Francisco Pino

External beam radiotherapy plus single-fraction high dose rate brachytherapy in the treatment of locally advanced prostate cancer

PURPOSE To evaluate the efficacy and toxicity of external beam radiation therapy (EBRT) plus high-dose-rate brachytherapy (HDRB) as a boost in patients (pts) with intermediate or high-risk prostate cancer. METHODS AND MATERIALS From 2002 to July 2012, 377 pts with a diagnosis of intermediate or high-risk prostate cancer were treated with EBRT plus HDRB. Median patient age was 66 years (range, 41-86). Most patients (347 pts; 92%) were classified as high-risk (stage T2c-T3, or PSA>20 ng/mL, or GS ⩾ 8), with 30 patients (8%) considered intermediate risk. All patients underwent EBRT at a prescribed dose of 60.0 Gy (range, 45-70 Gy) to the prostate and seminal vesicles. A total of 120 pts (31%) received a dose of 46 Gy (45-50 Gy) to the true pelvis. All pts received a single-fraction 9 Gy (9-15 Gy) HDR boost. Most patients (353; 94%) were prescribed complete androgen deprivation therapy (ADT). Overall survival (OS), cause-specific survival (CSS), and biochemical relapse-free survival (BRFS) rates were calculated. In the case of BRFS, patients with <26 months of follow-up (n=106) were excluded to minimize the impact of ADT. RESULTS The median follow-up for the entire sample was 50 months (range, 12-126), with 5-year actuarial OS and CSS, respectively, of 88% (95% confidence interval [CI]: 84-92) and 98% (95% CI: 97-99). The 5-year BRFS was 91% (95% CI: 87-95) in the 271 pts with ⩾ 26 months (median, 60 months) of follow-up. Late toxicity included grade 2 and 3 gastrointestinal toxicity in 17 (4.6%) and 6 pts (1.6%), respectively, as well as grades 2 and 3 genitourinary toxicity in 46 (12.2%) and 3 pts (0.8%), respectively. CONCLUSION These long-term outcomes confirm that EBRT plus a single-fraction HDRB boost provides good results in treatment-related toxicity and biochemical control. In addition to the excellent clinical results, this fractionation schedule reduces physician workload, treatment-related expenses, patient discomfort and risks associated with anaesthesia. We believe these findings support the use of single-fractionation boost techniques.

Development of a variable-radius pinhole SPECT system with a portable gamma camera.

OBJECTIVE To develop a small-animal SPECT system using a low cost commercial portable gamma camera equipped with a pinhole collimator, a continuous scintillation crystal and a position-sensitive photomultiplier tube. MATERIAL AND METHODS The gamma camera was attached to a variable radius system, which enabled us to optimize sensitivity and resolution by adjusting the radius of rotation to the size of the object. To investigate the capability of the SPECT system for small animal imaging, the dependence of resolution and calibration parameters on radius was assessed and acquisitions of small phantoms and mice were carried out. RESULTS Resolution values, ranging from 1.0mm for a radius of 21.4mm and 1.4mm for a radius of 37.2mm were obtained, thereby justifying the interest of a variable radius SPECT system. CONCLUSIONS The image quality of phantoms and animals were satisfactory, thus confirming the usefulness of the system for small animal SPECT imaging.

Multi-centre audit of VMAT planning and pre-treatment verification

BACKGROUND AND PURPOSE We performed a multi-centre intercomparison of VMAT dose planning and pre-treatment verification. The aims were to analyse the dose plans in terms of dosimetric quality and deliverability, and to validate whether in-house pre-treatment verification results agreed with those of an external audit. MATERIALS AND METHODS The nine participating centres encompassed different machines, equipment, and methodologies. Two mock cases (prostate and head and neck) were planned using one and two arcs. A plan quality index was defined to compare the plans and different complexity indices were calculated to check their deliverability. We compared gamma index pass rates using the centres equipment and methodology to those of an external audit (global 3D gamma, absolute dose differences, 10% of maximum dose threshold). Log-file analysis was performed to look for delivery errors. RESULTS All centres fulfilled the dosimetric goals but plan quality and delivery complexity were heterogeneous and uncorrelated, depending on the manufacturer and the planners methodology. Pre-treatment verifications results were within tolerance in all cases for gamma 3%-3mm evaluation. Nevertheless, differences between the external audit and in-house measurements arose due to different equipment or methodology, especially for 2%-2mm criteria with differences up to 20%. No correlation was found between complexity indices and verification results amongst centres. CONCLUSIONS All plans fulfilled dosimetric constraints, but plan quality and complexity did not correlate and were strongly dependent on the planner and the vendor. In-house measurements cannot completely replace external audits for credentialing.

