGNIFICANCE

Radiation is standard of care in prostate cancer. Yet, we have little understanding of its failure. We demonstrate a new paradigm that radioresistance is fractionation specific and identified POLQ as a radioresistance modulator.

Analysis of intra-fractional positioning correction performed by cone beam computed tomography in SBRT treatments

PURPOSE

This study aims to evaluate the positioning correction extracted from Intra-fraction Cone Beam (IF-CBCT) images obtained during Stereotactic Body Radiotherapy (SBRT) treatments, and to assess whether its magnitude justifies its acquisition. In addition, the results obtained in lung, liver, and pancreas SBRTs with two deep inspiration breath-hold systems (DIBH), and for prostate with/without ultrasound (US) monitoring were compared.

METHODS

1449 treatments, performed with two linear accelerators (LINACs) were retrospectively analyzed. DIBH were performed either with a spirometry-based device or a surface-guidance system and one LINAC was equipped with US monitoring system for prostate. Significance tests were used to account for differences between units.

RESULTS

Group systematic error (M) was approximately -0.7 mm for DIBH treatments in superior-inferior (SI) direction with no difference (p > 0.7) between LINACs. Moreover, there was a SI difference of 0.5 mm for prostate treatments (p = 0.008), in favor of the US monitored one. In anterior-posterior (AP) direction, only liver treatments exhibited differences between LINACs, with the spirometer-based system being 0.8 mm inferior (p = 0.003). M<0.4 mm in left-right (LR) direction was found for all locations and LINACs. The spirometer-based system resulted in lower standard deviation of systematic and random errors in most components and locations, with a greater effect observed in liver SBRTs.

CONCLUSIONS

The corrections made with IF-CBCT during SBRT treatments were not negligible. Both DIBH systems were effective in managing respiratory movements. However, the spirometry-based system was slightly more accurate. In addition, US monitoring of the prostate appeared to be useful in reducing target shift.

Weekly ultra-hypofractionated radiotherapy in localised prostate cancer

Background

Moderately hypofractionated radiotherapy regimens or stereotactic body radiotherapy (SBRT) are standard of care for localised prostate cancer. However, some patients are unable or unwilling to travel daily to the radiotherapy department and do not have access to, or are not candidates for, SBRT. For many years, The Royal Marsden Hospital NHS Foundation Trust has offered a weekly ultra-hypofractionated radiotherapy regimen to the prostate (36 Gy in 6 weekly fractions) to patients unable/unwilling to travel daily.

Methods

The current study is a retrospective analysis of all patients with non-metastatic localised prostate cancer receiving this treatment schedule from 2010 to 2015.

Results

A total of 140 patients were included in the analysis, of whom 86 % presented with high risk disease, with 31 % having Gleason Grade Group 4 or 5 disease and 48 % T3 disease or higher. All patients received hormone treatment, and there was often a long interval between start of hormone treatment and start of radiotherapy (median of 11 months), with 34 % of all patients having progressed to non-metastatic castrate-resistant disease prior to start of radiotherapy. Median follow-up was 52 months. Median progression-free survival (PFS) and overall survival (OS) for the whole group was 70 months and 72 months, respectively. PFS and OS in patients with hormone-sensitive disease at time of radiotherapy was not reached and 75 months, respectively; and in patients with castrate-resistant disease at time of radiotherapy it was 20 months and 61 months, respectively.

Conclusion

Our data shows that a weekly ultra-hypofractionated radiotherapy regimen for prostate cancer could be an option in those patients for whom daily treatment or SBRT is not an option.

Online Adaptive MR-Guided Ultrahypofractionated Radiotherapy of Prostate Cancer on a 1.5 T MR-Linac: Clinical Experience and Prospective Evaluation

