Patients with recurrent glioblastorna rnultiforrne Initial experience with p-[131I]iodo-L-phenylalanine and external beam radiation therapy

Aim: The objective of this study was to assess the feasibility, dosimetry, tolerability and efficacy of systemically administrated p-[I-131]iodo-L-phenylalanine ((131)IPA) combined with hypo-fractionated external beam radiation therapy (EBRT) in patients with recurrent glioblastoma multiforme (GBM). Patients, methods: Five patients (2 women, 3 men, aged 27-69) with recurrent GBM and exhaustion of regular therapy options were included. All had a positive O-(2-[F-18]Fluoroethyl)-L-tyrosine positron emission tomography (FET-PET) and pretherapeutic dosimetry was performed. Tumour targeting was verified by (131)IPA-SPECT up to six days after radiotracer administration. After (131)IPA therapy, patients were treated with hypo-fractionated EBRT in six fractions of 5 Gy (n = 4) or in eleven fractions of 2 Gy in one case. Results: Based on the individual dosimetry, the patients received a single intravenous administration of 2 to 7 GBq of (131)IPA, resulting in radiation absorbed doses to the blood of 0.80-1.47 Gy. The treatment was well tolerated; only minor complaints of nausea and vomiting that responded to ondansetron and pantoprazol were noticed in the first two patients. After preventive medication, the last three patients had no complaints during therapy. In none of the patients a decrease of leukocyte or thrombocyte counts below the baseline level or the lower normal limit was observed. Tumour doses from (131)IPA were low (<= 1 Gy) and all patients died three to eight (median 5.5) months after therapy. Conclusion: In this initial experience, treatment of GBM with (131)IPA in combination with EBRT was demonstrated to be safe and well tolerated, but less effective than suggested by the animal studies.