A4: IMRT-based hypofractionated re-irradiation of progressive glioblastoma: the initial results

Nikhil Tanna1,Olga Kirmi1,Matthew Williams1

1Imperial College Healthcare NHS Trust, London, UK

Presenting date: Monday 2 November
Presenting time: 13.10-14.00

Background

Glioblastoma (GBM) is the commonest malignant brain tumour in adults. Current standard of care is concurrent chemo-radiotherapy and adjuvant chemotherapy. There is varied literature on re-irradiation, but little consensus.

Method

We identified all patients treated at our centre from 1st January 2012 – 1st March 2015 with a histological diagnosis of glioblastoma who received radical chemo-radiotherapy and a second course of radiotherapy.

Results

We identified 6 patients. 5 had surgery (sub-total resection), and 1 had biopsy. All received radical chemo-radiotherapy (60Gy in 30 with concurrent Temozolamide) using IMRT.  4 stopped chemotherapy (1 sepsis, 1 rash & dyspnea, 2 thrombocytopenia). At relapse, 2 patients received 2nd line chemo before re-irradiation (1x Lomustine; 1x Irinotecan). 4 did not (2 due to thrombocytopenia, 1 clinical deterioration, 1 intolerance to chemo).

Re-irradiation was delivered as 40Gy in 10 fractions for 5 patients (35 Gy in 10 fractions for one), using IMRT, with a median time of 33 weeks between starting primary radiotherapy and re-irradiation. GTV was defined as the T1-contrast enhancing region, and PTV as GTV+3mm.

No patient developed radionecrosis or toxicity beyond grade 2. 3 patients demonstrated some reduction in tumour size on MRI at 4 weeks. 2 patients had stable disease and 1 showed tumour progression. By RANO criteria, 5 patients had stable disease.

2 patients have yet to progress radiologically. 4 progressed at 4, 17, 26 and 43 weeks post re-irradiation, 2 of whom died at 34 and 43 weeks. In all cases progression was noted at the primary disease site. Post-reirradiation, one patient enrolled in a clinical trial, and one had 3rd line Temozolamide and Irinotecan.

Conclusion

Reirradiation using IMRT for relapsed GBM has limited acute toxicity and in some patients offers a period of disease stability. However, optimal dose and sequencing of treatment remain unclear