Magnetic resonance linear accelerator technology and adaptive radiation therapy: An overview for clinicians.

Radiation therapy (RT) continues to play an important role in the treatment of cancer. Adaptive RT (ART) is a novel method through which RT treatments are evolving. With the ART approach, computed tomography or magnetic resonance (MR) images are obtained as part of the treatment delivery process. This enables the adaptation of the irradiated volume to account for changes in organ and/or tumor position, movement, size, or shape that may occur over the course of treatment. The advantages and challenges of ART maybe somewhat abstract to oncologists and clinicians outside of the specialty of radiation oncology. ART is positioned to affect many different types of cancer. There is a wide spectrum of hypothesized benefits, from small toxicity improvements to meaningful gains in overall survival. The use and application of this novel technology should be understood by the oncologic community at large, such that it can be appropriately contextualized within the landscape of cancer therapies. Likewise, the need to test these advances is pressing. MR-guided ART (MRgART) is an emerging, extended modality of ART that expands upon and further advances the capabilities of ART. MRgART presents unique opportunities to iteratively improve adaptive image guidance. However, although the MRgART adaptive process advances ART to previously unattained levels, it can be more expensive, time-consuming, and complex. In this review, the authors present an overview for clinicians describing the process of ART and specifically MRgART.

Adding 6 months of androgen deprivation therapy to postoperative radiotherapy for prostate cancer: a comparison of short-course versus no androgen deprivation therapy in the RADICALS-HD randomised controlled trial.

BACKGROUND: Previous evidence indicates that adjuvant, short-course androgen deprivation therapy (ADT) improves metastasis-free survival when given with primary radiotherapy for intermediate-risk and high-risk localised prostate cancer. However, the value of ADT with postoperative radiotherapy after radical prostatectomy is unclear. METHODS: RADICALS-HD was an international randomised controlled trial to test the efficacy of ADT used in combination with postoperative radiotherapy for prostate cancer. Key eligibility criteria were indication for radiotherapy after radical prostatectomy for prostate cancer, prostate-specific antigen less than 5 ng/mL, absence of metastatic disease, and written consent. Participants were randomly assigned (1:1) to radiotherapy alone (no ADT) or radiotherapy with 6 months of ADT (short-course ADT), using monthly subcutaneous gonadotropin-releasing hormone analogue injections, daily oral bicalutamide monotherapy 150 mg, or monthly subcutaneous degarelix. Randomisation was done centrally through minimisation with a random element, stratified by Gleason score, positive margins, radiotherapy timing, planned radiotherapy schedule, and planned type of ADT, in a computerised system. The allocated treatment was not masked. The primary outcome measure was metastasis-free survival, defined as distant metastasis arising from prostate cancer or death from any cause. Standard survival analysis methods were used, accounting for randomisation stratification factors. The trial had 80% power with two-sided α of 5% to detect an absolute increase in 10-year metastasis-free survival from 80% to 86% (hazard ratio [HR] 0·67). Analyses followed the intention-to-treat principle. The trial is registered with the ISRCTN registry, ISRCTN40814031, and ClinicalTrials.gov, NCT00541047. FINDINGS: Between Nov 22, 2007, and June 29, 2015, 1480 patients (median age 66 years [IQR 61-69]) were randomly assigned to receive no ADT (n=737) or short-course ADT (n=743) in addition to postoperative radiotherapy at 121 centres in Canada, Denmark, Ireland, and the UK. With a median follow-up of 9·0 years (IQR 7·1-10·1), metastasis-free survival events were reported for 268 participants (142 in the no ADT group and 126 in the short-course ADT group; HR 0·886 [95% CI 0·688-1·140], p=0·35). 10-year metastasis-free survival was 79·2% (95% CI 75·4-82·5) in the no ADT group and 80·4% (76·6-83·6) in the short-course ADT group. Toxicity of grade 3 or higher was reported for 121 (17%) of 737 participants in the no ADT group and 100 (14%) of 743 in the short-course ADT group (p=0·15), with no treatment-related deaths. INTERPRETATION: Metastatic disease is uncommon following postoperative bed radiotherapy after radical prostatectomy. Adding 6 months of ADT to this radiotherapy did not improve metastasis-free survival compared with no ADT. These findings do not support the use of short-course ADT with postoperative radiotherapy in this patient population. FUNDING: Cancer Research UK, UK Research and Innovation (formerly Medical Research Council), and Canadian Cancer Society.

