Stereotactic body radiotherapy as treatment for organ confined low- and intermediate-risk prostate carcinoma, a 7-year study

Overview of Radiation Therapy in the Management of Localized and Metastatic Prostate Cancer

PURPOSE OF REVIEW

The goal is to describe the evolution of radiation therapy (RT) utilization in the management of localized and metastatic prostate cancer.

RECENT FINDINGS

Long term data for a variety of hypofractionated definitive RT dose-fractionation schemes has matured, allowing patients and providers many standard-of-care options to choose from. Post-prostatectomy, adjuvant RT has largely been replaced by an early salvage approach. Multiparametric MRI and PSMA PET have enabled increasingly targeted RT delivery to the prostate and oligometastatic tumors. Areas of active investigation include determining the value of proton beam therapy and perirectal spacers, and optimally incorporate genomic tumor profiling and next generation hormonal therapies with RT in the curative setting. The use of radiation therapy to treat prostate cancer is rapidly evolving. In the coming years, there will be continued improvements in a variety of areas to enhance the value of RT in multidisciplinary prostate cancer management.

In Search of Variables Affecting Mental Adjustment and Acceptance of Cancer among Urological Patients

Background/Objectives: Genitourinary cancers are now considered a major problem in modern medicine. In urological oncology, the most frequently occurring diseases are prostate, bladder and renal cancer. Any cancer has a profound effect on the life of a patient. Therefore, disease acceptance and mental adjustment to the condition are the key elements in coping with cancer. Aim: The main aim of the study was the determination of the level of acceptance of illness and mental adjustment to cancer in urological patients undergoing surgical treatment and the assessment of the effect of mental adjustment on disease acceptance. Material and Methods: The study group comprised 150 patients treated at the Department of Urology and Urological Oncology at the Independent Public Clinical Hospital No 2 in Szczecin. The study made use of the diagnostic survey method with the original questionnaire and standardized research tools: Acceptance of Illness Scale (AIS) and Mental Adjustment to Cancer Scale (Mini-MAC). Results: The analysis of mental adjustment to cancer according to Mini-MAC revealed that the respondents most frequently adopted the fighting spirit strategy (M; 22.22). Slightly less frequently adopted strategies were positive re-evaluation (M; 21.28) and anxious preoccupation (M; 17.07). The least frequently adopted strategy was the helplessness-hopelessness strategy (M; 13.14). The analysis of data showed a statistically significant negative correlation (r = -0.245; p = 0.003) between disease acceptance according to AIS and age. The data analysis revealed a statistically significant positive correlation with helplessness-hopelessness and destructive style (p < 0.05). Conclusions: Mental adjustment to cancer was found to affect the acceptance of illness. When providing comprehensive care to cancer patients, it is equally crucial to consider the physical as well as mental health aspect, taking into account the aforementioned factors which affect both acceptance as well as adjustment to disease.

Treatment Optimization in Linac-Based SBRT for Localized Prostate Cancer: A Single-Arc versus Dual-Arc Plan Comparison

This study aimed to comprehensively present data on treatment optimization in linac-based SBRT for localized prostate cancer at a single institution. Moreover, the dosimetric quality and treatment efficiency of single-arc (SA) versus dual-arc (DA) VMAT planning and delivery approaches were compared. Re-optimization was performed on twenty low-to-intermediate-risk- (36.25 Gy in 5 fractions) and twenty high-risk (42.7 Gy in 7 fractions) prostate plans initially administered with the DA FFF-VMAT technique in 2021. An SA approach was adopted, incorporating new optimization parameters based on increased planning and clinical experience. Analysis included target coverage, organ-at-risk (OAR) sparing, treatment delivery time, and the pre-treatment verification's gamma analysis-passing ratio. The SA optimization technique has consistently produced superior plans. Rectum and bladder mean doses were significantly reduced, and comparable target coverage and homogeneity were achieved in order to maintain a urethra protection strategy. The mean SA treatment delivery time was reduced by 22%; the mean monitor units increased due to higher plan complexity; and dose measurements demonstrated optimal agreement with calculations. The substantial reduction in treatment delivery time decreased the probability of prostate motion beyond the applied margins, suggesting potential decrease in treatment-related toxicity and improved target coverage in prostate SBRT. Further investigations are warranted to assess the long-term clinical outcomes.

Stereotactic body radiotherapy with CyberKnife® System for low- and intermediate-risk prostate cancer: clinical outcomes and toxicities of CyPro Trial

Simple summary

Stereotactic body radiotherapy (SBRT) of 35-36.25 Gy in five fractions with the CyberKnife System yields excellent control with low toxicity in low-intermediate-risk prostate cancer patients. We found no differences in biochemical control and overall survival in relation to dose. There were no significant differences in toxicity or quality of life between the two groups.

Aims

Stereotactic body radiotherapy (SBRT) is an emerging therapeutic approach for low- and intermediate-risk prostate cancer. We present retrospective data on biochemical control, toxicity, and quality of life of CyPro Trial.

Materials and methods

A total of 122 patients with low- and intermediate-risk prostate cancer were treated with the CyberKnife System at a dose of 35 Gy or 36.25 Gy in five fractions. Biochemical failure (BF)/biochemical disease-free survival (bDFS) was defined using the Phoenix method (nadir + 2 ng/ml). Acute/late rectal and urinary toxicities were assessed by the Radiation Therapy Oncology Group (RTOG) toxicity scale. Quality of life (QoL) was assessed by the European Organisation for Research and Treatment of Cancer (EORTC) QLQ C30 and PR25. International Erectile Function Index-5 (IIEF5) and International Prostate Symptom Score (IPSS) questionnaires were administered at baseline, every 3 months after treatment during the first years, and then at 24 months and 36 months.

Results

The 1-, 2-, and 5-year DFS rates were 92.9%, 92.9%, and 92.3%, respectively, while the 1-, 2-, and 5-year bDFS rates were 100%, 100%, and 95.7%, respectively. With regard to risk groups or doses, no statistically significant differences were found in terms of DFS or bDFS. Grade 2 urinary toxicity was acute in 10% and delayed in 2% of patients. No Grade 3 acute and late urinary toxicity was observed. Grade 2 rectal toxicity was acute in 8% and late in 1% of patients. No Grade 3-4 acute and late rectal toxicity was observed. Grade 2 acute toxicity appeared higher in the high-dose group (20% in the 36.25-Gy group versus 3% in the 35-Gy group) but was not statistically significant.

Conclusion

Our study confirms that SBRT of 35-36.25 Gy in five fractions with the CyberKnife System produces excellent control with low toxicity in patients with low-intermediate-risk prostate cancer. We found no dose-related differences in biochemical control and overall survival. Further confirmation of these results is awaited through the prospective phase of this study, which is still ongoing.

Differential Use of Radiotherapy Fractionation Regimens in Prostate Cancer

Importance

Technical advances in treatment of prostate cancer and a better understanding of prostate cancer biology have allowed for hypofractionated treatment courses using a higher dose per fraction. Use of ultrahypofractionated stereotactic body radiotherapy (SBRT) has also been characterized.

Objective

To characterize US national trends of different RT fractionation schemes across risk groups of prostate cancer.

Design, Setting, and Participants

This retrospective cohort study used data collected by the National Cancer Database (NCDB) to characterize the fractionation regimens used for 302 035 patients diagnosed as having prostate cancer from January 1, 2004, to December 31, 2020, who underwent definitive RT. The analysis was performed between February 1 and April 30, 2023.

Exposure

Stereotactic body RT or ultrahypofractionation, defined as 5 or fewer fractions of external beam RT (EBRT), moderate hypofractionation, defined as 20 to 28 fractions of EBRT, or conventional fractionation, defined as all remaining EBRT fractionation schemes.

Main Outcomes and Measures

Temporal trends and clinical and sociodemographic factors associated with SBRT, moderate hypofractionation, and conventional fractionation use.

Results

A total of 302 035 men receiving EBRT for localized prostate cancer between 2004 and 2020 were identified (40.1% aged 60-69 years). Black patients comprised 17.6% of this cohort; White patients, 77.9%; and other races and ethnicities, 4.5%. Patients with low-risk disease comprised 17.5% of the cohort; favorable intermediate-risk disease, 23.5%; unfavorable intermediate-risk disease, 23.9%; and high-risk disease, 35.1%. Treatment consisted of conventional fractionation for 81.2%, moderate hypofractionation for 12.9%, and SBRT for 6.0%. The rate of increase over time in patients receiving SBRT compared with conventional fractionation was higher (adjusted odds ratio [AOR] for 2005 vs 2004, 3.18 [95% CI, 2.04-4.94; P < .001]; AOR for 2020 vs 2004, 264.69 [95% CI, 179.33-390.68; P < .001]) than the rate of increase in patients receiving moderate hypofractionation compared with conventional fractionation (AOR for 2005 vs 2004, 1.05 [95% CI, 0.98-1.12; P = .19]; AOR for 2020 vs 2004, 4.41 [95% CI, 4.15-4.69; P < .001]). Compared with White patients, Black patients were less likely to receive SBRT compared with conventional fractionation or moderate hypofractionation (AOR for conventional fractionation, 0.84 [95% CI, 0.80-0.89; P < .001]; AOR for moderate hypofractionation, 0.77 [95% CI, 0.72-0.81; P < .001]). Compared with 2019, patients treated with all fractionation regimens declined in 2020 by 24.4%.

Conclusions and Relevance

In this hospital-based cohort study of patients with prostate cancer treated with definitive EBRT, use of moderate hypofractionation and SBRT regimens for definitive prostate cancer treatment has increased from 2004 to 2020. Despite this increasing trend, findings suggest potential health care disparities for Black patients receiving EBRT for localized prostate cancer. The number of patients treated with EBRT in the year 2020 decreased, coinciding with official onset of the COVID-19 pandemic in March 2020.

