Dabrafenib and Trametinib Therapy for Advanced Anaplastic Thyroid Cancer - Real-World Outcomes From UK Centres

AIMS

Anaplastic thyroid cancer (ATC) is a rare but aggressive form of thyroid cancer with a median survival of 4 months. Recent advances in molecular profiling have shown that up to half of ATCs harbour the BRAF-V600E mutation. The aim of this study was to provide real-world data and experience on the use of combination therapy dabrafenib and trametinib in patients with BRAF-V600E-mutated advanced ATC.

MATERIALS AND METHODS

We retrospectively evaluated patients with confirmed BRAF-V600E-mutated ATC, defined as patients with locally advanced or metastatic ATC with no locoregional, radical treatment options. Outcomes measured were overall survival, progression-free survival, response rate, discontinuation rate, dose reduction rate and toxicity data.

RESULTS

Seventeen patients were evaluated and the mean age was 68 years. Ten patients died by the time of censoring. The median duration of follow-up was 12 months (3-43 months). The estimated median overall survival was 6.9 months (95% confidence interval 2.46 months - upper confidence interval not reached) and the median progression-free survival was 4.7 months (95% confidence interval 1.4-7.8 months). Dose interruptions and/or reductions were common, but none of the patients had to permanently discontinue treatment because of toxicities. Severe toxicities (grades 3 and 4) were uncommon.

CONCLUSIONS

This study supports the indication of dabrafenib and trametinib in BRAF-V600E-mutated ATC as an effective and well-tolerated treatment in an historically difficult to treat cancer.

Quality assurance of radiotherapy in the ongoing EORTC 1420 "Best of" trial for early stage oropharyngeal, supraglottic and hypopharyngeal carcinoma: results of the benchmark case procedure

INTRODUCTION

The current phase III EORTC 1420 Best-of trial (NCT02984410) compares the swallowing function after transoral surgery versus intensity modulated radiotherapy (RT) in patients with early-stage carcinoma of the oropharynx, supraglottis and hypopharynx. We report the analysis of the Benchmark Case (BC) procedures before patient recruitment with special attention to dysphagia/aspiration related structures (DARS).

MATERIALS AND METHODS

Submitted RT volumes and plans from participating centers were analyzed and compared against the gold-standard expert delineations and dose distributions. Descriptive analysis of protocol deviations was conducted. Mean Sorensen-Dice similarity index (mDSI) and Hausdorff distance (mHD) were applied to evaluate the inter-observer variability (IOV).

RESULTS

65% (23/35) of the institutions needed more than one submission to achieve Quality assurance (RTQA) clearance. OAR volume delineations were the cause for rejection in 53% (40/76) of cases. IOV could be improved in 5 out of 12 OARs by more than 10 mm after resubmission (mHD). Despite this, final IOV for critical OARs in delineation remained significant among DARS by choosing an aleatory threshold of 0.7 (mDSI) and 15 mm (mHD).

CONCLUSIONS

This is to our knowledge the largest BC analysis among Head and neck RTQA programs performed in the framework of a prospective trial. Benchmarking identified non-common OARs and target delineations errors as the main source of deviations and IOV could be reduced in a significant number of cases after this process. Due to the substantial resources involved with benchmarking, future benchmark analyses should assess fully the impact on patients' clinical outcome.

Outpatient clinic numbers: a review of standards and current practice

This article explores current recommendations for the safe and efficient running of outpatient clinics, why non-adherence exists, the consequences of non-adherence, and what can be done to improve standards. It promotes adherence to recommendations by both clinical and managerial staff.

Impact of Immunoglobulin Therapy in Intestinal Transplant Recipients With Posttransplantation Hypogammaglobulinemia

BACKGROUND

Severe hypogammaglobulinemia (HGG) (IgG <400 mg/dL) following intestinal transplantation is common. Although IgG replacement therapy is commonly used, clinical outcomes associated with increasing IgG levels to >400 mg/dL are not well described.