Penile brachytherapy—Retrospective review of a single institution

PURPOSE To analyze the results of exclusive brachytherapy (BT) to treat patients with penile squamous cell carcinoma confined to the glans or prepuce. METHODS AND MATERIALS Retrospective analysis of 25 patients treated for T1-T2 penile cancer with exclusive interstitial BT between July 1989 and March 2014 at our institution. RESULTS Median followup was 9.2 years (range, 0-19). The mean patient age was 65.3 years (range, 51-80). Most patients underwent exclusive low-dose-rate BT (56%; n = 14) or pulsed-dose-rate BT (40%; n = 10). Only 1 patient received high-dose-rate BT (4%). The median prescribed dose was 60 Gy. Eight patients died during follow-up because of systemic progression (one case) and other intercurrent causes (seven cases). Two failures were recorded (one local and one regional), both at 4 months after BT. The remaining patients continued follow-up at our institution and maintained response. Two patients underwent partial phallectomy for toxicity. At the time of this report, 12 of the 25 patients are alive and free of disease. The most common late toxicities were telangiectasia, urethral stenosis, and atrophy, in 48%, 43%, and 17.4% of patients, respectively. CONCLUSIONS BT with low dose rate/pulsed dose rate provides excellent locoregional control for small (≤4 cm) T1-T2 squamous cell carcinoma of the penile glans.

The performance of a hybrid analytical-Monte Carlo system response matrix in pinhole SPECT reconstruction

It is well-known that in pinhole SPECT (single-photon-emission computed tomography), iterative reconstruction methods including accurate estimations of the system response matrix can lead to submillimeter spatial resolution. There are two different methods for obtaining the system response matrix: those that model the system analytically using an approach including an experimental characterization of the detector response, and those that make use of Monte Carlo simulations. Methods based on analytical approaches are faster and handle the statistical noise better than those based on Monte Carlo simulations, but they require tedious experimental measurements of the detector response. One suggested approach for avoiding an experimental characterization, circumventing the problem of statistical noise introduced by Monte Carlo simulations, is to perform an analytical computation of the system response matrix combined with a Monte Carlo characterization of the detector response. Our findings showed that this approach can achieve high spatial resolution similar to that obtained when the system response matrix computation includes an experimental characterization. Furthermore, we have shown that using simulated detector responses has the advantage of yielding a precise estimate of the shift between the point of entry of the photon beam into the detector and the point of interaction inside the detector. Considering this, it was possible to slightly improve the spatial resolution in the edge of the field of view.

The use of an interstitial boost in the conservative treatment of breast cancer: how to perform it routinely in a radiotherapy department

Purpose To demonstrate the utility of a boost with interstitial brachytherapy (BT) in breast-conserving therapy (BCT) by doing a thorough review of the literature and describing in detail our technique for delivering this boost. Material and methods Our department has been delivering the boost with interstitial BT since 1989, in most cases with rigid needles and a theoretical dosimetry. In the early years, we used low-dose-rate (LDR) with iridium-192 wires. The dose administered was 15 Gy if there were no risk factors for local relapse or 20-25 Gy in the presence of risk factors. The risk factors considered were the presence of a close margin (less than 10 mm) and an extensive intraductal component (more than 25%). After 2002, we switched to high-dose-rate (HDR); using the linear quadratic model we changed the low dose to 3 fractions of 4.5 Gy in the case of no risk factors for local relapse or to 3 fractions of 5 Gy in the presence of risk factors. Results In 79 consecutive boost patients treated in our department between 2010 and 2011, with a median follow-up of 46 months, the local control rate was 97.47%. With respect to cosmesis, fibrosis occurred in 17 cases (21.5%) and hyperpigmentation in 26 cases (32.9%). Our hospitals results are comparable in terms of local control and cosmesis to those of other authors. Conclusions This educational article describes our departments boost technique with rigid needles and comments briefly on our results using this technique in a group of consecutively treated patients in our department. A review of the literature and the published results on local control and cosmesis is also described.

