Safety and feasibility of prostate stereotactic ablative radiotherapy using multimodality imaging and flattening filter free

Diversity in radiation therapist/therapeutic radiographer (RTT) advanced practice (AP) roles delivering on the four domains

INTRODUCTION

Advanced practice roles are well documented, and continue to respond to the changing landscape in radiotherapy and oncology. In the UK the highest level of AP for the therapeutic radiographer/radiation therapist (RTT) is the consultant radiographer. These posts should meet the four domains of practice, as set out in national guidance. Here we aim to describe well established roles that meet this criteria, and provide subgroups of examples.

METHODOLOGY

Three AP post holders with over 10 years AP experience completed a questionnaire adapted from the consultant radiographer toolkit. These were completed in conjunction with guidance and framework documents. The examples were to demonstrate how they achieve a high level of practice in clinical and expert practice; professional leadership and consultancy; education, training and development; and practice and service development, research and evaluation. Participants then categorised results to add subgroups to each domain.

RESULTS

The questionnaire was completed by three RTTs specialising as a lung consultant radiographer (LCR), a neuro-oncology consultant radiographer (NCR) and a lead research radiographer (RR). Each post holder described how they meet the criteria by discussing the benefit they make to their profession, department and patients. All posts had examples for all criteria, achieving consultant practice. Clinical and expert practice was the dominant domain for the clinical specialist posts, and professional leadership and research evaluation was the strongest domains for the RR.

CONCLUSION

All three consultant RTTs have demonstrated expert practice with clear and transparent examples of their professional practice which evidence the four domains of consultant practice. Following two decades of AP practice for RTTs there is a need to be strategic in the development of future posts with a prospective view on succession planning that safeguards their longevity.

Daily dosimetric variation between image-guided volumetric modulated arc radiotherapy and MR-guided daily adaptive radiotherapy for prostate cancer stereotactic body radiotherapy

AIM

To evaluate differences between MR-guided daily-adaptive RT (MRgRT) and image-guided RT (IGRT) with or without fiducial markers in prostate cancer (PCa) stereotactic body radiotherapy (SBRT) in terms of dose distribution on critical structures.

MATERIAL AND METHODS

Two hundred treatment sessions in 40 patients affected by low and intermediate PCa were evaluated. The prescribed dose was 35 Gy in 5 fractions delivered on alternate days. MRgRT patients (10) were daily recontoured, re-planned, and treated with IMRT technique. IGRT patients without (20) and with (10) fiducials were matched on soft tissues or fiducials and treated with VMAT technique. Respective CBCTs were retrospectively delineated and the prescribed plan was overlaid for dosimetric analysis. The daily dose for rectum, bladder, and prostate was registered.

RESULTS

MRgRT resulted in a significantly lower rate of constraints violation as compared to IGRT without fiducials, especially for rectum V28Gy, rectum V32Gy, rectum V35Gy, rectum Dmax, and bladder Dmax. IGRT with fiducials reported high accuracy levels, comparable to MRgRT. MRgRT and IGRT with fiducials reported no significant prostate CTV underdosage, while IGRT without fiducials was associated with occasional cases of prostate CTV under dosage.

CONCLUSION

MR-guided daily-adaptive SBRT seems a feasible and accurate strategy for treating prostate cancer with ablative doses. IGRT with the use of fiducials provides a comparable level of accuracy and acceptable real-dose distribution over treatment fractions. Future study will provide additional data regarding the tolerability and the clinical outcome of this new technological approach.

The Pivotal Role of the Therapeutic Radiographer/Radiation Therapist in Image-guided Radiotherapy Research and Development

The ability to personalise radiotherapy to fit the individual patient and their diagnosis has been realised through technological advancements. There is now more opportunity to utilise these technologies and deliver precision radiotherapy for more patients. Image-guided radiotherapy (IGRT) has enabled users to safely and accurately plan, treat and verify complex cases; and deliver a high dose to the target volume, while minimising dose to normal tissue. Rapid changes in IGRT have required a multidisciplinary team (MDT) approach, carefully deciding optimum protocols to achieve clinical benefit. Therapeutic radiographer/radiation therapists (RTTs) play a pivotal role in this MDT. There is already a great deal of evidence that illustrates the contribution of RTTs in IGRT development; implementation; quality assurance; and maintaining training and competency programmes. Often this has required the RTT to undertake additional roles and responsibilities. These publications show how the profession has evolved, expanding the scope of practice. There are now more opportunities for RTT-led IGRT research. This is not only undertaken in the more traditional aspects of practice, but in recent times, more RTTs are becoming involved in imaging biomarkers research and radiomic analysis. The aim of this overview is to describe the RTT contribution to the ongoing development of IGRT and to showcase some of the profession's involvement in IGRT research.

Dosimetric impact of organ at risk daily variation during prostate stereotactic ablative radiotherapy

OBJECTIVE

Prostate stereotactic ablative radiotherapy (SABR) delivers large doses using a fast dose rate. This amplifies the effect geometric uncertainties have on normal tissue dose. The aim of this study was to determine whether the treatment dose-volume histogram (DVH) agrees with the planned dose to organs at risk (OAR).

METHODS

41 low-intermediate risk prostate cancer patients were treated with SABR using a linac based technique. Dose prescribed was 35 Gy in five fractions delivered on alternate days, planned using volumetric modulated arc therapy (VMAT) with 10X flattening filter free (FFF). On treatment, prostate was matched to fiducial markers on cone beam CT (CBCT). OAR were retrospectively delineated on 205 pre-treatment CBCT images. Daily CBCT contours were overlaid on the planning CT for dosimetric analysis. Verification plan used to evaluate the daily DVH for each structure. The daily doses received by OAR were recorded using the D%.

RESULTS

The median rectum and bladder volumes at planning were 67.1 cm3 (interquartile range 56.4-78.2) and 164.4 cm3 (interquartile range 120.3-213.4) respectively. There was no statistically significant difference in median rectal volume at each of the five treatment scans compared to the planning scan (p = 0.99). This was also the case for median bladder volume (p = 0.79). The median dose received by rectum and bladder at each fraction was higher than planned, at the majority of dose levels. For rectum the increase ranged from 0.78-1.64Gy and for bladder 0.14-1.07Gy. The percentage of patients failing for rectum D35% < 18 Gy (p = 0.016), D10% < 28 Gy (p = 0.004), D5% < 32 Gy (p = 0.0001), D1% < 35 Gy (p = 0.0001) and bladder D1% < 35 Gy (p = 0.001) at treatment were all statistically significant.

CONCLUSION

In this cohort of prostate SABR patients, we estimate the OAR treatment DVH was higher than planned. This was due to rectal and bladder organ variation.

ADVANCES IN KNOWLEDGE

OAR variation in prostate SABR using a FFF technique, may cause the treatment DVH to be higher than planned.