Measurement of Uterine Radiation Exposure from Lymphoscintigraphy Indicates Safety of Sentinel Lymph Node Biopsy during Pregnancy

There is an increased incidence of breast cancer occurring during pregnancy. Controversy exists as to the safety of performing lymphoscintigraphy during pregnancy and no studies have reported the measured dose of uterine radiation.

We performed an institutional review board (IRB)-approved prospective study of uterine radiation resulting from lymphoscintigraphy. Abdominal, perineal, and urinary radiation was measured in 14 breast cancer patients and total uterine dose was calculated.

The average dose of 99m-Tc sulfur colloid was 39 ± 20 MBq (1.04 ± 0.53 mCi). Measured abdominal and pelvic radiation exposure demonstrated no correlation with patient age or body mass index. The average abdominal radiation exposure was 1.17 ± 0.87 μGy. The average perineal radiation exposure was 0.23 ± 0.17 μGy. The average dose to the uterus from bladder radioactivity determined from voided urine was 0.44 ± 0.44 μGy. The average radiation dose to the uterus (average of abdominal and perineal doses plus contribution from bladder dose) was 1.14 ± 0.76 μGy. One patient was 16 weeks pregnant at the time of sentinel lymph node biopsy (SLNB) and total calculated uterine dose was 1.67 μGy, suggesting that pregnancy does not significantly alter measured uterine radiation. These data were compared with the average background radiation, which is 3,000 μGy per year or 8.2 μGy per day.

The measured uterine dose of radiation from lymphoscintigraphy for SLNB was significantly less than the average daily background radiation. We conclude that lymphoscintigraphy does not expose the fetus to significant radiation and concern of radiation exposure should not preclude the use of SLNB during pregnancy.