Methodological considerations in the evaluation of radiotherapy technologies

Bayesian methods provide a practical real-world evidence framework for evaluating the impact of changes in radiotherapy

PURPOSE

Retrospective studies have identified a link between the average set-up error of lung cancer patients treated with image-guided radiotherapy (IGRT) and survival. The IGRT protocol was subsequently changed to reduce the action threshold. In this study, we use a Bayesian approach to evaluate the clinical impact of this change to practice using routine 'real-world' patient data.

METHODS AND MATERIALS

Two cohorts of NSCLC patients treated with IGRT were compared: pre-protocol change (N = 780, 5 mm action threshold) and post-protocol change (N = 411, 2 mm action threshold). Survival models were fitted to each cohort and changes in the hazard ratios (HR) associated with residual set-up errors was assessed. The influence of using an uninformative and a skeptical prior in the model was investigated.

RESULTS

Following the reduction of the action threshold, the HR for residual set-up error towards the heart was reduced by up to 10%. Median patient survival increased for patients with set-up errors towards the heart, and remained similar for patients with set-up errors away from the heart. Depending on the prior used, a residual hazard ratio may remain.

CONCLUSIONS

Our analysis found a reduced hazard of death and increased survival for patients with residual set-up errors towards versus away from the heart post-protocol change. This study demonstrates the value of a Bayesian approach in the assessment of technical changes in radiotherapy practice and supports the consideration of adopting this approach in further prospective evaluations of changes to clinical practice.

Radiotherapy respiratory motion management in hepatobiliary and pancreatic malignancies: a systematic review of patient factors influencing effectiveness of motion reduction with abdominal compression

BACKGROUND

The effectiveness of abdominal compression for motion management in hepatobiliary-pancreatic (HPB) radiotherapy has not been systematically evaluated.

METHODS & MATERIALS

A systematic review was carried out using PubMed/Medline, Cochrane Library, Web of Science, and CINAHL databases up to 1 July 2021. No date restrictions were applied. Additional searches were carried out using the University of Manchester digital library, Google Scholar and of retrieved papers' reference lists. Studies conducted evaluating respiratory motion utilising imaging with and without abdominal compression in the same patients available in English were included. Studies conducted in healthy volunteers or majority non-HPB sites, not providing descriptive motion statistics or patient characteristics before and after compression in the same patients or published without peer-review were excluded. A narrative synthesis was employed by tabulating retrieved studies and organising chronologically by abdominal compression device type to help identify patterns in the evidence.

RESULTS

The inclusion criteria were met by 6 studies with a total of 152 patients. Designs were a mix of retrospective and prospective quantitative designs with chronological, non-randomised recruitment. Abdominal compression reduced craniocaudal respiratory motion in the majority of patients, although in four studies there were increases seen in at least one direction. The influence of patient comorbidities on effectiveness of compression, and/or comfort with compression was not evaluated in any study.

CONCLUSION

Abdominal compression may not be appropriate for all patients, and benefit should be weighed with potential increase in motion or discomfort in patients with small initial motion (<5 mm). Patient factors including male sex, and high body mass index (BMI) were found to impact the effectiveness of compression, however with limited evidence. High-quality studies are warranted to fully assess the clinical impact of abdominal compression on treatment outcomes and toxicity prospective in comparison to other motion management strategies.

Estimating the percentage of patients who might benefit from proton beam therapy instead of X-ray radiotherapy

OBJECTIVES

High-energy Proton Beam Therapy (PBT) commenced in England in 2018 and NHS England commissions PBT for 1.5% of patients receiving radical radiotherapy. We sought expert opinion on the level of provision.

METHODS

Invitations were sent to 41 colleagues working in PBT, most at one UK centre, to contribute by completing a spreadsheet. 39 responded: 23 (59%) completed the spreadsheet; 16 (41%) declined, arguing that clinical outcome data are lacking, but joined six additional site-specialist oncologists for two consensus meetings. The spreadsheet was pre-populated with incidence data from Cancer Research UK and radiotherapy use data from the National Cancer Registration and Analysis Service. 'Mechanisms of Benefit' of reduced growth impairment, reduced toxicity, dose escalation and reduced second cancer risk were examined.

