Therapy Medical Events in 2018

2018 Event 1
Summary A therapy patient scheduled to receive five fractions of stereotactic body radiation therapy (SBRT) received two of the fractions to the T6 vertebral body, approximately 2.5 cm away from the intended treatment site which was the T5 vertebral body. 
Root Cause

The CT reference marks placed on the patient during simulation had washed off at the time of first treatment.  New marks were placed in the incorrect location affecting future treatment fractions.

There was no indisputable spinal anatomic landmark visible in the cone beam CT due to the limited field of view.

There is not a consistent procedure in how personnel perform manual and auto registrations for SBRT patients.
Corrective Action

Review and update the policy for simulation, planning, review of pre-treatment imaging, and treatment of SBRT spine patients.

Review and modify the SBRT spine treatment imaging procedure to include the type of imaging to be used and defining the anatomy to be used for alignment prior to treatment.

Develop a standard for defining the auto-registration structure and how auto-registration is used for alignment for spine SBRT patients.

Effect on Patient Due the misalignment, the delivered dose to the T5 vertebral body was 19 grays (Gy) instead of the planned 30 Gy.  Adjacent critical structure doses were deemed to be within acceptable tolerances.  The prescribing radiation oncologist decided not to compensate for the incorrect fractions because the intent of the treatment was palliative, and the delivered dose was deemed sufficient for palliation.
2018 Event 2
Summary Dose potentially delivered to wrong treatment site. Treatment was performed on patient without final positioning confirmation. It was discovered, after treatment, that the patient had moved at some point, possibly prior to treatment.
Root Cause Failure to perform the final positioning check.
Corrective Action Additional operator training with emphasis on the final positioning check.
Effect on Patient It was determined that the patient would not be harmed from the radiation amount administered incorrectly and full disclosure to the patient was made of the incident.
2018 Event 3
Summary Patient was planned to be treated with a single fraction using 6 MV (flattened) photon beam.  The plan was inadvertently created using 6MV FFF (flattening filter free) beam energy due to simple human error/miss-click by dosimetrist.
Root Cause The 6 MV FFF energy choice was noticed by the physicist but was not flagged as an error because it was still 6 MV and the dose distribution over the contoured target looked reasonable.
Corrective Action Increased awareness will be used to prevent this issue going forward.  The expectation that 6 MV FFF vs 6 MV will be explicitly identified in the prescription will eliminate ambiguity in interpretation by the staff preparing or checking plan.
Effect on Patient Since the field was relatively small the dose falloff was less than 20% off from the prescription and the target volume was well covered.  Patient was treated without issue and no clinical efficacy reduction is expected from the inadvertent use  of the FFF 6 MV beam.

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