Aligning tumor mutational burden (TMB) quantification across diagnostic platforms: phase II of the Friends of Cancer Research TMB Harmonization Project.

BACKGROUND: Tumor mutational burden (TMB) measurements aid in identifying patients who are likely to benefit from immunotherapy; however, there is empirical variability across panel assays and factors contributing to this variability have not been comprehensively investigated. Identifying sources of variability can help facilitate comparability across different panel assays, which may aid in broader adoption of panel assays and development of clinical applications. MATERIALS AND METHODS: Twenty-nine tumor samples and 10 human-derived cell lines were processed and distributed to 16 laboratories; each used their own bioinformatics pipelines to calculate TMB and compare to whole exome results. Additionally, theoretical positive percent agreement (PPA) and negative percent agreement (NPA) of TMB were estimated. The impact of filtering pathogenic and germline variants on TMB estimates was assessed. Calibration curves specific to each panel assay were developed to facilitate translation of panel TMB values to whole exome sequencing (WES) TMB values. RESULTS: Panel sizes >667 Kb are necessary to maintain adequate PPA and NPA for calling TMB high versus TMB low across the range of cut-offs used in practice. Failure to filter out pathogenic variants when estimating panel TMB resulted in overestimating TMB relative to WES for all assays. Filtering out potential germline variants at >0% population minor allele frequency resulted in the strongest correlation to WES TMB. Application of a calibration approach derived from The Cancer Genome Atlas data, tailored to each panel assay, reduced the spread of panel TMB values around the WES TMB as reflected in lower root mean squared error (RMSE) for 26/29 (90%) of the clinical samples. CONCLUSIONS: Estimation of TMB varies across different panels, with panel size, gene content, and bioinformatics pipelines contributing to empirical variability. Statistical calibration can achieve more consistent results across panels and allows for comparison of TMB values across various panel assays. To promote reproducibility and comparability across assays, a software tool was developed and made publicly available.

The roles of HOXD10 in the development and progression of head and neck squamous cell carcinoma (HNSCC).

BACKGROUND: HOX gene expression is altered in many cancers; previous microarray revealed changes in HOX gene expression in head and neck squamous cell carcinoma (HNSCC), particularly HOXD10. METHODS: HOXD10 expression was assessed by qPCR and immunoblotting in vitro and by immunohistochemistry (IHC) in tissues. Low-expressing cells were stably transfected with HOXD10 and the phenotype assessed with MTS, migration and adhesion assays and compared with the effects of siRNA knockdown in high-HOXD10-expressing cells. Novel HOXD10 targets were identified using expression microarrays, confirmed by reporter assay, and validated in tissues using IHC. RESULTS: HOXD10 expression was low in NOKs, high in most primary tumour cells, and low in lymph node metastasis cells, a pattern confirmed using IHC in tissues. Overexpression of HOXD10 decreased cell invasion but increased proliferation, adhesion and migration, with knockdown causing reciprocal effects. There was no consistent effect on apoptosis. Microarray analysis identified several putative HOXD10-responsive genes, including angiomotin (AMOT-p80) and miR-146a. These were confirmed as HOXD10 targets by reporter assay. Manipulation of AMOT-p80 expression resulted in phenotypic changes similar to those on manipulation of HOXD10 expression. CONCLUSIONS: HOXD10 expression varies by stage of disease and produces differential effects: high expression giving cancer cells a proliferative and migratory advantage, and low expression may support invasion/metastasis, in part, by modulating AMOT-p80 levels.

Genetic influence on the kinetics and associated pathology of the early stage (intestinal-hepatic) migration of Ascaris suum in mice.

The generative mechanism(s) of aggregation and predisposition to Ascaris lumbricoides and A. suum infections in their host population are currently unknown and difficult to elucidate in humans and pigs for ethical/logistical reasons. A recently developed, optimized murine model based on 2 inbred strains, putatively susceptible (C57BL/6j) and resistant (CBA/Ca) to infection, was exploited to elucidate further the basis of the contrasting parasite burdens, most evident at the pulmonary stage. We explored the kinetics of early infection, focusing on the composite lobes of the liver and lung, over the first 8 days in an effort to achieve a more detailed understanding of the larval dispersal over time and the point at which worm burdens diverge. Larval recoveries showed a heterogenous distribution among the lobes of the lungs, being higher in the right lung of both strains, and in the susceptible strain larvae accumulating preferentially in 2 (caudal and middle) of the 4 lobes. Total larval burdens in these 2 lobes were largely responsible for the higher worm burdens in the susceptible strain. While total lung larval recoveries significantly differed between mouse strains, a difference in liver larval burdens was not observed. However, an earlier intense inflammatory response coupled with more rapid tissue repair in the hepatic lobes was observed in CBA/Ca mice, in contrast to C57BL/6j mice, and it is possible that these processes are responsible for restricting onward pulmonary larval migration in the resistant genotype.

