Deep Seated Tumour Treatments With Electrons of High Energy Delivered at FLASH Rates: The Example of Prostate Cancer.

Different therapies are adopted for the treatment of deep seated tumours in combination or as an alternative to surgical removal or chemotherapy: radiotherapy with photons (RT), particle therapy (PT) with protons or even heavier ions like 12C, are now available in clinical centres. In addition to these irradiation modalities, the use of Very High Energy Electron (VHEE) beams (100-200 MeV) has been suggested in the past, but the diffusion of that technique was delayed due to the needed space and budget, with respect to standard photon devices. These disadvantages were not paired by an increased therapeutic efficacy, at least when comparing to proton or carbon ion beams. In this contribution we investigate how recent developments in electron beam therapy could reshape the treatments of deep seated tumours. In this respect we carefully explored the application of VHEE beams to the prostate cancer, a well-known and studied example of deep seated tumour currently treated with high efficacy both using RT and PT. The VHEE Treatment Planning System was obtained by means of an accurate Monte Carlo (MC) simulation of the electrons interactions with the patient body. A simple model of the FLASH effect (healthy tissues sparing at ultra-high dose rates), has been introduced and the results have been compared with conventional RT. The study demonstrates that VHEE beams, even in absence of a significant FLASH effect and with a reduced energy range (70-130 MeV) with respect to implementations already explored in literature, could be a good alternative to standard RT, even in the framework of technological developments that are nowadays affordable.

Treatment Complications and Long-term Outcomes of Total Body Irradiation in Patients with Acute Lymphoblastic Leukemia: A Single Institute Experience.

BACKGROUND: The aim of this study was to evaluate treatment-related toxicity and clinical outcomes of total body irradiation (TBI) in patients with acute lymphoblastic leukemia (ALL). PATIENTS AND METHODS: We performed a retrospective review of all patients with ALL who underwent TBI-based conditioning regimen at our Institution between 2000 and 2012. RESULTS: A total of 211 patients were included. The median follow-up was 40 months. The 5-year overall survival and disease-free survival were 64.7% and 62.8%, respectively. The 5-year overall survival rate for the 163 children was 67.6% (95% confidence interval=55-77%). Disease status at time of transplant did not improve disease-free survival. Gastrointestinal acute toxicity was the most common early side-effect (19.9%). Acute graft-versus-host disease was reported in 31 patients (14.7%). Main late toxicities were cataract induction (12.8%) and growth, gonadal and endocrine effects (36%). CONCLUSION: TBI-based conditioning regimen led to a high survival rate with remarkably low radiation-related toxicity, suggesting that TBI provides a feasible therapeutic option in patients with ALL.

A generalized calibration procedure for in vivo transit dosimetry using siemens electronic portal imaging devices.

A practical and accurate generalized in vivo dosimetry procedure has been implemented for Siemens linacs supplying 6, 10, and 15 MV photon beams, equipped with aSi electronic portal imaging devices (EPIDs). The in vivo dosimetry method makes use of correlation ratios between EPID transit signal, s (t) (0) (TPR,w,L), and phantom mid-plane dose, D (0)(TPR,w,L), as functions of phantom thickness, w, square field dimensions, L, and tissue-phantom ratio TPR(20,10). The s (t) (0) (TPR,w,L) and D (0)(TPR,w,L) values were defined to be independent of the EPID sensitivity and monitor unit calibration, while their dependence on TPR(20,10) was investigated to determine a set of generalized correlation ratios to be used for beams with TPR(20,10) falling in the examined range. This way, other radiotherapy centers can use the method with no need to locally perform the whole set of measurements in solid water phantoms, required to implement it. Tolerance levels for 3D conformal treatments, ranging between ±5 and ±6% according to tumor type and location, were estimated for comparison purposes between reconstructed isocenter dose, D (iso), and treatment planning system (TPS) computed dose D (iso,TPS). Finally a dedicated software, interfaceable with record and verify (R&V) systems used in the centers, was developed to obtain in vivo dosimetry results in less than 2 min after beam delivery.