A cost-outcome analysis of adjuvant postmastectomy locoregional radiotherapy in high-risk postmenopausal breast cancer patients.
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Breast Neoplasms↗
Biomedical subjects
P Dunscombe
Publications and source records attributed to P Dunscombe.
Radiotherapy service delivery models for a dispersed patient population.
Access to health care interventions can be impeded when significant patient travel is required. In this economic evaluation we compare, from a societal perspective, three scenarios for the delivery of radiation treatment to an idealized population of 1,600 patients distributed between two urban nodes (1,200 + 400 patients each) separated by up to 500 km. As it is implicitly assumed that the clinical outcome for those patients who access the system is independent of the service delivery model, this study constitutes a cost minimization analysis from a societal perspective. The costs to the health care system are based on an activity costing model developed by us and consistent with recent Canadian studies. The costs to the patient are approximated by a formula that includes direct costs (travel and accommodation) and indirect (time) costs, with the latter based on a human capital approach. A sensitivity analysis has been performed to confirm the robustness of our conclusions both to uncertainties in the input data and to the inclusion of time costs, the estimation of which remains controversial. From a societal cost perspective only, we show that outreach radiotherapy (central comprehensive facility and satellite) is the economically superior service delivery model for separations between 30 km and 170 km. Beyond 170 km, a fully decentralized service would be warranted if the only consideration were societal economic advantage.
Community-Institutional Relations↗
A cost-outcome analysis of adjuvant postmastectomy locoregional radiotherapy in premenopausal node-positive breast cancer patients.
PURPOSE: To calculate cost-effectiveness and cost-utility ratios for adjuvant postmastectomy locoregional radiotherapy in premenopausal node-positive breast cancer patients and to place these ratios in the context of generally accepted medical expenditures. MATERIALS AND METHODS: A spreadsheet-based activity costing model using 1997 Canadian (cdn) capital, operating, and administrative costs has been used to identify, from the institutional perspective, the incremental cost of adding radiotherapy to surgery and chemotherapy for this group of patients. Outcome data were derived from two recently published clinical trials and were converted to discounted incremental life years and quality-adjusted life years gained. Recommended health economics principles were employed in the quantification of both costs and outcomes, and a sensitivity analysis was performed. Three referenced publications provide a context within which to evaluate the calculated cost-effectiveness and cost-utility ratios. RESULTS: The incremental cost of adjuvant radiotherapy for this group of patients is calculated to be approximately $7,000cdn in 1997 Canadian dollars and in the Canadian socialized health-care environment. Based on published work the discounted incremental outcome benefit is calculated to be 0.5 life years or 0.45 quality-adjusted life years at ten years. Thus, cost effectiveness and cost-utility ratios are estimated to be $14,000cdn and $15,600cdn, respectively. CONCLUSION: Within the context of generally accepted medical expenditures, adjuvant postmastectomy locoregional radiotherapy for premenopausal node-positive breast cancer patients would be regarded as a cost-effective treatment strategy.
Breast Neoplasms↗
An economic framework for evaluating a multileaf collimator.
OBJECTIVES: As health care budgets continue to face close scrutiny, any new acquisition must be evaluated for both costs and outcomes. This study was undertaken to demonstrate the application of an economic framework for the evaluation of a multileaf collimator as an example of a new technology that can have both quantifiable and nonquantifiable benefits for patients, staff, and cancer care institutions. METHODS: Using financial data from the Northeastern Ontario Regional Cancer Centre (NEORCC) and a recognized staffing model, a commercial spreadsheet, developed to economically characterize the principal radiotherapy processes has been used to determine the net incremental annual cost of a multileaf collimator (MLC). RESULTS: The incremental annual cost of purchasing an MLC is estimated at approximately $85,000 (1997 CDN $). Without increasing patient throughput, this increases the average cost of a course of radiotherapy by approximately CDN $200. Savings can be accrued by decreasing mold room activity, increasing the hourly patient capacity on each treatment machine, and decreasing sick time due to strain injuries. CONCLUSIONS: Although the clinical outcome of techniques facilitated by MLCs, such as intensity-modulated radiation therapy, are unknown at this time, an economic context within which to objectively evaluate this technology is presented. The framework presented suggests a method of quantifying outcome-justified expenditures, such as improved patient outcome and greater treatment flexibility, which, when offset against the incremental annual equipment cost, may be used to help justify the acquisition of multileaf technology.
