United States Nuclear Regulatory Commission - Protecting People and the Environment

Information Notice No. 95-39: Brachytherapy Incidents Involving Treatment Planning Errors

UNITED STATES
NUCLEAR REGULATORY COMMISSION
OFFICE OF NUCLEAR MATERIAL SAFETY AND SAFEGUARDS
WASHINGTON, D.C. 20555-0001

September 19, 1995


NRC INFORMATION NOTICE 95-39:  BRACHYTHERAPY INCIDENTS INVOLVING TREATMENT     
                               PLANNING ERRORS


Addressees

All U.S. Nuclear Regulatory Commission Medical Licensees.

Purpose

The U.S. Nuclear Regulatory Commission (NRC) is issuing this information
notice to alert addressees to brachytherapy incidents involving treatment
planning errors.  It is expected that recipients will review the information
for applicability to their facilities and consider actions, as appropriate, to
avoid similar problems.  However, suggestions contained in this information
notice are not new NRC requirements; therefore, no specific action nor written
response is required.

Description of Circumstances

NRC has become aware of the following brachytherapy incidents related to
treatment planning errors:

1)    On November 21, 1994, an NRC licensee discovered that an error had
      occurred during the programming of a high-dose-rate (HDR) Gamma Med II-i
      brachytherapy device on November 18, 1994.  While programming treatment
      data into the HDR unit, the technologist failed to press the AUTOMATIC
      TIME FACTOR button.  After entering the dwell positions and the total
      treatment time, the technologist attempted to start the treatment by
      pressing the START and SOURCE IN IRRAD. POS. buttons.  The HDR unit
      displayed an error message on the screen indicating the need for MANUAL
      TIME FACTOR.  The technologist interpreted this to mean that the
      computer had not received the total treatment time data and reentered
      the data.  The total treatment time data were inadvertently used as the
      MANUAL TIME FACTOR, resulting in the administration of approximately
      twice the intended radiation dose.  The failure of the technologist to
      press the AUTOMATIC TIME FACTOR button, during initial entry of the
      treatment data, was exacerbated by an apparent defect, in the GAMUHR
      card, that permitted the technologist to manually enter and accept the
      inappropriate decay factor during the programming process.  The device
      contained a nominal 370-giga becquerel (GBq) (10-curie (Ci)) iridium-192
      sealed source.  As a result, the patient received a dose of 12 Gray (Gy)
      (1200 rad) to the vaginal cavity instead of the prescribed dose of 6 Gy
      (600 rad).

2)    On September 23, 1994, a licensee informed Region III that a patient
      undergoing a uterine brachytherapy implant received a 31 percent

9509130018.                                                            IN 95-39
                                                            September 19, 1995
                                                            Page 2 of 4


      underdose.  On September 13, 1994, the patient was implanted with two
      cesium-137 (Cs-137) brachytherapy sources, in an ovoid applicator, to
      deliver 65 Gy (6500 rad) to the uterine lining, in approximately 
      48 hours.  During review of the completed treatment, the licensee's
      medical physicist determined that the wrong tissue volume was used
      during the treatment planning process, resulting in a smaller volume
      being treated than the administering physician intended.  Although the
      physician reviewed and approved the treatment plan before
      administration, it was not apparent that a smaller tissue volume was
      represented in the plan.  The licensee believes that the dosimetrist who
      prepared the treatment plan used incorrect spatial coordinates to define
      the treatment volume and failed to verify the dose calculations.  The
      licensee determined that the treatment of the smaller volume resulted in
      the delivery of 45 Gy (4500 rad) to the intended treatment volume, which
      was a 31 percent underdose.  To compensate for the 20 Gy (2000 rad)
      underdose, the administering physician modified a previously intended
      boost dose, using external beam therapy (via a linear accelerator).

3)    An Agreement State licensee reported an event in which an incorrect dose
      conversion factor was used for planning a treatment.  One patient was
      treated with three Cs-137 seeds during a gynecological implant procedure
      during the period of May 4-8, 1994.  The patient received approximately
      91.3 Gy (9130 rad) to the treatment area, which was about 283 percent
      greater than prescribed.  Further investigation revealed that the error
      involved six additional patients, with the patients receiving doses from
      37 percent to 144 percent in excess of their intended doses.  The
      calculation error was caused when the physicist entered the wrong gamma
      constant when editing the treatment planning program.  The physicist was
      attempting to convert from �milligram radium equivalent� to �millicurie�
      and entered 3.256 �radium� instead of �millicurie,� resulting in an
      error ratio that was 2.5 times greater than expected.