Prostate Stereotactic Body Radiation Therapy With a Focal Simultaneous Integrated Boost: 5-Year Toxicity and Biochemical Recurrence Results From a Prospective Trial

PURPOSE

Stereotactic body radiation therapy (SBRT) is increasingly used as a definitive treatment option for patients with prostate adenocarcinoma. The aim of this study was to assess the late toxicity, patient-reported quality of life outcomes, and biochemical recurrence rates after prostate SBRT with simultaneous integrated boost (SIB) targeting lesions defined by magnetic resonance imaging (MRI).

METHODS AND MATERIALS

Patients were eligible if they had biopsy-proven low- or intermediate-risk prostate adenocarcinoma, one or more focal lesions on MRI, and an MRI-defined total prostate volume of <120 mL. All patients received SBRT delivered to the entire prostate to a dose of 36.25 Gy in 5 fractions with an SIB to the lesions seen on MRI to 40 Gy in 5 fractions. Late toxicity was defined as any possible treatment-related adverse event occurring after 3 months from the completion of SBRT. Patient-reported quality of life was ascertained using standardized patient surveys.

RESULTS

A total of 26 patients were enrolled. Six patients (23.1%) had low-risk disease and 20 patients had intermediate-risk disease (76.9%). Seven patients (26.9%) received androgen deprivation therapy. Median follow-up was 59.5 months. No biochemical failures were observed. Three patients (11.5%) experienced late grade 2 genitourinary (GU) toxicity requiring cystoscopy, and 7 patients (26.9%) had late grade 2 GU toxicity requiring oral medications. Three patients (11.5%) had late grade 2 gastrointestinal toxicity characterized by hematochezia requiring colonoscopy and steroids per rectum. There were no grade 3 or higher toxicity events observed. The patient-reported quality-of-life metrics at the time of last follow-up were not significantly different than the pre-treatment baseline.

CONCLUSIONS

The results of this study support that SBRT to the entire prostate to a dose of 36.25 Gy in 5 fractions with focal SIB to 40 Gy in 5 fractions has excellent biochemical control and is not associated with undue late gastrointestinal or GU toxicity or long-term quality of life decrement. Focal dose escalation with an SIB planning approach may be an opportunity to improve biochemical control while limiting dose to nearby organs at risk.

Dosimetric Impact of Intrafraction Prostate Motion and Interfraction Anatomical Changes in Dose-Escalated Linac-Based SBRT

The dosimetric impact of intrafraction prostate motion and interfraction anatomical changes and the effect of beam gating and motion correction were investigated in dose-escalated linac-based SBRT. Fifty-six gated fractions were delivered using a novel electromagnetic tracking device with a 2 mm threshold. Real-time prostate motion data were incorporated into the patient's original plan with an isocenter shift method. Delivered dose distributions were obtained by recalculating these motion-encoded plans on deformed CTs reflecting the patient's CBCT daily anatomy. Non-gated treatments were simulated using the prostate motion data assuming that no treatment interruptions have occurred. The mean relative dose differences between delivered and planned treatments were -3.0% [-18.5-2.8] for CTV D99% and -2.6% [-17.8-1.0] for PTV D95%. The median cumulative CTV coverage with 93% of the prescribed dose was satisfactory. Urethra sparing was slightly degraded, with the maximum dose increased by only 1.0% on average, and a mean reduction in the rectum and bladder doses was seen in almost all dose metrics. Intrafraction prostate motion marginally contributed in gated treatments, while in non-gated treatments, further deteriorations in the minimum target coverage and bladder dose metrics would have occurred on average. The implemented motion management strategy and the strict patient preparation regimen, along with other treatment optimization strategies, ensured no significant degradations of dose metrics in delivered treatments.

Overview of the current role of stereotactic body radiotherapy in the treatment of unfavorable intermediate- and high-risk prostate cancer

Stereotactic body radiotherapy (SBRT) is well accepted for low- and intermediate-favorable risk prostate cancer. Available evidence about the application of SBRT in unfavorable- and high-risk prostate cancer is less solid. During last year's multiple variations in treatment, techniques have been reported making comparisons more complicated. This review's objective is to review current evidence in application of SBRT in intermediate unfavourable and high-risk prostate cancer and to outline variations in SBRT treatment techniques and relevant results.

Prospective validation of stringent dose constraints for prostatic stereotactic radiation monotherapy: results of a single-arm phase II toxicity-oriented trial

PURPOSE

There are no safety-focused trials on stereotactic body radiotherapy (SBRT) for localized prostate cancer. This prospective 3‑year phase II trial used binomial law to validate the safety and efficacy of SBRT with stringent organ at risk dose constraints that nevertheless permitted high planning target volume doses.

METHODS

All consecutive ≥ 70-year-old patients with localized prostate adenocarcinoma who underwent SBRT between 2014 and 2018 at the National Radiotherapy Center in Luxembourg were included. Patients with low Cancer of Prostate Risk Assessment (CAPRA) scores (0-2) and intermediate scores (3-5) received 36.25 Gy. High-risk (6-10) patients received 37.5 Gy. Radiation was delivered in 5 fractions over 9 days with Cyberknife-M6™ (Accuray, Sunnyvale, CA, USA). Primary study outcome was Common Terminology Criteria for Adverse Events version 4 (CTCAEv4) genitourinary and rectal toxicity scores at last follow-up. Based on binomial law, SRBT was considered safe in this cohort of 110 patients if there were ≤ 2 severe toxicity (CTCAEv4 grade ≥ 3) cases. Secondary outcomes were biochemical progression-free survival (bPFS) and patient quality of life (QOL), as determined by the IPPS and the Urinary Incontinence QOL questionnaire.

RESULTS

The first 110 patients who were accrued in a total cohort of 150 patients were included in this study and had a median follow-up of 36 months. Acute grade ≥ 3 toxicity never occurred. One transient late grade 3 case was observed. Thus, our SBRT program had an estimated severe toxicity rate of < 5% and was safe at the p < 0.05 level. Overall bPFS was 90%. QOL did not change relative to baseline.

CONCLUSION

The trial validated our SBRT regimen since it was both safe and effective.

Cost-Utility Analysis of Radiation Treatment Modalities for Intermediate-Risk Prostate Cancer

INTRODUCTION

Variable costs of different radiation treatment modalities have played an important factor in selecting the most appropriate treatment for patients with intermediate-risk prostate cancer.

METHODS

Analysis using a Markov model was conducted to simulate 20-year disease trajectory, quality-adjusted life years (QALYs) and health system costs of a cohort of intermediate-risk prostate cancer patients with mean age of 60 years. Clinical outcomes on toxicity and disease recurrence were measured and a probabilistic sensitivity analysis was performed, varying input parameters simultaneously according to their distributions.

RESULTS

Among the six radiation treatment modalities, including conventionally fractionated intensity-modulated radiation therapy (IMRT), hypofractionated IMRT, IMRT combined with high-dose-rate (HDR) brachytherapy, HDR brachytherapy monotherapy, low-dose-rate brachytherapy monotherapy, and stereotactic body radiotherapy (SBRT), SBRT was found to be more cost-effective when compared with LDR-b and other treatment modalities, resulting in an incremental cost-utility ratio of $2985 per QALY.

CONCLUSIONS

Stereotactic body radiotherapy is the most cost-effective radiation treatment modality in treatment of intermediate-risk prostate cancer, while treatment toxicity and cost data are the key drivers of the cost-utility. Further work is required with long-term follow-up for SBRT.

Progress and prospects of flattening filter free beam technology in radiosurgery and stereotactic body radiotherapy

The aim of this work is to summarize and evaluate the current status of knowledge on flattening filter free (FFF) beams and their applications in stereotactic radiosurgery (SRS) and stereotactic body radiotherapy (SBRT). A PubMed search was undertaken in order to identify relevant publications using FFF and stereotactic radiotherapy as keywords. On a clinical aspect, lung tumors treated with FFF SBRT show promising results in terms of local control and overall survival with acute toxicities consistent with those that occur with standard radiotherapy. Beside lung, SBRT is suitable for different anatomical sites such as liver, prostate, cervix, etc. offering similar results: reduced treatment time, good tumor control and mild acute toxicities. Regarding brain tumors, the employment of SRS with FFF beams significantly reduces treatment time and provides notable normal tissue sparing due to the sharp dose fall-off outside the tumor.

MR-Guided Radiotherapy for Prostate Cancer

External beam radiotherapy remains the primary treatment modality for localized prostate cancer. The radiobiology of prostate carcinoma lends itself to hypofractionation, with recent studies showing good outcomes with shorter treatment schedules. However, the ability to accurately deliver hypofractionated treatment is limited by current image-guided techniques. Magnetic resonance imaging is the main diagnostic tool for localized prostate cancer and its use in the therapeutic setting offers anatomical information to improve organ delineation. MR-guided radiotherapy, with daily re-planning, has shown early promise in the accurate delivery of radiotherapy. In this article, we discuss the shortcomings of current image-guidance strategies and the potential benefits and limitations of MR-guided treatment for prostate cancer. We also recount present experiences of MR-linac workflow and the opportunities afforded by this technology.

Biochemical Control and Toxicity Outcomes of Stereotactic Body Radiation Therapy Versus Low-Dose-Rate Brachytherapy in the Treatment of Low- and Intermediate-Risk Prostate Cancer

PURPOSE

Low-dose-rate (LDR) brachytherapy and stereotactic body radiation therapy (SBRT) have both shown acceptable outcomes in the treatment of low- and intermediate-risk prostate cancer. Minimal data have been published directly comparing rates of biochemical control and toxicity with these 2 modalities. We hypothesize that LDR and SBRT will provide similar rates of biochemical control.

METHODS AND MATERIALS

All low- and intermediate-risk patients with prostate cancer treated definitively with SBRT or LDR between 2010 and 2018 were captured. Phoenix definition was used for biochemical failure. Independent t tests were used to compare baseline characteristics, and repeated measure analysis of variance test was used to compare American Urologic Association (AUA) and the Expanded Prostate Cancer Index Composite (EPIC) scores between treatment arms over time. Biochemical control was estimated using the Kaplan-Meier method. Differences in acute and late toxicity were assessed via Pearson χ².