Capital Expenditures↗
Preventative maintenance and unscheduled downtime from an economic perspective.
A spreadsheet-based model for economically characterizing the operation of a radiation treatment program has been used to perform a quantitative financial analysis of scheduled and unscheduled downtime. The incremental cost of downtime is broken down into three categories: remuneration of in-house or third party service technologists, decreased patient capacity, and local operating procedures for dealing with downtime. Different service arrangements and operating procedures are simulated to demonstrate the financial cost of treatment machine unavailability due to either preventative maintenance or unexpected breakdown. Depending on the service arrangement and operating policies for accommodating downtime, the combined cost of scheduled and unscheduled downtime (at 5%) can exceed 10% of the total cost of the radiation treatment program. It has also been demonstrated that the greatest cost component of downtime is decreased patient capacity, which can exceed $400,000 (CAN) when unscheduled downtime reaches 5%. The interpretation of this cost depends on the funding environment. Although the emphasis of this study has been the financial consequences of downtime, there are other factors which must be considered when developing policies and procedures for accommodating downtime such as effects on treatment, patient convenience and quality of life for staff. Even though the numerical results are strictly valid only within the context of the simulations performed, they do provide a broad framework within which medical physicists can make recommendations regarding service support and downtime.
Canada↗
A test tool for the visual verification of light and radiation fields using film or an electronic portal imaging device.
We describe the design and evaluation of a simple test tool which can be used in conjunction with either film or an electronic portal imaging device (EPID) to verify light and radiation fields and their congruence. The precision of the technique is better than 0.5 mm under all conditions tested. When used with film the accuracy or offset of the technique (the difference between test tool observations and a scanned conventional film) is better than 0.5 mm but, with an EPID as the image receptor, the accuracy dropped to, in one trial, 0.86 mm. The offset may be due to a systematic observer bias in determining the 50% O.D. level on the image, compounded, in the case of EPID measurements, by image acquisition and display parameters. Thus, when used with an EPID, calibration of the system will be required if absolute field dimensions are required. When used with film, the test tool method described here is of sufficient accuracy and precision to confirm the compliance of light and radiation field parameters with currently accepted quality control protocols.
Absorptiometry, Photon↗
The cost of radiotherapy as a function of facility size and hours of operation.
Against a background of constant or decreasing budgets, this study was undertaken to investigate the economic effects of changes in selected operational parameters within a radiation treatment programme. Using financial data from the Northeastern Ontario Regional Cancer Centre and a recognized staffing model, a commercial spreadsheet has been used to calculate the cost of an 18 fraction course of radiotherapy, including all the major preparatory processes such as simulation and treatment planning. Using the spreadsheet, and on the basis of explicit and reasonable assumptions, the cost of radiotherapy has been calculated as the facility size (i.e. equipment complement) and hours of operation are varied. Based on the assumptions used, the cost of radiotherapy in a facility treating less than about 1600 patients per year starts to rise. At 400 patients per year, a course costs approximately 50% more than at 1600 patients per annum. Extended hours of operation do not appear to generate significant, if any, savings when realistic assumptions about machine lifetime and overtime payments are made. Using a spreadsheet to simulate changes in a radiation treatment programme can be an important decision-making tool, as the effects of changes in operating parameters can be demonstrated.
Health Care Costs↗
The Siemens virtual wedge.
A Siemens Virtual Wedge has recently been installed and commissioned at the Northeastern Ontario Regional Cancer Centre. Measurements reported below show that 1) Virtual Wedge factors are within 1.5% of 1; 2) percentage depth doses down to 15 cm for open and virtually wedged fields are identical to within 0.7%; 3) relative cross beam profiles for 60 degrees virtual and physical wedges are very similar except at the toe end where a 5% difference in relative dose has been observed and 4) the peripheral dose from the 60 degrees Virtual Wedge is about half of that from the 60 degrees physical wedge. A clinical protocol requiring combined open and 60 degrees wedged fields has been developed and validated. This protocol, which does not impair the utility of the Virtual Wedge, facilitates the use of on-line portal imaging and significantly reduces the effort required to commission the system.
Humans↗
Intestinal metaplasia subtyping: evaluation of Gomori's aldehyde fuchsin for routine diagnostic use.
