A service evaluation of on-line image-guided radiotherapy to lower extremity sarcoma: Investigating the workload implications of a 3 mm action level for image assessment and correction prior to delivery
Section snippets
Introduction and background
Sarcoma is a relatively rare diagnosis, accounting for 1% of cancer diagnoses; with around 25% of cases occurring in the limbs.1, 2 Surgery is the primary treatment used in the management of sarcoma3 and whilst conservative surgery is the major goal, amputation is indicated in some cases.4 In cases where limb preservation is possible, lower limb sarcomas are typically treated with conservative surgery and adjuvant or neo-adjuvant radiotherapy and this combination achieves high rates of local
Methods
Approval was gained from the institution's clinical governance committee and The University of Liverpool Ethics Committee to conduct a retrospective imaging evaluation. All patients treated with radiotherapy for sarcoma of the lower limb between 25th May 2015 and 25th May 2016 were initially identified by treatment site in the MOSAIQ (Version 2.5 Elekta, Sweden) electronic booking system and the Webpublisher (V2.3.25 Phillips, The Netherlands) electronic prescription software at The Christie
Results
30 consecutive patients with complete CBCT data sets were evaluated. Treatment subsites for the 30 evaluated patients are recorded in Table 2. 18 received postoperative radiotherapy, 11 received preoperative radiotherapy and 1 patient received radiotherapy alone. 826 fractions were delivered, the mean number of fractions per patient was 27.5 (range 20–30) and dose ranged between 45 and 60 Gy.
436 CBCT images were delivered (per patient: range 8–22, median 13.5, mean of 14.5; per fraction: mean
Discussion
Although daily on-line image analysis and correction with no specified action level will achieve the largest reduction of systematic and random error, it is believed to be time consuming and labour intensive,17, 18 and there is a duty to keep concomitant exposure as low as reasonably possible.19 For sarcoma of the limb, patient specific factors such as: pre/postoperative status; tumour location in the limb; and limb swelling could potentially affect the magnitude and fluctuation of
Conclusion
This evaluation aimed to investigate the impact of a 3 mm action level for online assessment and correction in our departmental IGRT practice for lower extremity sarcoma. This strategy reduced the imaging burden and focussed intervention on patients that exhibited greater positional variability. The evaluation suggests that the impact of image matching and positional correction was greatest at the beginning of treatment, and that time trend errors were small, despite common site-specific
Conflict of interest
None.
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