Errors in manual radiotherapy treatment procedures and their evolution in a low resource setting: Uganda's experience.

PURPOSE: In Uganda, two-dimensional (2D) radiotherapy treatments have been in use since the establishment of radiotherapy in 1995. Preliminary investigations of treatment records in November 2019 showed evidence of gaps requiring urgent attention. The purpose of this study was to improve the safety of the treatments. METHODS: Records of 1164 patients treated in 1387 courses (1412 sites) on Cobalt-60 units were reviewed todetermine the frequency and dosimetric implications of events that occurred at different stepsof the radiotherapy process. The results were presented and discussed with the differentprofessionals for learning purposes. RESULTS: Most common dosimetric eventswere omission of block tray, bolus and couch transmission factors in time calculations, incorrect field sizes and depths, wrong beam weighting, independent calculations and prescription doses contributing 28.6 %, 10.1 %, 6.0 %,11.9 %, 10.1 %, 5.4 %, 4.8 % and 8.9 % to the 168 observed errors. Comparison of the calculated treatment doses with the prescribed doses showed that 88 % of the 1412 sites were treated with radiation doses within an accuracy of ± 5 %. However, an analysis of the evolution along the years demonstrated an improvement from 82.8 % in 2018 to 86.1 % in 2019, and 93.2 % in 2020. Most common procedural events were incomplete setup instructions and missing patient data in the record and verify system of the Co-60 units for 57 % and 60.1 % of the 1164 patients. CONCLUSIONS: Opportunities for improvement of safety in the delivery of radiotherapy treatments were identified. Learning from these past errors should raise awareness in the team leading to a safer treatments.

Remote Global Radiation Oncology Education and Training: A Pathway to Increase Access to High-Quality Radiation Therapy Services in Low- and Middle-Income Countries.

Purpose: There is a vital need to train radiation therapy professionals in low- and middle-income countries (LMICs) to develop sustainable cancer treatment capacity and infrastructure. LMICs have started to introduce intensity modulated radiation therapy (IMRT), which is the standard of care in high-income countries, because of improved outcomes and reduced toxicities. This work reports the efficacy of a complementary asynchronous plus synchronous virtual-training approach on improving radiation therapy professions' self-confidence levels and evaluating participants' attitudes toward asynchronous and synchronous didactic hands-on learning in 3 LMICs. Methods and Materials: Training was provided to 37 participants from Uganda, Guatemala, and Mongolia, which included 4 theoretical lectures, 4 hands-on sessions, and 8 self-guided online videos. The 36-day training focused on IMRT contouring, site-specific target/organ definition, planning/optimization, and quality assurance. Participants completed pre- and postsession confidence surveys on a 0 to 10 scale, which was converted to a 5-point Likert rating scale to evaluate the training outcomes. The pros and cons of the 3 different training formats were compared. Results: The participants included 15 (40.5%) radiation oncologists, 11 (29.7%) medical physicists, 6 (16.2%) radiation therapists, and 5 (13.5%) dosimetrists. Approximately 50% had more than 10 years of radiation therapy experience, 70.8% had no formal IMRT training, and only 25% had IMRT at their institutions. The average experience and confidence levels in using IMRT at baseline were 3.2 and 2.9, which increased to 5.2 and 4.9 (P < .001) after the theoretical training. After the hands-on training, the experience and confidence levels further improved to 5.4 and 5.5 (P < .001). After the self-guided training, the confidence levels increased further to 6.9 (P < .01). Among the 3 different training sessions, hands-on trainings (58.3%) were most helpful for the development of participants' IMRT skills, followed by theoretical sessions with 25%. Conclusions: After completing the training sessions, Uganda and Mongolia started IMRT treatments. Remote training provides an excellent and feasible e-learning platform to train radiation therapy professionals in LMICs. The training program improved the IMRT confidence levels and treatment delivery. The hands-on trainings were most preferred.

