Postoperative radiotherapy for synovial sarcoma of the head and neck during pregnancy: clinical and technical management and fetal dose estimates.
OBJECTIVE
In vivo and phantom dosimetry is reported to estimate the fetal dose and evaluate the effectiveness of a special shielding device to reduce fetal exposure in a woman undergoing postoperative radiation therapy for synovial oral cavity sarcoma at the 30th week of pregnancy.


METHODS
In vivo measurements were performed by placing thermoluminescent dosimeters on 3 points for fetal dose estimation: uterine fundus, umbilicus and pubis. A Rando anthropomorphic phantom was used to simulate radiotherapy. We also performed off-axis dose measurements for wedged beams to estimate the dose contribution of this accessory used in the treatment.


RESULTS
The special shielding device reduced the fetal dose by 70% on average, despite the presence of wedges, which increased the dose by a factor of about 2.5. Before delivery the patient received 48 Gy, and from the in vivo measurements a fetal dose of 8.5, 1.7 and 0.7 cGy was estimated to the uterine fundus, umbilicus and pubis, respectively.


CONCLUSIONS
Pre-treatment simulation in the same irradiation conditions is the only reliable approach to predict the fetal dose. By using a special shielding device, radiotherapy can be optimized while keeping the fetal exposure below the risk of deterministic damage.
Orlandi
Ester
E
Department of Radiation Oncology I, Istituto Nazionale per lo Studio e la Cura dei Tumori, Milan, Italy. ester.orlandi@istitutotumori.mi.it
Zonca
Giancarlo
G
Pignoli
Emanuele
E
Stucchi
Claudio
C
Borroni
Marta
M
Collini
Paola
P
Cantù
Giulio
G
Casali
Paolo G
PG
Grosso
Federica
F
Cerrotta
Annamaria
A
Fallai
Carlo
C
Olmi
Patrizia
P
D000328:Adult; D005260:Female; D005333:Fetus / Q000528:radiation effects*; D006801:Humans; D008297:Male; D009062:Mouth Neoplasms / Q000532:radiotherapy* / Q000601:surgery; D019047:Phantoms, Imaging; D011247:Pregnancy; D011252:Pregnancy Complications, Neoplastic / Q000532:radiotherapy* / Q000601:surgery; D011262:Pregnancy Trimester, Second; D011829:Radiation Dosage; D011835:Radiation Protection / Q000379:methods*; D011874:Radiometry / Q000379:methods; D013584:Sarcoma, Synovial / Q000532:radiotherapy* / Q000601:surgery