Stereotactic body radiotherapy for primary renal cell carcinoma: a systematic review and practice guideline from the International Society of Stereotactic Radiosurgery (ISRS).

Surgery is the standard of care for patients with primary renal cell carcinoma. Stereotactic body radiotherapy (SBRT) is a novel alternative for patients who are medically inoperable, technically high risk, or who decline surgery. Evidence for using SBRT in the primary renal cell carcinoma setting is growing, including several rigorously conducted prospective clinical trials. This systematic review was performed to assess the safety and efficacy of SBRT for primary renal cell carcinoma. Review results then formed the basis for the practice guidelines described, on behalf of the International Stereotactic Radiosurgery Society. 3972 publications were screened and 36 studies (822 patients) were included in the analysis. Median local control rate was 94·1% (range 70·0-100), 5-year progression-free survival was 80·5% (95% CI 72-92), and 5-year overall survival was 77·2% (95% CI 65-89). These practice guidelines addressed four key clinical questions. First, the optimal dose fractionation was 25-26 Gy in one fraction, or 42-48 Gy in three fractions for larger tumours. Second, routine post-treatment biopsy is not recommended as it is not predictive of patient outcome. Third, SBRT for primary renal cell carcinoma in a solitary kidney is safe and effective. Finally, guidelines for post-treatment follow-up are described, which include cross-axial imaging of the abdomen including both kidneys, adrenals, and surveillance of the chest initially every 6 months. This systematic review and practice guideline support the practice of SBRT for primary renal cell carcinoma as a safe and effective standard treatment option. Randomised trials with surgery and invasive ablative therapies are needed to further define best practice.

Delphi consensus on stereotactic ablative radiotherapy for oligometastatic and oligoprogressive renal cell carcinoma-a European Society for Radiotherapy and Oncology study endorsed by the European Association of Urology.

The purpose of this European Society for Radiotherapy and Oncology (ESTRO) project, endorsed by the European Association of Urology, is to explore expert opinion on the management of patients with oligometastatic and oligoprogressive renal cell carcinoma by means of stereotactic ablative radiotherapy (SABR) on extracranial metastases, with the aim of developing consensus recommendations for patient selection, treatment doses, and concurrent systemic therapy. A questionnaire on SABR in oligometastatic renal cell carcinoma was prepared by a core group and reviewed by a panel of ten prominent experts in the field. The Delphi consensus methodology was applied, sending three rounds of questionnaires to clinicians identified as key opinion leaders in the field. At the end of the third round, participants were able to find consensus on eight of the 37 questions. Specifically, panellists agreed to apply no restrictions regarding age (25 [100%) of 25) and primary renal cell carcinoma histology (23 [92%] of 25) for SABR candidates, on the upper threshold of three lesions to offer ablative treatment in patients with oligoprogression, and on the concomitant administration of immune checkpoint inhibitor. SABR was indicated as the treatment modality of choice for renal cell carcinoma bone oligometatasis (20 [80%] of 25) and for adrenal oligometastases 22 (88%). No consensus or major agreement was reached regarding the appropriate schedule, but the majority of the poll (54%-58%) retained the every-other-day schedule as the optimal choice for all the investigated sites. The current ESTRO Delphi consensus might provide useful direction for the application of SABR in oligometastatic renal cell carcinoma and highlight the key areas of ongoing debate, perhaps directing future research efforts to close knowledge gaps.

Focal radiotherapy boost to MR-visible tumor for prostate cancer: a systematic review.