METHODS

Kaplan-Meier analysis was performed to estimate survival, the log-rank test to compare survival distributions between groups, and the Fisher exact test to determine the association between HGG and rejection.

RESULTS

A total of 23 intestinal transplant (IT) recipients with a median age of 2.3 years (range, 0.7-41 years) at the time of HGG diagnosis were included. The types of transplants were liver-small bowel (73.9%), liver-small bowel-kidney (8.7%), and small bowel only (17.4%). The 3-year survival after the diagnosis of HGG was 50.2% (95% confidence interval [CI] = 28.2%-68.7%). There was no difference in survival (P = .67) when patients were dichotomized based upon IgG level at last follow-up (IgG ≥400 mg/dL, n = 14; and IgG <400 mg/dL, n = 9). There was no also evidence of an association between survival and: total dose (P = .58), frequency (P = .11), and number of IgG doses administered (P = .8). There was no difference in survival between patients receiving (n = 12) or not receiving (n = 11) cytomegalovirus hyperimmunoglobulin (P = .10).

CONCLUSIONS

Improved survival rates were not found in our IT recipients with severe HGG with immunoglobulin therapy to IgG levels of ≥400 mg/dL, even when cytomegalovirus hyperimmunoglobulin was administered.

A single-dose, randomized, double-blind, placebo-controlled trial of sublingual asenapine for acute agitation

OBJECTIVE

To assess sublingual asenapine for acute agitation.

METHOD

Agitated adults 18-65 years (any diagnosis) presenting for treatment in an emergency department and found to have a score of ≥14 on the Positive and Negative Syndrome Scale-Excited Component (PANSS-EC) were randomized to receive either a single dose of a sublingual 10 mg tablet of asenapine or placebo. Primary outcome measure was change in the PANSS-EC score from baseline to 2 h after medication or placebo administration. Secondary outcomes included the percentage of responders with a ≥ 40% reduction from baseline on the PANSS-EC score at 2 h.

RESULTS

A total of 120 subjects were randomized, 60 each to sublingual asenapine or placebo. Mean (SE) baseline PANSS-EC scores for the asenapine-treated and placebo-treated subjects were 19.4 ± 0.66 and 20.1 ± 0.61, respectively. Mean PANSS-EC scores at endpoint (LOCF) was 7.4 ± 0.65 for the asenapine-treated subjects and 14.7 ± 0.98 for the placebo-treated subjects. Change in PANSS-EC score at 2 h was statistically significantly greater for the asenapine-treated subjects compared with the placebo-treated subjects. NNT for response vs. placebo was 3 (95% CI 2-4).

CONCLUSION

Sublingual asenapine was efficacious in the treatment of agitation with an effect size comparable to that observed in prior studies of intramuscular antipsychotics.

SU-E-T-210: Surviving a Visit by the Radiological Physics Center

PURPOSE

To demonstrate an objective approach to determining if a negative report from the Radiological Physics Center (RPC) of greater than 10% error is valid or has clinical significance.

METHODS

The discrepancy involved the clinical activity (mgRaEq) of Cs-137 sources, some manufactured by 3M and some by Amersham. Measurements were made in the proprietary RPC Well Counter calibrated by the MD Anderson ADCL and our Well Counter (CNMC, Model 44D) calibrated by the same laboratory as well as the University of Wisconsin ADCL. In addition, we possess an Amersham Cs-137 Check Source that had been calibrated by the UW-ADCL in 2002. All clinical sources were checked in both Well Counters on the first visit. One clinical source and the Check Source were measured in a second visit that occurred 51 days later.

RESULTS

On the initial RPC visit, 9 of 25 sources had a minimum of an 8% discrepancy between the RPC and the Institution, with a maximum of 11%. Contributing errors included using the incorrect straw position by us, an unexplained 2.3% error in the RPC data identified 73 days post-visit, a 2% variation in Chamber Factors for our Well Counter from the two ADCL's. When we use the 2004 value of Air Kerma Strength for the Check Source to determine a Calibration Factor of the Well Counter, all sources were within 0.5% of their decayed value established in 2002.