RESULTS

In the study, 219 and 118 patients were treated with LDR and SBRT. Median follow-up was 4.3 years (interquartile range, 3.1-6.1). All patients treated with LDR received 125.0 Gy in a single fraction. SBRT consisted of 42.5 Gy in 5 fractions. Five-year biochemical control for LDR versus SBRT was 91.6% versus 97.6% (P = .108). LDR patients had a larger increase in mean AUA scores at 1 month (17.2 vs 10.3, P < .001) and 3 months posttreatment (14.0 vs 9.7, P < .001), and in mean EPIC scores at 1 month (15.7 vs 13.8, P < .001). There was no significant difference between LDR and SBRT in late grade 3 genitourinary toxicity (0.9% vs 2.5%, P = .238); however, LDR had lower rates of late grade 3 gastrointestinal toxicity (0.0% vs 2.5%, P = .018).

CONCLUSIONS

Our data show similar biochemical control and genitourinary toxicity rates at 5 years for both SBRT and LDR, with slightly higher gastrointestinal toxicity with SBRT and higher AUA and EPIC scores with LDR.

Stereotactic Body Radiation Therapy for Intermediate-risk Prostate Cancer With VMAT and Real-time Electromagnetic Tracking: A Phase II Study

OBJECTIVES

Stereotactic body radiation treatment represents an intriguing therapeutic option for patients with early-stage prostate cancer. In this phase II study, stereotactic body radiation treatment was delivered by volumetric modulated arc therapy with flattening filter free beams and was gated using real-time electromagnetic transponder system to maximize precision of radiotherapy and, potentially, to reduce toxicities.

MATERIALS AND METHODS

Patients affected by histologically proven prostate adenocarcinoma and National Comprehensive Cancer Network (NCCN) intermediate class of risk were enrolled in this phase II study. Beacon transponders were positioned transrectally within the prostate parenchyma 7 to 10 days before simulation computed tomography scan. The radiotherapy schedule was 38 Gy in 4 fractions delivered every other day. Toxicity assessment was performed according to Common Terminology Criteria for Adverse Events (CTCAE), v4.0.

RESULTS

Thirty-six patients were enrolled in this study. Median initial prostate-specific antigen was 7.0 ng/mL (range: 2.3 to 14.0 ng/mL). Median nadir-prostate-specific antigen after treatment was 0.2 ng/mL (range: 0.006 to 4.8 ng/mL). A genitourinary acute toxicity was observed in 21 patients (dysuria grade [G] 1: 41.7%, G2: 16.7%). Gastrointestinal acute toxicity was found in 9 patients (proctitis G1: 19.4%, G2: 5.6%). Late toxicity was mild (genitourinary toxicity G1: 30.6%; G2: 8.3%; gastrointestinal toxicity G1: 13.9%; G2: 19.4%). At a median follow-up time of 41 months, 3 biochemical recurrences were observed (2 local recurrences, 1 distant metastasis). Three-year biochemical recurrence-free survival was 89.8% (International Society of Urologic Pathology Grade Group 2: 100%, Grade Group 3: 77.1%, P=0.042).

CONCLUSION

Ultrahypofractionated radiotherapy, delivered with flattening filter free-volumetric modulated arc therapy and gated by electromagnetic transponders, is a valid option for intermediate-risk prostate cancer.

Prostate SBRT: Comparison the Efficacy and Toxicity of Two Different Dose Fractionation Schedules

Background: CyberKnife SBRT is capable of producing dosimetry comparable to that created by HDR brachytherapy. Our original CyberKnife prostate SBRT schedule of 3,800 cGy/4 fractions (“high dose”) was based upon favorable published prostate HDR brachytherapy experience. Subsequently, our trial was modified to allow a lower dose of 3,400 cGy/5 fractions (“moderate dose”) in selected cases.

Methods: Two hundred eighty-nine low and intermediate-risk patients were treated to either high dose (178 pts) or moderate dose (111 pts). The dose selection was individualized; high dose more commonly used in younger, intermediate-risk patients, and moderate dose more commonly used in older, low-risk patients.

Results: Median PSA reached 5-year nadir levels of 0.034 ng/mL in the high dose, vs. 0.1 ng/mL in the moderate dose groups, respectively (p = 0.044 by year 4), with 62 vs. 44% reaching an ablation PSA nadir (<0.1 ng/mL) by year 5, respectively. Five year biochemical relapse free survival rates measured 98.3% for moderate dose and 94.3% for high dose groups, respectively (p = 0.1946). Five-year actuarial grade 2 genitourinary (GU) toxicity rates measured 11.6 vs. 8.7% for high dose vs. moderate dose groups, respectively, with a far lower incidence of grade ≥3 GU and grade ≥2 GI toxicity rates in both groups.

Conclusions: Both regimens are efficacious in their respective, selected groups. Both arms have low grade ≥3 GU toxicity and ≥grade 2 GI toxicity. In favor of the original high dose regimen, it has longer follow-up, produces a lower PSA nadir value and is more likely to eventually produce an ablation PSA nadir (<0.1 ng/mL). In favor of the lower dose regimen, it also produces a low PSA nadir, and does so with a slightly lower grade 2 GU toxicity rate. As a lower PSA nadir could be the initial predictor a lower clinical relapse rate far beyond 5 years, even if no difference is apparent within that time frame, a practical strategy could be to more strongly consider the high dose regimen in those with the greatest potential longevity, while for those with a more limited longevity, particularly if they have minimal negative prognostic factors, the moderate dose regimen could be more attractive.

Triggered Imaging With Auto Beam Hold and Pre-/Posttreatment CBCT During Prostate SABR: Analysis of Time Efficiency, Target Coverage, and Normal Volume Changes

PURPOSE

Our purpose was to investigate time efficiency and target coverage for prostate stereotactic ablative radiation therapy (SABR) using triggered imaging (TI) and auto beam hold.

METHODS AND MATERIALS

A total of 20 patients were treated with volumetric modulated arc-based SABR. Treatment verification consisted of pre- and post-radiation therapy cone beam computed tomography (CBCT) with gold marker-based TI every 3 seconds. In case of ≥3 mm (deviation limit) displacement, the treatment was interrupted and imaging-based correction was performed. Beam interruptions, intrafractional shifts, and treatment times were recorded. Prostate, rectum, and bladder were delineated on each CBCT. Target coverage was evaluated by comparing the individual prostate delineations with 98% isodose contour volumes (% of the evaluated volumes exceeding the reference). Both inter- and intrafractional changes of bladder and rectal volumes were assessed.

RESULTS

The average overall treatment time (±standard deviation) was 18 ± 11 min, with a radiation delivery time of 6 ± 3 min if no intrafractional CBCT acquisitions were necessary (91% of fractions). On average, 1.2 beam interruptions per fraction were required with 0/1 correction in 71% of the fractions. The mean residual 3-dimensional shift was 1.6 mm, exceeding the deviation limit in 8%. In the case of intrafractional CBCT and/or ≥2 corrections the treatment time dramatically increased. The 98% isodose lines did not encompass the prostate in only 8/180 (4%) evaluations in 6 different patients, leading to a loss of D98 between 0.1%-6% as a worst case scenario. The bladder volumes showed significant increases during treatment (P < .01) while rectal volumes were stable.

CONCLUSIONS

Time efficiency of TI + auto beam hold with 3 mm/3 sec threshold during prostate SABR is comparable with competitive techniques, resulting in minimal 3-dimensional residual errors with maintained target coverage. Technical developments are necessary to further reduce radiation delivery time. Use of CBCT allowed full control of rectal volumes, while bladder volumes showed significant increases over time.

Trends in the Use of Stereotactic Body Radiotherapy for Treatment of Prostate Cancer in the United States

IMPORTANCE

Stereotactic body radiotherapy is a hypofractionated, cost-effective treatment option for localized prostate cancer.

OBJECTIVE

To characterize US national trends and the clinical and socioeconomic factors associated with the use of stereotactic body radiotherapy in prostate cancer.

DESIGN, SETTING, AND PARTICIPANTS

This retrospective cohort study used data collected by the National Cancer Database to assess the clinical and socioeconomic factors among 106 926 men diagnosed as having prostate cancer from 2010 to 2015 who underwent definitive radiotherapy and the trends in the use of this therapy. The initial analysis was performed between January and February 2018, with final updates performed August 2019.

EXPOSURE

Stereotactic body radiotherapy, defined as 5 fractions of radiotherapy.

MAIN OUTCOMES AND MEASURES

Temporal trends and clinical and sociodemographic factors associated with stereotactic body radiotherapy use.

RESULTS

In total, 106 926 patients diagnosed as having localized prostate cancer between 2010 and 2015 and receiving definitive radiotherapy were identified. White patients composed 77.3% of this cohort, whereas black patients composed 18.7%. Government-issued insurance was used by 61.2% of patients. More than 80% of patients had a Charlson-Deyo Comorbidity Index score of 0 (range, 0 to ≥3, with lower numbers indicating fewer comorbidities). In the study population, 25.7% had low-risk disease; 26.3%, favorable intermediate-risk disease; 23.3%, unfavorable intermediate-risk disease; and 24.7%, high-risk disease. The proportion of patients who underwent radiotherapy and received stereotactic body radiotherapy (a total of 5395 patients) increased from 3.1% in 2010 to 7.2% in 2015 (odds ratio, 0.36; 95% CI, 0.33-0.40; P < .001). Among the entire cohort, patients received a median dose of 36.25 Gy (range, 30.00-50.00 Gy). Androgen deprivation therapy use increased significantly as disease risk level increased among all patients receiving radiotherapy (9.5% with low risk to 76.6% with high risk; P = .02) and among those receiving stereotactic body radiotherapy (4.1% with low risk to 33.2% with high risk; P = .04) or not receiving stereotactic body radiotherapy (9.9% with low risk to 77.6% with high risk; P = .04). Patients treated at an academic center, living in an urban area, or possessing higher incomes and those who were healthier, white individuals, or were diagnosed as having lower-risk prostate cancer had higher odds of receiving stereotactic body radiotherapy.