Dose-dependent impact of larval Ascaris suum on host body weight in the mouse model.

Ascaris lumbricoides and Ascaris suum are important helminth parasites of humans and pigs, respectively. Although it is now well established that the presence of mature adult worms in the host intestine contributes to significant nutritional morbidity, the impact of larval migratory ascariasis is far less well understood. The development of a mouse model to explore susceptibility and resistance to larval ascariasis in the lungs provided an opportunity to observe the impact of larval migration on host growth during the course of infection. Changes in body weight were monitored in two strains of inbred mice, the susceptible C57BL/6j and the resistant CBA/Ca. Groups of mice received one of four doses: 100, 500, 1000 and 3000 fully embryonated A. suum ova. Infected mice underwent post-mortem on days 6, 7 and 8 post-infection. Control mice received a placebo dose of intubation medium and underwent post-mortem on day 7 post-infection. Mice were weighed pre-infection (day 0) and post-infection on the day of post-mortem. At post-mortem, the lungs of each mouse were removed for enumeration of Ascaris larval burdens by means of the modified Baermann method. Control mice of each strain showed an increase in weight from pre-infection to post-infection day. Within the C57BL/6j strain, mice infected with higher doses of Ascaris eggs experienced a reduction in body weight; for those given 3000 eggs this was on all three post-mortem days, and for those given 1000, on days 7 and 8. For CBA/Ca mice, only mice receiving the 3000 dose demonstrated a reduction in body weight. These findings suggest that larval migratory ascariasis has a significant negative impact upon host growth and that this is related to infective dose and larval burden.

Contamination of fox hair with eggs of Toxocara canis.

Eighty-seven red foxes were investigated for the presence of Toxocara eggs on a sample of their hair from the peri-anal region. The worm burden of Toxocara in each fox intestine was also assessed and the relationship between eggs on the hair and worms in the intestine explored. Twenty-eight per cent of the foxes were found to have Toxocara eggs on their hair, with an average of 1.31 +/- 3.21 eggs per gram of hair (+/- SD). Sixty-one per cent of foxes harboured Toxocara worms within their intestines, with a mean worm burden (+/- SD) of 4 +/- 8. Host age and sex did not significantly influence the observed eggs on the hair or the worm burden. No significant correlation was found between the numbers of eggs on the hair and the worm burden within the intestine. These data collected from foxes are explored in the context of data from stray dogs and the possible epidemiological differences are discussed.

Sodium Hypochlorite Treatment and Nitinol Performance for Medical Devices.

Processing of nitinol medical devices has evolved over the years as manufacturers have identified methods of reducing surface defects such as inclusions. One recent method proposes to soak nitinol medical devices in a 6% sodium hypochlorite (NaClO) solution as a means of identifying surface inclusions. Devices with surface inclusions could in theory then be removed from production because inclusions would interact with NaClO to form a visible black material on the nitinol surface. To understand the effects of an NaClO soak on performance, we compared as-received and NaClO-soaked nitinol wires with two different surface finishes (black oxide and electropolished). Pitting corrosion susceptibility was equivalent between the as-received and NaClO-soaked groups for both surface finishes. Nickel ion release increased in the NaClO-soaked group for black oxide nitinol, but was equivalent for electropolished nitinol. Fatigue testing revealed a lower fatigue life for NaClO-soaked black oxide nitinol at all alternating strains. With the exception of 0.83% alternating strain, NaClO-soaked and as-received electropolished nitinol had similar average fatigue life, but the NaClO-soaked group showed higher variability. NaClO-soaked electropolished nitinol had specimens with the lowest number of cycles to fracture for all alternating strains tested with the exception of the highest alternating strain 1.2%. The NaClO treatment identified only one specimen with surface inclusions and caused readily identifiable surface damage to the black oxide nitinol. Damage from the NaClO soak to electropolished nitinol surface also appears to have occurred and is likely the cause of the increased variability of the fatigue results. Overall, the NaClO soak appears to not lead to an improvement in nitinol performance and seems to be damaging to the nitinol surface in ways that may not be detectable with a simple visual inspection for black material on the nitinol surface.

