Risk of second brain tumour after radiotherapy for pituitary adenoma or craniopharyngioma: a retrospective, multicentre, cohort study of 3679 patients with long-term imaging surveillance.

Background: Radiotherapy is a valuable treatment in the management algorithm of pituitary adenomas and craniopharyngiomas. However, the risk of second brain tumour following radiotherapy is a major concern. We assessed this risk using non-irradiated patients with the same primary pathology and imaging surveillance as controls.
Methods: In this multicentre, retrospective cohort study, 4292 patients with pituitary adenoma or craniopharyngioma were identified from departmental registries at six adult endocrine centres (Birmingham, Oxford, Leeds, Leicester, and Bristol, UK and Ferrara, Italy). Patients with insufficient clinical data, known genetic predisposition to or history of brain tumour before study entry (n=532), and recipients of proton beam or stereotactic radiotherapy (n=81) were excluded. Data were analysed for 996 patients exposed to 2-dimensional radiotherapy, 3-dimensional conformal radiotherapy, or intensity-modulated radiotherapy, and compared with 2683 controls.
Findings: Over 45 246 patient-years, second brain tumours were reported in 61 patients (seven malignant [five radiotherapy, two controls], 54 benign [25 radiotherapy, 29 controls]). Radiotherapy exposure and older age at pituitary tumour detection were associated with increased risk of second brain tumour. Rate ratio for irradiated patients was 2·18 (95% CI 1·31-3·62, p<0·0001). Cumulative probability of second brain tumour was 4% for the irradiated and 2·1% for the controls at 20 years.
Interpretation: Irradiated adults with pituitary adenoma or craniopharyngioma are at increased risk of second brain tumours, although this risk is considerably lower than previously reported in studies using general population controls with no imaging surveillance. Our data clarify an important clinical question and guide clinicians when counselling patients with pituitary adenoma or craniopharyngioma on the risks and benefits of radiotherapy.
Funding: Pfizer.
Competing Interests: Declaration of interests AC has received a grant from Health Education England for a radiotherapy contouring analysis website tool in 2020. MCZ is a consultant for Novartis, Eli Lilly, and Genzyme. KB has received honoraria from HRA Pharma and Ipsen UK for talks and professional consultancy services; conference and travel grants from Novo Nordisk; and has completed a National Health Service service development project with Novartis. RDM has received research funding from Pfizer, Sandoz, and Ipsen; consultancy fees from Takeda, Sandoz, and Diurnal; conference grant from Recordati Rare Diseases UK; and honoraria for talks from Pfizer, Ipsen, Sandoz, and Novartis. RH has received a conference grant from Recordati Rare Diseases UK. NK has received honoraria from Pfizer, Ipsen, HRA Pharma and Recordati Rare Diseases for lectures; research funding from Pfizer, Ipsen, and Shire and has served as a member in Scientific Advisory Boards for Pfizer, Ipsen, and Recordati Rare Diseases. All other authors declare no competing interests.
(Copyright © 2022 The Author(s). Published by Elsevier Ltd. This is an Open Access article under the CC BY 4.0 license. Published by Elsevier Ltd.. All rights reserved.)