Challenges in the implementation of PDR

The Christie is in the minority in the United Kingdom,Reference Tan⁵ having opted for PDR rather than HDR to replace the aging LDR Selectron unit to treat gynaecological brachytherapy patients. This has necessitated a greater emphasis on ‘lean’ principles,Reference Jones⁶ improved communication, a paring down of workflow steps by reducing bottlenecks and improving patient throughput, with the aim of streamlining and enhancing the patient experience throughout the pathway. The aim was to incorporate best practice throughout the patient journey and emphasises the importance of the ‘process’ whilst allowing the accommodation of increasing patient numbers within current resource capacity.

The move to 3D image-based planning for cervix treatments has significantly altered the patient pathway and impacted on the departmental workflow, with increased imaging requirements and planning time. In addition, a reduction in dose rate compared with LDR led to the requirement to fractionate PDR treatments, while maintaining lengthy treatment times. This is more demanding of resources compared with LDR with respect to both staffing and clinical systems. Also, two PDR machines are required to treat in the same way as a single LDR Selectron (i.e., two patients were treated with the Selectron unit concurrently). This also results in added requirements for routine machine calibration and QA checks, which in turn reduces the time available for clinical use. Treatment times are typically in the region of 13–19 hours and require two fractions one week apart.Reference Baker, Pooler, Hendry and Davidson⁴ However, when compared with HDR multiple fractionation schedules, the PDR schedule requires correspondingly less planning and imaging time over the entire brachytherapy course. With ∼180 patients per year treated for gynaecological cancers at the Christie, treating each with three to four fractions of HDR as well as continuing provision for other patient sites would be unsustainable. However, the long PDR treatment times mean that there is a significant time pressure to complete treatments efficiently to allow the next day's patients to begin treatment in a timely manner.

Patient pathway

An efficient workflow requires an enhanced multidisciplinary approach to the patient pathway from admission, through theatre, imaging, planning, treatment and aftercare.

Adherence to the timetable shown in Figure 1 is essential to allow treatments to complete efficiently with time available for turnaround of the treatment room. Much effort has been put into streamlining the process; however, issues do still persist in some areas. Common issues encountered can affect the timings of a normal week and cause a knock-on effect for the patients being treated the following day. Examples are patient referrals from other cancer centres and the difficulties that sometimes occur in communication between centres. Different systems of work, in particular with pre-treatment assessment (to assess suitability for both anaesthetic and treatment, as these patients are completing an intensive course of concurrent chemo-radiotherapy), mean that issues are often not highlighted before the patient travelling long distances for treatment, which can cause delays for patients and a loss in treatment capacity. In some cases, this has meant patients have had to be rescheduled for their treatment, which can be stressful for the patient who may be eager for their treatment to start as soon as possible, and has a substantial impact upon treatment scheduling. This remains a significant problem within the pathway and is yet to be totally overcome. It is hoped that by improving the pre-admission workflow at the main site this will allow more time for administration staff and encourage a more efficient referral process from external centres through improved transparency and a closer working relationship.

Figure 1

Breakdown of a normal cervix patient pathway

As patients are being admitted on the day of their treatment, they first have to arrive at the admission suite for pre-theatre checks before they arrive on the ward; this represents an additional step in the patient pathway, which can result in delays. It has been found through our previous experience that a ‘lean’ approachReference Jones⁶ to the pathway has had positive impacts upon workflow efficiency and the future incorporation of these checks into the ward environment by brachytherapy trained nurses is expected to give a time saving benefit.

For vaginal vault insertions, the whole process takes part on the ward with the sizing and insertion of the applicator carried out by the clinical oncologist or advanced practitioner radiographer (who has undergone specialist training as an extension of their role) assisted by brachytherapy staff (radiographer, technician or dosimetrist). These patients are not individually planned and their treatment is delivered using a standard library plan saved on the TCS (Treatment Control System) depending on the applicator size inserted. This means that once the checks have been completed, these patients can start their treatment more quickly and so timing is not as critical in the process.

Multidisciplinary working

The use of multidisciplinary teams (MDT) to improve the provision of service for all patients was outlined in the National Health Service (NHS) cancer plan⁷; this also stated that the benefits of multidisciplinary working would be a reduction in treatment delays and a faster more coordinated treatment pathway. This type of working has also been shown to improve job satisfaction for all involved which is vital in promotion of good working relationships and overall better care for the patient.Reference Fleissig, Jenkins, Catt and Fallowfield⁸

The complex pathway the patient experiences throughout the whole process of their treatment, through several disciplines within the hospital, presents numerous opportunities for delays and it was decided early in the process that good communication and an in-depth knowledge of the workflow as a whole would be hugely beneficial. A forum was therefore established to discuss problems affecting the patient's progress in the form of an MDT type meeting. The Christie multidisciplinary gynaecological brachytherapy pathway team meets once a month to discuss new developments, interesting cases and changes in practice and communicate this to all staff involved in the treatment pathway; it has yielded vital improvements to the overall patient pathway.