Lack of apparent difference in outcome between clinically staged IIIA and IIIB non-small-cell lung cancer treated with radiation therapy.

The current American Joint Committee on Cancer (AJCC) staging system for bronchogenic carcinoma, which divides stage III M0 cases into stages IIIA and IIIB, is based on the observation that selected patients with IIIA disease (T3 or N2) can undergo complete surgical resection, in distinction to IIIB patients (T4 or N3). To understand the value of this system when applied to clinically staged (CS) patients treated with a standard nonoperative approach, the records of patients with squamous cell, large-cell, and adenocarcinoma of the lung treated with radiation therapy (RT) at the Fox Chase Cancer Center from 1978 to 1987 were reviewed. Three hundred sixteen patients were identified as having CS III M0 disease treated with single daily fraction RT without chemotherapy or sensitizers. Of these, the distinction between IIIA (166) and IIIB (140) could be made for 306 patients. The median survival time (MST) for all CS III patients was 9.6 months, and the 2-year survival was 17%. No difference was observed in MST between CS IIIA and IIIB patients (9.4 v 9.8 months, P = .78), in 2-year survival (17% v 18%), or in rate of first failure within the RT field (43% v 44%). MSTs for the 157 CS IIIA and IIIB patients with less than 5% weight loss and Zubrod performance status (PS) 0 to 1 were 13.0 and 15.8 months (P = .29), respectively. This lack of difference in outcome for CS IIIA and IIIB patients receiving RT has important implications in the design and stratification of future nonoperative trials for stage III lung cancer.

Microdosimetry of a 42 MeV therapy neutron beam.

Radiation quality of fast neutron therapy beams can change with depth. For a neutron beam generated by p----Be, the primary effect is a "hardening" of the neutron beam produced by the scattering of slow neutron components. A 42 MeV neutron therapy beam was investigated using microdosimetric techniques. We report measurements of dose mean and saturation-corrected lineal energy in water phantom at build-up depth, 5, 15, and 30 cm, and show representative logarithmic dose distributions in lineal energy. RBE is also calculated using assumptions based on the Theory of Dual Radiation Action and presented as a function of dose and depth.

Long-term results of infusional 5-FU, mitomycin-C and radiation as primary management of esophageal carcinoma.

An analysis of the results of 90 patients with esophageal cancer treated prospectively with combined chemotherapy and radiation without surgery and with a median follow-up of 45 months is presented. Fifty-seven patients with Stage I or II disease received definitive treatment consisting of 6,000 cGy in 6 to 7 weeks and 5-FU (1,000 mg/m2/24 hr) as a continuous intravenous (IV) infusion for 96 hours, starting on days 2 and 29. Mitomycin C (10 mg/m2) was administered as a bolus injection on day 2. Thirty-three patients received palliative treatment (5,000 cGy plus above chemotherapy) for Stage III, IV, or otherwise advanced disease (extraesophageal spread, distant metastases, multiple primary tumors). Follow-up ranged from 1 month to 96 months. Overall median survival of Stage I and II patients was 18 months with 3- and 5-year actuarial survival of 29% and 18%, respectively, while the median disease specific survival was 20 months with an actuarial disease specific survival of 41% and 30% at 3 and 5 years, respectively. A multivariate analysis of sex, histology, tumor location, and tumor size on survival revealed that the effect of stage was highly significant (Stage I versus II, 73% versus 33% at 3 years, p = .01), whereas the effect of sex approached significance (females versus males, 57% versus 34% at 3 years, p = less than .1). The actuarially determined local relapse-free rate for Stage I and II patients at both 3 and 5 years was 70%. Multivariate analysis again indicated stage to be highly significant (Stage I versus II, 100% versus 60% at 3 years, p = less than .01), whereas sex approached significance (female versus male, 75% versus 66% at 3 years, p = .07). The pattern of failure may be altered with this treatment regimen from local to one dominated by distant metastases. Of 29 patients who have failed, 14 (48%) had any component of local failure, whereas 21 (72%) had a distant failure as a component of failure. The median survival of patients with Stage III or IV disease was 9 months and 7 months, respectively. Palliation in this group of patients with advanced disease was good as 77% were rendered free of dysphagia post-treatment, and 60% were without dysphagia until death with a median dysphagia-free duration of 5 months. Severe toxicities were uncommon and nearly all were transient. Eleven of 90 patients (12.2%) had severe acute toxicities, whereas only 3 patients (3.3%) developed significant late treatment-related complications requiring hospitalization for management.

