[Optimisation and evaluation of the foetal dose during a radiotherapy of the right parotid].
Purpose was to optimize and to estimate the dose delivered to the foetus during a postoperative irradiation of a 5-month twin pregnant woman presenting with adenocarcinoma of the right parotid. The treatment protocol aimed to deliver 66 Gy conformal radiation therapy on the tumour bed associated to a prophylactic irradiation of 50 Gy on the upper cervical nodes. A series of measurements allowed to estimate the delivered dose in the abdomen by the means of an ion chamber inserted in a water phantom placed side by side of an anthropomorphic Alderson Rando phantom simulating the body of the patient from the head to the pelvis. An appropriate optimisation of the number and orientation of beams were performed in order to minimize the peripheral dose, which is mostly dependent of the total number of monitor unit per fraction: cervical nodes and tumour site included in the same fields, limitation of the irradiated volume, 6 MV X-ray beams rather than Cobalt beams. The measured doses at the upper, in the middle and at the lower part of the abdomen were 17.0, 11.0 and 11.9 mGy, respectively, for the entire treatment, representing 0.025, 0.016 and 0.017%, respectively of the prescribed dose. The actions conducted to optimise the treatment allowed to lower doses delivered to the foetus under the limits proposed by international recommendations (100 mGy). Thus, the treatment of the pregnant patient had been performed with a minimized risk for the foetus.
Marchesi
V
V
Unité de radiophysique médicale, centre Alexis-Vautrin, avenue de Bourgogne - Brabois, 54511 Vandoeuvre-lès-Nancy, France. v.marchesi@nancy.fnclcc.fr
Graff
P
P
Noel
A
A
Beckendorf
V
V
Peiffert
D
D
D000230:Adenocarcinoma / Q000532:radiotherapy*; D000328:Adult; D005260:Female; D005333:Fetus / Q000528:radiation effects; D006801:Humans; D010307:Parotid Neoplasms / Q000532:radiotherapy*; D011247:Pregnancy; D011252:Pregnancy Complications, Neoplastic / Q000532:radiotherapy*; D011879:Radiotherapy Dosage