CONCLUSIONS AND RELEVANCE

This study found that stereotactic body radiotherapy use in prostate cancer more than doubled from 2010 to 2015 but accounted for less than 10% of all patients undergoing radiotherapy. Androgen deprivation therapy use increased with disease risk among patients overall, regardless of receiving stereotactic body radiotherapy. Socioeconomic and clinical determinants of stereotactic body radiotherapy included risk category, Charlson-Deyo Comorbidity Index score, facility type and location, income, race/ethnicity, and year of diagnosis. These results are hypothesis generating; further studies evaluating potential disparities in stereotactic body radiotherapy use in localized prostate cancer are warranted.

RADIOTHERAPY OF PROSTATE CANCER: PRIMARY RADIOTHERAPY AND RADIOTHERAPY IN DISEASE RELAPSE

Radiotherapy presents one of the essential modes of treatment in patients with prostate cancer at almost any stage of the disease. It can be delivered as external beam radiotherapy, as brachytherapy or two methods combined. Higher radiation doses are proven to be more effective than low doses and moderate hypofractionation with doses up to 3.4 Gy per fraction is proven equivalent to standard fractionation using 1.8- 2 Gy per fraction. Stereotactic body radiotherapy (SBRT) with doses from 3.4 to 7.25 Gy per fraction presents valuable option in certain subgroups of patients. In case of local regional disease relapse, radiotherapy is used in curative setting.

Extreme hypofractionated proton radiotherapy for prostate cancer using pencil beam scanning: Dosimetry, acute toxicity and preliminary results

INTRODUCTION

Extreme hypofractionated radiotherapy for prostate cancer is a common modality in photon therapy. Pencil beam scanning (PBS) in similar fractionation allows better dose distribution and makes proton therapy more available for such patients. The purpose of this study is the feasibility of extreme proton hypofractionated radiotherapy and publication of early clinical results.

METHODS

Two hundred patients with early-stage prostate cancer were treated with IMPT (intensity-modulated proton therapy), extreme hypofractionated schedule (36.25 GyE in five fractions) between February 2013 and December 2015. Mean age of the patients was 64.3 years, and the mean value of prostate-specific antigen (PSA) before treatment was 6.83 μg/L (0.6-17.3 μg/L). Ninety-three patients (46.5%) were in the low-risk group. One hundred and seven patients (53.5%) were in the intermediate-risk group. Twenty-nine patients (14.5%) had neoadjuvant hormonal therapy, and no patients had adjuvant hormonal therapy. Acute toxicity, late toxicity and short-term results were evaluated.

RESULTS

All patients finished radiotherapy without interruptions. The median follow-up time was 36 months. The mean treatment time was 9.5 days (median 9 days). Acute toxicity according to Common Terminology Criteria for Adverse Events (CTCAE) v 4.0 was (gastrointestinal toxicity) GI (grade) G1-17%, G2-3.5%; (genitourinary toxicity) GU G1-40%, G2-19%; and no G3 toxicity was observed. Late toxicity was GI G1-19%, G2-5.5%; GU G1-17%, G2-4%; and no G3 toxicity was observed. PSA relapse was observed in one patient (1.08%) in the low-risk group (pelvic lymph node involvement was detected) and in seven patients (6.5%) in the intermediate-risk group (three lymph node metastases, two lymph node and bone metastases, two PSA relapses). No patient died of prostate cancer, and three patients died from other reasons. No local recurrence of cancer in the prostate was observed.

CONCLUSIONS

Proton beam radiotherapy for prostate cancer is feasible with a low rate of acute toxicity and promising late toxicity and effectivity.

TROG 18.01 phase III randomised clinical trial of the Novel Integration of New prostate radiation schedules with adJuvant Androgen deprivation: NINJA study protocol

INTRODUCTION

Stereotactic body radiotherapy (SBRT) is a non-invasive alternative to surgery for the treatment of non-metastatic prostate cancer (PC). The objectives of the Novel Integration of New prostate radiation schedules with adJuvant Androgen deprivation (NINJA) clinical trial are to compare two emerging SBRT regimens for efficacy with technical substudies focussing on MRI only planning and the use of knowledge-based planning (KBP) to assess radiotherapy plan quality.

METHODS AND ANALYSIS

Eligible patients must have biopsy-proven unfavourable intermediate or favourable high-risk PC, have an Eastern Collaborative Oncology Group (ECOG) performance status 0-1 and provide written informed consent. All patients will receive 6 months in total of androgen deprivation therapy. Patients will be randomised to one of two SBRT regimens. The first will be 40 Gy in five fractions given on alternating days (SBRT monotherapy). The second will be 20 Gy in two fractions given 1 week apart followed 2 weeks later by 36 Gy in 12 fractions given five times per week (virtual high-dose rate boost (HDRB)). The primary efficacy outcome will be biochemical clinical control at 5 years. Secondary endpoints for the initial portion of NINJA look at the transition of centres towards MRI only planning and the impact of KBP on real-time (RT) plan assessment. The first 150 men will demonstrate accrual feasibility as well as addressing the KBP and MRI planning aims, prior to proceeding with total accrual to 472 patients as a phase III randomised controlled trial.

ETHICS AND DISSEMINATION

NINJA is a multicentre cooperative clinical trial comparing two SBRT regimens for men with PC. It builds on promising results from several single-armed studies, and explores radiation dose escalation in the Virtual HDRB arm. The initial component includes novel technical elements, and will form an important platform set for a definitive phase III study.

TRIAL REGISTRATION NUMBER

ANZCTN 12615000223538.

Stereotactic Body Radiation Therapy for Localized Prostate Cancer: A Systematic Review and Meta-Analysis of Over 6,000 Patients Treated On Prospective Studies

PURPOSE

Utilization of stereotactic body radiation therapy (SBRT) for treatment of localized prostate cancer is increasing. Guidelines and payers variably support the use of prostate SBRT. We therefore sought to systematically analyze biochemical recurrence-free survival (bRFS), physician-reported toxicity, and patient-reported outcomes after prostate SBRT.

METHODS AND MATERIALS

A systematic search leveraging Medline via PubMed and EMBASE for original articles published between January 1990 and January 2018 was performed. This was supplemented by abstracts with sufficient extractable data from January 2013 to March 2018. All prospective series assessing curative-intent prostate SBRT for localized prostate cancer reporting bRFS, physician-reported toxicity, and patient-reported quality of life with a minimum of 1-year follow-up were included. The study was performed according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses statement. Meta-analyses were performed with random-effect modeling. Extent of heterogeneity between studies was determined by the I2 and Cochran's Q tests. Meta-regression was performed using Hartung-Knapp methods.

RESULTS

Thirty-eight unique prospective series were identified comprising 6116 patients. Median follow-up was 39 months across all patients (range, 12-115 months). Ninety-two percent, 78%, and 38% of studies included low, intermediate, and high-risk patients. Overall, 5- and 7-year bRFS rates were 95.3% (95% confidence interval [CI], 91.3%-97.5%) and 93.7% (95% CI, 91.4%-95.5%), respectively. Estimated late grade ≥3 genitourinary and gastrointestinal toxicity rates were 2.0% (95% CI, 1.4%-2.8%) and 1.1% (95% CI, 0.6%-2.0%), respectively. By 2 years post-SBRT, Expanded Prostate Cancer Index Composite urinary and bowel domain scores returned to baseline. Increasing dose of SBRT was associated with improved biochemical control (P = .018) but worse late grade ≥3 GU toxicity (P = .014).

CONCLUSIONS

Prostate SBRT has substantial prospective evidence supporting its use, with favorable tumor control, patient-reported quality of life, and levels of toxicity demonstrated. SBRT has sufficient evidence to be supported as a standard treatment option for localized prostate cancer while ongoing trials assess its potential superiority.

A Pooled Analysis of Biochemical Failure in Intermediate-risk Prostate Cancer Following Definitive Stereotactic Body Radiotherapy (SBRT) or High-Dose-Rate Brachytherapy (HDR-B) Monotherapy

OBJECTIVES

To investigate biochemical relapse-free survival (BRFS) in men with National Comprehensive Cancer Network-defined intermediate-risk prostate cancer (PC) treated with either stereotactic body radiotherapy (SBRT) or high-dose-rate brachytherapy (HDR-B) monotherapy.

MATERIALS AND METHODS

A retrospective, multi-institutional analysis of 437 patients with intermediate-risk PC treated with SBRT (N=300) or HDR-B (N=137) was performed. Men who underwent SBRT were treated to 35 to 40 Gy in 4 to 5 fractions. A total of 95.6% who underwent HDR-B were treated to 42 Gy in 6 fractions. Baseline patient characteristics were compared using a T test for continuous variables and the Mantel-Haenszel χ metric or Fisher exact test for categorical variables. Kaplan-Meier curves were generated to estimate 5-year actuarial BRFS. Multivariate analysis using a Cox proportional-hazards model was used to evaluate factors associated with biochemical failure.

RESULTS

The mean age at diagnosis was 68.4 (SD±7.8) years. T-category was T1 in 63.6% and T2 in 36.4%. Mean initial prostate-specific antigen was 7.4 (SD±3.4) ng/mL. Biopsy Gleason score was ≤3+4 in 82.8% and 4+3 in 17.2%. At a median of 4.1 years of follow-up, the BRFS rate (Phoenix definition) was 96.3%, with no difference when stratifying by treatment modality or biologically equivalent dose (BED1.5). On multivariate analysis, age (hazard ratio 1.08, P=0.04) and biopsy Gleason score (hazard ratio 2.48, P=0.03) were significant predictors of BRFS.