CONCLUSIONS

This work emphasizes the value of having simple Constancy Check systems in a Quality Assurance program as 'Accuracy' has error bars. The disagreement in calibration data between the ADCL Laboratories, which was at the 2% maximum quoted in their Calibration Reports, is a reminder that there is uncertainty in measurements. Constancy Checks allow one to sort out discrepancies and to answer challenges to the validity of your program.

Incidence, risk factors, and outcomes associated with cytomegalovirus disease in small bowel transplant recipients

Despite improved prophylaxis, monitoring, and more efficient immunosuppression, CMV infection remains a common opportunistic infection in transplant recipients. We assessed the incidence of CMV disease in pediatric SBT recipients, the timing of CMV disease after transplantation, and its impact on patient outcome. The medical records of 98 SBT recipients were reviewed. We performed descriptive analysis, regression analysis, and Kaplan-Meier curves to determine the time-to-event after transplantation. Fifty-three percent patients were male and 47% female, with a mean age of 38.3 months. Thirty-five percent of patients received prophylactic VGC, 55% GCV, 10% a combination of GCV/VGC, and 99% CMV immunoglobulins. A total of 24.5% recipients were CMV D+/R- (CMV serostatus donor positive/recipient negative). Seven (c. 7%) patients developed CMV disease. CMV disease was associated with 2.5 times (0.52-12.1; p = 0.25) higher rate of CMV mismatch and 11.1 times (1.3-95.9; p = 0.03) higher risk of death. CMV prophylaxis increased time-to-death (p = 0.074). Time-to-CMV disease was shorter in patients with enteritis (p < 0.0001), and CMV disease was associated with shorter time-to-death after transplantation (p = 0.001). CMV disease in SBT recipients was associated with an 11-fold mortality increase and a fourfold faster time-to-death. Time-to-death was significantly shorter with CMV enteritis.

The strain-specific dynamics of Escherichia coli O157:H7 faecal shedding in cattle post inoculation

This study reports analysis of faecal shedding dynamics in cattle for three Escherichia coli O157:H7 (ECO157) strains (S1, S2 and S3) of different genotype and ecological history, using experimental inoculation data. The three strains were compared for their shedding frequency and level of ECO157 in faeces. A multistate Markov chain model was used to compare shedding patterns of S1 and S2. Strains S1 and S2 were detected seven to eight times more often and at 10(4) larger levels than strain S3. Strains S1 and S2 had similar frequencies and levels of shedding. However, the total time spent in the shedding state during colonization was on average four times longer for S1 (15 days) compared to S2 (4 days). These results indicate that an ECO157 strain effect on the frequency, level, pattern and the duration of faecal shedding may need to be considered in control of ECO157 in the cattle reservoir.

Staphylococcus aureus infections after liver transplantation

BACKGROUND

More data on the risk factors and outcomes after Staphylococcus aureus infections in liver transplantation are needed.

METHODS

Liver recipients with S. aureus infections (cases) were retrospectively identified and compared to gender-, age-, and transplant type-matched (1:2) non-S. aureus-infected controls. Risk factors associated with S. aureus infections were identified by conditional logistic regression analysis.

RESULTS

We evaluated 51 patients (median age 52 years). First S. aureus infections developed at a median time of 29 days after transplantation, with 52.94% of them in the first month; 88.24% were nosocomial, 41.18% were polymicrobial, and 47.06% were caused by methicillin-resistant S. aureus (MRSA). Surgical site infections represented 58.82% and bacteremia 23.53%. By univariate analysis, patients with S. aureus infections were intubated more frequently (odds ratio [OR] 26.92, 95% confidence interval [CI] 3.23-3,504.15, p = 0.0006), had a central line (OR 11.69, 95% CI 1.42-95.9, p = 0.02), or recent surgery (OR 26.92, 95% CI 3.23-3,504.15, p = 0.0006) compared with controls. By multivariate analysis, subjects who underwent surgery within 2 weeks prior to infection had a 26.9 times higher risk of developing S. aureus infection (95% CI 3.23-3,504.15, p = 0.0006); these results were adjusted for matched criteria. S. aureus infections did not affect graft or patient survival, but the study was not powered for such outcomes.