A Retrospective Analysis of the Impact of HIV Infection on Outcomes of Locally Advanced Cervical Cancers Treated With Either Conventional or Hypofractionated Radiotherapy: The Uganda Experience.

PURPOSE: We annually treat more than 800 new patients with cervical cancer, where the majority (approximately 60%) have locally advanced disease and approximately 40% of them are infected with HIV. To optimally care for this large number of patients in low-income settings is difficult. From July 2011, we started using 45.0 Gy/15# hypofractionated radiotherapy (HFRT) as a substitute to 50.0 Gy/25# conventional fractionated radiotherapy (CFRT), for the treatment of locally advanced cervical cancer (LACC). This study aims at comparing the 5-year treatment outcomes between patients with LACC, known HIV serostatus, and treated with either CFRT or HFRT. METHODS: A retrospective study was conducted according to demographic/clinical data, radiotherapy fractionations, and outcomes. Factors considered were FIGO stages IIB-IIIB, known HIV serostatus, and had completed external-beam radiotherapy and intracavitary brachytherapy. The primary end point was overall survival; the secondary end points were toxicity and compliance. RESULTS: The study included 221 patients. Squamous cell carcinomas were 95.1% and adenocarcinomas 2.3%. The median age was 45.0 (interquartile range, 38.0-52.0) years. Stages IIB, IIIA, and IIIB were 38.9%, 6.3%, and 54.8%, respectively. HIV-positive and HIV-negative were 87 (39.4%) and 134 (60.6%), respectively. Chemoradiation was administered in 100 (45.2%), and 52 (52.0%) completed chemotherapy. CFRT/HFRT were 116 (52.5%)/105 (47.5%). At 24 months, the overall response was 54.1% for HIV-negative compared with 45.0% for HIV-positive (P value .262). There was no significant differences in acute/late toxicity grades ≥ 2 for HIV-negative/positive treated with HFRT/CFRT. At 60 months, the survival probabilities were 45.7% and 27.7% for HIV-negative and HIV-positive treated with CFRT (P value = .006), whereas it was 44.2% and 30.7% for HIV-negative and HIV-positive treated with HFRT (P value = .048), respectively. CONCLUSION: For the treatment of LACC with known HIV serology, there was no significant statistical difference in terms of response, toxicity, and compliance between CFRT and HFRT. However, the difference in overall survival between HIV-negative and HIV-positive was significant.

Calculation of exit dose for conformal and dynamically-wedged fields, based on water-equivalent path length measured with an amorphous silicon electronic portal imaging device.

In this study, we use the quadratic calibration method (QCM), in which an EPID image is converted into a matrix of equivalent path lengths (EPLs) and, therefore, exit doses, so as to model doses in conformal and enhanced dynamic wedge (EDW) fields. The QCM involves acquiring series of EPID images at a reference field size for different thicknesses of homogeneous solid water blocks. From these, a set of coefficients is established that is used to compute the EPL of any other irradiated material. To determine the EPL, the irradiated area must be known in order to establish the appropriate scatter correction. A method was devised for the automatic calculation of areas from the EPID image that facilitated the calculation of EPL for any field and exit dose. For EDW fields, the fitting coefficients were modified by utilizing the linac manufacturer's golden segmented treatment tables (GSTT) methodology and MU fraction model. The nonlinear response of the EPL with lower monitor units (MUs) was investigated and slight modification of the algorithm performed to account for this. The method permits 2D dose distributions at the exit of phantom or patient to be generated by relating the EPL with an appropriate depth dose table. The results indicate that the inclusion of MU correction improved the EPL determination. The irradiated field areas can be accurately determined from EPID images to within ± 1% uncertainty. Cross-plane profiles and 2D dose distributions of EPID predicted doses were compared with those calculated with the Eclipse treatment planning system (TPS) and those measured directly with MapCHECK 2 device. Comparison of the 2D EPID dose maps to those from TPS and MapCHECK shows that more than 90% of all points passed the gamma index acceptance criteria of 3% dose difference and 3 mm distance to agreement (DTA), for both conformal and EDW study cases. We conclude that the EPID QCM is an accurate and convenient method for in vivo dosimetry and may, therefore, complement existing techniques.

