Radiodynamic Therapy (RDT) With Gliolan in Patients With First Recurrence of Brain Tumor

Inclusion Criteria: * Written patient consent after comprehensive information * Age \>/= 18 years * Recurrence of supratentorial glioblastoma after initial resection and adjuvant therapy (e.g. radio-chemotherapy, targeted therapies, antiangiogenic therapies as determined by the tumor board) (with planned second resection cohort 0 and 1), second or third recurrences permitted * Clinically indicated further radiotherapy as per decision of the tumor board as part of therapy for recurrence * Histological verification of recurrent glioblastoma independent of methylated MGMT promotor status when alkylating chemotherapy failed at this time. * Karnofsky Performance Score ≥ 60 * For female and male patients and their female partners of childbearing/reproductive potential(\*): Willingness to apply highly effective contraception (Pearl index \<1) during the entire study (and for at least 6 months after the first application of 5-ALA). Such methods include: 1. combined (estrogen and progestogen containing) hormonal contraception associated with inhibition of ovulation: I. oral II. intravaginal III. transdermal 2. progestogen only hormonal contraception associated with inhibition of ovulation: I. oral II. injectable III. implantable 3. intrauterine device (IUD) 4. intrauterine hormone-releasing system (IUS) 5. bilateral tubal occlusion 6. vasectomised partner 7. male patients have to use a condom 8. sexual abstinence * Pre-menopausal(\*) female patients with childbearing potential: a negative pregnancy test must be obtained max. 72h prior to treatment start * Adequate liver function: bilirubin \< 1.5 times above upper limit of normal range (ULN), alanine transaminase (ALT/SGPT) and aspartate transaminase (AST/SGOT) \< 3 times ULN. In the case of documented or suspected Gilbert's disease bilirubin \< 3 times ULN. * Adequate renal function: creatinine \< 3 times above ULN; eGFR \>/= 60 ml/min, Blood clotting: INR/Quick/PT and PTT within acceptable limits according to the investigator. (\*) Definition: A man is considered of reproductive potential after puberty unless permanently sterile by bilateral orchidectomy. A woman is considered of childbearing potential (WOCBP), i.e. fertile, following menarche and until becoming post-menopausal unless permanently sterile. Permanent sterilisation methods include hysterectomy, bilateral salpingectomy and bilateral oophorectomy. A post-menopausal state is defined as no menses for 12 months without an alternative medical cause. A high follicle stimulating hormone (FSH) level in the postmenopausal range may be used to confirm a post-menopausal state in women not using hormonal contraception or hormonal replacement therapy. However in the absence of 12 months of amenorrhea, a single FSH measurement is insufficient. Exclusion Criteria: * Patient unable to undergo imaging by MRI, PET or contrast-enhanced CT for whatever reason (e.g. pace-maker) * Pregnant and breastfeeding women * Past medical history of diseases with poor prognosis, e.g., severe coronary heart disease, heart failure (NYHA III/IV), severe and poorly controlled diabetes, immune deficiency, residual deficits after stroke, severe mental retardation or other serious concomitant systemic disorders incompatible with the study (at the discretion of the investigator) * Any active infection (at the discretion of the investigator) * Hypersensitivity against porphyrins * Known diagnosis of porphyria * Participation in another clinical trial with therapeutic intervention or use of any other therapeutic interventional agent other than the standard therapy since diagnosis of glioblastoma * Known intolerance to study medication * Pre-treatment with other potentially phototoxic or photosensitizing substances (e.g. tetracyclines, sulfonamides, fluoroquinolones, hypericin extracts, products containing St. John's wort ) during the 2 weeks preceding RDT