Double scattering and pencil beam scanning Monte Carlo workflows for proton therapy retrospective studies on radiation-induced toxicities.

PURPOSE: Monte Carlo (MC) simulations can be used to accurately simulate dose and linear energy transfers (LET) distributions, thereby allowing for the calculation of the relative biological effectiveness (RBE) of protons. We present hereby the validation and implementation of a workflow for the Monte Carlo modelling of the double scattered and pencil beam scanning proton beamlines at our institution. METHODS: The TOPAS/Geant4 MC model of the clinical nozzle has been comprehensively validated against measurements. The validation also included a comparison between simulated clinical treatment plans for four representative patients and the clinical treatment planning system (TPS). Moreover, an in-house tool implemented in Python was tested to assess the variable RBE-weighted dose in proton plans, which was illustrated for a patient case with a developing radiation-induced toxicity. RESULTS: The simulated range and modulation width closely matches the measurements. Gamma-indexes (3%/3mm 3D), which compare the TPS and MC computations, showed a passing rate superior to 98%. The calculated RBE-weighted dose presented a slight increase at the necrosis location, within the PTV margins. This indicates the need for reporting on the physical and biological effects of irradiation in high dose regions, especially at the healthy tissues and increased LET distributions location. CONCLUSION: The results demonstrate that the Monte Carlo method can be used to independently validate a TPS calculation, and to estimate LET distributions. The features of the in-house tool can be used to correlate LET and RBE-weighted dose distributions with the incidence of radiation-induced toxicities following proton therapy treatments.

[New indications of protontherapy for adults intracranial tumours]. / Nouvelles indications de protonthérapie et essais cliniques en cours : tumeurs intracrâniennes.

Considering intracranial tumours, only few indications of protontherapy, such as chordoma, chondrosarcoma or uveal melanoma, are uniformly approved in the world. Other indications, excluding paediatric pathologies, are still debated. The aim of this article is to describe the rationale for the use of protonbeam irradiation for meningioma, pituitary adenoma, craniopharyngioma, paraganglioma, glioma, and schwannoma, and to inform the radiation oncologists if prospective studies or randomized studies are opened for inclusions. This article deals only with indications for adults.

First proton minibeam radiation therapy treatment plan evaluation.

Proton minibeam radiation therapy (pMBRT) is a novel dose delivery method based on spatial dose fractionation. pMBRT has been shown to be promising in terms of reduced side effects and superior tumour control in high-grade glioma-bearing rats compared to standard irradiation. These findings, together with the recent optimized implementation of pMBRT in a clinical pencil beam scanning system, have triggered reflection on the possible application to patient treatments. In this context, the present study was designed to conduct a first theoretical investigation of the clinical potential of this technique. For this purpose, a dedicated dose engine was developed and used to evaluate two clinically relevant patient treatment plans (high-grade glioma and meningioma). Treatment plans were compared with standard proton therapy plans assessed by means of a commercial treatment planning system (ECLIPSE-Varian Medical systems) and Monte Carlo simulations. A multislit brass collimator consisting of 0.4 mm wide slits separated by a centre-to-centre distance of 4 or 6 mm was placed between the nozzle and the patient to shape the planar minibeams. For each plan, spread-out Bragg peaks and homogeneous dose distributions (±7% dose variations) can be obtained in target volumes. The Peak-to-Valley Dose Ratios (PVDR) were evaluated between 9.2 and 12.8 at a depth of 20 mm for meningioma and glioma, respectively. Dose volume histograms (DVHs) for target volumes and organs at risk were quantitatively compared, resulting in a slightly better target homogeneity with standard PT than with pMBRT plans, but similar DVHs for deep-seated organs-at-risk and lower average dose for shallow organs. The proposed delivery method evaluated in this work opens the way to an effective treatment for radioresistant tumours and will support the design of future clinical research.

Spatial fractionation of the dose in proton therapy: Proton minibeam radiation therapy.

In radiation therapy, a renewed interest is emerging for the study of spatially fractionated irradiation. In this article, a few applications using spatial fractionation of the dose will be discussed with a focus on proton minibeam radiation therapy. Examples of calculated dose (1D profiles and 2D dose distributions) and biological evidence obtained so far will be presented for various spatially fractionated techniques GRID, micro- and minibeam radiation therapy. Recent results demonstrating that proton minibeam radiation therapy leads to an increase in normal tissues sparing will be discussed, which opens the door to a dose escalation in the tumour and a possibly efficient treatment of very radioresistant tumours.