CONCLUSIONS

With a median follow-up period of 4 years, SBRT and HDR-B monotherapy provide excellent BRFS in intermediate-risk PC. Longer-term follow-up is necessary to determine the ultimate efficacy of these hypofractionated approaches, but they appear promising relative to standard fractionation outcomes.

The role of radiotherapy in localised and locally advanced prostate cancer

For a patient suffering from non-metastatic prostate cancer, the individualized recommendation of radiotherapy has to be the fruit of a multidisciplinary approach in the context of a Tumor Board, to be explained carefully to the patient to obtain his informed consent. External beam radiotherapy is now delivered by intensity modulated radiotherapy, considered as the gold standard. From a radiotherapy perspective, low-risk localized prostate cancer is treated by image guided intensity modulated radiotherapy, or brachytherapy if patients meet the required eligibility criteria. Intermediate-risk patients may benefit from intensity modulated radiotherapy combined with 4–6 months of androgen deprivation therapy; intensity modulated radiotherapy alone or combined with brachytherapy can be offered to patients unsuitable for androgen deprivation therapy due to co-morbidities or unwilling to accept it to preserve their sexual health. High-risk prostate cancer, i.e. high-risk localized and locally advanced prostate cancer, requires intensity modulated radiotherapy with long-term (≥2 years) androgen deprivation therapy with luteinizing hormone releasing hormone agonists. Post-operative irradiation, either immediate or early deferred, is proposed to patients classified as pT3pN0, based on surgical margins, prostate-specific antigen values and quality of life. Whatever the techniques and their degree of sophistication, quality assurance plays a major role in the management of radiotherapy, requiring the involvement of physicians, physicists, dosimetrists, radiation technologists and computer scientists. The patients must be informed about the potential morbidity of radiotherapy and androgen deprivation therapy and followed regularly during and after treatment for tertiary prevention and evaluation. A close cooperation is needed with general practitioners and specialists to prevent and mitigate side effects and maintain quality of life.

Long-term Outcomes of Stereotactic Body Radiotherapy for Low-Risk and Intermediate-Risk Prostate Cancer

Importance

Stereotactic body radiotherapy harnesses improvements in technology to allow the completion of a course of external beam radiotherapy treatment for prostate cancer in the span of 4 to 5 treatment sessions. Although mounting short-term data support this approach, long-term outcomes have been sparsely reported.

Objective

To assess long-term outcomes after stereotactic body radiotherapy for low-risk and intermediate-risk prostate cancer.

Design, Setting, and Participants

This cohort study analyzed individual patient data from 2142 men enrolled in 10 single-institution phase 2 trials and 2 multi-institutional phase 2 trials of stereotactic body radiotherapy for low-risk and intermediate-risk prostate cancer between January 1, 2000, and December 31, 2012. Statistical analysis was performed based on follow-up from January 1, 2013, to May 1, 2018.

Main Outcomes and Measures

The cumulative incidence of biochemical recurrence was estimated using a competing risk framework. Physician-scored genitourinary and gastrointestinal toxic event outcomes were defined per each individual study, generally by Radiation Therapy Oncology Group or Common Terminology Criteria for Adverse Events scoring systems. After central review, cumulative incidences of late grade 3 or higher toxic events were estimated using a Kaplan-Meier method.

Results

A total of 2142 men (mean [SD] age, 67.9 [9.5] years) were eligible for analysis, of whom 1185 (55.3%) had low-risk disease, 692 (32.3%) had favorable intermediate-risk disease, and 265 (12.4%) had unfavorable intermediate-risk disease. The median follow-up period was 6.9 years (interquartile range, 4.9-8.1 years). Seven-year cumulative rates of biochemical recurrence were 4.5% (95% CI, 3.2%-5.8%) for low-risk disease, 8.6% (95% CI, 6.2%-11.0%) for favorable intermediate-risk disease, 14.9% (95% CI, 9.5%-20.2%) for unfavorable intermediate-risk disease, and 10.2% (95% CI, 8.0%-12.5%) for all intermediate-risk disease. The crude incidence of acute grade 3 or higher genitourinary toxic events was 0.60% (n = 13) and of gastrointestinal toxic events was 0.09% (n = 2), and the 7-year cumulative incidence of late grade 3 or higher genitourinary toxic events was 2.4% (95% CI, 1.8%-3.2%) and of late grade 3 or higher gastrointestinal toxic events was 0.4% (95% CI, 0.2%-0.8%).

Conclusions and Relevance

In this study, stereotactic body radiotherapy for low-risk and intermediate-risk disease was associated with low rates of severe toxic events and high rates of biochemical control. These data suggest that stereotactic body radiotherapy is an appropriate definitive treatment modality for low-risk and intermediate-risk prostate cancer.

A novel model to correlate hydrogel spacer placement, perirectal space creation, and rectum dosimetry in prostate stereotactic body radiotherapy

BACKGROUND

The SpaceOAR hydrogel is employed to limit rectal radiation dose during prostate radiotherapy. We identified a novel parameter - the product of angle θ and hydrogel volume - to quantify hydrogel placement. This parameter predicted rectum dosimetry and acute rectal toxicity in prostate cancer patients treated with stereotactic body radiotherapy to 36.25 Gy in 5 fractions.

METHODS

Twenty men with low- and intermediate-risk prostate cancer underwent hydrogel placement from 2015 to 2017. Hydrogel symmetry was assessed on the CT simulation scan in 3 axial slices (midgland, 1 cm above midgland, 1 cm below midgland). Two novel parameters quantifying hydrogel placement - hydrogel volume and angle θ formed by the prostate, hydrogel, and rectum - were measured, and the normalized product of θ and hydrogel volume calculated. These were then correlated with perirectal distance, rectum maximum 1-3 cc point doses (rD_max 1-3 cc), and rectum volumes receiving 80-95% of the prescription dose (rV80-95%). Acute rectal toxicity was recorded per RTOG criteria.

RESULTS

In 50% of patients, hydrogel placement was symmetric bilaterally to within 1 cm of midline in all three CT simulation scan axial slices. Lateral hydrogel asymmetry < 2 cm in any one axial slice did not affect rectum dosimetry, but absence of hydrogel in the inferior axial slice resulted in a mean increase of 171 cGy in the rD_max 1 cc (p < 0.005). The perirectal distance measured at prostate midgland, midline (mean 9.1 ± 4.3 mm) correlated strongly with rV95 (R² 0.6, p < 0.001). The mean hydrogel volume and θ were 10.3 ± 4.5 cc and 70 ± 49°, respectively. Perirectal distance, rV95 and rD_max 1 cc correlated with hydrogel angle θ (p < 0.01), and yet more strongly with the novel metric θ*hydrogel volume (p < 0.001). With a median follow up of 14 months, no rectal toxicity >grade 2 was observed. Low grade rectal toxicity was observed in a third of men and resolved within 1 month of SBRT. Men who had these symptoms had higher rD_max 1 cc and smaller θ*hydrogel volume measurements.

CONCLUSIONS

Optimal hydrogel placement occurs at prostate midgland, midline. The novel parameter θ*hydrogel volume describes a large proportion of rectum dosimetric benefit derived from hydrogel placement, and can be used to assess the learning curve phenomenon for hydrogel placement.

Prostate Stereotactic Body Radiation Therapy With a Focal Simultaneous Integrated Boost: Acute Toxicity and Dosimetry Results From a Prospective Trial

Purpose

This study aimed to report the early toxicity results of a prospective clinical trial of prostate stereotactic body radiation therapy (SBRT) to the entire prostate with a simultaneous integrated boost (SIB) to magnetic resonance imaging (MRI)-defined focal lesions.

Methods and materials

Eligible patients included men with biopsy-proven prostate stage T1c to T2c adenocarcinoma, a Gleason score ≤7, and prostate-specific antigen values of ≤20 ng/mL, who had at least 1 focal lesion visible on MRI and a total prostate volume no greater than 120 cm³. SBRT consisted of a dose of 36.25 Gy to the entire prostate with an SIB of 40 Gy to the MRI-defined lesions, delivered in 5 fractions. The primary purpose of the study was to confirm the feasibility of treatment planning/delivery and to estimate the rate of urinary retention requiring placement of a Foley catheter within 90 days of treatment. This study was to be considered successful if urinary retention occurred in no more than 15% of cases, with a planned enrollment of at least 25 patients.

Results

A total of 26 men were enrolled, and all underwent SBRT as planned. Twenty patients (77%) had intermediate-risk features, and the remainder were low risk. A treatment plan that met the protocol-defined goals for all cases was developed. Two patients (7.7%) developed acute urinary symptoms that required the temporary placement of a Foley catheter. No grade 3+ toxicity events were observed.

Conclusions

Planning and delivery of prostate SBRT with a whole prostate dose of 36.25 Gy and a focal 40 Gy SIB is feasible. Early follow-up suggests that this treatment is not associated with undue morbidity.

[Technical aspects and indications of extracranial stereotactic radiotherapy]

Extracranial stereotactic radiotherapy has developed considerably in recent years and is now an important part of the therapeutic alternatives to be offered to patients with cancer. It offers opportunities that have progressively led physicians to reconsider the therapeutic strategy, for example in the case of local recurrence in irradiated territory or oligometastatic disease. The literature on the subject is rich but, yet, there is no real consensus on therapeutic indications. This is largely due to the lack of prospective, randomized studies that have evaluated this technique with sufficient recoil. We propose a review of the literature on the technical aspects and indications of extracranial stereotactic radiotherapy.

Multicenter Trial of Stereotactic Body Radiation Therapy for Low- and Intermediate-Risk Prostate Cancer: Survival and Toxicity Endpoints

PURPOSE

The radiobiology of prostate cancer may favor the extreme hypofractionation inherent in stereotactic body radiation therapy (SBRT); however, data from a large multicenter study are lacking. We therefore examined the hypothesis that dose-escalated SBRT can be safely administered across multiple institutions, with favorable 5-year disease-free survival (DFS) rates compared with historical controls.

