Abstract
The management of a pregnant patient in radiation oncology is an infrequent event requiring careful consideration by both the physician and physicist. The aim of this manuscript was to highlight treatment planning techniques and detail measurements of fetal dose for a pregnant patient recently requiring treatment for a brain cancer. A 27‐year‐old woman was treated during gestational weeks 19–25 for a resected grade 3 astrocytoma to 50.4 Gy in 28 fractions, followed by an additional 9 Gy boost in five fractions. Four potential plans were developed for the patient: a 6 MV 3D‐conformal treatment plan with enhanced dynamic wedges, a 6 MV step‐and‐shoot (SnS) intensity‐modulated radiation therapy (IMRT) plan, an unflattened 6 MV SnS IMRT plan, and an Accuray TomoTherapy HDA helical IMRT treatment plan. All treatment plans used strategies to reduce peripheral dose. Fetal dose was estimated for each treatment plan using available literature references, and measurements were made using thermoluminescent dosimeters (TLDs) and an ionization chamber with an anthropomorphic phantom. TLD measurements from a full‐course radiation delivery ranged from 1.0 to 1.6 cGy for the 3D‐conformal treatment plan, from 1.0 to 1.5 cGy for the 6 MV SnS IMRT plan, from 0.6 to 1.0 cGy for the unflattened 6 MV SnS IMRT plan, and from 1.9 to 2.6 cGy for the TomoTherapy treatment plan. The unflattened 6 MV SnS IMRT treatment plan was selected for treatment for this particular patient, though the fetal doses from all treatment plans were deemed acceptable. The cumulative dose to the patient's unshielded fetus is estimated to be 1.0 cGy at most. The planning technique and distance between the treatment target and fetus both contributed to this relatively low fetal dose. Relevant treatment planning strategies and treatment delivery considerations are discussed to aid radiation oncologists and medical physicists in the management of pregnant patients.
Highlights
Patients requiring radiation therapy are seldom simultaneously pregnant
This study reports on a brain tumor patient treated recently in our clinic to a total dose of 59.4 Gy in 33 fractions during her second trimester of pregnancy
Estimates of fetal dose for each plan were made using published literature, and measurements of fetal dose were made for each plan using a modified anthropomorphic phantom
Summary
Patients requiring radiation therapy are seldom simultaneously pregnant. When both conditions apply, unique considerations are required from the radiation oncologist and the medical physicist. Radiation therapy can play a net-beneficial role in the management of a pregnant patient, but depending on the treatment site, special treatment planning techniques to reduce peripheral dose and/or fetal radiation shields may be necessary. While breast cancer and hematologic malignancies make up the preponderance of cancers seen in a pregnant population, other tumor types are found with some frequency, including brain tumors.[3]. Common brain malignancies (e.g., gliomas) found in a patient population of child-bearing age are often treated with shaped radiation fields or arcs that enter the patient’s head from many angles, including so-called “vertex” beams. Numerous reports have detailed planning strategies to reduce peripheral dose.[4–10]. Numerous reports have detailed planning strategies to reduce peripheral dose.[4–10] While IMRT is a common choice for intracranial treatments, IMRT often results in higher peripheral dose than 2D- or 3D-conformal treatment techniques.[5,10]
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