AIMS: Intestinal metaplasia (IM) has been implicated in the pathogenesis of gastro-oesophageal carcinoma, but because of its common occurrence, its specificity for use in cancer surveillance is low. IM subtypes characterized by mucin phenotype have been studied to try and improve specificity. METHODS AND RESULTS: On balance, type III IM seems the most promising for use in gastric cancer surveillance. The situation is problematic at the gastro-oesophageal junction where the normal occurrence of acidic mucins raises doubt on the value of subtyping. High iron diamine-Alcian blue combination (HID-AB) is commonly used for IM subtyping, but its potential toxicity and long staining period (up to 24 hours) precludes widespread clinical use. This study has compared the sulphomucin staining ability of Gomori's aldehyde fuchsin-Alcian blue combination (GAF-AB) against HID-AB for identifying and subtyping IM in gastric and oesophageal biopsies. CONCLUSIONS: Compared to HID-AB, a sensitivity of 85%, a specificity of 100% and a staining time of less than 30 minutes, shows this stain to be a simple and effective technique for identifying and subtyping IM in routine laboratories.
Biopsy↗
Quantitative vs. subjective portal verification using digital portal images.
PURPOSE: Off-line, computer-aided prescription (simulator) and treatment (portal) image registration using chamfer matching has been implemented on PC based viewing station. The purposes of this study were (a) to evaluate the performance of interactive anatomy and field edge extraction and subsequent registration, and (b) to compare observer's perceptions of field accuracy with measured discrepancies following anatomical registration. METHODS AND MATERIALS: Prescription-treatment image pairs for 48 different patients were examined in this study. Digital prescription images were produced with the aid of a television camera and a digital frame grabber, while the treatment images were obtained directly from an on-line portal imaging system. To facilitate perception of low contrast anatomical detail, on-line portal images were enhanced with selective adaptive histogram equalization prior to extraction of anatomical edges. Following interactive extraction of anatomical and field border information by an experienced observer, the identified anatomy was registered using chamfer matching. The degree of conformity between the prescription and treatment fields was quantified using several parameters, which included relative prescription field coverage and overcoverage, as well as the translational and rotational displacements as measured by chamfer matching applied to the boundaries of the two fields. These quantitative measures were compared with subjective evaluations made by four radiation oncologists. RESULTS: All the images in this series that included a range of the most commonly seen treatment sites were registered and the conformity parameters were found. The mean treatment/prescription field coverage and overcoverage were approximately 95 and 7%, respectively before registration. The mean translational displacement in the transverse and cranio-caudal directions were 2.9 and 3.4 mm, respectively. The mean rotational displacement was approximately 2 degrees. For all four oncologists, the portals classified as unacceptable, in terms of the field placement, exhibited significantly higher (p < 0.03) translational errors in the transverse direction. The field coverages were significantly lower (p < 0.05) and the translational errors in the cranio-caudal direction were significantly higher (p < 0.05) for the portals rated as unacceptable by two of the oncologists. CONCLUSIONS: From the parameters that were used to quantify the degree of conformity between the prescription and treatment fields, the translational error in the transverse direction correlated best with the oncologists' assessments on the field placement. Field coverage and translational error in the cranio-caudal direction correlated well with assessments of only two out of the four participating oncologists. This can be explained by the fact that for the majority of treatment sites included in the study the positioning of field borders was more critical for the transverse direction. A conclusion for the design of future quantitative and automated on-line portal verification systems is that they will have to model different perceived significances of different types of localization errors intrinsic to oncologist evaluation of portal images.
Algorithms↗
Anthropomorphic phantom measurements for the validation of a treatment planning system.
A series of eight irradiations of an anthropomorphic phantom has been performed as part of a programme of treatment planning system (TPS) validation. The "treatment' configurations used represent a realistic cross section of those carried out routinely in a radiotherapy centre. The dose distributions within the phantom were determined using 75 LiF TLD chips per irradiation and the measured dose distributions were compared with calculations performed on a TPS for three ranges of dose gradient. The accuracy of the technique per measurement point is estimated to be 3% in dose (low dose gradient) and 3 mm in position (high dose gradient). The measurement and data analysis techniques used permit evaluation of a TPS against recently recommended criteria of acceptability although it is noted that is is not possible to isolate TPS performance from factors depending on, for example, open beam data fitting and treatment set up accuracy.
