946 poster GLIOBLASTOMA IN ELDERLY: IS ADJUVANT RADIOCHEMOTHERAPY EFFECTIVE AND FEASIBLE?

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used for kV and MV imaging applications in radiotherapy is amorphous silicon (aSi:H) flat panel technology. While new aSi:H panels provide relatively good MV images, the quality and dosimetrical usefulness of devices suffers significantly from radiation damages under normal clinical use. After average life spans of 18 months, detectors have to be replaced. A novel flat panel imaging technology, based on gas electron multipliers (GEMs), is promising unlimited life span due to increased radiation hardness. Materials: A new GEM detector was installed on a clinical linear accelerator (retro-fit), and integrated in our software open-radART (a record and verify system with fast image feedback loops to enable robotic applications in adaptive IGRT on conventional linacs). In several test plans, we compare images from the GEM detector with the aSi:H flat panel devices. Focus is set on exact specification of framerate, digital quantum efficiency, linearity of response to doserate, spatial resolution (MTF), temperature behaviour, ghosting (image lag) and aging / radiation hardness. Besides phantom studies, first clinical images of the GEM detector are captured. Results: The clinical test environment was successfully implemented and all test cases were performed in this setting. At a first glance, 16 bit image quality is comparable to that of aSi:H imaging devices with the advantage of higher possible framerates of the GEM panel (20 Hz vs. 2 Hz). Ghosting effects have not been seen with GEM (intrinsic: no trapped charges), digital quantum efficiency (SNR at lower doses per frame) is significantly increased compared to aSi:H. Although pixel size and active area are comparable, depending on adjustable high voltage settings on the GEMs, the spatial resolution (MTF) can be slightly lower compared to aSi:H technology. The GEM system appears to be stable, and re-calibration intervals are reasonable. However, long term follow up data of radiation hardness in a typical clinical setting is not yet available. Conclusions: Relating to the measurement results, the GEM detector has proven its potential to be a suitable imaging device in radiotherapy. However, further investigations need to be done to gain more expertise on tuning of the new detector’s properties and to quantify aging effects due to radiation damages. 946 poster GLIOBLASTOMA IN ELDERLY: IS ADJUVANT RADIOCHEMOTHERAPY EFFECTIVE AND FEASIBLE? A. Fiorentino1 , C. Chiumento1 , A. M. Mileo1 , V. Fusco1 1 IRCCS/CROB, Department of Radiation Oncology, Rionero in Vulture, Italy Purpose: Glioblastoma (GBM) is frequent among elderly patients (>65yars). The Purpose of this retrospective study was to evaluate the feasibility and the effective of Standard Radiochemotherapy (RTCHT) in GBM elderly patients. Materials: Patients (pts) >65 yrs old with histological proven GBM (WHO grade IV); were retrospectively evaluated. Patients received a surgical resection or biopsy and standard RTCHT with TMZ. The Clinical Target Volume was defined as surgical bed + residual tumor + oedema + 0.5 cm and the Planning Target Volume was defined as CTV + 0.7 cm. RTOG scale was used to define acute toxicity. Results: From March 2005 to June 2010, 27 GBM patients (pts) >65 yrs were treated in our Institution (21 pts > 70 yrs). Fourteen are female and 13 male. Eight pts (29.6%) received a complete resection. After a median follow-up of 27 (range 3-65) months, median progression-free survival (PFS) was 7 months (mts) and median Overall Survival (OS) was 12 months. Extent of resection (p:0.03) and RPA class (p:0.05) correlated with OS. At multivariate analysis only the extent of resection was a significant prognostic factor (p:0.032).During RTCHT toxicity was mild, thrombocytopenia G3-4 occurred in 3 pts and Neurological toxicity G3-4 in 2 pts. Conclusions: In conclusion, our data suggest that the association of RT with TMZ could be considered as a safe and effective strategy to treat GBM in elderly pts. 947 poster HAS COMBINED MODALITY TREATMENT OF GLIOBLASTOMA MULTIFORME CHANGED THE PATTERNS OF PROGRESSION? G. Ryan1 , A. Gunjur2 , Y. Taouk3