RESULTS

The most reliable figure for percentage of radical radiotherapy patients likely to benefit from PBT was that agreed by 95% of the 23 respondents at 4.3%, slightly larger than current provision. The median was 15% (range 4-92%) and consensus median 13%. The biggest estimated potential benefit was from reducing toxicity, median benefit to 15% (range 4-92%), followed by dose escalation median 3% (range 0 to 47%); consensus values were 12 and 3%. Reduced growth impairment and reduced second cancer risk were calculated to benefit 0.5% and 0.1%.

CONCLUSIONS

The most secure estimate of percentage benefit was 4.3% but insufficient clinical outcome data exist for confident estimates. The study supports the NHS approach of using the evidence base and developing it through randomised trials, non-randomised studies and outcomes tracking.

ADVANCES IN KNOWLEDGE

Less is known about the percentage of patients who may benefit from PBT than is generally acknowledged. Expert opinion varies widely. Insufficient clinical outcome data exist to provide robust estimates. Considerable further work is needed to address this, including international collaboration; much is already underway but will take time to provide mature data.

Demystifying radiation oncology clinical trial concerns for protocol scientific review and institutional review board committee members

Clinical trials are essential for evaluating advanced technologies and treatment approaches involving radiation therapy to improve outcomes for cancer patients. Clinical trials at cancer centers with designation from the National Cancer Institute must undergo scientific review in additional to Institutional Review Board approval. Given the highly specialized nature and rapidly advancing technologies of radiation therapy, and the small number of radiation oncology investigators at some centers, a lack of radiation oncology expertise among reviewers may present challenges at some cancer centers. This commentary aims to provide an overview of radiation therapy and special considerations for radiation oncology research that will serve as a helpful resource in the scientific review of clinical trials involving cancer patients.

Proton beam therapy: perspectives on the National Health Service England clinical service and research programme

The UK has an important role in the evaluation of proton beam therapy (PBT) and takes its place on the world stage with the opening of the first National Health Service (NHS) PBT centre in Manchester in 2018, and the second in London coming in 2020. Systematic evaluation of the role of PBT is a key objective. By September 2019, 108 patients had started treatment, 60 paediatric, 19 teenagers and young adults and 29 adults. Obtaining robust outcome data is vital, if we are to understand the strengths and weaknesses of current treatment approaches. This is important in demonstrating when PBT will provide an advantage and when it will not, and in quantifying the magnitude of benefit.The UK also has an important part to play in translational PBT research, and building a research capability has always been the vision. We are perfectly placed to perform translational pre-clinical biological and physical experiments in the dedicated research room in Manchester. The nature of DNA damage from proton irradiation is considerably different from X-rays and this needs to be more fully explored. A better understanding is needed of the relative biological effectiveness (RBE) of protons, especially at the end of the Bragg peak, and of the effects on tumour and normal tissue of PBT combined with conventional chemotherapy, targeted drugs and immunomodulatory agents. These experiments can be enhanced by deterministic mathematical models of the molecular and cellular processes of DNA damage response. The fashion of ultra-high dose rate FLASH irradiation also needs to be explored.

Proton Beam Therapy - the Challenges of Delivering High-quality Evidence of Clinical Benefit

The use of proton beam therapy (PBT) offers the opportunity to improve greater conformality of radiotherapy treatment delivery in some patients. However, it is associated with a high capital cost and the need to build new dedicated facilities. We discuss how the global radiotherapy community can respond to the challenge of producing high-quality evidence of clinical benefit from PBT in adult patients. In the UK, the National Cancer Research Institute-funded Clinical and Radiotherapy Translational group has established the PBT Clinical Trial Strategy Group. An eight-point framework is described that can assist the development and delivery of high-quality clinical trials.

Exploiting biological and physical determinants of radiotherapy toxicity to individualize treatment