PURPOSE: The FLAME trial provides strong evidence that MR-guided external beam radiation therapy (EBRT) focal boost for localized prostate cancer increases biochemical disease-free survival (bDFS) without increasing toxicity. Yet, there are many barriers to implementation of focal boost. Our objectives are to systemically review clinical outcomes for MR-guided EBRT focal boost and to consider approaches to increase implementation of this technique. METHODS: We conducted literature searches in four databases according to the Preferred Reporting Items for Systematic Reviews and Meta-Analysis guideline. We included prospective phase II/III trials of patients with localized prostate cancer underdoing definitive EBRT with MR-guided focal boost. The outcomes of interest were bDFS and acute/late gastrointestinal and genitourinary toxicity. RESULTS: Seven studies were included. All studies had a median follow-up of greater than 4 years. There were heterogeneities in fractionation, treatment planning, and delivery. Studies demonstrated effectiveness, feasibility, and tolerability of focal boost. Based on the Phoenix criteria for biochemical recurrence, the reported 5-year biochemical recurrence-free survival rates ranged 69.7-100% across included studies. All studies reported good safety profiles. The reported ranges of acute/late grade 3 + gastrointestinal toxicities were 0%/1-10%. The reported ranges of acute/late grade 3 + genitourinary toxicities were 0-13%/0-5.6%. CONCLUSIONS: There is strong evidence that it is possible to improve oncologic outcomes without substantially increasing toxicity through MR-guided focal boost, at least in the setting of a 35-fraction radiotherapy regimen. Barriers to clinical practice implementation are addressable through additional investigation and new technologies.

Impact of centralization of prostate cancer services on the choice of radical treatment.

OBJECTIVE: To assess the impact of centralization of prostate cancer surgery and radiotherapy services on the choice of prostate cancer treatment. PATIENTS AND METHODS: This national population-based study used linked cancer registry data and administrative hospital-level data for all 16 621 patients who were diagnosed between 1 January 2017 and 31 December 2018 with intermediate-risk prostate cancer and who underwent radical prostatectomy (RP) or radical radiation therapy (RT) in the English National Health Service (NHS). Travel times by car to treating centres were estimated using a geographic information system. We used logistic regression to assess the impact of the relative proximity of alternative treatment options on the type of treatment received, with adjustment for patient characteristics. RESULTS: Of the 78 NHS hospitals that provide RT or RP for prostate cancer, 41% provide both, 36% provide RT and 23% provide RP. Compared to patients who had both treatment options available at their nearest centre where overall 57% of patients received RT and 43% RP, patients were less likely to receive RT if their nearest centre offered RP only and the extra travel time to a hospital providing RT was >15 min (52% of patients received RT and 48% RP%, odds ratio [OR] 0.70 (0.58-0.85); P < 0.001). Conversely, patients were more likely to receive RT if their nearest centre offered RT and the extra travel time to a hospital providing RP was >15 min (63% of patients received RT and 37% RP, OR 1.23 (1.08-1.40); P < 0.001). There was a negligible impact on the type of treatment received if centres providing alternative treatment options were ≤15-min travel time from each other. CONCLUSION: The relative proximity of prostate cancer treatment options to a patient's residence is an independent predictor for the type of radical treatment received. Centralization policies for prostate cancer should not focus on one treatment modality but should consider all treatments to avoid a negative impact on treatment choice.

Intensity-modulated radiotherapy versus stereotactic body radiotherapy for prostate cancer (PACE-B): 2-year toxicity results from an open-label, randomised, phase 3, non-inferiority trial.