CONCLUSION

Only recent surgical procedure was found to be a significant independent risk factor for S. aureus infections after liver transplantation.

Safety and efficacy of repeat transradial access for cardiac catheterization procedures

To determine the safety and efficacy of repeat transradial cardiac catheterization, 1,362 consecutive transradial procedures were examined. Repeat transradial procedures were identified (group I, n = 73) and compared with index procedures (group II, n = 1,289). Baseline patient characteristics, procedure success rates (100% vs. 97.9%; P = NS), complication rates (0% vs. 0.08%; P = NS), and procedure times (23.9 +/- 27.3 min vs. 18.2 +/- 14.7 min; P = NS) were similar between groups. This study suggests that repeat transradial catheterization procedures can be performed safely and successfully in appropriately selected patients.

The F-actin side binding activity of the Arp2/3 complex is essential for actin nucleation and lamellipod extension

Most eukaryotic cells rely on localized actin polymerization to generate and sustain the protrusion activity necessary for cell movement [1, 2]. Such protrusions are often in the form of a flat lamellipod with a leading edge composed of a dense network of actin filaments [3, 4]. The Arp2/3 complex localizes within that network in vivo [3, 4] and nucleates actin polymerization and generates a branched network of actin filaments in vitro [5-7]. The complex has thus been proposed to generate the actin network at the leading edge of crawling cells in vivo [3, 4, 8]. However, the relative contributions of nucleation and branching to protrusive force are still unknown. We prepared antibodies to the p34 subunit of the Arp2/3 complex that selectively inhibit side binding of the complex to F-actin. We demonstrate that side binding is required for efficient nucleation and branching by the Arp2/3 complex in vitro. However, microinjection of these antibodies into cells specifically inhibits lamellipod extension without affecting the EGF-stimulated appearance of free barbed ends in situ. These results indicate that while the side binding activity of the Arp2/3 complex is required for nucleation in vitro and for protrusive force in vivo, it is not required for EGF-stimulated increases in free barbed ends in vivo. This suggests that the branching activity of the Arp2/3 complex is essential for lamellipod extension, while the generation of nucleation sites for actin polymerization is not sufficient.

Intensity modulated conformal therapy for intracranial lesions

The Peacock planning and delivery system was used to create treatment plans and deliver these plans to patients. The system involves an arc therapy delivery of small (2 cm long) slices of radiation combined with indexing of the couch to achieve target coverage. Two clinical examples are shown to demonstrate the system's capability and evaluate the resources required to produce and deliver the plans. One plan is an optic sheath meningioma and the other is a craniopharyngioma that surrounded the optic chiasm. The optic sheath meningioma was treated to 50 Gy in 25 fractions. The treatment involved delivery of two arcs. The total time to set up the patient and deliver the treatment was less than 15 min. Planning and plan validation after computed tomography required approximately 3 days. The patient had 100% restoration of her field of vision and is stable 3 years post therapy. The second patient is a 9-year-old who had a craniopharyngioma which surrounded the optic chiasm. The tumor was treated to 50.4 Gy in 28 fractions and the dose to the optic chiasm was limited to 45 Gy. The treatment required three arcs and total treatment time was less than 20 min. The patient is stable 15 months post therapy. The system is able to create and deliver radiation patterns that are unique. These plans can be created and delivered in times that rival conventional forward planning conformal radiotherapy systems that cannot produce or conveniently deliver such plans.