Patterns of change in the physics and technical support of radiation therapy in the USA 1975-1986.

Information on the patterns of personnel and related equipment support and availability at various types of radiation oncology facilities are included in the Facilities Master List surveys conducted by the American College of Radiology. This paper summarizes the surveyed data obtained during 1975-1986. The data presented include the use of equipment and the degree of personnel support at government owned, hospital or university based, and freestanding facilities. There is increasing use of linear accelerators, simulators, and treatment planning computers among all types of facilities. The use of 60Co units has been progressively decreasing. Almost all types of facilities show inadequate, but slowly improving, numbers of physicians, physicists, dosimetrists, and technologists when compared with the level recommended by the Blue Book.

Significance of prone positioning in planning treatment for esophageal cancer.

The treatment of esophageal cancer is made difficult by the close proximity of the esophagus to the spinal cord and the requirement to treat the esophageal target volume to doses greater than or equal to 60 Gy while limiting the spinal cord dose to less than or equal to 46 Gy. By placing the patient in the prone position, the esophagus can be displaced away from the spinal cord. We explored the results of this commonly used technique on 16 patients who have undergone simulation in both supine and prone positions. Both AP and lateral orthogonal radiographs were obtained in both positions. The distance between contrast material in the esophagus and spinal cord was noted in at least four transverse planes through the thoracic esophagus on each of the 16 patients. These four transverse planes were located at 3 cm above the carina, at the carina, 3 cm below the carina and 6 cm below the carina. The mean displacement (+/- 1 SD) of the esophagus away from the spinal cord when the patient was in the prone position compared to supine at each of these levels was 1.3 (+/- 0.8) cm, 1.8 (+/- 0.9) cm, 1.8 (+/- 1.0) cm, and 1.9 (+/- 1.1) cm. The range of displacement for all 64 displacement determinations was 0 to 4.2 cm with a mean of 1.7 cm. To evaluate further the consequences of prone positioning on treatment planning and doses received to target volumes and critical structures, we performed 3-dimensional treatment planning with a patient in both prone and supine positions. The requirements were to achieve a tumor volume dose of 60 Gy while keeping the spinal cord dose below 46 Gy. Two types of conventional treatment plans were examined in prone and supine positions. A 6-field plan consisted of delivery of 40 Gy through a large 3-field beam arrangement followed by delivery of 20 Gy through a similar 3-field cone down. An 8-field plan involved the delivery of 30 Gy through AP/PA beams followed by a 3-field beam arrangement to 40 Gy and a subsequent 3-field cone-down for the final 20 Gy. Comparison of dose volume histograms revealed that the 6-field plan spared relatively more heart whereas the 8-field plan spared relatively more lung. Regarding the primary consideration of coverage of target volume with avoidance of spinal cord, prone positioning was superior to supine positioning whether 6- or 8-field arrangements were used.

Endometrial cancer with para-aortic adenopathy: patterns of failure and opportunities for cure.

