Pre-operative versus post-operative radiosurgery for brain metastasis: Effects on treatment volume and inter-observer variability

PURPOSE/OBJECTIVES

Compared to post-operative whole brain radiotherapy, resection cavity radiosurgery reduces impact on neuro-cognitive function and improves quality-of-life. However, coverage of the operative tract, in addition to tumour bed, may lead to large treatment volumes and inter-observer variability. We hypothesized that pre-operative radiosurgery reduces target volume size and inter-observer variability compared to post-operative radiosurgery.

MATERIALS/METHODS

We identified 10 consecutive patients, with solitary brain metastasis, treated with post-operative cavity radiosurgery.Pre- and post-operative axial T1 contrast MRI were co-registered with the planning CT scans. Three radiation oncologists independently contoured the target volumes on the pre- and post-operative imaging. A 2mm-PTV margin was utilized for both strategies and radiosurgery treatment plans were generated. The following parameters were evaluated in the 2 plans: Mean target volume (cc), 50% isodose volume (cc), Inter-observer variability (Jaccard Index JI) and Conformity Index (CI).

RESULTS

There was no significant difference in the mean target volume, nor 50% isodose volume, between pre- and post-operative strategies. (17.6 (95% CI 9.98 - 25.22) versus 19.4 (95% CI 10.11 - 28.69) cc, P=0.80; 61.7 (95% CI 38.4 - 85.0) vs 77.7 (95% CI 34.94 - 120.46) cc, P=0.65). There was significantly less inter-observer variability and improved conformity in the pre-operative group (Mean JI 0.84(95% CI 0.82 - 0.86) versus 0.70 (95% CI 0.62 - 0.78), P = 0.005; Mean CI 1.32 (95% CI 1.26 - 1.38) vs 1.45 (95% CI 1.36 - 1.54), P= 0.01). Planned subgroup analysis did not reveal any significant difference (between pre- vs post-op) in the mean volume of cystic versus non-cystic metastasis. Deep lesions (>2.5cm from dura) had a larger post-operative target volume (25.8 (95% CI 15.1 - 36.5) vs 12.3 (95% CI 6.54 - 18.06) cc, P=0.06) compared to superficial lesions.

CONCLUSION

Pre-operative radiosurgery has less inter-observer variability and improved plan conformity. However, there was no difference in mean target volume between the pre- versus post-operative radiation. Contouring guidelines, and peer review, may help to reduce inter-observer variability for cavity radiosurgery.

Randomized, double-blind, placebo-controlled phase II study of AMG 386 in combination with cisplatin and capecitabine (CX) in patients (pts) with metastatic gastroesophageal adenocarcinoma

66

Background: AMG 386, a first-in-class investigational peptide-Fc fusion protein (peptibody), blocks angiogenesis via inhibiting the interaction between angiopoietins-1 and -2 and the Tie2 receptor. We evaluated the efficacy and tolerability of AMG 386 or placebo plus CX in the first-line treatment of metastatic gastroesophageal adenocarcinoma.

Methods: Pts with confirmed metastatic adenocarcinoma of the stomach, gastroesophageal junction or distal esophagus were randomized 1:1:1 to receive CX (cisplatin, 80 mg/m2 IV Q3W; capecitabine, 1,000 mg/m2 orally BID for 14 days Q3W) plus AMG 386 10 mg/kg (Arm A), 3 mg/kg (Arm B), or placebo (Arm C) IV QW. The primary endpoint was progression-free survival (PFS). Secondary endpoints included objective response rate (ORR; in pts with measurable disease), adverse events (AEs), and pharmacokinetics (PK).

Results: 171 pts were randomized (Arm A/B/C, n = 56/59/56). Efficacy results are summarized in the table. The incidence of grade ≥ 3 AEs in Arms A/B/C was 80/84/75%. Serious AEs occurred in 73/60/47% and serious AEs grade ≥ 3 in 66/60/43% of pts. AEs in Arms A/B/C included abdominal pain (30/40/17%; grade ≥ 3, 18/3/4%), peripheral edema (13/29/6%; grade ≥ 3, 0/2/0%), venous thromboembolic events (20/22/19%; grade ≥ 3, 20/19/17%), and pulmonary embolism (9/3/15%; grade ≥ 3, 9/2/13%). Median AMG 386 Cmax and Cmin values at steady state after CX coadministration were dose-proportional. Coadministration with CX did not markedly affect AMG 386 exposure.