The recent advances in radiation delivery can improve tumour control probability (TCP) and reduce treatment-related toxicity. The use of intensity-modulated radiotherapy (IMRT) in particular can reduce normal tissue toxicity, an objective in its own right, and can allow safe dose escalation in selected cases. Ideally, IMRT should be combined with image guidance to verify the position of the target, since patients, target and organs at risk can move day to day. Daily image guidance scans can be used to identify the position of normal tissue structures and potentially to compute the daily delivered dose. Fundamentally, it is still the tolerance of the normal tissues that limits radiotherapy (RT) dose and therefore tumour control. However, the dose-response relationships for both tumour and normal tissues are relatively steep, meaning that small dose differences can translate into clinically relevant improvements. Differences exist between individuals in the severity of toxicity experienced for a given dose of RT. Some of this difference may be the result of differences between the planned dose and the accumulated dose (DA). However, some may be owing to intrinsic differences in radiosensitivity of the normal tissues between individuals. This field has been developing rapidly, with the demonstration of definite associations between genetic polymorphisms and variation in toxicity recently described. It might be possible to identify more resistant patients who would be suitable for dose escalation, as well as more sensitive patients for whom toxicity could be reduced or avoided. Daily differences in delivered dose have been investigated within the VoxTox research programme, using the rectum as an example organ at risk. In patients with prostate cancer receiving curative RT, considerable daily variation in rectal position and dose can be demonstrated, although the median position matches the planning scan well. Overall, in 10 patients, the mean difference between planned and accumulated rectal equivalent uniform doses was -2.7 Gy (5%), and a dose reduction was seen in 7 of the 10 cases. If dose escalation was performed to take rectal dose back to the planned level, this should increase the mean TCP (as biochemical progression-free survival) by 5%. Combining radiogenomics with individual estimates of DA might identify almost half of patients undergoing radical RT who might benefit from either dose escalation, suggesting improved tumour cure or reduced toxicity or both.

Evaluating competing and emerging technologies for stereotactic body radiotherapy and other advanced radiotherapy techniques

Stereotactic body radiotherapy (SBRT) refers to the precise irradiation of an image-defined extracranial lesion, using a high total radiation dose delivered in a small number of fractions. A significant proportion of SBRT treatment has been successfully delivered using conventional gantry-based linear accelerators with appropriate image guidance and motion management techniques, although a number of specialist systems are also available. Evaluating the competing SBRT technologies is difficult due to frequent refinements to all major platforms. Comparison of geometric accuracy or treatment planning performance can be hard to interpret and may not provide much useful information. Nevertheless, a general specification overview can provide information that may help radiotherapy providers decide on an appropriate system for their centre. A number of UK randomised controlled trials (RCTs) have shown that better radiotherapy techniques yield better results. RCTs should play an important part in the future evaluation of SBRT, especially where there is a smaller volume of existing data, and where outcomes from conventional radiotherapy are very good. RCT comparison of SBRT with surgery is more difficult due to the radically different treatment arms, although successful recruitment can be possible if the lessons from previous failed trials are learned. The evaluation of new technology poses a number of challenges to the conventional RCT methodology, and there may be situations where it is genuinely not possible, with careful observational studies or decision modelling being more appropriate. Further development in trial design may have an important role in providing clinical evidence in a more timely manner.

IMRT utilization in Ontario: qualitative deployment evaluation

Purpose

– The purpose of this paper is to describe a jurisdiction-wide implementation and evaluation of intensity-modulated radiation therapy (IMRT) in Ontario, Canada, highlighting innovative strategies and lessons learned.

Design/methodology/approach

– To obtain an accurate provincial representation, six cancer centres were chosen (based on their IMRT utilization, geography, population, academic affiliation and size) for an in-depth evaluation. At each cancer centre semi-structured, key informant interviews were conducted with senior administrators. An electronic survey, consisting of 40 questions, was also developed and distributed to all cancer centres in Ontario.

Findings

– In total, 21 respondents participated in the interviews and a total of 266 electronic surveys were returned. Funding allocation, guidelines and utilization targets, expert coaching and educational activities were identified as effective implementation strategies. The implementation allowed for hands-on training, an exchange of knowledge and expertise and the sharing of responsibility. Future implementation initiatives could be improved by creating stronger avenues for clear, continuing and comprehensive communication at all stages to increase awareness, garner support and encourage participation and encouraging expert-based coaching. IMRT utilization for has increased without affecting wait times or safety (from fiscal year 2008/2009 to 2012/2013 absolute increased change: prostate 46, thyroid 36, head and neck 29, sarcoma 30, and CNS 32 per cent).

Originality/value

– This multifaceted, jurisdiction-wide approach has been successful in implementing guideline recommended IMRT into standard practice. The expert based coaching initiative, in particular presents a novel training approach for those who are implementing complex techniques. This paper will be of interest to those exploring ways to fund, implement and sustain complex and evolving technologies.