131I-IPA and Concurrent XRT in Recurrent GBM

Inclusion Criteria:

1. Previously confirmed histological diagnosis of GBM, with current clinical or imaging evidence for first recurrence according to modified RANO criteria (2017). History of GBM standard therapy (debulking surgery, followed by radio-chemotherapy (50-60 Gy in 2 Gy fractions, temozolomide)
2. Interval since end of 1st line XRT ≥6 months
3. Amino acid-based molecular imaging (preferably 18F-FET-PETor 11C-methionine, as institutionally established) indicating pathologically increased amino acid uptake inside or in the vicinity of the tumour, clearly discernible from background activity.
4. Current indication for repeat radiation therapy as discussed at the multidisciplinary neuro-oncological tumour board meeting, planned as standard fractionated dose schedule (18\*2 Gy)
5. Male or female ≥18 years of age.
6. Karnofsky performance status ≥70. Life expectancy of at least 16 weeks.
7. Haematological, liver and renal function test results as follows:

   * WBC: \>3\*109/L
   * Haemoglobin \>80 g/L
   * PLT \>100\*109/L
   * ALT, ALP, AST: ≤5 times upper international limit of normal (UILN)
   * Bilirubin ≤3 times UILN
   * Serum creatinine: within normal limits or \<120 μmol/L for patients aged 60 years or older
   * Urine protein dipstick: no protein
8. Female patients surgically sterile or postmenopausal for at least 2 years. Participants of generative potential agreeing to use effective contraception during the period of therapy and 6 months after the end of study.
9. Written informed consent

Exclusion Criteria:

1. Primary XRT dose \< 60 Gy
2. Doses to organs at risk defined by Yasar and Tugrul (2005) exceeded or reached by prior radiation therapy; e.g. cumulative total dose on the optical chiasm \>54 Gy for 2 Gy/fraction, alphas/beta=2
3. Multifocal distant recurrence, defined as tumour lesion outside the primary XRT field, as evidenced by amino acid-based PET imaging
4. Prior treatment with brachytherapy
5. Prior treatment with bevacizumab
6. Baseline steroid requirement , exceeding physiologic replacement doses ( \<1.5 mg dexamethasone or equivalent per day)
7. History or evidence of delayed-type hypersensitivity (DTH)-dependent chronic infection (e.g. tuberculosis, systemic fungal or parasitic infection), potentially exacerbating under systemic corticoid therapy
8. Localisation of tumour related to brain stem or axis, unless sufficient reserve capacity (e.g. remnant resection cavity, marked atrophy) to accommodate possible post-procedural tissue reactions, or pre-therapeutic consent for emergency trepanation
9. Haemostaseologic conditions, precluding catheterisation or invasive procedures
10. Clinically significant illness or clinically relevant trauma within 2 weeks before the administration of the investigational product
11. Known impairment of liver or kidney function or known liver or kidney disease, such as hepatitis, cirrhosis, renal failure
12. Known human immunodeficiency virus (HIV) positive serology or chronically active hepatitis B or C
13. Ongoing toxicity \> grade 2 NCI-CTC (version 4.03) from previous standard or investigational therapies
14. Administration of another investigational medicinal product within 90 days prior to screening
15. Expected non-compliance with longer-term admission at isolated nuclear medicine ward
16. In pre-menopausal women: Pregnant as evidenced by a positive pregnancy test, or breast-feeding
17. Patients with known phenylketonuria