to analyse the pattern of progression of GBM in our institution, to guide us in future research and treatment protocols. Materials: Patients with GBM treated as per Stupp protocol between October 2004 and August 2009 at the Peter MacCallum Cancer Centre in Melbourne were reviewed retrospectively. Sixty-eight eligible patients with complete follow-up were identified, of whom 54 were found to have progressed following treatment. MRI scans at progression and original radiotherapy plans were available for 47 patients, and were fused in the radiotherapy planning system and analysed for site(s) of progression. Results: There was an over-representation of males and patients over 60 years in our patient group (66% and 38% respectively) compared to the Stupp study population. Coverage of site(s) of progression by the radiotherapy planning target volume was defined as: central >95% coverage, in-field >80-95%, marginal 20-80%, and out-offield <20%. In our patient group 77% of progressions were central, 15% in-field, 6% marginal and 2% out-of-field. Given the small number of out-of-field recurrences, no temporal trends could be identified. Overall survival for the cohort was 11.6 months, with the 1 and 2 year survival rates 50% and 18%. Conclusions: There is no evidence of an increase in out-of-field progressions in our patient group. The relatively unfavourable demographics of the group may have contributed to this negative result. Further patient data will be collected prospectively to address potential biases, and will be correlated with MGMT methylation status and newer imaging modalities. 948 poster HDR BRACHYTHERAPY IN SKIN CANCERS: TARGET DETERMINATION AND OUTCOME VERSUS CONVENTIONAL RADIOTHERAPY F. Piro1 , R. Siciliano2 , D. Cosentino1 , P. Indrieri1 , L. Ziccarelli1 , P. Ziccarelli1 , L. Marafioti1 1 O SPEDALE M ARIANO S ANTO, Department of Radiotherapy, Cosenza, Italy 2 O SPEDALE M ARIANO S ANTO, Fisica Sanitaria, Cosenza, Italy Purpose: Brachitherapy in skin cancers is a interesting alternative to conventional radiotherapy because offers personalized treatment (also in multisite cancers) and due to new fractionation used in our Center the treatment time is shorter than conventional RT. Otherwise the leterature data for these treatment are few. So we performed this rewiew to evaluate outcome, toxicity and or target missing in patients treated with high dose rate brachytherapy, and with minimum follow up of 60 months. Materials: From August 1999 to September 2010, 118 consecutive pts. with skin cancer (20% squamous cell) (5% with cancer larger >4 cm) were enrolled in this perspective study: HDR treatment consisting of twice-daily fractionation of 350 cGy each, 6 hour apart final dose delivered 49 Gy as esclusive modality or as postoperative treatment for positive margins; as postoperative treatment for squamous cell with clear margins the final dose delivered was 42 Gy. To provide the maximum coverage of the tumor the implants were performed with afterloading spaced (at least 1 cm) catheters embedded in personalized surface molds or interstitial implant both planned with a semi-3-D technique aided by simulator. Radiopaque markers for target definition around the cancer were obbligatory (minimum space 5 mm maximum 10 mm). So implant dosimetry was performed as 100% of prescription at each skin marker. The follow up consisted in clinical examination of each cancer site. We studied the pts. with a minimum follow up of 5 years. For failure cases a rewiew of dosimetry was performed. Results: The eligible pts. were 93, the median follow up 84 months (range 60-96). The cosmetics results were poor in 6% of cases; the only important toxicity was a telangectasia of the skin. The local relapse were 10% (9 cases) especially for bulky cases (6), for 3 of these cases a full-dose reirradiation was performed after the dosimetry rewiew without severe toxicity. The cases of missing target 3% (3 cases). Conclusions: According the letterature this treatment schedule is effective and can be used in skin cancers with a good compliance of the treated pts. (seven days of treatment). HDR brachytherapy is a tecnique with a good learning curve that offers personalized treatments without radiation damage to OAR ( as eye ) in alternative to conventional radiotherapy. Actually this schedule is the standard for skin cancer in our Center. 949 poster

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P ETER M AC C ALLUM C ANCER C ENTRE, Radiation Oncology, Melbourne, Australia 2 P ETER M AC C ALLUM C ANCER C ENTRE, Medical Student, Melbourne, Australia 3 P ETER M AC C ALLUM C ANCER C ENTRE, Biostatistics and Clinical Trials, Melbourne, Australia Purpose: More than 90% of patients with glioblastoma multiforme (GBM) treated with adjuvant radiotherapy alone post-surgery progress within 2cm of the enhancing tumour/surgical cavity, and this information is currently used in defining radiotherapy field margins. With the introduction of combined modality adjuvant treatment incorporating temozolomide chemotherapy (the "Stupp Protocol"), there is emerging literature suggesting that the risk of progression beyond these margins is substantially increased. This study therefore aims

HIGH DOSE RATE BRACHYTHERAPY BOOST FOR RESIDUAL MALIGNANT GLIOMA: CLINICAL RESULTS FROM SINGLE INSTITUTION M. H. Elnaggar1 , H. El Bakry1 , A. Fakhr2 , A. Hassouna1 , M. El-Sayed1 1

E GYPTIAN N ATIONAL C ANCER I NSTITUTE , C AIRO U NIVERSITY, Radiation Oncology Department, Cairo, Egypt 2 FACULTY OF M EDICINE , A IN S HAMS U NIVERSITY, Neurosurgery, Cairo, Egypt Purpose: Investigate the role of additional brachytherapy boost in malignant glioma patients having residual lesion after conventional radiotherapy treatment. Materials: After initial surgical intervention and external beam radiotherapy