The use of hypofractionated radiotherapy in prostate cancer has been increasingly evaluated, whereas accumulated evidence demonstrates comparable oncologic outcomes and toxicity rates compared to normofractionated radiotherapy. In this prospective study, we evaluate all patients with intermediate-risk prostate cancer treated with ultrahypofractionated (UHF) MRI-guided radiotherapy on a 1.5 T MR-Linac within our department and report on workflow and feasibility, as well as physician-recorded and patient-reported longitudinal toxicity. A total of 23 patients with intermediate-risk prostate cancer treated on the 1.5 T MR-Linac with a dose of 42.7 Gy in seven fractions (seven MV step-and-shoot IMRT) were evaluated within the MRL-01 study (NCT04172753). The duration of each treatment step, choice of workflow (adapt to shape-ATS or adapt to position-ATP) and technical and/or patient-sided treatment failure were recorded for each fraction and patient. Acute and late toxicity were scored according to RTOG and CTC V4.0, as well as the use of patient-reported questionnaires. The median follow-up was 12.4 months. All patients completed the planned treatment. The mean duration of a treatment session was 38.2 min. In total, 165 radiotherapy fractions were delivered. ATS was performed in 150 fractions, 5 fractions were delivered using ATP, and 10 fractions were delivered using both ATS and ATP workflows. Severe acute bother (G3+) regarding IPS-score was reported in five patients (23%) at the end of radiotherapy. However, this tended to normalize and no G3+ IPS-score was observed later at any point during follow-up. Furthermore, no other severe genitourinary (GU) or gastrointestinal (GI) acute or late toxicity was observed. One-year biochemical-free recurrence survival was 100%. We report the excellent feasibility of UHF MR-guided radiotherapy for intermediate-risk prostate cancer patients and acceptable toxicity rates in our preliminary study. Randomized controlled studies with long-term follow-up are warranted to detect possible advantages over current state-of-the-art RT techniques.

Current Evidence on Local Therapies in Advanced Adrenocortical Carcinoma

International guidelines emphasise the role of local therapies (LT) for the treatment of advanced adrenocortical carcinoma (ACC). However, large studies are lacking in this field. Therefore, we performed a review of the literature to synthesise current evidence and develop clinical guidance. PubMed database was searched for systematic literature. We identified 119 potentially relevant articles, of which 21 could be included in our final analysis. All were retrospective and reported on 374 patients treated with LT for advanced ACC (12 studies on radiotherapy, 3 on transarterial chemoembolisation and radioembolisation, 4 on image-guided thermal ablation [radiofrequency, microwave ablation, and cryoablation, and two studies reporting treatment with several different LT]). Radiotherapy was frequently performed with palliative intention. However, in most patients, disease control and with higher dosage also partial responses could be achieved. Data for other LT were more limited, but also point towards local disease control in a significant percentage of patients. Very few studies tried to identify factors that are predictive on response. Patients with a disease-free interval after primary surgery of more than 9 months and lesions<5 cm might benefit most. Underreporting of toxicities may be prevalent, but LT appear to be relatively safe overall. Available evidence on LT for ACC is limited. LT appears to be safe and effective in cases with limited disease and should be considered depending on local expertise in a multidisciplinary team discussion.

Dosimetric comparison between stereotactic body radiotherapy and carbon-ion radiation therapy for prostate cancer

Background

Prostate cancer rates have been steadily increasing in recent years. As high-precision radiation therapy methods, stereotactic body radiation therapy (SBRT) and carbon-ion radiation therapy (CIRT) have unique advantages. Analyzing the dosimetric differences between SBRT and CIRT in the treatment of localized prostate cancer can help provide patients with more accurate, individualized treatment plans.

Methods

We selected computed tomography positioning images and the contours of target volumes of 16 patients with localized prostate cancer who received radiotherapy. We delineated the organs at risk (OARs) on the CyberKnife (CK) treatment planning system (TPS) MultiPlan4.0, which were imported into the CIRT uniform scanning TPS HIMM-1 ci-Plan. Two treatment plans, SBRT and CIRT, were designed for the same patient, and we used SPSS 22.0 for the statistical analysis of data.

Results

Both SBRT and CIRT plans met the prescribed dose requirements. In terms of target volume exposure dose, D2 (P<0.001), D5 (P<0.001), D50 (P<0.001), D90 (P=0.029), D95 (P<0.001), D98 (P<0.001), and Dmean (P<0.001) under SBRT were significantly higher than those under CIRT; the conformity index (CI) under SBRT was significantly better than that under CIRT (P<0.001); the target volume coverage rate (V95%) and dose homogeneity index (HI) under CIRT were significantly better than those under SBRT (P<0.001). In terms of OAR exposure dosage, the Dmax of the bladder and rectum under SBRT was significantly lower than that under CIRT (P<0.001), but Dmean was in the other direction; the exposure dose of the intestinal tract under CIRT was significantly lower than that under SBRT (P<0.05); Dmax of the femoral head under CIRT was significantly lower than that under SBRT (P<0.05), and there was no statistical difference between them at other doses.