BACKGROUND: Localised prostate cancer is commonly treated with external beam radiotherapy and moderate hypofractionation is non-inferior to longer schedules. Stereotactic body radiotherapy (SBRT) allows shorter treatment courses without impacting acute toxicity. We report 2-year toxicity findings from PACE-B, a randomised trial of conventionally fractionated or moderately hypofractionated radiotherapy versus SBRT. METHODS: PACE is an open-label, multicohort, randomised, controlled, phase 3 trial conducted at 35 hospitals in the UK, Ireland, and Canada. In PACE-B, men aged 18 years and older with a WHO performance status 0-2 and low-risk or intermediate-risk histologically-confirmed prostate adenocarcinoma (Gleason 4 + 3 excluded) were randomly allocated (1:1) by computerised central randomisation with permuted blocks (size four and six), stratified by centre and risk group to control radiotherapy (CRT; 78 Gy in 39 fractions over 7·8 weeks or, following protocol amendment on March 24, 2016, 62 Gy in 20 fractions over 4 weeks) or SBRT (36·25 Gy in five fractions over 1-2 weeks). Androgen deprivation was not permitted. Co-primary outcomes for this toxicity analysis were Radiation Therapy Oncology Group (RTOG) grade 2 or worse gastrointestinal and genitourinary toxicity at 24 months after radiotherapy. Analysis was by treatment received and included all patients with at least one fraction of study treatment assessed for late toxicity. Recruitment is complete. Follow-up for oncological outcomes continues. The trial is registered with ClinicalTrials.gov, NCT01584258. FINDINGS: We enrolled and randomly assigned 874 men between Aug 7, 2012, and Jan 4, 2018 (441 to CRT and 433 to SBRT). In this analysis, 430 patients were analysed in the CRT group and 414 in the SBRT group; a total of 844 (97%) of 874 randomly assigned patients. At 24 months, RTOG grade 2 or worse genitourinary toxicity was seen in eight (2%) of 381 participants assigned to CRT and 13 (3%) of 384 participants assigned to SBRT (absolute difference 1·3% [95% CI -1·3 to 4·0]; p=0·39); RTOG grade 2 or worse gastrointestinal toxicity was seen in 11 (3%) of 382 participants in the CRT group versus six (2%) of 384 participants in the SBRT group (absolute difference -1·3% [95% CI -3·9 to 1·1]; p=0·32). No serious adverse events (defined as RTOG grade 4 or worse) or treatment-related deaths were reported within the analysis timeframe. INTERPRETATION: In the PACE-B trial, 2-year RTOG toxicity rates were similar for five fraction SBRT and conventional schedules of radiotherapy. Prostate SBRT was found to be safe and associated with low rates of side-effects. Biochemical outcomes are awaited. FUNDING: Accuray.

Long-term multicentre experience of adjuvant radiotherapy for pN3 squamous cell carcinoma of the penis.

OBJECTIVE: To present the long-term adjuvant radiotherapy outcomes of patients with pN3 squamous cell carcinoma of the penis (SCCp) treated at two UK centres. PATIENTS AND METHODS: We conducted a retrospective audit of all pN3 SCCp patients, deemed suitable for adjuvant therapy by a specialist multidisciplinary team at St George's and Leeds Hospitals, who received adjuvant radiotherapy. Primary outcomes were recurrence-free survival (RFS), cancer-specific survival (CSS) and overall survival (OS). Secondary outcomes were time to adjuvant treatment, frequency of in-field recurrence, site and side of recurrence, and dose and schedule of radiotherapy. RESULTS: A total of 146 patients were included: 121 completed radiotherapy, 4 did not complete radiotherapy and 21 did not start it. The median (interquartile range [IQR]) age was 59 (54-70)years. The 5-year RFS was 51%, CSS was 51% and OS was 44%. Adjuvant radiotherapy was started at a median (IQR) of 75 (48-106) days. A dose of 45 Gy in 20 fractions was most commonly used. Of the 125 patients who started adjuvant treatment, 55 relapsed. Of these relapses, 30 occurred in an inguinal or pelvic nodal station and 26 of the 30 were in a radiation field. Relapses in 18 of the 55 cases were in visceral sites only and seven were in both nodal (non-irradiated sites) and visceral sites. Doses of <50 Gy were used more commonly before 2013 and higher doses (>50 Gy) were more commonly used after 2013. CONCLUSIONS: Application of a standard radiotherapy protocol within a centralized supra-network setting has achieved survival outcomes that would appear better than those previously documented for either radiotherapy or chemotherapy in a cohort with solely pN3 disease. The addition of adjuvant chemotherapy may improve these outcomes further. These data suggest that adjuvant radiotherapy has a role to play in the management of men with pN3 SCCp.

The Emerging Role of Local Therapy in Metastatic Prostate Cancer.