METHODS AND MATERIALS

Twenty-one centers enrolled 309 patients with prostate adenocarcinoma: 172 with low-risk (LR) and 137 with intermediate-risk (IR) disease. All were treated with a non-coplanar robotic SBRT platform using real-time tracking of implanted fiducials. The prostate was prescribed 40 Gy in 5 fractions of 8 Gy. We assessed toxicities using Common Terminology Criteria for Adverse Events (CTCAE) version 3 and biochemical failure using the "nadir + 2" definition. The study population yielded 90% power to identify excessive (>10%) rates of grade ≥3 genitourinary (GU) or gastrointestinal toxicities and, in the LR group, 80% power to show superiority in DFS over a 93% historical comparison rate.

RESULTS

At a median follow-up of 61 months, 2 LR patients (1.2%) and 2 IR patients (1.5%) experienced grade 3 GU toxicities, far below the 10% toxicity rate deemed excessive (upper limits of 95% confidence interval, 3.5% and 4.3%, respectively). No grade 4 or 5 toxicities occurred. All grade 3 toxicities were GU, occurring 11 to 51 months after treatment. For the entire group, the actuarial 5-year overall survival rate was 95.6% and the DFS rate was 97.1%. The 5-year DFS rate was 97.3% for LR patients (superior to the 93% DFS rate for historical controls; P = .0008; lower limit of 95% confidence interval, 94.6%) and 97.1% for IR patients.

CONCLUSIONS

Dose-escalated prostate SBRT was administered with minimal toxicity in this multi-institutional study. Relapse rates compared favorably with historical controls. SBRT is a suitable option for LR and IR prostate cancer.

Stereotactic Body Radiation Therapy for Prostate Cancer: An Institutional Experience Using MRI-guided Treatment Planning

With 222,500 new cases estimated for 2017, prostate cancer makes up approximately 10% of all new cancer diagnoses in the United States and is the third most common cancer after breast and lung cancer. In 2013, the American Society of Radiation Oncology (ASTRO) policy model recognized that stereotactic body radiation therapy (SBRT) may be used as an alternative to standard treatment modalities, i.e. intensity modulated radiation therapy (IMRT), to treat prostate cancer. In this study, we report outcomes for a cohort of 30 patients with prostate cancer treated with SBRT at our institution. We also describe, in detail, the technical aspects of SBRT planning and delivery for these patients, specifically the use of MRI in determining treatment volumes and detecting gross lesions.

After institutional review board (IRB) approval, a retrospective analysis was done of 30 males with the diagnosis of prostate cancer treated in the Department of Radiation Oncology at the Baylor College of Medicine between January 2011 and June 2016. All patients received image-guided SBRT. Treatment planning was performed using a non-contrast computed tomography (CT) scan as well as a contrast thin-slice open MRI with the patient in the treatment position. Patient comparisons were done using the Mann-Whitney U, Fishers Exact, and Kaplan-Meier tests.

Thirty patients were treated between January 2011 and June 2016. Twenty-six had follow-up data available and were included in the analysis. Median follow-up was 32 months (range 2-72 months). Mean and median ages at diagnosis were both 68.5 years. A total of 64% of the patients had foci on magnetic resonance imaging (MRI) or a palpable nodule on an exam. The median prostate-specific antigen (PSA) at diagnosis was 7.35 ng/mL (range 2.8-13), and the median PSA nadir after treatment was 0.4 ng/mL (range 0.01-4.5). The biochemical disease-free recurrence rate per Phoenix definition was 96%, with only one patient experiencing a biochemical recurrence four years after treatment. The patient with a recurrence was T2c, high-intermediate risk with a Gleason score of 7(3+4). He had a focus visible on MRI. Overall survival was 96%, with the only patient death unrelated to his prostate cancer. There was no statistical significance associated with recurrence and nodule on MRI (p=0.318), T-stage (p=0.222), Gleason score (p=0.890), risk group (p=0.654), age (p=0.692), or race (p=0.509). There were no grade three or four acute or long-term toxicities.

SBRT of the prostate is an effective method for treating prostate cancer. We saw excellent PSA control and minimal acute or long-term toxicities after a median of three years of follow-up.

Stereotactic body-radiotherapy boost dose of 18 Gy vs 21 Gy in combination with androgen-deprivation therapy and whole-pelvic radiotherapy for intermediate- or high-risk prostate cancer: a study protocol for a randomized controlled, pilot trial

Background

Combination therapy using external-beam radiotherapy (EBRT) with a brachytherapy boost has demonstrated superior biochemical control than dose-escalated EBRT alone. Whereas brachytherapy is disadvantageous because it is an invasive procedure, stereotactic body-radiotherapy (SBRT) using CyberKnife could emulate the dose distribution of brachytherapy and is a non-invasive and safe modality to control intra-fractional movement. We therefore adopted SBRT using CyberKnife as a boost therapy after whole-pelvic radiotherapy (WPRT).

Methods/design

In this prospective, randomized, single-center, pilot study for intermediate- and high-risk prostate cancer without nodal or distant metastasis, after androgen-deprivation therapy and WPRT, patients will be randomized to one of two SBRT boost regimens, i.e., 18 or 21 Gy administered in three fractions every other day.

Discussion

The aim of this trial is to evaluate acute toxicities using both physician- and patient-reported outcomes and short-term biochemical control with SBRT boost following WPRT. Additionally, chronic toxicities and long-term biochemical control will be evaluated as secondary endpoints in this trial. Based on the generated results, we will plan the full-scale phase II study for selecting the SBRT boost dose.

Trial registration

ClinicalTrials.gov, ID; NCT03322020. Retrospectively registered on 26 October 2017.

Electronic supplementary material

The online version of this article (10.1186/s13063-018-2574-y) contains supplementary material, which is available to authorized users.

Stereotactic Body Radiotherapy for Primary Prostate Cancer

Prostate cancer is the most common non-cutaneous cancer in males. There are a number of options for patients with localized early stage disease, including active surveillance for low-risk disease, surgery, brachytherapy, and external beam radiotherapy. Increasingly, external beam radiotherapy, in the form of dose-escalated and moderately hypofractionated regimens, is being utilized in prostate cancer, with randomized evidence to support their use. Stereotactic body radiotherapy, which is a form of extreme hypofractionation, delivered with high precision and conformality typically over 1 to 5 fractions, offers a more contemporary approach with several advantages including being non-invasive, cost-effective, convenient for patients, and potentially improving patient access. In fact, one study has estimated that if half of the patients currently eligible for conventional fractionated radiotherapy in the United States were treated instead with stereotactic body radiotherapy, this would result in a total cost savings of US$250 million per year. There is also a strong radiobiological rationale to support its use, with prostate cancer believed to have a low α/β ratio and therefore being preferentially sensitive to larger fraction sizes. To date, there are no published randomized trials reporting on the comparative efficacy of stereotactic body radiotherapy compared to alternative treatment modalities, although multiple randomized trials are currently accruing. Yet, early results from the randomized phase III study of HYPOfractionated RadioTherapy of intermediate risk localized Prostate Cancer (HYPO-RT-PC) trial, as well as multiple single-arm phase I/II trials, indicate low rates of late adverse effects with this approach. In patients with low- to intermediate-risk disease, excellent biochemical relapse-free survival outcomes have been reported, albeit with relatively short median follow-up times. These promising early results, coupled with the enormous potential cost savings and implications for resource availability, suggest that stereotactic body radiotherapy will take center stage in the treatment of prostate cancer in the years to come.

Variability in Outcomes for Patients with Intermediate-risk Prostate Cancer (Gleason Score 7, International Society of Urological Pathology Gleason Group 2-3) and Implications for Risk Stratification: A Systematic Review

CONTEXT

Optimal management for patients with intermediate-risk (IR) prostate cancer (PCa) remains controversial. Clinical metrics provide guidance on appropriate management options.

OBJECTIVE

To report estimates for clinically relevant outcomes in men with IR PCa based on clinical and pathological features.

EVIDENCE ACQUISITION

PubMed and programs from key 2015 uro-oncology congresses were searched using the terms "intermediate", "Gleason 3 + 4", "Gleason 4 + 3", "active surveillance", "treatment", "adverse pathology", AND "prostate cancer." Articles meeting prespecified criteria were retrieved. Bibliographies were scanned for additional relevant references.

EVIDENCE SYNTHESIS

Men with IR PCa have a wide range of predicted clinically relevant outcomes. Within the IR category, estimate ranges for adverse surgical pathology and 5-yr disease progression are 15-64% and 21-91%, respectively. Clinical parameters and predictive nomograms refine these estimates, but do not uniformly differentiate favorable and unfavorable IR PCa. Variations in study design and data quality in source manuscripts mandate caution in interpreting results.

CONCLUSIONS

Outcomes in IR PCa are heterogeneous. Refinements in personalized risk assessment are needed to better select IR PCa patients for surveillance.

PATIENT SUMMARY

Current and future risk stratification tools may provide additional information to identify men with intermediate-risk prostate cancer who may consider active surveillance.

Stereotactic Body Radiotherapy for Low-Risk Prostate Cancer: A Ten-Year Analysis

Objective This study represents the first 10 year analysis of the efficacy and toxicity of stereotactic body radiotherapy (SBRT) in the treatment of early low-risk prostate cancer. Materials and methods Two hundred and thirty males were treated with Cyberknife SBRT to a dose of 35 Gray (Gy) or 36.25 Gy in five consecutive days. All patients had a Gleason score of six and a PSA < 10ng/ml. Median follow-up is nine years. The median age was 69.5 years and median prostate specific antigen (PSA) was 5.6ng/ml. The treatment was delivered with homogeneous planning with a dose prescription of 82-87% of the maximum dose to cover the planning target volume (PTV). Results Ten-year biochemical disease free survival was 93% with either dose. Local control was 98.4%. Median prostate specific antigen (PSA) dropped to 0.1 by five years and has remained there. Toxicity was mild with 10% of patients having Grade two-three late urinary toxicity and 4% having the late grade two rectal toxicity. Mean Expanded Prostate Cancer Index Composite (EPIC) Quality of Life (QOL) scores declined initially for bowel and urinary domains, but recovered to baseline, where they remain. EPIC sexual scores have declined by 40%. Discussion/Conclusions Stereotactic body radiotherapy to a dose of 35 Gy-36.25 Gy is an effective treatment for early low-risk prostate cancer, with acceptably low toxicity. There appears to be no benefit to increasing the dose beyond 35 Gy. Ten-year biochemical disease free survival appears to be higher than with standard intensity modulated radiotherapy (IMRT).