PURPOSE: To examine the outcome of patients with advanced endometrial cancer whose para-aortic involvement was diagnosed pathologically or lymphographically. METHODS AND MATERIALS: Fifty patients from four institutions were treated between 1959 and 1990 with preoperative, post-operative, and primary radiotherapy. Para-aortic disease was diagnosed pathologically in 26 patients and lymphographically in the remaining 24 patients. Pathologically diagnosed patients underwent debulking of grossly involved nodes. All patients received external beam treatment through pelvic and para-aortic portals. Median prescribed dose to the pelvic and para-aortic fields was 50 and 47 Gy, respectively. Those treated with primary or pre-operative irradiation also received intrauterine brachytherapy. RESULTS: The actuarial 5-year disease-free survival was 46% for all patients. Para-aortic failure was significantly decreased among patients undergoing lymph node resection (13% versus 39%, respectively). Relapse-free survival and pelvic control tended to improve among patients receiving surgery plus irradiation in comparison to those treated by irradiation alone. Distant metastases were most common among patients with high grade lesions. CONCLUSIONS: Long-term disease-free survival is achievable in endometrial cancer patients with para-aortic lymphadenopathy who are treated with extended-field radiotherapy. Cure is mot attainable among patients with well differentiated, early clinical stage disease who receive combined modality treatment. Survival and local failure are similar for radiologically and pathologically diagnosed patients; however, para-aortic failure as a component of local failure was increased in patients who did not undergo surgical debulking of the adenopathy.

Should patients with post-resection locoregional recurrence of lung cancer receive aggressive therapy?

The outcome of thirty-seven patients with a post-resection locoregional recurrence of non-small cell lung cancer treated with radiation therapy alone between 1979 and 1989 was compared to that of 759 patients with unresected non-small cell lung cancer also treated with standard radiation during the same period. Each patient's locoregional recurrence was staged using the current American Joint Committee on Cancer staging system. Comparison of pretreatment characteristics between the two groups, including age, sex, extent of weight loss, performance status, stage, and histologic subtype revealed fewer patients with greater than 5% weight loss (35 vs. 47%, p = 0.04) and more cases with squamous histology (54 vs. 28%, p = 0.01) among the patients with locoregional recurrences than those with newly diagnosed lesions. Over 80% of both groups had clinical stage III lesions. The median radiation doses were 56 and 59 Gy for recurrent and newly diagnosed cases (p = NS). For the patients with locoregional recurrences, the median time from resection to recurrence was 13 months (range: 3-118 months), and the recurrences were predominantly nodal in 25 cases, chest wall/pleural in four and at the bronchial stump in eight. When measured from the date of documented recurrence, the median survival time and 2-year actuarial survival rate of the patients with recurrent lesions were 12 months and 22%, as compared to 12 months and 26% for the newly diagnosed patients (p = NS). Freedom from documented locoregional tumor progression at 2 years was 30% for both groups. Patients with bronchial stump lesions had superior survival to those with nodal or chest wall recurrences, with a median survival time of 36 versus 9 months. A therapeutic approach to selected patients with post-resection locoregional recurrence of non-small cell lung cancer equally aggressive to that for newly diagnosed lung cancer patients is justified by these results, especially for patients with bronchial stump recurrences.

Adverse influence of younger age on outcome in patients with non-small cell lung carcinoma (NSCLC) treated with radiation therapy (RT) alone.

Treatment outcome of 63 patients younger than 50 years of age initiated on a course of once-daily definitive radiation therapy without concurrent or preirradiation chemotherapy for clinical Stages I-III unresected non-small cell lung carcinoma from 1978 to 1988 was compared to the outcome of 695 patients over the age of 50. Follow-up ranged from 24-110 months with follow-up until death in 88% of patients. The actuarial overall survival rate for all patients was 22% at 2 years with a median survival time of 11.5 months. Patients less than 50 and greater than or equal to 50 years old were similar in male:female ratio, distribution of histologic subtype, performance status, and extent of weight loss. Poorly differentiated histologic grade was more prevalent among the younger patients (59% vs 41%, p = .005). Ninety-four percent of younger patients and 86% of older patients had clinical stage III disease (p = NS). Survival was significantly worse for patients who were younger than 50 years old (p = .05), with a median survival time of 7.8 months. Median survival time for those patients 50 years of age or older was 12.4 months. Poorer survival outcome among young patients was most pronounced among patients with unfavorable characteristics of poor performance status (greater than or equal to 2) or weight loss (greater than 5%) (p = .002). Distant failure (p = .029) and brain failure (p = .003) as initial site of relapse was more common among younger patients. Among young patients, poor histologic grade was associated with both distant failure (p = .003) and brain metastasis (p = .002). The difference in distribution of histologic grade, incidence of distant failure, particularly in the brain, and poorer survival outcome among patients less than 50 may be indicative of more aggressive tumor behavior in the younger patients. These results indicate that patients less than 50 may require alternate treatment strategies. Age should be considered a stratification variable in non-operative randomized trials of non-small cell lung carcinoma which include patients with non-favorable characteristics.