Improved image quality in pinhole SPECT by accurate modeling of the point spread function in low magnification systems

PURPOSE Single photon emission computed tomography (SPECT) has become an important noninvasive imaging technique in small-animal research. Due to the high resolution required in small-animal SPECT systems, the spatially variant system response needs to be included in the reconstruction algorithm. Accurate modeling of the system response should result in a major improvement in the quality of reconstructed images. The aim of this study was to quantitatively assess the impact that an accurate modeling of spatially variant collimator/detector response has on image-quality parameters, using a low magnification SPECT system equipped with a pinhole collimator and a small gamma camera. METHODS Three methods were used to model the point spread function (PSF). For the first, only the geometrical pinhole aperture was included in the PSF. For the second, the septal penetration through the pinhole collimator was added. In the third method, the measured intrinsic detector response was incorporated. Tomographic spatial resolution was evaluated and contrast, recovery coefficients, contrast-to-noise ratio, and noise were quantified using a custom-built NEMA NU 4-2008 image-quality phantom. RESULTS A high correlation was found between the experimental data corresponding to intrinsic detector response and the fitted values obtained by means of an asymmetric Gaussian distribution. For all PSF models, resolution improved as the distance from the point source to the center of the field of view increased and when the acquisition radius diminished. An improvement of resolution was observed after a minimum of five iterations when the PSF modeling included more corrections. Contrast, recovery coefficients, and contrast-to-noise ratio were better for the same level of noise in the image when more accurate models were included. Ring-type artifacts were observed when the number of iterations exceeded 12. CONCLUSIONS Accurate modeling of the PSF improves resolution, contrast, and recovery coefficients in the reconstructed images. To avoid the appearance of ring-type artifacts, the number of iterations should be limited. In low magnification systems, the intrinsic detector PSF plays a major role in improvement of the image-quality parameters.

Validation of a GEANT4 simulation model for pinhole SPECT including calibration parameters

A tool for the MC simulation of pinhole SPECT cameras that includes the main calibration parameters has been developed and validated.

EP-1266: Interstitial brachytherapy using MUPIT in locally advanced or recurrent gynecological malignancies

Purpose/Objective: Uterine cervical carcinoma is still remaining one of the main mortality reasons for female population in the developing world. Inspite of widely accessible screening and diagnostic procedures in the vast majority of cases in our country cervical cancer is revealed in locally advanced stages with metastasis in pelvic and paraaortal lymph nodes in up to 34% of patients. Concurrent chemoradiotherapy is the treatment of choice for cervical cancer today but the presence of positive lymph nodes require escalation of EBRT dose to these targets. The aim of this research was analysis of treatment results of 62 node positive cervical cancer patients. Materials and Methods: We used the method of integrated boost by volumetric arc therapy (VMAT) to increase the EBRT dose in target while keeping relatively low doses at the organs at risk (bowel, rectum, bladder, femoral heads, pelvic bones). Planning was done in automatic regimen and the dose distribution was better (more conformal) if two dynamic arcs with 15 MV photon beams were used. Number of fractions were 25. Fraction dose prescribed to the pelvis (primary tumor and regional zone) was 2.0 Gy while to the metastatic lymph nodes – 2.3 Gy at the same fraction what makes totally 50 and 59 Gy respectively (EQD2 by α/β = 10). From the first day of treatment patients received concurrently weekly cisplatin in dose 40 mg/m (max. 70 mg), 5 infusions. After 46 Gy of EBRT we started HDR brachytherapy which was consisted of two weekly 9.0 Gy fractions to HRCTV. Results: We analysed close results of the treatment which were assessed one month after the course completed. Complete regression, partial regression and stabilisation of the tumor developed in 83,9% (n=52), 11,3% (n=7), and 4,8% (n=3) cases respectively. Early hematological toxicity, enteritis, rectitis and cystitis of II – III stages observed in 42,3%, 15,4%, 11,2% and in 4,3% cases accordingly. Conclusions: VMAT EBRT with integrated boost, HDR brachytherapy and concurrent cisplatin appears to be safe and effective treatment modality for pelvic lymph node metastatic uterine cervical carcinoma providing high rate local tumor control and acceptable early toxicity. But to do final conclusions we need longer follow up period.