PURPOSE OF REVIEW: This review summarizes the prospective clinical evidence regarding local therapy in metastatic prostate cancer. RECENT FINDINGS: The phase 3 STAMPEDE trial showed that prostate radiotherapy confers a survival benefit for newly diagnosed patients with low volume metastatic hormone-sensitive prostate cancer (HSPC). No survival benefit was noted for those with high volume disease. A subsequent meta-analysis combining the data of the STAMPEDE trial with that of the HORRAD trial corroborated these findings. The phase 2 randomized STOMP trial investigated local treatment of metastases in patients with oligometastatic HSPC, and showed an improvement in hormone therapy-free survival. Local prostate radiotherapy should be offered to patients with newly diagnosed low volume metastatic HSPC. Early clinical evidence suggests that local treatment to metastatic disease might be beneficial for patients with oligometastatic HSPC, but larger trials are awaited.

Intensity-modulated fractionated radiotherapy versus stereotactic body radiotherapy for prostate cancer (PACE-B): acute toxicity findings from an international, randomised, open-label, phase 3, non-inferiority trial.

BACKGROUND: Localised prostate cancer is commonly treated with external-beam radiotherapy. Moderate hypofractionation has been shown to be non-inferior to conventional fractionation. Ultra-hypofractionated stereotactic body radiotherapy would allow shorter treatment courses but could increase acute toxicity compared with conventionally fractionated or moderately hypofractionated radiotherapy. We report the acute toxicity findings from a randomised trial of standard-of-care conventionally fractionated or moderately hypofractionated radiotherapy versus five-fraction stereotactic body radiotherapy for low-risk to intermediate-risk localised prostate cancer. METHODS: PACE is an international, phase 3, open-label, randomised, non-inferiority trial. In PACE-B, eligible men aged 18 years and older, with WHO performance status 0-2, low-risk or intermediate-risk prostate adenocarcinoma (Gleason 4 + 3 excluded), and scheduled to receive radiotherapy were recruited from 37 centres in three countries (UK, Ireland, and Canada). Participants were randomly allocated (1:1) by computerised central randomisation with permuted blocks (size four and six), stratified by centre and risk group, to conventionally fractionated or moderately hypofractionated radiotherapy (78 Gy in 39 fractions over 7·8 weeks or 62 Gy in 20 fractions over 4 weeks, respectively) or stereotactic body radiotherapy (36·25 Gy in five fractions over 1-2 weeks). Neither participants nor investigators were masked to allocation. Androgen deprivation was not permitted. The primary endpoint of PACE-B is freedom from biochemical or clinical failure. The coprimary outcomes for this acute toxicity substudy were worst grade 2 or more severe Radiation Therapy Oncology Group (RTOG) gastrointestinal or genitourinary toxic effects score up to 12 weeks after radiotherapy. Analysis was per protocol. This study is registered with ClinicalTrials.gov, NCT01584258. PACE-B recruitment is complete and follow-up is ongoing. FINDINGS: Between Aug 7, 2012, and Jan 4, 2018, we randomly assigned 874 men to conventionally fractionated or moderately hypofractionated radiotherapy (n=441) or stereotactic body radiotherapy (n=433). 432 (98%) of 441 patients allocated to conventionally fractionated or moderately hypofractionated radiotherapy and 415 (96%) of 433 patients allocated to stereotactic body radiotherapy received at least one fraction of allocated treatment. Worst acute RTOG gastrointestinal toxic effect proportions were as follows: grade 2 or more severe toxic events in 53 (12%) of 432 patients in the conventionally fractionated or moderately hypofractionated radiotherapy group versus 43 (10%) of 415 patients in the stereotactic body radiotherapy group (difference -1·9 percentage points, 95% CI -6·2 to 2·4; p=0·38). Worst acute RTOG genitourinary toxicity proportions were as follows: grade 2 or worse toxicity in 118 (27%) of 432 patients in the conventionally fractionated or moderately hypofractionated radiotherapy group versus 96 (23%) of 415 patients in the stereotactic body radiotherapy group (difference -4·2 percentage points, 95% CI -10·0 to 1·7; p=0·16). No treatment-related deaths occurred. INTERPRETATION: Previous evidence (from the HYPO-RT-PC trial) suggested higher patient-reported toxicity with ultrahypofractionation. By contrast, our results suggest that substantially shortening treatment courses with stereotactic body radiotherapy does not increase either gastrointestinal or genitourinary acute toxicity. FUNDING: Accuray and National Institute of Health Research.