[Boost in proton for locally advanced nasopharyngeal carcinoma: A Curie Institute experience]. / Complément de dose de protons pour les cancers du nasopharynx localement évolués : une expérience de l'institut Curie.

PURPOSE: The aim of this study was to assess the treatment outcome and toxicity for patients with locally advanced nasopharyngeal carcinoma treated with a complementary dose with proton. PATIENTS AND METHODS: Between November 1999 and September 2016, 17 patients have been treated for a stage III-IVa nasopharyngeal carcinoma in the proton therapy centre of Curie Institute. Bilateral lymph node in the neck (I-V levels) received from 40 to 54Gy with photon beam. The primary tumor volume including microscopically extensions received a complementary dose with proton in order to reach the dose of 70 to 78Gy. All the patients received a concomitant chemotherapy. The end-points of the study were loco-regional control, survival, and treatment-related toxicity. RESULTS: Patients characteristics were: median age 49, 71 % male, 88% stage IVa, with a majority (82%) of T4N0M0. The median follow-up was 99 months. The 2-, 5- and 10-year actuarial locoregional free survival and overall survival were 94% and 88%, 86% and 74%, and 86% and 66%, respectively. The grade≥3 late adverse events were sphenoid bone radionecrosis (5.9%) and hearing loss (23.5%). CONCLUSION: This study showed that a complementary dose with proton seems to be a good option for the treatment of locally advanced nasopharyngeal carcinoma, particularly for T4N0M0.

[Reirradiation of spine and lung tumor with CyberKnife]. / Réirradiation des tumeurs du rachis et du poumon par CyberKnife).

We present the results of two retrospective studies, one regarding reirradiation of spinal tumours and the second, concerning lung tumours. In the first case, primary or secondary tumours were located in or in contact with the vertebrae and spinal cord. The first irradiation has given a full dose to the spinal cord. In the second case, primary or secondary lung tumours have already been treated by irradiation alone or by radiochemotherapy. No grade 3 or 4 early toxicity has been found. Preliminary clinical results are encouraging. The use of CyberKnife represents a major therapeutic advance in the management of irradiated spinal or lung lesions. The possibility of sparing organs at risk and increasing the dose in the tumour target volume are the main advantages.

[Cyberknife robotic stereotactic radiotherapy: technical aspects and recent developments]. / La radiothérapie stéréotaxique avec Cyberknife (R) : aspects pratiques et développements technologiques récents.

Cyberknife (Accuray Inc. Sunnyvale, USA) stereotactic body radiation therapy (SBRT) involves the delivery of a small number of large doses of radiation to a target volume using continuously evolving advanced technology. It has emerged as a novel treatment modality for cancer and modified some concepts of cancer treatment. It is indicated in early-stage primary cancer, sometimes as an alternative to surgery. It is also indicated for patients with oligometastatic disease who have relatively long survival with the aim to optimize disease control with a good quality of life. Although there remain some uncertainties regarding the radiobiology of hypofractionation, local control and tolerance have been promising. Indications are increasing under strict quality assurance programs worldwide and prospective clinical evaluation.

[Spinals and paraspinals tumors treated by CyberKnife: feasibility and efficacy]. / Tumeurs spinales et paraspinales traitées par irradiation stéréotaxique par CyberKnife((R)) au centre Antoine-Lacassagne de Nice.

PURPOSE: Stereotactic radiotherapy using the CyberKnife has become a key treatment in the multidisciplinary management of secondary tumours, as well as primary benign or malignant tumours located within or adjacent to vertebral bodies and the spinal cord. The aim of this treatment is to improve local control and clinical response, including previously irradiated cases. PATIENTS AND METHODS: In this study, we present the first patients treated with CyberKnife between December 2006 and December 2007 for spinal or paraspinal tumours. The primary aim was to assess the feasibility and tolerance of stereotactic radiotherapy using the CyberKnife. Secondary aims were to establish the short-term local control, to calculate the local progression-free survival and overall survival. Clinical examination and imaging procedures were performed every three months. Response was assessed according to RECIST criteria. RESULTS: During that period, 16 patients were treated with CyberKnife. Thirteen patients had been pre-treated, three of whom had received spinal cord doses considered to be maximal. Three patients did not receive previous irradiation. The median age was 59 (36-74). The most frequent symptoms were pain (n = 8) and motor weakness (n = 4). The median dose was 30 Gy (16-50). The median number of fractions was 3 (1-5). No patient developed acute myelitis. Three patients developed acute reaction. Overall survival at 18 months was 72.4%, with a mean survival of 18.2 months (95% CI: 15.4-20.9). Local progression-free survival at 18 months was 58.4%, with a mean value of 16.9 months (95% CI: 13.6-20.2). CONCLUSION: The use of stereotactic radiotherapy with CyberKnife represents a major progress in the management of paraspinal tumours. The main advantages are better sparing of the spinal cord and the possibility of increasing the dose to the tumour target volume.