Although not an MDT in the traditional sense, as individual patients' treatments and disease are not discussed to inform treatment decisions, this group acts more like a forum for all the different professions responsible for the patients’ treatment at different stages, to get together and discuss any issues that may be hindering a part of the service at any point.

This has helped to streamline the service as issues have been quickly identified and dealt with so they have had a minimal impact on the patients and change can be implemented quickly. It also has helped to identify training requirements for staff which is a major issue as responsibility for operating the PDR, patient care and radiation protection is delegated to specially trained PDR nursing staff (with on-call radiographer/physicist support) outside of normal working hours.

Staff emergency response training

The move from Caesium-137 LDR Selectron to a higher instantaneous dose rate with Iridium-192 PDR, while maintaining long treatment times similar to those used with LDR, presented several issues to be addressed with regard to ward-based brachytherapy. Patients have traditionally been in the care of trained nurses who had undergone further radiation protection training allowing them to care for patients undergoing treatment on the LDR Selectron unit, those with I-125 seed implants and those undergoing I-131 ablation. Radiographer/physicist support was provided during working hours and on-call support during the night. Due to the lower dose rate of the Caesium-137 Selectron, ward staff were not expected to perform an emergency source retraction in the same way as with PDR as in the event of a source stick this could be provided by on-call radiographer and physicist support without endangering the patient due to the uniform LDR of the treatment.

With the move to PDR, and the associated higher dose rate, the need for swift on-site support in the case of emergency became apparent, and it was decided that the present nursing role would be expanded to included first-line error response and if necessary emergency source retraction. While it is recognised that this is traditionally the domain of a radiographer/physicist (24-hour on-call telephone support is still available to provide technical and clinical advice and fault resolution), with additional training and annual updates it was decided that the present nursing staff, with past experience of caring for LDR patients, could be designated operators under IRMER and be responsible for the afterloader out of working hours. IRMER does not specifically mention staff groups in its regulations; nursing staff are able to work under this designation providing adequate training and support is in place and operators are assessed as competent and reviewed annually.

Training was approached as it would for any new member of staff and basic functionality and common causes of errors explained in a scenario based format with special focus placed on the emergency retraction procedure including a minimum of annual dummy runs and practicing operating the source retraction handle during planned preventative maintenance.

In common with many NHS facilities, the department is faced with servicing an aging population and has had occasional challenges to face in the treatment of patients suffering with dementia, or indeed from patients with substance dependencies; they have become confused or distressed and started moving within their beds with applicators in situ. This clearly presents a risk to the patients and staff, both from physical injury and potential radiation safety issues. In response to this, risk assessments are produced for these patients to ensure nursing staff are made aware of any issues in order to reduce this risk as much as possible. Developments with biphasic radiobiological modelling are underway with a possible move towards a shorter ‘office hours’ schedule making use of an increased dose per hourly pulse to reduce the number of hours total treatment time.Reference Underwood, Dale, Bidmead and Nalder⁹ This would involve an increase in dose rate to around 1·5 Gy/hour which is closer to the dose rate achieved from Caesium 137, however, due to the higher instantaneous dose rate of the PDR and the associated radiobiological uncertainties, care must be taken with implementation of the schedule. Daytime scheduling might be of benefit for these patients, enabling closer supervision of the treatment by brachytherapy staff, and reducing the total treatment time for this patient group. Indeed it has been informally noted by nurses in the department that this patient group are more likely to experience problems during the night so daytime treatment schedules may offer substantial benefits.

Imaging and contouring

The incorporation of enhanced imaging techniques to allow the 3D planning of brachytherapy patients has affected the patient workflow perhaps more than any other aspect of the move to PDR. Imaging requirements and planning technique are almost identical to HDR, with the added considerations of long treatment times. The gynaecological multi-disciplinary brachytherapy group has done much to facilitate the provision of magnetic resonance (MR) scan slots and the continued refinement of imaging protocols. A positive working relationship has been developed between all departments and this has allowed the development and implementation of new ideas and practices with the minimum amount of delay.⁷ By incorporating clinical expertise from the different professional areas, the MDT has influenced the decision-making process and the development of the service.

Original patient imaging consisted of computed tomography (CT) imaging for applicator alignment and OAR delineation, due to the reduced uncertainties during applicator reconstruction compared with MR as described by Krempien et al.Reference Krempien, Daeuber, Hensley, Wannenmacher and Harms¹⁰ This was then fused to the T2 weighted MR image used for tumour delineation as per GEC-ESTRO GYN guidelines.Reference Hellebust, Kirisits and Berger¹¹ The geometric uncertainties when fusing CT to MR are well knownReference Krempien, Daeuber, Hensley, Wannenmacher and Harms^10, Reference Hellebust, Kirisits and Berger¹¹ and combined with logistical and time issues surrounding the more complex CT/MR patient pathway a decision was made early-on to move solely to MR imaging for both applicator reconstruction and tumour/OAR delineation.

