The challenges of treating a high grade glioma in a pregnant patient

Abstract

Glioblastoma diagnosis carries a poor prognosis. A combination of surgical resection and chemo-radiotherapy is the current standard of care with median survival rates of 15 months. A 33 year old lady, pregnant at 26 + 3 weeks gestation presented with a left parietal tumour. Complete resection confirmed a grade IV glioblastoma. Foetal health remained stable and termination was not considered. The patient attended for discussion on adjuvant treatments and was informed of the time critical nature of radiotherapy; temozolomide was not advised during pregnancy. With the patient understanding the increased risks to the foetus, the radiotherapy process for delivering 60Gy/30 fractions was initiated. Standard radiotherapy plans were created using both VMAT and 3D-CRT technique. At the planning CT fiducials were placed at the xiphersternum to represent the maximum superior foetal extent and measurements taken. Using a phantom and TLDs, an estimated dose to the foetus was 30mGy from a VMAT plan and 20mGy from 3-field 3DCRT, assuming a 0.5mm equivalent lead apron. The effects to the foetus were calculated using the Health Protection Agency document RCE-9. Radiotherapy increased the incidence of childhood cancer from 1/500 to 1/250. Additional risk of inheritable effects was (1/6700) and deterministic effects was below the threshold. The increased dose of 10mGy from 3DCRT to VMAT plan meant the additional risk of childhood cancer increased from 1/625 to 1/400. Although considered safe, the patient decided against radiotherapy until after delivery at 32 weeks. We will also present a case of a patient diagnosed with a frontal anaplastic astrocytoma at 19 weeks gestation. The patient consented to go ahead with radiotherapy with similar foetal radiation doses. Considering the health of the foetus and mother brings a unique challenge when planning the management of high grade gliomas.