No abstract

No abstract

The purpose of this work is to assess eight detectors performance for output factor (OF), percent depth dose (PDD), and beam profiles in a 6‐MV Clinac stereotactic radiosurgery mode for cone irradiation using Monte Carlo simulation as reference. Cones with diameters comprised between 30 and 4 mm have been studied. The evaluated detectors were ionization chambers: pinpoint and pinpoint 3D, diodes: SRS, P and E, Edge, MicroDiamond and EBT3 radiochromic films. The results showed that pinpoints underestimate OF up to −2.3% for cone diameters ≥10 mm and down to −12% for smaller cones. Both nonshielded (SRS and E) and shielded diodes (P and Edge) overestimate the OF respectively up to 3.3% and 5.2% for cone diameters ≥10 mm and in both cases more than 7% for smaller cones. MicroDiamond slightly overestimates the OF, 3.7% for all the cones and EBT3 film is the closest to Monte Carlo with maximum difference of ±1% whatever the cone size is. For the profiles and the PDD, particularly for the small cones, the size of the detector predominates. All diodes and EBT3 agree with the simulation within ±0.2 mm for beam profiles determination. For PDD curve all the active detectors response agree with simulation up to 1% for all the cones. EBT3 is the more accurate detector for beam profiles and OF determinations of stereotactic cones but it is restrictive to use. Due to respectively inappropriate size of the sensitive volume and composition, pinpoints and diodes do not seem appropriate without OF corrective factors below 10 mm diameter cone. MicroDiamond appears to be the best detector for OF determination regardless all cones. For off‐axis measurements, the size of the detector predominates and for PDD all detectors give promising results.

Purpose/ObjectivesTo assess feasibility and toxicity of Helical TomoTherapy® for treating anal cancer patients.MethodsFrom 2007 to 2011, 64 patients were consecutively treated with TomoTherapy® in three centres for locally advanced squamous-cell anal carcinoma (T2 > 4 cm or N positive). Prescribed doses were 45 Gy to the pelvis including inguinal nodes and 59.4 Gy to the primary site and involved nodes with fractions of 1.8 Gy, five days a week. A positional Megavoltage Computed Tomography was performed before each treatment session. All acute and late toxicities were graded according to Common Terminology Criteria for Adverse Events version 3.0. Survival analysis was performed using the Kaplan-Meier method.ResultsMedian follow-up was 22.9 months. Fifty-four women and 10 men were treated (median age: 62 years). Nineteen patients (29.7 %) had T2, 16 patients (25.0 %) T3, and 27 patients (42.2 %) T4 tumours. Thirty-nine patients (60.9 %) had nodal involvement. Median tumour size was 45 mm (range, 10–110 mm). Seven patients had a colostomy before treatment initiation. Fifty-seven patients received concomitant chemotherapy (5-FU/cisplatin or 5-FU/mitomycin-based therapy). Forty-seven patients (73.4 %) experienced a complete response, 13 a partial response or local recurrence, and 11 had salvage surgery; among these, six became complete responders, three experienced metastatic failure, and two local failure. At least four patients experienced metastatic recurrence (concomitant to a local failure for one patient). The two-year overall survival was 85.6 % (95 %CI [71.1 %–93.0 %]), and the one-year disease-free survival, and colostomy-free survival were 68.7 % (95 %CI [54.4 %–79.4]), and 75.5 % (95 %CI [60.7 %–85.3 %]) respectively. Overall survival, disease-free survival and colostomy free-survival were significantly better for women than men (p = 0.002, p = 0.004, and p = 0.002 respectively). Acute grade ≥3 toxicity included dermatologic (46.9 % of patients), gastrointestinal (20.3 %), and hematologic (17.2 %) toxicity. Acute grade 4 hematologic toxicity occurred in one patient. No grade 5 event was observed.ConclusionsTomoTherapy® for locally advanced anal cancer is feasible. In our three centres of expertise, this technique appeared to produce few acute gastrointestinal toxicities. However, high rates of dermatologic toxicity were observed. The therapeutic efficacy was within the range of expectations and similar to previous studies in accordance with the high rates of locally advanced tumours and nodal involvement.

No abstract