One MR sequence tested, using a 1·5 T Siemens Avanto scanner (Siemens Healthcare, Erlangen, Germany), employed a high-spatial-resolution 3D FSE with Variable Flip Angle sequence (SPACE) using a 1 mm isotropic voxel size, similar to the sequences described by Dimopoulos et al.Reference Dimopoulos, Petrow and Tanderup¹² However, problems were encountered visualising tumour due to poor contrast, which led to the GTV/HRCTV being delineated on a standard set of axial/sagittal sequences and then being automatically fused with the SPACE sequence used for applicator reconstruction.

The SPACE sequence, given its high resolution and enhanced 3D reconstruction attributes was found to work very well for applicator reconstruction, however, the length of time taken to acquire the SPACE sequence and the subsequent axial/sagittal/coronal imaging (30+ minutes) lead, in our opinion to an unacceptable risk of patient movement and subsequent errors created by auto-registering of the sequences, as well as a delay in treatment start time, which corroborates the findings of other centres.Reference Hellebust, Kirisits and Berger¹¹ Finally, due to the logistical issues and in order to minimise the time between MR sequences, a FSE T2 weighted sequence was employed using 2·5 mm slice thickness with a 2·5 mm interslice gap (see Figure 2) to minimise random reconstruction errorsReference Tanderup, Paulsen and Lang¹³ while giving improved tumour visualisation and contouring on the same image acquisition.Reference Tanderup, Paulsen and Lang¹³

Figure 2

MR sequences.

As recommended as mandatory by GEC-ESTRO IVReference Dimopoulos, Petrow and Tanderup¹² para-axial, sagittal and coronal T2 image sequences are acquired and orientated in relation to the intra-uterine tube.

If indicated, patients are scanned with an MR compatible marker positioned in the cervix, which can also be used as a reference point to assess applicator movement. Vaginal packing is soaked in proflavin 0·1%, which shows a contrasting signal to both ovoids and tumour tissue. The proflavin, with minimal unit cost, provides improved visualisation of the vaginal packing and increases the ease of packing removal. All patients are screened for sensitivity for the ingredients of proflavin before theatre.

Applicators are reconstructed on the treatment planning system (Oncentra Brachy v.4.0, Nucletron, Veenendall, The Netherlands) by alignment onto the image sets of a 3D applicator library model from the manufacturer in the method described in Hellebust et al.Reference Hellebust, Kirisits and Berger¹¹ Slice thickness, scan time, MRI availability, both pre-RT and during brachytherapy, as well as image resolution and contrast are all variables and each individual centre will need to develop a suitable protocol matched to their local requirements.

New sequences are currently being trialled in order to continually improve image quality and accuracy of reconstruction as well as organ/tumour delineation whilst attempting to improve planning accuracy and efficiency.

Treatment planning and optimisation

Planning and plan checks are carried out by a small group of specialist brachytherapy radiographers, physicists and dosimetrists. The contouring method follows the GEC-ESTRO GYN working group recommendationsReference Haie-Meder, Potter and Limber¹⁴ and is performed by planners and the clinician. Basic library plans are based on standard Manchester system dosimetry prescribing to point A. Plans then may be optimised based on OAR tolerance doses based on the Royal College of Radiologists (RCR) recommendations.² This represents a level III benefit (conformation of dose distribution) as defined by the ‘Implementation of Image-guided Brachytherapy for Cervix Cancer in the UK’ report.² The tolerance dose (expressed in terms of equivalent 2 Gy fractions dose, EQD2) currently used for OAR assuming an α–β ratio of 3 and a repair half time of 1·5 hours, can be found in Figure 3 and are based on the upper limits of the guideline doses found in the RCR recommendations. For this purpose, the full external beam dose 40/45 Gy in 20# (dose and field borders dependent on nodal status), is considered to have been delivered to the D2cc volume of the OAR.Reference Potter, Haie-Meder and Van Limbergen¹⁵

Figure 3

Local OAR tolerances doses based on RCR recommendations.Reference Jones⁶

Abbreviations: OAR, organ at risk; RCR, Royal College of Radiologists

At present the Christie, while technically meeting the criteria set out in the RCR report² to perform dose escalation (level IV benefit), has yet to undertake this form of dose optimisation. Uncertainties as to organ position throughout the longer PDR treatment times and their impact on OAR doses may need to be considered in more depth locally before moving towards dose escalation.