Conclusions

In this study, we found that when CIRT was used for treating localized prostate cancer, the dose distribution in target volume was more homogeneous and the coverage rate was higher; the average dose of OARs was lower. SBRT had a better CI and higher dose in target volume; the dose hotspot was lower in OARs. It is important to comprehensively consider the dose relationship between local tumor and surrounding tissues when selecting treatment plans.

Gastrointestinal/genitourinary adverse event after intensity modulated versus three-dimensional primary radiation therapy in the treatment of prostate cancer: systematic review and meta-analysis

Objective: Prostate cancer (PCa) is one of the most common cancers in the world. The potential benefits of intensity modulated radiation therapy (IMRT) over three-dimensional conformal radiation therapy (3D-CRT) for PCa primary radiation therapy treatment have not yet been clarified. Therefore, this meta-analysis was conducted to assess whether IMRT could improve clinical outcomes in comparison with 3D-CRT in patients diagnosed with PCa. Materials and methods: Relevant studies were identified through searching related databases till December, 2022. Hazard ratio (HR) or risk ratio (RR) with its corresponding 95% confidence interval (CI) was used as pooled statistics for all analyses. Results: The incidence of grade 2 or worse acute adverse gastrointestinal (GI) event was analyzed and the pooled data revealed a clear decreasing trend in the IMRT compared with 3D-CRT (RR=0.62, 95% CI: 0.45-0.84, p=0.002). IMRT slightly increased the grade ≥ 2 acute genitourinary (GU) adverse event in comparison with the 3D-CRT (RR=1.10, 95% CI: 1.02-1.19, p=0.015). The IMRT and the 3D-CRT of patients showed no substantial differences in grade ≥ 2 late GI adverse event (RR =0.62, 95% CI: 0.36-1.09, p=0.1). In those included studies, there was no significant difference between IMRT and 3D-CRT in grade 2-4 late GU adverse event (RR =1.08, 95% CI: 0.77-1.51, p=0.65). There was a significant difference in biochemical control favoring IMRT (RR =1.13, 95% CI: 1.05-1.22, p=0.002). IMRT showed modest increase in biochemical control in comparison with 3D-CRT. Conclusion: In general, based on the above results, IMRT should be considered as a better choice for the treatment of PCa. More randomized controlled trials are needed to determine the subset of patients diagnosed with PCa.

The Current Trend of Radiation Therapy for Patients with Localized Prostate Cancer

A recent approach to radiotherapy for prostate cancer is the administration of high doses of radiation to the prostate while minimizing the risk of side effects. Thus, image-guided radiotherapy utilizes advanced imaging techniques and is a feasible strategy for increasing the radiation dose. New radioactive particles are another approach to achieving high doses and safe procedures. Prostate brachytherapy is currently considered as a combination therapy. Spacers are useful to protect adjacent organs, specifically the rectum, from excessive radiation exposure.

Linac-based versus MR-guided SBRT for localized prostate cancer: a comparative evaluation of acute tolerability

AIM

This study aims to compare acute toxicity of prostate cancer (PCa) stereotactic body radiotherapy (SBRT) delivered by MR-guided radiotherapy (MRgRT) with 1.5-T MR-linac or by volumetric modulated arc (VMAT) with conventional linac.

METHODS

Patients with low-to-favorable intermediate risk class PCa were treated with exclusive SBRT (35 Gy in five fractions). Patients treated with MRgRT were enrolled in an Ethical Committee (EC) approved trial (Prot. n° 23,748), while patients treated with conventional linac were enrolled in an EC approved phase II trial (n° SBRT PROG112CESC). The primary end-point was the acute toxicity. Patients were included in the analysis if they had at least 6 months of follow-up for the primary end-point evaluation. Toxicity assessment was performed according to CTCAE v5.0 scale. International Prostatic Symptoms Score (IPSS) was also performed.