Impact of Ga-68-PSMA PET/CT on management in prostate cancer patients with very early biochemical recurrence after radical prostatectomy.

PURPOSE: With the availability of ultra-sensitive PSA assays, early biochemical relapse (eBCR) of prostate cancer is increasingly being detected at values much lower than the conventional threshold of 0.2 ng/ml. Accurate localisation of disease in this setting may allow treatment modification and improved outcomes, especially in patients with pelvis-confined or extra-pelvic oligometastasis (defined as up to three pelvic nodal or distant sites). We aimed to measure the detection rate of [68]Ga-PSMA-HBNED-CC (PSMA)-PET/CT and its influence on patient management in eBCR of prostate cancer following radical prostatectomy (RP). METHODS: We retrospectively identified 28 patients who underwent PSMA-PET/CT for post-RP eBCR (PSA < 0.5 ng/ml) at our tertiary care cancer centre. Two nuclear medicine physicians independently recorded the sites of PSMA-PET/CT positivity. Multidisciplinary meeting records were accessed to determine changes in management decisions following PSMA-PET/CT scans. RESULTS: The mean age of patients was 65.6 years (range: 50-76.2 years); median PSA was 0.22 ng/ml (interquartile range: 0.15 ng/ml to 0.34 ng/ml). Thirteen patients (46.4%) had received radiotherapy in the past. PSMA-PET/CT was positive in 17 patients (60.7%). Only one patient had polymetastasis (> 3 sites); the remainder either had prostatectomy bed recurrence (n = 2), pelvic oligometastasis (n = 10), or extra-pelvic oligometastasis (n = 4). PSMA-PET/CT resulted in management change in 12 patients (42.8%), involving stereotactic body radiotherapy (n = 6), salvage radiotherapy (n = 4), and systemic treatment (n = 2). CONCLUSIONS: Our findings show that PSMA-PET/CT has a high detection rate in the eBCR setting following RP, with a large proportion of patients found to have fewer than three lesions. PSMA-PET/CT may be of value in patients with early PSA failure, and impact on the choice of potentially curative salvage treatments.

Stereotactic body radiotherapy for bone oligometastatic disease in prostate cancer.

PURPOSE: There are sparse data describing outcomes of bone-only oligometastatic prostate cancer in comparison with lymph node disease treated with stereotactic body radiotherapy (SBRT). The primary aim of this study was to report progression-free survival (PFS) data for patients with bone-only disease. Influence of hormone sensitivity and androgen deprivation therapy use was also assessed. METHODS: This is a single-centre retrospective cohort study. Hormone-sensitive and castrate-resistant patients with oligometastatic (≤ 3) bone-only prostate cancer treated with SBRT were included. Data were collected using electronic records. Kaplan-Meier survivor function, log rank test, as well as Cox regression were used to calculate PFS and overall survival. RESULTS: In total, 51 patients with 64 bone metastases treated with SBRT were included. Nine patients were castrate resistant and 42 patient's hormone sensitive at the time of SBRT. Median follow-up was 23 months. Median PFS was 24 months in hormone-sensitive patients and 3 months in castrate-resistant patients. No patients experienced grade 3 or 4 toxicities. There were three in-field recurrences. CONCLUSIONS: In this study, patients with bone oligometastatic disease showed potential benefit from SBRT with a median PFS of 11 months. Hormone-sensitive patients showed the greatest benefit, with results similar to that published for oligometastatic pelvic nodal disease treated with SBRT. Prospective randomised control trials are needed to determine the survival benefit of SBRT in oligometastatic bone-only prostate cancer and to determine prognostic indicators.

Trends in Management of Oligometastatic Hormone-Sensitive Prostate Cancer.

