2228 - Practical Considerations for Reducing and Managing Fetal Radiation in Pregnant Patients with Brain, Eye, and Head and Neck Tumors
Presenter(s)
A. Skipper1, J. P. Kirkpatrick1, D. M. Brizel2, F. F. Yin3, W. Giles3, and A. Rodrigues4; 1Department of Radiation Oncology, Duke University Medical Center, Durham, NC, 2Department of Head and Neck Surgery and Communication Sciences, Duke University Medical Center, Durham, NC, 3Duke University, Durham, NC, 4Department of Radiation Oncology, Duke Cancer Institute, Durham, NC
Purpose/Objective(s): Typically, radiation therapy is contraindicated during pregnancy due to potential fetal risks, including malformations and cancer induction, with risks varying based on fetal development stages. Risks <0.05 Gy have been reported to be negligible. Minimizing fetal dose involves reducing contributions to out-of-field dose sources from head leakage, collimator scatter, and internal patient scatter. Treatment planning optimization and physical shielding reduce fetal dose, however physical shielding can present practical and safety challenges. We present our approach to treatment planning in the pregnant patient with cranial and head-and-neck cancers.
Materials/Methods: This study describes the treatment of three pregnant patients with different tumor sites using linac-based external beam radiation therapy (EBRT) without shielding bridges. The cases involved a patient with GBM (Case 1; 25 Gy in 5 fractions; gestational age 10 weeks), another with head and neck squamous cell carcinoma of the left tonsil (Case 2; IMRT; 44 Gy in 22 fractions primary + 26 Gy in 13 fractions boost to a total of 70 Gy; gestational age 20 weeks), and a third with metastatic breast cancer affecting the eye (Case 3; SRS; 25 Gy in 5 fractions; gestational age 15 weeks). Each case highlights the importance of the evaluation of optimal treatment technique, reduction of MU modulation, beam energy, field size, gantry, and collimator angle tailored to minimize fetal exposure while effectively treating the maternal cancer. Gestational age was used to assess the approximate fetal location during treatment. Patient dimensions from treatment isocenter to xiphoid process, umbilicus, and pubic symphysis were used as initial dose estimation locations. Comprehensive dosimetric studies used anthropomorphic phantoms with ionization chambers and optically stimulated luminescent dosimeters at these patient-specific distances and various depths (surface, 5 cm, and patient mid-plane).
Results: All patients utilized 6XFFF, as it reduces head leakage contributions. The use of non-zero collimator angles and mostly posterior gantry angles further reduces peripheral dosimetry. Field size was kept as small as possible (e.g. with jaw tracking). Likewise, MU modulation factor was minimized. A posterior lead shield that the patient lies on was utilized in Case 1 but minimally reduced the dose to subsequent patients. In-vivo surface dosimetry at the most superiorly estimated fetal location at time of treatment resulted in a total dose for the entire treatment course of 0.002, 0.06, and 0.002 Gy for cases 1, 2, and 3, respectively.
Conclusion: These case studies suggest practical approaches for managing complex clinical scenarios involving radiation therapy during pregnancy. Personalized planning and attention to detail must be employed on a case-by-case basis.