Propensity Score Matched Comparison of Intensity Modulated Radiation Therapy vs Stereotactic Body Radiation Therapy for Localized Prostate Cancer: A Survival Analysis from the National Cancer Database

PURPOSE

No direct comparisons between extreme hypofractionation and conventional fractionation have been reported in randomized trials for the treatment of localized prostate cancer. The goal of this study is to use a propensity score matched (PSM) analysis with the National Cancer Database (NCDB) for the comparison of stereotactic body radiation therapy (SBRT) and intensity modulated radiation therapy (IMRT) for organ confined prostate cancer.

METHODS

Men with localized prostate cancer treated with radiation dose ≥72 Gy for IMRT and ≥35 Gy for SBRT to the prostate only were abstracted from the NCDB. Men treated with previous surgery, brachytherapy, or proton therapy were excluded. Matching was performed to eliminate confounding variables via PSM. Simple 1-1 nearest neighbor matching resulted in a matched sample of 5,430 (2,715 in each group). Subset analyses of men with prostate-specific antigen (PSA) > 10, GS = 7, and GS > 7 yielded matched samples of 1,020, 2,194, and 247, respectively.

RESULTS

No difference in survival was noted between IMRT and SBRT at 8 years (p = 0.65). Subset analyses of higher risk men with PSA > 10 or GS = 7 histology or GS > 7 histology revealed no difference in survival between IMRT and SBRT (p = 0.58, p = 0.68, and p = 0.62, respectively). Variables significant for survival for the matched group included: age (p < 0.0001), primary payor (p = 0.0001), Charlson/Deyo Score (p = 0.0002), PSA (p = 0.0013), Gleason score (p < 0.0001), and use of hormone therapy (p = 0.02).

CONCLUSION

Utilizing the NCDB, there is no difference in survival at 8 years comparing IMRT to SBRT in the treatment of localized prostate cancer. Subset analysis confirmed no difference in survival even for intermediate- and high-risk patients based on Gleason Score and PSA.

Stereotactic Body Radiation Therapy for Localized Prostate Cancer

Stereotactic body radiation therapy (SBRT) has become a viable treatment option for the many patients who receive a diagnosis of localized prostate cancer each year. Technological advancements have led to tight target conformality, allowing for high-dose-per-fraction delivery without untoward normal tissue toxicity. Biochemical control, now reported up to 5 years, appears to compare favorably with dose-escalated conventionally fractionated radiotherapy. Moreover, toxicity and quality of life follow-up data indicate genitourinary and gastrointestinal toxicities are likewise comparable to conventional radiation therapy. Nevertheless, because of the long natural history of prostate cancer, extended follow-up will be necessary to confirm these impressive initial results. Within this prostate SBRT review, we explore the detailed rationale for SBRT treatment, the diverse SBRT techniques utilized and their unique technical considerations, and finally data for SBRT clinical efficacy and treatment-related toxicity.

Hypofractionated stereotactic body radiotherapy for localized prostate cancer - first Nordic clinical experience

BACKGROUND

The use of hypofractionated stereotactic body radiotherapy (SBRT) as primary treatment modality in clinically localized prostate cancer (PCa) is emerging, because the low α/β-ratio favors the use of high dose per fraction in PCa. There is a need for more data about SBRT, especially in high-risk PCa patients. The purpose of this retrospective study was to evaluate the safety and the short-term efficacy of robotic SBRT in a clinical patient cohort with localized PCa including also high-risk patients (D'Amico risk stratification).

MATERIALS AND METHODS

A total of 240 consecutive patients with clinically localized PCa were treated primarily with SBRT to total doses of 35 Gy or 36.25 Gy in 5 fractions using a robotic SBRT device (CyberKnife^®). All risk groups (D'Amico risk stratification) were represented as follows: 48 (22%), 59 (27%) and 111 (51%) of the patients representing low-, intermediate- and high-risk group, respectively. Data on acute and intermediate-term toxicities and early PSA responses were analyzed.

RESULTS

Neither acute grade 3 or higher GU nor rectal toxicity was observed. Regardless of the fact that 29 (13.3%) patients experienced intermediate-term toxicity requiring diagnostic interventions, the rates of intermediate-term grade 3 GU, rectal and infectious toxicity were low, 1.8%, 0.9% and 1.4%, respectively. A biochemical relapse was observed in ten (4.6%) patients. With the median follow-up time of 23 months the biochemical relapse-free survival (bRFS) rate was 100%, 96.6% and 92.8% in low-, intermediate- and high-risk group, respectively.

CONCLUSIONS

The toxicity of robotic SBRT in a large clinical cohort of PCa patients was tolerable and the early PSA response was good in all risk groups. The hypofractionated SBRT offers a possibility to high dose per fraction and to provide the whole radiotherapy treatment within two to three weeks.

Cyberknife Radioablation of Prostate Cancer – Preliminary Results for 400 Patients

Objectives: To evaluate the tolerance and effectiveness of stereotactic ablative radiotherapy (SABR) applied in the treatment of low and intermediate risk (LR & IR) prostate cancer patients (PCP) and provide an evaluation of the level of risk group impact on treatment results. In addition, androgen deprivation therapy (ADT) usage and prostatic specific antigen (PSA) decline after SABR were assessed. Material and Methods: A total of 400 PCP (213 LR and 187 IR, including T2c) were irradiated with a CyberKnife using fd 7.25 Gy to TD 36.25 Gy. At the start of treatment, 60.3% of patients were undergoing ADT and this gradually decreased to 0% after 38 months. Follow-up was for a median of 15.0 months. Patients were monitored on SABR completion and 1, 4, 8 months later and then subsequently every 6 months. GI (Gastro-Intestinal) and GU (Genito-Urinary) acute and late adverse effects, PSA and ADT usage were evaluated. Results: Failure was noted in 9 patients (2.25%) (5 in LR and 4 in IR groups) - 4 relapses and 5 nodal metastases. No G3/4 late adverse effects (EORTC/RTOG) were observed. Some 0.5% of G3 GU and 0.3% of G3 GI acute reactions were noted respectively on the SABR completion day and one month later. The median of PSA declined 1.5 ng/ml during the first month and 0.6 ng/ml during the next three months. No impact of risk groups on treatment results was found. An impact of ADT on PSA decline was only confirmed for time point interactions. Conclusions: SABR for LR and IR PCP is a safe and effective treatment. The inclusion of T2c patients and the low percentage of IR patient failure permit us the assumption that this procedure could be utilized in the treatment of more advanced cases. The results do not allow clear definition of the impact of ADT on radioablation results in LR and IR+ T2c cases.

Stereotactic prostate adaptive radiotherapy utilising kilovoltage intrafraction monitoring: the TROG 15.01 SPARK trial

BACKGROUND

This paper describes the multi-institutional prospective phase II clinical trial, SPARK: Stereotactic Prostate Adaptive Radiotherapy utilizing Kilovoltage Intrafraction Monitoring (KIM). KIM is a real-time image guided radiotherapy technology being developed and clinically pioneered for prostate cancer treatment in Australia. It has potential for widespread use for target radiotherapy treatment of cancers of the pelvis, thorax and abdomen.

METHODS

In the SPARK trial we will measure the cancer targeting accuracy and patient outcomes for 48 prostate cancer patients who will be treated in five treatment sessions as opposed to the conventional 40 sessions. The reduced number of treatment sessions is enabled by the KIM's increased cancer targeting accuracy.

DISCUSSION

Real-time imaging in radiotherapy has the potential to decrease the time taken during cancer treatment and reduce the imaging dose required. With the imaging being acquired during the treatment, and the analysis being automated, there is potential for improved throughput. The SPARK trial will be conducted under the auspices of the Trans-Tasman Radiation Oncology Group (TROG).

TRIAL REGISTRATION

This trial was registered on ClinicalTrials.gov on 09 March 2015. The identifier is: NCT02397317.

Stereotactic Body Radiotherapy for Low- and Intermediate-Risk Prostate Cancer

With over a decade׳s worth of clinical experience to guide stereotactic body radiotherapy (SBRT) for the treatment of clinically localized prostate cancer (PCa), sufficient data exist for robust conclusions to be made regarding its efficacy and the toxicities associated with this treatment. We briefly review the fundamental radiobiological basis of SBRT for PCa and provide a comprehensive synthesis of the medical literature to date, focusing on clinical outcomes and toxicities. When possible, we draw comparisons to comparable data for conventionally fractionated radiotherapy. Finally, a brief overview of technical considerations is presented. Although randomized clinical trials comparing SBRT with conventionally fractionated radiotherapy are underway, the current body of evidence supports the efficacy and safety of SBRT for PCa.

[Clinical to planning target volume margins in prostate cancer radiotherapy]

The knowledge of inter- and intrafraction motion and deformations of the intrapelvic target volumes (prostate, seminal vesicles, prostatectomy bed and lymph nodes) as well as the main organs at risk (bladder and rectum) allow to define rational clinical to planning target volume margins, depending on the different radiotherapy techniques and their uncertainties. In case of image-guided radiotherapy, prostate margins and seminal vesicles margins can be between 5 and 10mm. The margins around the prostatectomy bed vary from 10 to 15mm and those around the lymph node clinical target volume between 7 and 10mm. Stereotactic body radiotherapy allows lower margins, which are 3 to 5mm around the prostate. Image-guided and stereotactic body radiotherapy with adequate margins allow finally moderate or extreme hypofractionation.