Transradial cardiac catheterization in elderly patients

The safety and efficacy of transradial cardiac catheterization in elderly patients is unknown. This study examines procedure success rates for transradial catheterization in appropriately selected patients < 70 (n = 195) and >/= 70 (n = 83) years old. Elderly patients were less likely to be selected for the transradial approach (46% vs. 61%; P = 0.05). Although patients >/= 70 years old were more often female (39.7% vs. 24.1%; P = 0.008) and had a smaller body surface area (1.89 +/- 0.18 vs. 2.01 +/- 0.24 m2; P = 0. 001), procedure success rates did not differ (95.1% vs. 94.8%; P = NS). Procedure-related variables including procedure time (15.4 +/- 12.6 vs. 16.1 +/- 11.6 min; P = NS), amount of radiographic contrast (90.1 +/- 31.9 vs. 86.4 +/- 29.8 cc; P = NS), and number of catheters used (1.5 +/- 0.9 vs. 1.5 +/- 0.7; P = NS) were similar between groups. We conclude that transradial catheterization can be safely and effectively performed in selected elderly patients. Cathet. Cardiovasc. Intervent. 51:287-290, 2000.

A prospective study of psychological predictors of lumbar surgery outcome

STUDY DESIGN

Prospective design in which 102 patients were evaluated with a battery of psychological assessment tests 1-2 weeks before surgery, and outcome was assessed 6 months and 1 year after surgery.

OBJECTIVES

The study examined whether three aspects of psychological distress (depression, anxiety, and hostility) predict several surgical outcomes (employment status, subjective pain change ratings, and changes in functional abilities).

SUMMARY OF BACKGROUND DATA

Surgery for back pain has been shown to yield poor results in 15-45% of patients. Tools are needed to identify those "at risk" for poor outcome. Aspects of emotional distress, including anxiety, depression, and hostility, have been found to be relevant to various illness outcomes (e.g., cancer, heart disease), but their influence has not been prospectively evaluated for back pain surgical outcome.

METHODS

Study patients completed measures of distress before surgery, including the Spielberger Trait Anxiety Inventory, Zung Depression Scale, Modified Somatic Perception Questionnaire, and Cook-Medley Hostility Scale. At 1-year follow-up, patients completed pain change ratings, functional abilities measure (Dallas Pain Questionnaire), and questions about employment status.

RESULTS

Multivariate regression analyses, controlling for significant demographic variables, found that failure to return to work was predicted by presurgical anxiety (P < 0.001) and depression (P < 0. 01); failure to report improvement in pain was predicted by presurgical somatic anxiety (P < 0.01) and depression (P < 0.058); and failure to report improved functional abilities was predicted by presurgical somatic anxiety (P < 0.01) and depression (P < 0.05). Hostility did not predict any outcome. Regression analyses found a strong predictor to be a combination of the Zung Depression Scale and Modified Somatic Perception Questionnaire, known as the Distress and Risk Assessment Method (DRAM).

CONCLUSIONS

These results indicate that screening for presurgical distress is likely to identify those patients at risk for poor outcome. Studies to evaluate whether presurgical psychological treatment improves outcome are warranted.

Applying the equivalent uniform dose formulation based on the linear-quadratic model to inhomogeneous tumor dose distributions: Caution for analyzing and reporting

We apply the concept of equivalent uniform dose (EUD) to our data set of model distributions and intensity modulated radiotherapy (IMRT) treatment plans as a method for analyzing large dose inhomogeneities within the tumor volume. For large dose nonuniformities, we find that the linerar-quadratic based EUD model is sensitive to the linear-quadratic model parameters, alpha and beta, making it necessary to consider EUD as a function of these parameters. This complicates the analysis for inhomogeneous dose distributions. EUD provides a biological estimate that requires interpretation and cannot be used as a single parameter for judging an inhomogeneous plan. We present heuristic examples to demonstrate the dose volume effect associated with EUD and the correlation to statistical parameters used for describing dose distributions. From these examples and patient plans, we discuss the risk of incorrectly applying EUD to IMRT patient plans.

