Medical Event Case 0001
Patient safety is a critical goal for all of those involved in delivering brachytherapy treatment. Safety reporting followed by analysis of any errors in treatment delivery are essential steps in optimizing patient safety. The series of Brachyblast submissions will focus on sharing brachytherapy events with the ABS membership to prevent any future events. We are two graduate Medical Physics students at a CAMPEP accredited institution who share an interest in both brachytherapy and patient safety. We are directly overseen by Zoubir Ouhib who, along with the ABS Patient Safety Committee, has graciously allowed us to pursue this task.
Over the next few months, you will be presented with a series of medical events in brachytherapy that have occurred around the world. Please be aware that the details on the reporting information might not be as complete as we hope to have. Your objective will be to suggest corrective action for each event. We also welcome any preventive actions that you might have in place to prevent such events from occuring. The responses received will then be prioritized and disseminated with the goal of sharing a focus on patient safety culture. Without further ado, here is your first case:
Wrong Source Transfer Tube Length
Introductory Information: Reported to SAFRON on October 31, 2016, this major incident affected 68 patients treated with the Varian Varisource iX HDR afterloader & planned with BrachyVision V13.5. The event was discovered post treatment completion by the radiation oncologist during a clinical review of the patient. The range of dose deviation was 20-50% of the prescribed dose. Two related errors that occurred will be discussed.
This afterloader model accommodates variable length catheters, and as a pre-treatment check, performs a channel too short test, but not a channel too long test. The vendor also provides source transfer tubes of various lengths, through which the source is transferred between the afterloader and applicators. The transfer tubes attach to the applicators or needles using a “click-fit” connector, and to the afterloader using a “Quick-Connect” mechanism.
(11 patients): The Varisource iX HDR system was commissioned with a click-fit set of predefined length named "Click-fit Set A". A few months following commissioning, a new Miami applicator was procured with a new "Click-fit set B" that is 10cm longer than "Click-fit set A". In July 2016, the central channel of "Click-Fit set A" broke and the planning team decided to use the transfer tube from "Click-Fit Set B" until it can be replaced. Hence the planning team planned treatments using "Click Fit Set B" for the central channel and used "Click fit Set A" for the two ovoids. The above was communicated to the radiotherapists responsible for connecting the Click-fit tubes and administering the treatment of the patients. Unfortunately, some radiotherapists misunderstood the change and thought all 3 connections must now use "Click-Fit Set B". This resulted in 11 patients being treated on the ovoids 10 cm lower than they should have been treated. An in-depth investigation was done on all brachytherapy patients treated from June 2016. All affected patient plans were re-planned to include the error showing the differences in doses from what was prescribed and what was administered. This error unfortunately resulted in major differences in planned vs. delivered dose.
(57 patients): During investigation of Error 1 it was decided to remeasure and confirm lengths of all the brachytherapy transfer tubes and applicators used at this facility. During this verification it was found that the length of the Tandem (channel 1) for the Miami applicator was incorrectly entered in the TPS (Treatment Planning System). When using "Click-fit set B" the length of the transfer tube with the tandem of the Miami applicator measured 133.5 cm. The vendor confirmed the measurement of 133.5 cm. Therefore, the planning applicator length should be 132 cm (the extra 1.5 cm accounts for the Quick Connect part of the machine). The planning team was using 130 cm planning length instead of 132 cm. The 130 cm that had been used to plan the patient plans was a default applicator length and was also used in the BrachyVision demo plans. This hadn’t been manually measured or tested at this facility after the new applicator was procured. This resulted in all patients in error 1 being treated a further 2 cm lower that prescribed and an additional 57 patients also treated 2 cm lower that what was required. All affected patient plans were re-planned to include the error showing the differences in doses from what was prescribed and what was administered.
When you are considering corrective actions try answering the following:
What safety barrier failed to identify the incident?
What possible safety barrier identified the incident?
What safety barrier might have identified the incident?
What possible factors contributed to the incident?
These questions can lead you to address the key question:
What preventive action(s) could stop reoccurrence of a similar event?
Please send corrective action suggestions before August 6, 2018 to:
including the title of the event (or case #), your name, your institution (Optional), and your profession (Med. Phys., Rad. Onc., etc.).
We are eager to receive your reply on how you would have dealt with the situation if it had occurred in your institution and what you have in place that would have prevented similar events. Please look for our follow up report in next month’s Brachyblast where we will present the committee’s selected responses. The next medical event case (0002) will be presented in the following Brachyblast newsletter. Thank you in advance for your feedback that will make a difference.
“Noticing that something is broken is an essential prerequisite for coming up with a creative solution to fix”