4)    On April 8, 1994, an NRC licensee reported an incident involving a data
      entry error in the treatment planning process.  The written directive
      specified two fractions of 6 Gy (600 rad) per fraction for a total dose
      of 12 Gy (1200 rad).  Before the first treatment, a radiation therapist
      correctly entered the treatment parameters into the GammaMed II-i HDR. 
      A second radiation therapist and the radiation physicist verified that
      this entry of data was correct.  The GammaMed II-i HDR device used the
      European date format (day-month-year) for this parameter.  At the time
      of the treatment, the radiation therapist recalled the correct treatment
      parameters from the computer memory, but inadvertently entered the
      treatment date in the incorrect format (i.e., 4.06.94 instead of
      6.04.94).  Because the HDR computer automatically adjusts for source
      decay, the exposure time was modified by a factor of 3.17 (for June 4)
      instead of the required modifying factor of 1.83 (for April 6).  This
      resulted in an administered fractional dose of 10.39 Gy (1039 rad)
      instead of the intended prescribed 6 Gy (600 rad).  However, the total
      prescribed dose of 12 Gy (1200 rad) was not exceeded because the error
      was detected before the second treatment was administered..                                                            IN 95-39
                                                            September 19, 1995
                                                            Page 3 of 4


5)    On October 11, 1993, an NRC licensee reported a therapeutic
      misadministration, discovered during a routine review of records, that
      occurred on April 23, 1993, during a brachytherapy procedure involving a
      high-dose-rate (HDR) remote afterloader.  According to the medical
      physicist, a patient was scheduled to receive vaginal brachytherapy
      treatment using a Nucletron HDR unit with a 157.14 GBq (4.247 Ci)
      iridium-192 source.  The prescribed dose for the fraction was 5 Gy 
      (500 rad).  During the planning of the second of the three treatments,
      an error was made in the input of the offset distance.  Instead of 
      992 millimeter (mm), a distance of 920 mm was entered.  The source was
      programmed to travel 45 mm outward from the offset distance in nine
      increments of 5 mm each.  The medical physicist indicated that the
      treatment progressed as was planned.  However, because of the erroneous
      input for the offset distance, a portion of the dose was administered to
      the wrong site.

6)    On August 18, 1993, a therapeutic misadministration occurred at a
      licensee's facility when a patient who was scheduled to receive a 6 Gy 
      (600 rad) dose of radiation to his esophagus actually received a 10 Gy 
      (1000 rad) dose.  The licensee identified the error during a routine
      physics check conducted that same day.  The licensee indicated that a
      treatment plan was developed to deliver the 6 Gy (600 rad) dose and that
      this plan was reviewed by the physicist and physician and found to be
      correct.  However, before administering the dose, the physicist
      reaccessed the HDR treatment planning system to modify a noncritical
      factor.  The physicist reported having a problem maneuvering between the
      various menus in the treatment planning system, which involved pressing
      the �Esc� key several times.  This caused the treatment planning program
      to change the value of the treatment dose to 10 Gy (1000 rad). 
      According to the licensee, the modified plan was put into the HDR
      control computer without an additional in-depth review and the treatment
      was delivered.

Discussion

The incidents listed above demonstrate the importance of following plans and
procedures to meet the objective stated in 10 CFR 35.32(a)(3) that final
treatment plans and related calculations are in accordance with the written
directive.  Attention to details in treatment planning and independent
verification of treatment plans may be involved in meeting this objective.  If
independent verification of treatment plans is so relied upon, it should
include verification of the data used to calculate the initial treatment plan,
as well as the calculations.  It is important to note that recalculation of
the treatment plan from the same data set used to prepare the initial
treatment may not catch errors introduced by initially inputting incorrect
treatment parameters.  .                                                            IN 95-39
                                                            September 19, 1995
                                                            Page 4 of 4


This information notice requires no specific action nor written response.  If
you have any questions about the information in this notice, please contact
the technical contact listed below, or the appropriate NRC regional office.

                                    /s/'d by Larry W. Camper/for


                                    Donald A. Cool, Director
                                    Division of Industrial and 
                                      Medical Nuclear Safety
                                    Office of Nuclear Material Safety 
                                      and Safeguards


Technical contact:  James A. Smith, NMSS
                    (301) 415-7904

Page Last Reviewed/Updated Monday, November 18, 2013