Anthropometry↗
Segmented chamfer matching for the registration of field borders in radiotherapy images.
Optimum conformity between treated and prescribed radiotherapy fields is likely to be achieved when the full versatility of modern therapy equipment is reflected in the field registration method. To allow for independent jaws and custom shielding, chamfer matching has been used to register selected segments of field borders independently. In a study involving 50 clinical prescription-treatment field pairs it is shown that segmented chamfer matching is superior not only to conventional unsegmented chamfer matching but also to several other methods. An example of the clinical value of segmented chamfer matching applied to electronic portal images is given.
Algorithms↗
Radiotherapy portal verification: an observer study.
In many radiotherapy facilities radiotherapy portal verification is currently a subjective process based on the visual comparison of a treatment or portal image with a prescription or simulation image. The reliability of this process is unknown. We describe here a study in which 16 observers (oncologists, physicists and therapists) independently evaluated the geometric accuracy of 530 treatment fields on 45 patients. The treatment images were acquired by the BEAMVIEW on-line portal imaging system (Siemens Medical Laboratories, Concord, CA, USA). Illustrative examples of the large variation in observers' assessments of the same field are given. The kappa statistic is used to evaluate the degree of agreement between observers and between on-line (at the treatment unit) and off-line (in a quiet viewing room) assessments. The best interobserver agreement was between the four oncologists contributing to the study although this level of agreement was rated only as "fair". Comparison of on-line and off-line decisions made by therapists exhibited "poor" agreement. This study has provided statistical confirmation of the suspicions of many workers in the field of radiotherapy portal verification, viz that the subjective evaluation of field accuracy is unreliable. However, the degree of unreliability is surprisingly large. The inconsistencies between observers documented in this study need to be clearly acknowledged in the development of protocols for the clinical use of on-line portal imaging systems. Acceptable reliability in radiotherapy portal verification will only be achieved when subjective decision making is eliminated.
Humans↗
Technical note: an aid to radiation therapy simulation.
We have mounted a transmission liquid crystal display unit on the head of a radiotherapy simulator and projected, using the field light, a digitized fluoroscopic image with treatment prescription overlay. It is suggested that this approach (i) can aid visualization on the patient of complex field borders including those defined by multileaf collimators; (ii) could play a role in computed tomography or magnetic resonance based treatment planning and (iii) contributes to configuring non-coplanar beams.
Computer Simulation↗
Sizes and sources of field placement error in routine irradiation for prostate cancer.
Discrepancies between prescribed and treated field edges have been measured from 76 film pairs taken on 29 patients being treated for prostate cancer. The distribution of field edge discrepancies is described by a standard deviation of 4.5 mm and has an average absolute value of 3.5 mm. The observed discrepancies are shown to be attributable to field position errors and hence, in principle, are easily rectifiable.
Carcinoma↗
An efficient approach to routine TL dosimetry.
A new labour-saving protocol for clinical dosimetric measurements based on the thermoluminescence (TL) of lithium fluoride is presented. The accuracy of dose measurements resulting from the application of this protocol is examined with particular emphasis on the linearity, reproducibility, and fading of TL response. It is shown that the technique described here is capable of yielding an accuracy of +/- 5% at the 95% confidence level for doses in excess of 1cGy. This study establishes that adoption of the protocol can result in significant savings in labour whilst maintaining a level of accuracy that is adequate for clinical dosimetry.
Reproducibility of Results↗
Portal radiography practice in Canada.
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Canada↗
A simplified method for measuring cerebral blood flow with xenon-enhanced computed tomography.
The measurement of cerebral blood flow using the xenon-enhanced computed tomography (XECT) technique requires that the build-up of xenon in both brain tissue and end-tidal expired air be determined as a function of time. Monitoring of the former is carried out using CT scanning and the latter, most often, using a thermoconductivity analyser or mass spectrometer. This paper examines the possibility of greatly simplifying the XECT technique by eliminating the need for either thermoconductivity analyser or mass spectrometer. In the proposed approach, the patient's expired air is channelled through the scan field using a flexible plastic tube and sampled by the CT scanner in conjunction with the build-up of xenon in brain tissue. Phantom measurements have demonstrated the ability of the CT scanner to detect variations in the xenon concentration in expired air while computer simulations have shown that errors arising as a result of the proposed methodology are small compared to other inherent sources in the XECT technique.
Brain↗