The Comparison of Stereotactic Body Radiation Therapy and Intensity-Modulated Radiation Therapy for Prostate Cancer by NCCN Risk Groups

OBJECTIVES

The primary objective of this study is to compare freedom from biochemical failure (FFBF) between stereotactic body radiation therapy (SBRT) and intensity-modulated radiation therapy (IMRT) for patients with organ confined prostate cancer treated between 2007 through 2012 utilizing the 2015 National Comprehensive Cancer Network (NCCN) risk stratification guidelines. A secondary objective is to compare our updated toxicity at last follow-up compared with pretreatment with respect to bowel, bladder, sexual functioning, and need for invasive procedures between the two groups.

METHODS

We retrospectively reviewed 270 consecutive men treated with either SBRT (n = 150) or IMRT (n = 120) at a community hospital with two distinct radiation departments and referral patterns. Charts were reviewed for pretreatment and treatment factors including race, age, clinical T stage, initial PSA, Gleason score, use of androgen deprivation therapy, treatment with SBRT vs. IMRT, as well as stratification by 2015 NCCN guidelines. Kaplan-Meier (KM) methodology was used to estimate FFBF, with statistical comparisons accomplished using log rank tests. Multivariable Cox proportional hazard modeling was used to establish independent factors prognostic of biochemical failure. Descriptive statistics were used to describe toxicity graded by a modified Radiation Therapy Oncology Group (RTOG) late radiation morbidity scoring system.

RESULTS

Significant prognostic factors in univariate analysis for FFBF included NCCN risk groups (p = 0.0032), grade (p = 0.019), and PSA (p = 0.008). There was no significant difference in FFBF between SBRT vs. IMRT (p = 0.46) with 6-year actuarial FFBF of 91.9% for SBRT and 88.9% for IMRT. Multivariable analysis revealed only the NCCN risk stratification to be significant predictor for FFBF (p = 0.04). Four-year actuarial FFBF by NCCN risk stratification was 100% very low risk, 100% low risk, 96.5% intermediate risk, 94.5% high risk, and 72.7% very high risk. There were no grade 3 gastrointestinal or genitourinary toxicities for either SBRT or IMRT at last follow-up.

CONCLUSION

No significant difference in FFBF was found between SBRT and IMRT for organ confined prostate cancer in multivariable analysis within this retrospective data set. Overall toxicity was low. The 2015 NCCN risk stratification was validated in this population and was the only significant factor for FFBF in multivariable analysis.

A comparison of robotic arm versus gantry linear accelerator stereotactic body radiation therapy for prostate cancer

Prostate cancer is the most prevalent cancer diagnosed in men in the United States besides skin cancer. Stereotactic body radiation therapy (SBRT; 6–15 Gy per fraction, up to 45 minutes per fraction, delivered in five fractions or less, over the course of approximately 2 weeks) is emerging as a popular treatment option for prostate cancer. The American Society for Radiation Oncology now recognizes SBRT for select low- and intermediate-risk prostate cancer patients. SBRT grew from the notion that high doses of radiation typical of brachytherapy could be delivered noninvasively using modern external-beam radiation therapy planning and delivery methods. SBRT is most commonly delivered using either a traditional gantry-mounted linear accelerator or a robotic arm-mounted linear accelerator. In this systematic review article, we compare and contrast the current clinical evidence supporting a gantry vs robotic arm SBRT for prostate cancer. The data for SBRT show encouraging and comparable results in terms of freedom from biochemical failure (>90% for low and intermediate risk at 5–7 years) and acute and late toxicity (<6% grade 3–4 late toxicities). Other outcomes (eg, overall and cancer-specific mortality) cannot be compared, given the indolent course of low-risk prostate cancer. At this time, neither SBRT device is recommended over the other for all patients; however, gantry-based SBRT machines have the abilities of treating larger volumes with conventional fractionation, shorter treatment time per fraction (~15 minutes for gantry vs ~45 minutes for robotic arm), and the ability to achieve better plans among obese patients (since they are able to use energies >6 MV). Finally, SBRT (particularly on a gantry) may also be more cost-effective than conventionally fractionated external-beam radiation therapy. Randomized controlled trials of SBRT using both technologies are underway.

Predicting Biochemical Disease-Free Survival after Prostate Stereotactic Body Radiotherapy: Risk-Stratification and Patterns of Failure

Background and purpose

To determine appropriate risk-stratification factors for prostate cancer patients undergoing stereotactic body radiotherapy (SBRT).

Materials and methods

Between 2006 and 2010, 515 patients with organ-confined prostate cancer were treated with a regimen of five-fraction SBRT to dose of 35–36.25 Gy. By NCCN criteria, 324 patients were low risk, 153 were intermediate risk, and 38 were high risk. Patients were defined as unfavorable intermediate risk if Gleason 4 + 3 = 7 or >1 intermediate-risk factors (cT2b, c, PSA 10–20, Gleason 3 + 4 = 7). Cox regression analysis was used to determine risk factors significantly associated biochemical failure, and patterns of failure analyzed.

Results

With median follow-up of 84 months, the 8-year disease-free survival was 93.6, 84.3, and 65.0% for low, intermediate, and high-risk group patients, respectively. Based on the above definition, 106 favorable intermediate-risk patients had excellent outcomes, with no significant difference compared to low-risk patients (7-year DFS 95.2 vs. 93.2%, respectively). The 47 unfavorable intermediate-risk patients had worse outcomes, similar to high-risk patients (7-year DFS 68.2 vs. 65.0%, respectively). Gleason score was the only significant factor associated with biochemical failure on multivariate analysis (p = 0.0003).

Conclusion

Patients with favorable intermediate-risk disease have excellent outcomes, comparable to low-risk patients. Patients with unfavorable intermediate-risk disease have significantly worse outcomes after SBRT, and should be considered for clinical trials or treatment intensification.

What is the best way to radiate the prostate in 2016?

Prostate cancer treatment with definitive radiation therapy (RT) has evolved dramatically in the past 2 decades. From the initial 2-dimensional planning using X-rays, advances in technology led to 3-dimensional conformal RT, which used computerized tomography-based planning. This has allowed delivery of higher doses of radiation to the prostate while reducing dose to the surrounding organs, resulting in improved cancer control. Today, intensity-modulated RT (IMRT) is considered standard, where radiation beams of different shapes and intensities can be delivered from a wide range of angles, thus further decreasing doses to normal organs and likely reducing treatment-related toxicity. In addition, image guidance ascertains the location of the prostate before daily treatment delivery. Brachytherapy is the placement of radioactive seeds directly in the prostate, and has a long track record as a monotherapy for low-risk prostate cancer patients with excellent long-term cancer control and quality of life outcomes. Recent studies including several randomized trials support the use of brachytherapy in combination with external beam RT for higher-risk patients. RT for prostate cancer continues to evolve. Proton therapy has a theoretical advantage over photons as it deposits most of the dose at a prescribed depth with a rapid dose fall-off thereafter; therefore it reduces some doses delivered to the bladder and rectum. Prospective studies have shown the safety and efficacy of proton therapy for prostate cancer, but whether it leads to improved patient outcomes compared to IMRT is unknown. Hypofractionated RT delivers a larger dose of daily radiation compared to conventional IMRT, and thus reduces the overall treatment time and possibly cost. An extreme form of hypofractionation is stereotactic body radiation therapy where highly precise radiation is used and treatment is completed in a total of 4 to 5 sessions. These techniques take advantage of the biological characteristic of prostate cancer, which is more sensitive to larger radiation doses per fraction, and therefore could be more effective than conventional IMRT. Multiple randomized trials have demonstrated noninferiority of moderately hypofractionated RT compared to conventional fractionation. There is also a growing body of data demonstrating the safety and efficacy of stereotactic body radiation therapy for low- and intermediate-risk prostate cancer.

Use, complications, and costs of stereotactic body radiotherapy for localized prostate cancer

BACKGROUND

Stereotactic body radiotherapy (SBRT) for localized prostate cancer has potential advantages over traditional radiotherapies. Herein, the authors compared national trends in use, complications, and costs of SBRT with those of traditional radiotherapies.

METHODS

The authors identified men who underwent SBRT, intensity-modulated radiotherapy (IMRT), brachytherapy, and proton beam therapy as primary treatment of prostate cancer between 2004 and 2011 from Surveillance, Epidemiology, and End Results Program (SEER)-Medicare linked data. Temporal trend of therapy use was assessed using the Cochran-Armitage test. Two-year outcomes were compared using the chi-square test. Median treatment costs were compared using the Kruskal-Wallis test.

RESULTS

A total of 542 men received SBRT, 9647 received brachytherapy, 23,408 received IMRT, and 800 men were treated with proton beam therapy. There was a significant increase in the use of SBRT and proton beam therapy (P<.001), whereas brachytherapy use decreased (P<.001). A higher percentage of patients treated with SBRT and brachytherapy had low-grade cancer (Gleason score ≤ 6 vs ≥ 7) compared with individuals treated with IMRT and proton beam therapy (54.0% and 64.2% vs 35.2% and 49.6%, respectively; P<.001). SBRT compared with brachytherapy and IMRT was associated with equivalent gastrointestinal toxicity but more erectile dysfunction at 2-year follow-up (P<.001). SBRT was associated with more urinary incontinence compared with IMRT and proton beam therapy but less compared with brachytherapy (P<.001, respectively). The median cost of SBRT was $27,145 compared with $17,183 for brachytherapy, $37,090 for IMRT, and $54,706 for proton beam therapy (P<.001).

CONCLUSIONS

The use of SBRT and proton beam therapy for localized prostate cancer has increased over time. Despite men of lower disease stage undergoing SBRT, SBRT was found to be associated with greater toxicity but lower health care costs compared with IMRT and proton beam therapy. Cancer 2016;122:2496-504. © 2016 American Cancer Society.