Decreasing gastrointestinal morbidity with the use of small bowel contrast during treatment planning for pelvic irradiation.

Small bowel tolerance is a major dose-limiting factor in treating the pelvis with radiation therapy (RT). The use of small bowel contrast during RT simulation is one technique used to localize the bowel and identify the treatment plan that would exclude the greatest volume. To determine the influence of treatment planning with oral contrast on gastrointestinal injury, acute and chronic small bowel morbidity was analyzed in 115 patients with endometrial and rectal carcinoma who received postoperative radiation therapy at the Fox Chase Cancer Center. Mean and median time of follow-up were 31 and 27 months, respectively. Acute diarrhea was seen in 82% of the patient population. Ten percent of patients experienced major complications requiring hospitalization. Ninety-three percent of patients simulated without contrast experienced side effects compared to 77% of patients simulated with contrast (p = .026). There was an increased incidence of chronic complications in patients who were not simulated with contrast dye (50% vs 23%, p = .014). Median duration of minor side effects was 4 months for patients planned without oral contrast and 1 month for patients who had contrast at the time of simulation (p = .036). The superior aspect of the treatment field was determined to be at a more inferior location in patients simulated with contrast, thereby excluding small bowel from treatment. Seventy-four percent of patients simulated without contrast had the upper border of the field placed at the superior aspect of the sacroiliac joint or above, compared to only 40% of patients planned with oral contrast (p = .002). This study has demonstrated decreased complications (both overall and chronic) as well as a change in the location of the treatment field with the use of small bowel contrast. Multivariate analysis revealed that both the use of oral contrast (p = .026) and a lower superior border of the treatment field (p = .007) were predictive for fewer sequelae to RT, indicating that planning with contrast leads to changes in the technical delivery of RT other than field placement (e.g., block placement). The reduced incidence and duration of small bowel morbidity may be in part caused by alterations of the treatment plan made when the small bowel is visualized at the time of simulation. It is therefore recommended that oral small bowel contrast be used during treatment planning for pelvic irradiation.

Recovery of locomotion correlated with axonal regeneration after a complete spinal transection in the eel.

This research has examined the relationship between axonal regeneration and the return of normal movement following complete transection of the spinal cord. We made measurements of tail beat frequency and amplitude of the caudal body wave from video recordings of eels (Anguilla anguilla) swimming in a water tunnel at several speeds. Each eel was then anaesthetised and the spinal cord cut caudal to the anus; in some animals the resulting gap was filled with a rubber block. All animals were kept at 25 degrees C for recovery periods ranging from 7 to 128 days, during which their swimming performance was monitored regularly. Each fish was then re-anaesthetised and perfused with fixative and the regrowing descending axons labelled with 1,1'-diotadecyl-3,3,3',3'-tetramethylindocarbocyanine perchlorate. For all animals and at all speeds after surgery, tail beat frequency increased, while amplitude decreased. In non-blocked animals, an improvement in performance was first seen from 8 days following transection and thereafter tail beat frequency decreased progressively until it had returned to normal after 35 to 45 days, while amplitude remained below baseline until at least 45 days. In these animals, few axonal growth cones had penetrated the caudal stump by 7 days, but some had extended as much as 3 mm by 15 days. Many had reached as far as 6 mm between 25 and 36 days, while by 128 days they had progressed up to 10.5 mm. Contralateral crossing was never observed. Functional recovery was never witnessed in animals in which the cord had been blocked and these eels swam at all times with elevated tail beat frequency and reduced caudal amplitude. No labelled axons could be traced into the caudal spinal cord at any recovery stage in such animals. We conclude that re-innervation of only 1-2 segments caudal to the injury is necessary for functional recovery, although continued axonal growth may be important for the refinement of some aspects of movement.

Quantitative analysis of signal-averaged P waves in idiopathic paroxysmal atrial fibrillation.