[Current indications and ongoing clinical trials with CyberKnife stereotactic radiotherapy in France in 2009]. / Indications du CyberKnife et essais cliniques en cours en 2009.

Image-guided frameless fractionated stereotactic radiotherapy can be performed with millimetric accuracy using the CyberKnife (Accuray Inc. Sunnyvale, USA) equipped with an integrated tracking system for intra- and extracranial lesions. Highly conformal hypofractionated irradiation has been used to treat lesions with curative or palliative intent. It is advantageous for radioresistant tumors, re-irradiating lesions, boosting small volumes and treating tumors that move with respiration. It also limits travel costs and improves the quality of life. Over 60,000 patients have been treated worldwide using CyberKnife including 600 patients in the three French cancer centres of Nice, Nancy and Lille. These expert Cyberknife centres follow quality assurance programs and work together with the "Haute Autorité de santé" and the French National Cancer Institute (INCa) to promote clinical developments. The CyberKnife has been used to treat intracranial lesions including (but not limited to) meningiomas, acoustic schwannomas, brain oligometastases, as well as skull base tumors like chordomas, or para- or intraspinal tumors, and extracranial tumors such as lung cancers. Currently, extracranial stereotactic radiotherapy is particularly attractive for tumors moving with respiration and is being evaluated in liver, prostate and re-irradiation including head and neck tumors.

[Conformal radiotherapy to 76Gy in localized prostate cancer. Therapeutic modalities and preliminary results]. / Radiothérapie conformationnelle à 76Gy des cancers localisés de la prostate. Modalités thérapeutiques et résultats préliminaires.

PURPOSE: To describe therapeutic modalities for localized prostate cancer treated by conformal radiation to 76Gy with or without androgen ablation. To evaluate the preliminary results in terms of survival, biological control and toxicity. PATIENTS AND METHOD: Between January 1998 and June 2001, 321 patients with localized prostate cancer were irradiated at institut Curie. Tumors were stratified into the three Memorial Sloan-Kettering Cancer Center prognostic groups (1998) for analysis: favorable risk group (FG) 23%, intermediate risk group (IG) 36.5%, unfavorable risk group (UG) 40.5%. Androgen deprivation, mainly neoadjuvant, less or equal to one year was prescribed to 93.8% of patients (72.6% less or equal to six months). Planning target volume prescription doses were: prostate: 76Gy, seminal vesicles: 56 to 76Gy, and pelvic lymph nodes: 44Gy to 16.8% of patients. RESULTS: The five-year actuarial overall survival was 94% (95% IC: 90-97%). The median post-therapeutic follow-up was 36 months (nine to 60 months). The 48-month actuarial rates of biochemical control for the three prognostic groups were statistically different according to both the American Society for Therapeutic Radiology and Oncology consensus (ASTRO 1997) and the Fox Chase Cancer Center definitions of biochemical failure (FCCC 2000) with respectively 87 and 94% for FG, 78 and 84% for IG, 54 and 58% for UG (P<10(-6) and P<10(-8)). At time of our analysis, late post-treatment rectal and bladder bleedings were 17,4 and 13,6%, respectively. According to a 1-4 scale adapted from M.D. Anderson Cancer Center criteria: rectal bleedings were grade 1 (9.6%), grade 2 (6.2%) and grade 3 (1.6%). Bladder bleedings were grade 2 (13%) and grade 3 (0.6%). Analysis of rectal bleeding risk factors showed significant correlations with pelvic lymph nodes irradiation for grade 2 and 3, (P=0.02), and for all grades, a correlation with smaller rectal wall volumes (P=0.03), and greater percentages of rectal wall irradiated to higher doses: 65, 70, 72 and 75Gy (P=0.02, P=0.01, P=0.0007 and P=0.003, respectively). CONCLUSIONS: These results are comparable to those previously reported with the same follow-up. Impact of dose escalation with short androgen deprivation on local control, survival and complications needs longer follow-up and further analysis.