Future developments

Applicator choice was initially focussed on ease of use, and to closely resemble the old LDR applicators. It was decided not to vary too many things at once and a steady transition to the new system was preferred. Initially, the choice was to use the titanium Rotterdam style tube and ovoid applicators; an in-house inter-observer study proved that the titanium applicator can be reconstructed to a high degree of accuracy <2 mm using the present method. However, as planning technique developed to utilise MR for applicator reconstruction it was soon realised that to make the transition to dose escalated optimisation based on MR, plastic applicators would be preferable due to reduced artefacts, and also the ability to insert an MR marker to track the actual source path.Reference Tanderup, Hudej and Lowe^16, Reference Haack, Kynde, Lindegaard, Gelineck and Tanderup¹⁷

In the longer term, changing applicators will offer the possibility to investigate the use of interstitial needles to boost bulky disease as per the Vienna groupReference Pötter, Georg and Dimopoulos¹⁸ and to move towards fully implementing image-guided brachytherapy for cervix cancer in the United Kingdom.²

PDR treatment room design

In reference to room design, the decision to move to PDR in 2011 was a compromised one: we were required in the medium term to retro-fit the existing Selectron facility, which was outdated and sub-optimal. The increased radiation protection requirements and the location of the treatment room meant the control room was by necessity in an unsatisfactory location inside the primary barrier making quality control (QC) inefficient. It also meant that in practice both patients had to start treatment at the same time, which led to unavoidable delays and inefficiencies. The control room was not designed for purpose, it is too cramped and it is recognised that a poor working environment can contribute to errors.Reference Donaldson¹⁹ It was recognised that to fulfil the future needs of the service, a new purpose built facility, incorporating enhanced patient facilities and improved staff workspaces would be required.

Because of development of surgical facilities in the trust, an opportunity arose to secure finances for a purpose built unit. The new brachytherapy facility will house accommodation for all brachytherapy patients on a day case and in-patient basis. PDR treatment rooms will be operated independently meaning patients will no longer have to start treatment concurrently and will free up extra time for QC and maintenance. Source changes could also be staggered and so have a minimal impact upon patient throughput. Moreover, patients are currently admitted to an admissions unit where they wait until their bed is ready. The intention is that patients will proceed directly to the ward and check in directly to an available room. This will enable patients attending for simple treatments (such as vaginal vault patients), to be able to be seen and assessed straight away and treatment commenced as quickly as possible before the main brachytherapy theatre list starting. It is also envisaged that more theatre lists will start on time as patients will arrive at their beds at a set time and any blood tests/assessments that need to be done will be completed as soon as the patient arrives or in the pre-clerking clinic a few days before.

The purpose built unit was developed in conjunction with and after consultation between manufacturers, engineers, architects and project managers as well as clinical staff including brachytherapy radiographers, nurses, clinicians, physicists (both from radiation protection and brachytherapy), patient groups and infection control experts. The discussions were able to use and build on the multidisciplinary framework originally established during the move from LDR to PDR. Site visits nationally and internationally were made to compare room designs and included input from interior designers and artists in order to make the shielded windowless treatment rooms as comfortable as possible to improve patient experience during the lengthy PDR treatments. Aspects such as providing technology such as WiFi to allow internet access, lighting to replicate night and day and audio visual relaxation programmes have been included as well as increased patient access to our complimentary therapies team. Increased functionality and treatment capacity in the future is provided by the addition of a third PDR bunker in the development plans with the expectation of a third afterloader in the near future.

Basic issues, such as the proximity of facilities are an important aspect when considering expansion and development of services. The CT/MR unit is located close by and on the same level as the brachytherapy theatre and the new purpose built suite will be opposite the theatre entrance making access easier. This allows swift transfer of patients between departments and minimises delays in the treatment process. In future, the Radiotherapy department hope to purchase a dedicated MR unit for pre-treatment imaging, and placement of this in brachytherapy theatre is one possible option that we are keen to investigate. Again by cutting out unnecessary steps in the patient pathway, efficiency savings can be made further improving workflow.

Continuing the theme of lean principles,Reference Jones⁶ the future treatment room is designed so that all the necessary equipment is available in each room and is positioned in a sensible, logical location to increase efficiency and reducing the need to leave the room during applicator insertion. Our plans also include the instalment of decant room facilities, encompassing an en-suite recovery room where patients can go as soon as their applicators are removed. This allows them to have a shower and recover at their leisure; meanwhile the treatment room is cleaned and made ready for the next patient. We also plan to reduce the amount of documentation that we create, moving towards paperless working utilising our Oncology Management System that is already commissioned for use in the main radiotherapy department, saving time, storage space and streamlining the plan approval process by allowing remote review of plans by clinicians.

Small changes to practice such as these have been found to have relatively large impacts in treatment efficiency. The estimated completion date for the new Christie Brachytherapy unit is autumn 2013.