Detailed analysis of the QRS complex can identify patients at risk from ventricular arrhythmias, but similar techniques applied to the atria have been disappointing. This study attempts to quantitate differences in the fine morphology of P waves in a group of 9 patients with paroxysmal atrial fibrillation (AF) versus 15 control subjects. Atrial triggered signal-averaging was combined with a detailed investigation of P-wave duration, high-frequency spatial voltage and spatial velocity. Signal-averaged P-wave duration was significantly increased in patients with paroxysmal AF (135 +/- 8 vs 126 +/- 4 ms, p less than 0.05). The root-mean-square voltage at frequencies greater than 35 Hz in these patients was also significantly greater (16 +/- 3 vs 12 +/- 1 microV, p less than 0.05). Similar observations were made at frequencies greater than 40 Hz (10 +/- 3 vs 7 +/- 1 microV, p less than 0.05). These differences appeared to be confined to the third quarter of the P wave (third quarter root-mean-square voltage at greater than 40 Hz expressed as a ratio of total P-wave root-mean-square voltage, 1.4 +/- 0.1 vs 1.2 +/- 0.1, p = 0.005). Spatial velocity was also increased in the paroxysmal AF group (peak spatial velocity 6.4 +/- 1.8 vs 4.6 +/- 0.5 mV/s, p less than 0.05). These observations support previous intracardiac data that implicate delay and fragmentation of intraatrial conduction in the pathogenesis of paroxysmal AF.

The haemodynamic actions of ZENECA ZD7288, a novel sino-atrial node function modulator, in the exercising beagle: a comparison with zatebradine and propranolol.

1. ZENECA ZD7288 (4-(N-ethyl-N-phenylamino)-1,2-dimethyl-6-(methylamino) pyrimidinium chloride, formerly ICI D7288) is a novel sino-atrial node function modulator which selectively slows heart rate. 2. The haemodynamic effects of ZD7288 (0.1, 0.3 and 1.0 mg kg-1, i.v.) have been evaluated and compared with those of placebo (physiological saline), zatebradine (ULFS 49, 0.1, 0.3 and 1.0 mg kg-1, i.v.) and propanolol (0.03, 0.1, and 0.3 mg kg-1, i.v.) in beagles chronically instrumented for measurement of heart rate, aortic pressure, aortic flow and dPLV/dtmax. The dogs were trained to run at 6.5 k h-1 on a level treadmill for 5 min at half hourly intervals over a period of 4 h. Drugs were dosed cumulatively after the second, fourth and sixth exercise periods. 3. Control experiments demonstrated a degree of accommodation to repeated exercise over a period of 4 h. Resting heart rate decreased by 21 beats min-1, but heart rate response to exercise was maintained, whereas dPLV/dtmax at rest remained steady while the response to exercise decreased significantly (by 25% after 2 h, P < 0.05). 4. ZD7288 and zatebradine both decreased heart rate during exercise in a dose-dependent manner, whilst heart rate at rest did not differ from resting heart rates in saline dosed control animals. In contrast, heart rate at rest and during exercise were lowered equally by the lowest doses of propranolol (approximately by 30 beats min-1), and additional doses caused only minor additional decreases. The exercise-induced tachycardia was maintained within 12% of pre-dose levels, presumably by withdrawal of vagal tone.5. Cardiac inotropism, as indicated by dPLv/dt max, was not affected by ZD7288 or zatebradine at rest,although the inotropic response to exercise decreased in proportion to the decreases in exercise-induced tachycardia. Propranolol caused a marked dose-dependent decrease in the exercise-induced inotropic response (by 85% at 0.3mg kg-1).6. Whilst the sino-atrial node modulators increased stroke volume at rest, and augmented increases in response to exercise, propranolol did not affect resting stroke volume and decreased the responses to exercise.7. Cardiac output at rest and cardiac output increases during exercise were well maintained in the presence of ZD7288 and zatebradine in contrast to propranolol which induced a significant depression of cardiac output, both at rest and during exercise. Propranolol also caused significant systemic vasoconstriction.8. In conclusion, ZD7288 has haemodynamic actions comparable to those of zatebradine despite their chemical dissimilarity. ZD7288 may be of benefit in the treatment of ischaemic heart disease by reducing heart rate without impairing cardiac function.

Dose to superficial node for patients with head and neck cancer treated with 6 MV and 60Co photons.

The superficial neck nodes in only 1 out of 7 patients with head and neck cancer studied received more than 90% of the prescribed dose when treated with opposed 6 MV photons. Beam spoilers placed upstream from the patient enhanced the dose to the superficial node at the expense of higher dose to the skin.