A clinical evaluation of setup errors for a prostate immobilization system

A prostate treatment immobilization system was evaluated with respect to setup errors and efficiency for a specific treatment setup. Prostate patients were treated in the prone position with a rectal catheter using the NOMOS intensity modulated radiotherapy system. Immobilization and setup consisted of a Vac-Loktrade mark bag (MED-TEC, Orange City, IO) fitted within a registration carrier box where patients were aligned to the bag using skin marks along the lower leg. Daily setup errors were analyzed using lateral portal films, registration plates mounted to the carrier box, and the pubic symphasis as a bony reference. Two studies were conducted to evaluate setup technique. In the first study, patient setup required 3-5 minutes for patient positioning and the corresponding superior/inferior errors were found to have a standard deviation of 3.5 mm. In the second study, the technique standards were reduced to allow for faster setup times and, consequently, larger errors; setup times were 1-2 minutes and the mean and standard deviation errors were approximately 2 and 5 mm, respectively.

Transradial cardiac catheterization in patients with prior brachial artery cutdown

The safety and efficacy of transradial cardiac catheterization in patients with prior ipsilateral brachial cutdown is not known. Using standard techniques we performed transradial catheterization in 278 consecutive patients, of which 63 had prior brachial cutdown. All patients had a strongly palpable radial pulse and a negative Allen's test. Although patients with prior cutdown were older and had a higher incidence of hypertension and prior coronary artery bypass surgery, there was no significant difference in success rates for transradial catheterization (93.6% vs. 95.3%; P = NS). There were no periprocedural complications. Brachial artery occlusion was responsible for only two unsuccessful catheterization attempts. We conclude that, with careful preprocedural screening, ipsilateral transradial cardiac catheterization can be successfully performed in a majority of patients with prior brachial cutdown.

Intensity-modulated radiotherapy: first results with this new technology on neoplasms of the head and neck

Intensity-modulated beam radiotherapy (IMRT) delivers a highly conformal, three-dimensional (3-D) distribution of radiation doses that is not possible with conventional methods. When administered to patients with head and neck tumors, IMRT allows for the treatment of multiple targets with different doses, while simultaneously minimizing radiation to uninvolved critical structures such as the parotid glands, optic chiasm, and mandible. With 3-D computerized dose optimization, IMRT is a vast improvement over the customary trial-and-error method of treatment planning. We retrospectively reviewed the charts of the first 28 head and neck patients at our institution who were treated with IMRT. All had head and neck neoplasms, including squamous cell carcinoma, adenoid cystic carcinoma, paraganglioma, and angiofibroma. Total radiation doses ranged from 1,400 to 7,100 cGy, and daily doses ranged from 150 to 400 cGy/day. A quality assurance system ensured that computer-generated dosimetry matched film dosimetry in all cases. For midline tumors, this system allowed us to decrease the dose to the parotid glands to less than 3,000 cGy. The incidence of acute toxicity was drastically lower than that seen with conventional radiotherapy delivery to similar sites. This is the first report of the application of IMRT strictly to head and neck neoplasms. We discuss the indications, technique, and initial results of this promising new technology. We also introduce the concept of the Simultaneous Modulated Accelerated Radiation Therapy boost technique, which has several advantages over other altered fractionation schemes.

Clinical and financial issues for intensity-modulated radiation therapy delivery

Intensity-modulated radiation therapy (IMRT) is a term applied to a new technology that uses nonuniform radiation beams to achieve conformal dose distributions. This article reviews the use of a commercial system, the Peacock system, which uses a special multileaf collimator (MIMiC) to deliver the dose distribution using arc therapy and segmented fields, similar to a moving strip. Although initially designed for stereotactic radiosurgery, this system has been employed to treat various body sites. More than 300 patients have been treated at our institution in the past 4 years, mainly for cranial, head-and-neck, and prostate tumors. Presently, we treat 40 to 45 patients per day with this technology using two linear accelerators operating with 10 MV and 15 MV x-rays, as Peacock has become a standard therapy procedure. Cases are presented that show the unique ability of IMRT to deliver conformal dose distributions. Why this type of technology can become a standard procedure and why it is cost-effective therapy for both the institution and the patient are discussed.