PURPOSE OF REVIEW: Systemic therapy for patients with hormone-sensitive oligometastatic prostate cancer is non-curative and associated with toxicities. Meanwhile, this population presents unique clinical opportunities to improve outcomes, including the demonstrated benefits of radiotherapy to the primary tumor or oligometastatic sites. RECENT FINDINGS: Recently published randomized studies have demonstrated benefits with the addition of radiotherapy to the primary disease or metastatic lesions in patients with synchronous or metachronous disease. The introduction of novel PET imaging has improved the sensitivity and specificity for detecting metastatic disease and provides an opportunity to better select patients who will benefit from local therapy. The data presented in this review supports revisiting practice guidelines for patients with hormone-sensitive metastatic prostate cancer, particularly in relation to the role of radiotherapy to the primary tumor and sites of oligometastatic disease. Future trials will aim to further establish the role of metastasis-directed therapies in metachronous, synchronous, and castrate-resistant disease.

Improving fiducial and prostate capsule visualization for radiotherapy planning using MRI.

BACKGROUND AND PURPOSE: Intraprostatic fiducial markers (FM) improve the accuracy of radiotherapy (RT) delivery. Here we assess geometric integrity and contouring consistency using a T2*-weighted (T2*W) sequence alone, which allows visualization of the FM. MATERIAL AND METHODS: Ten patients scanned within the Prostate Advances in Comparative Evidence (PACE) trial (NCT01584258) had prostate images acquired with computed tomography (CT) and Magnetic Resonance (MR) Imaging: T2-weighted (T2W) and T2*W sequences. The prostate was contoured independently on each imaging dataset by three clinicians. Interobserver variability was assessed using comparison indices with Monaco ADMIRE (research version 2.0, Elekta AB) and examined for statistical differences between imaging sets. CT and MR images of two test objects were acquired to assess geometric distortion and accuracy of marker positioning. The first was a linear test object comprising straight tubes in three orthogonal directions, the second was a smaller test object with markers suspended in gel. RESULTS: Interobserver variability for prostate contouring was lower for both T2W and T2*W compared to CT, this was statistically significant when comparing CT and T2*W images. All markers are visible in T2*W images with 29/30 correctly identified, only 3/30 are visible in T2W images. Assessment of geometric distortion revealed in-plane displacements were under 0.375 mm in MRI, and through plane displacements could not be detected. The signal loss in the MR images is symmetric in relation to the true marker position shown in CT images. CONCLUSION: Prostate T2*W images are geometrically accurate, and yield consistent prostate contours. This single sequence can be used to identify FM and for prostate delineation in a mixed MR-CT workflow.

The Role of Hypofractionated Radiotherapy in Prostate Cancer.

PURPOSE OF REVIEW: It is now accepted that prostate cancer has a low alpha/beta ratio, establishing a strong basis for hypofractionation of prostate radiotherapy. This review focuses on the rationale for hypofractionation and presents the evidence base for establishing moderate hypofractionation for localised disease as the new standard of care. The emerging evidence for extreme hypofractionation in managing localized and oligometastatic prostate cancer is reviewed. RECENT FINDINGS: The 5-year efficacy and toxicity outcomes from four phase III studies have been published within the last 12 months. These studies randomizing over 6000 patients to conventional fractionation (1.8-2.0 Gy per fraction) or moderate hypofractionation (3.0-3.4 Gy per fraction). They demonstrate hypofractionation to be non-inferior to conventional fractionation. Moderate hypofractionation for localized prostate cancer is safe and effective. There is a growing body of evidence in support of extreme hypofractionation for localized prostate cancer. Extreme hypofractionation may have a role in managing prostate oligometastases, but further studies are needed.

The delineation of intraprostatic boost regions for radiotherapy using multimodality imaging.

Dose escalation to the prostate improves tumor control but at the expense of increased rectal toxicity. Modern imaging can be used to detect the most common site of recurrence, the intraprostatic lesion (IPL), which has led to the concept of focusing dose escalation to the IPL in order to improve the therapeutic ratio. Imaging must be able to detect lesions with adequate sensitivity and specificity to accurately delineate the IPL. This information must be carefully integrated into the radiotherapy planning process to ensure the dose is targeted to the IPL. This review will consider the role and challenges of multiparametric MRI and PET computed tomography in delineating a tumor boost to be delivered by external beam radiotherapy.