• Histologically proven glioblastoma (WHO criteria 2021), absence of IDH mutation demonstrated by negative IDH1 R132H staining on Immunohistochemistry.

• Patient must have received prior first line therapy that must have contained both:

∙ Prior surgery or biopsy and standard fractionated radiotherapy (1.8-2 Gy/fraction, \>56 Gy\<66 Gy) or hypofractionated radiotherapy (15 x 2.66 Gy or similar regimen)

‣ One line of maintenance chemotherapy and/or immune- or biological therapy, (with or without Tumor-Treating Fields)

• First, unequivocal disease progression with

∙ measurable tumor (\>100 mm2 or 1 cm3, based on RANO criteria) documented (e.g., increase of 25% in tumor diameter) on MRI performed within 14 days of inclusion and,

‣ interval of a minimum of 12 weeks since the completion of prior radiotherapy, unless there is a new lesion outside the radiation field or unequivocal evidence of viable tumor on histopathological sampling

• Patient is candidate for craniotomy and at least 50% resection of enhancing region

• Maximal enhancing tumor diameter prior to inclusion ≤ 5 cm on T1w. (In case of planned lobectomy, post operative peritumoral brain or residual size ≤5 cm)

• WHO performance status ≤ 2 (equivalent to Karnofsky Performance Status (KPS) ≥ 70)

• Age ≥ 18 years

• Participant must be recovered from acute toxic effects (\<grade 2) of all prior anticancer therapy. Interval since last therapy to presumed date of surgery of at least:

∙ ≥ 4 weeks or 5 half-lives (whichever is shorter) for

⁃ Cytotoxic

• Other small chemical entity (e.g., targeted therapy)

• For biologics (e.g., antibodies, except bevacizumab)

‣ ≥ 6 weeks of prior bevacizumab

• Adequate hematologic, hepatic, and renal laboratory values within 14 days of inclusion i.e.:

∙ Hemoglobin ≥ 10 g/dL, platelets ≥ 100,000/mm3, neutrophils ≥ 1500/mm3.

‣ Liver function test with ≤ grade 1 alterations, except if due to antiepileptic drug therapy or isolated increased bilirubin due to Gilbert syndrome

‣ Estimated glomerular filtration rate (eGFR) of at least 60 mL/min/1.73 m2 using Cockcroft Gault formula

⁃ Patient able to understand clinical trial information and willing to provide signed and informed consent

⁃ Patient of childbearing potential must have a negative pregnancy test within 14 days of inclusion and must agree to use a medically-acceptable method of birth control during the treatment period and, if randomized in the experimental arm, for at least 1 month after the last cycle of carboplatin

⁃ A male patient must agree to use condoms during the treatment period and, if randomized in the experimental arm, for at least 3 months after the last cycle of carboplatin; the patient must also refrain from donating sperm during this period.

⁃ Patient must be a beneficiary of a health plan that covers routine patient care costs. Patient must be a beneficiary of or affiliated with a social security scheme (according to country-specific requirements)