Family environment, glycemic control, and the psychosocial adaptation of adults with diabetes

OBJECTIVE

To evaluate whether the family system variables of adults with diabetes relate to the adequacy of metabolic control or the psychosocial adaptation to the illness.

RESEARCH DESIGN AND METHODS

A total of 150 insulin-requiring adults were assessed on a single occasion. They completed two family system measures (the Family Environment Scale [FES] and the Diabetes Family Behavior Checklist [DFBC]), two quality-of-life measures (the Diabetes Quality of Life Scale and the Medical Outcomes Study Health Survey-36), and one measure of cognitive appraisal (the Appraisal of Diabetes Scale). Glycemic control was assessed using HbA1c results. Demographic data (age, sex, diabetes type, duration of diabetes, and number of diabetes-related medical complications) were gathered from the patients' charts.

RESULTS

Concerning glycemic control, none of the family system measures were significant predictors of HbA1c. Older age and longer duration of diabetes predicted higher HbA1c values. For psychosocial adaptation, when family members behaved in ways that supported the diabetes care regimen (measured by the DFBC), the individual with diabetes was more satisfied with his or her adaptation to the illness and reported less interference in role function due to emotional problems. Family cohesion (measured by the FES) also related to better physical function. Women reported higher levels of diabetes satisfaction. The Appraisal of Diabetes Scale predicted glycemic control and psychosocial adaptation.

CONCLUSIONS

For insulin-treated adults with diabetes, family system variables do not relate to glycemic control, but they do relate to psychosocial adaptation. Future work should explore the impact of family-centered interventions on adaptation, sex differences in adaptation, and the use of the Appraisal of Diabetes Scale as a first-line clinical screening tool.

Modulated beam conformal therapy for head and neck tumors

PURPOSE

The goal of modulated-beam conformal therapy is to reduce the dose to healthy tissue and sensitive structures around a uniformly irradiated target volume. Multiple intensity-modulated fields offer improved tissue-sparing dose distributions. New computer-based systems for planning and delivering such treatments may soon be available from different commercial sources that will make the formulation of an intensity-modulated treatment plan and its execution widely available at any treatment facility that has the resources to acquire the necessary equipment. This work reports on a study of the integration of two such systems.

METHODS AND MATERIALS

Treatment planning was done using a commercially available inverse planning algorithm based on simulated annealing. The plans arbitrarily assumed nine coplanar x-ray beams at nonopposed gantry angles. Intensity modulation was computed for each beam. The modulated field at each gantry angle was broken down into a series of uniform (nonmodulated) subfields, which could be delivered as a sequence to produce the desired dose distribution. Because a large number of subfields was delivered, a multileaf collimator (MLC) was used for field shaping. This allowed rapid and accurate field shaping for treatments made up of several hundred subfields. Computer control of the MLC and linear accelerator allowed delivery of doses less than .01 Gy per subfield. Treatment was delivered on a prototype, computer-controlled accelerator and MLC system. Resulting dose distributions were analyzed using film and an anatomically specific, homogeneous phantom.

RESULTS

The treatment plans were evaluated using dose-volume histogram analysis. The plans provided acceptably uniform irradiation of the target volume without exceeding dose tolerances for nearby critical structures. The plans were successfully delivered by a prototype dynamic MLC. The time needed to deliver a sequence of subfields at one gantry angle ranged from 0.7 to 2.0 min. Isodoses from film agreed reasonably well with planned isodose distributions.

CONCLUSIONS

It is feasible to plan and deliver fixed gantry, modulated-beam conformal therapy for head and neck tumors with systems being developed commercially. The planned dose distributions exhibit significant potential for sparing closely spaced normal tissue structures in the head and neck.