A novel method for patient exit and entrance dose prediction based on water equivalent path length measured with an amorphous silicon electronic portal imaging device.

In vivo dosimetry is one of the quality assurance tools used in radiotherapy to monitor the dose delivered to the patient. Electronic portal imaging device (EPID) images for a set of solid water phantoms of varying thicknesses were acquired and the data fitted onto a quadratic equation, which relates the reduction in photon beam intensity to the attenuation coefficient and material thickness at a reference condition. The quadratic model is used to convert the measured grey scale value into water equivalent path length (EPL) at each pixel for any material imaged by the detector. For any other non-reference conditions, scatter, field size and MU variation effects on the image were corrected by relative measurements using an ionization chamber and an EPID. The 2D EPL is linked to the percentage exit dose table, for different thicknesses and field sizes, thereby converting the plane pixel values at each point into a 2D dose map. The off-axis ratio is corrected using envelope and boundary profiles generated from the treatment planning system (TPS). The method requires field size, monitor unit and source-to-surface distance (SSD) as clinical input parameters to predict the exit dose, which is then used to determine the entrance dose. The measured pixel dose maps were compared with calculated doses from TPS for both entrance and exit depth of phantom. The gamma index at 3% dose difference (DD) and 3 mm distance to agreement (DTA) resulted in an average of 97% passing for the square fields of 5, 10, 15 and 20 cm. The exit dose EPID dose distributions predicted by the algorithm were in better agreement with TPS-calculated doses than phantom entrance dose distributions.

Assessment of dosimetrical performance in 11 Varian a-Si-500 electronic portal imaging devices.

Dosimetrical characteristics of 11 Varian a-Si-500 electronic portal imaging devices (EPIDs) in clinical use for periods ranging between 10 and 86 months were investigated for consistency of performance and portal dosimetry implications. Properties studied include short-term reproducibility, signal linearity with monitor units, response to reference beam, signal uniformity across the detector panel, signal dependence on field size, dose-rate influence, memory effects and image profiles as a function of monitor units. The EPID measurements were also compared with those of the ionization chambers' to ensure stability of the linear accelerators. Depending on their clinical installation date, the EPIDs were interfaced with one of the two different acquisition control software packages, IAS2/IDU-II or IAS3/IDU-20. Both the EPID age and image acquisition system influenced the dosimetric characteristics with the newer version (IAS3 with IDU-20) giving better data reproducibility and linearity fit than the older version (IAS2 with IDU-II). The relative signal response (uniformity) after 50 MU was better than 95% of the central value and independent of detector. Sensitivity for all EPIDs reduced continuously with increasing dose rates for the newer image acquisition software. In the dose-rate range 100-600 MU min(-1), the maximum variation in sensitivity ranged between 1 and 1.8% for different EPIDs. For memory effects, the increase in the measured signal at the centre of the irradiated field for successive images was within 1.8% and 1.0% for the older and newer acquisition systems, respectively. Image profiles acquired at a lower MU in the radial plane (gun-target) had gradients in measured pixel values of up to 25% for the older system. Detectors with software/hardware versions IAS3/IDU-20 have a high degree of accuracy and are more suitable for routine quantitative IMRT dosimetrical verification.

Epidemic and endemic Kaposi's sarcoma: a comparison of outcomes and survival after radiotherapy.

We retrospectively studied the outcomes of 80 Epidemic and African-Endemic Kaposi's Sarcoma (EKS and AKS) patients treated with radiotherapy doses of 8.0 Gy. The objective response for EKS at one month was 74 and 58% for AKS while 5-year survival for EKS was 27 and 46% for AKS.