RESULTS

A total of 135 patients were included in the analysis. Seventy-two (53.3%) were treated with MR-linac and 63 (46.7%) with conventional linac. The median initial PSA before RT was 6.1 ng/ml (range 0.49-19). Globally, acute G1, G2, and G3 toxicity occurred in 39 (28.8%), 20 (14.5%), and 5 (3.7%) patients. At the univariate analysis, acute G1 toxicity did not differ between MR-linac and conventional linac (26.4% versus 31.8%), as well as G2 toxicity (12.5% versus 17.5%; p = 0.52). Acute G2 gastrointestinal (GI) toxicity occurred in 7% and 12.5% of cases in MR-linac and conventional linac group, respectively (p = 0.06), while acute G2 genitourinary toxicity occurred in 11% and 12.8% in MR-linac and conventional linac, respectively (p = 0.82). The median IPSS before and after SBRT was 3 (1-16) and 5 (1-18). Acute G3 toxicity occurred in two cases in the MR-linac and three cases in the conventional linac group (p = n.s.).

CONCLUSION

Prostate SBRT with 1.5-T MR-linac is feasible and safe. Compared to conventional linac, MRgRT might to potentially reduce the overall G1 acute toxicity at 6 months, and seems to show a trend toward a lower incidence of grade 2 GI toxicity. A longer follow-up is necessary to assess the late efficacy and toxicity.

Advances in Urological Cancer in 2022, from Basic Approaches to Clinical Management

This Special Issue includes 12 articles and 3 reviews dealing with several basic and clinical aspects of prostate, renal, and urinary tract cancer published during 2022 in Cancers, and intends to serve as a multidisciplinary chance to share the last advances in urological neoplasms [...].

Targeted Radiation and Immune Therapies-Advances and Opportunities for the Treatment of Prostate Cancer

Prostate cancer is the most diagnosed malignancy in men in the United States and the second leading cause of cancer-related death. For localized disease, radiation therapy is a standard treatment that is often curative. For metastatic disease, radiation therapy has been primarily used for palliation, however, several newer systemic radiation therapies have been demonstrated to significantly improve patient outcomes and improve survival. In particular, several targeted radionuclide therapies have been approved for the treatment of advanced-stage cancer, including strontium-89, samarium-153, and radium-223 for bone-metastatic disease, and lutetium-177-labeled PSMA-617 for patients with prostate-specific membrane antigen (PSMA)-expressing metastatic castration-resistant prostate cancer (mCRPC). Contrarily, immune-based treatments have generally demonstrated little activity in advanced prostate cancer, with the exception of the autologous cellular vaccine, sipuleucel-T. This has been attributed to the presence of an immune-suppressive prostate cancer microenvironment. The ability of radiation therapy to not only eradicate tumor cells but also potentially other immune-regulatory cells within the tumor immune microenvironment suggests that targeted radionuclide therapies may be well poised to combine with immune-targeted therapies to eliminate prostate cancer metastases more effectively. This review provides an overview of the recent advances of targeted radiation agents currently approved for prostate cancer, and those being investigated in combination with immunotherapy, and discusses the challenges as well as the opportunities in this field.

Comparison of toxicities between ultrahypofractionated radiotherapy versus brachytherapy with or without external beam radiotherapy for clinically localized prostate cancer

To compare gastrointestinal (GI) and genitourinary (GU) toxicities in patients with localized prostate cancer treated with ultrahypofractionated radiotherapy (UHF) or brachytherapy [BT; low dose rate, LDR or high dose rate (HDR) with or without external beam radiotherapy (EBRT)]. We compared 253 UHF and 1664 BT ± EBRT groups. The main outcomes were the incidence and severity of acute and late GU and GI toxicities. The secondary endpoint was biochemical control rate. Cumulative late actuarial GU toxicity did not differ for grade ≥ 2 (8.6% at 5-years in UHF and 13.3% in BT ± EBRT, hazard ratio [HR], 0.7066; 95% CI, 0.4093–1.22, p = 0.2127). Actuarial grade ≥ 2 late GI toxicity was higher in UHF (5.8% at 5-years, HR: 3.619; 95% CI, 1.774–7.383, p < 0.001) than in BT ± EBRT (1.1%). In detailed subgroup analyses, the high-dose UHF group (H-UHF) using BED ≥ 226 Gy_1.5, showed higher GI toxicity profiles than the other subgroups (HDR + EBRT, LDR + EBRT, and LDR monotherapy, and L-UHF BED < 226 Gy_1.5) with equivalent GU toxicity to other modalities. With a median follow-up period of 32 months and 75 months, the actuarial biochemical control rates were equivalent between the UHF and BT ± EBRT groups. UHF showed equivalent efficacy, higher GI and equivalent GU accumulated toxicity to BT ± EBRT, and the toxicity of UHF was largely dependent on the UHF schedule.