Conclusions: In this study, AMG 386 plus CX did not significantly improve PFS or ORR over placebo plus CX in this patient population. The toxicity of the combination of AMG 386 plus CX, compared with placebo, was greater but manageable. No unexpected AEs occurred.

[Table: see text]

[Table: see text]

Vandetanib plus mFOLFOX6 in patients with advanced colorectal cancer (CRC): A randomized, double-blind, placebo-controlled phase II study

4084

Background: Vandetanib is a once-daily oral agent that selectively targets key signaling pathways in cancer by inhibiting VEGF, EGF and RET receptor tyrosine kinases. Methods: Eligible patients with advanced CRC and who had previously progressed after an irinotecan- and fluoropyrimidine-containing regimen were randomized 1:1:1 to receive once-daily oral vandetanib (100 or 300 mg) + modified FOLFOX6 (mFOLFOX6) or placebo + mFOLFOX6; mFOLFOX6 was given as standard 14-day treatment cycles (oxaliplatin 85 mg/m2 2-hr and leucovorin 400 mg/m2 2-hr i.v. infusions, followed by 5- fluorouracil [5-FU] 400 mg/mg2 i.v. bolus and 5-FU 2400 mg/m2 46-hr i.v. infusion). The primary objective was to compare the number of patients with a progression event on or before a mandatory tumor assessment visit at data cut-off (∼4 months after last patient randomized). A progression event was defined as the earliest of objective and/or clinical disease progression, or death from any cause. Results: Between March and November 2007, 104 patients (aged 32–81 years) were randomized to receive study treatment ( Table ). At data cut-off on 8 March 2008, there was a greater % of progression events in the vandetanib 100 mg arm compared with placebo (72% [n=23] versus 65% [n=24]; HR=1.21, 2-sided 80% CI 0.82–1.80; 2-sided P=0.53), and also in the vandetanib 300 mg arm compared with placebo (77% [n=27] versus 65% [n=24]; HR=1.41, 2-sided 80% CI 0.96–2.07; 2-sided P=0.25). All except one patient in each group experienced an adverse event (AE) during the study with diarrhea, nausea, thrombocytopenia, and peripheral sensory neuropathy the most commonly reported AEs ( Table ). Neutropenia was the only CTC grade 4 AE to occur in >1 patient in any group (n=2, vandetanib 100 mg arm; n=0, vandetanib 300 mg arm; n=3, placebo arm). Conclusions: In this study of patients with advanced, previously treated CRC, there was no efficacy benefit for vandetanib (100 or 300 mg) + mFOLFOX6 versus placebo + mFOLFOX6.

[Table: see text]

[Table: see text]

Cationic liposomal paclitaxel in combination with gemcitabine in patients with advanced pancreatic cancer: A phase II trial

4526

Background: EndoTAG-1 is a novel cationic liposomal formulation of paclitaxel being developed for the treatment of solid malignancies. It acts by targeting activated negatively charged endothelial cells of tumor blood vessels. We present safety and efficacy data of a randomized, controlled phase II trial in pancreatic cancer (PC). Methods: 200 patients with advanced PC were randomized to 1st line treatment with weekly gemcitabine (GEM: 1000 mg/m2) and twice weekly infusions of EndoTAG-1 (E) at 3 different dose levels (Elow: 11 mg/m2, Emed: 22 mg/m2, Ehigh: 44 mg/m2) or GEM monotherapy. Patients were treated for 7 weeks and followed up for overall survival (OS) for at least 1 year. After finishing study treatment, any anti-tumor therapy was allowed. A subgroup of patients had the option to receive repeated cycles of combination therapy in case of at least stable disease according to RECIST until disease progression. Results: Median OS was substantially higher in the GEM+Emed and GEM+ Ehigh groups than the GEM monotherapy group. Adjusted hazard ratios for OS were 0.72 (95% CI 0.46–1.13) and 0.67 (0.43–1.07). In patients receiving >1 treatment cycle, median OS was 11.5 months (GEM+Ehigh); in the GEM+Emed group 75% of patients were alive at 1 year. Treatment with EndoTAG-1 and gemcitabine was generally well tolerated. A trend for increasing adverse event frequency with EndoTAG-1 dose was observed for infusion-related reactions associated with chills and pyrexia, and thrombocytopenia. The overall frequency of serious adverse events in the GEM+E groups was low, the most frequent SAE being pyrexia in 4 (8%) patients in the GEM+Ehigh group. There was no indication for significant organ toxicity associated with EndoTAG-1, even in patients receiving multiple treatment cycles. Conclusions: This phase II trial indicates a considerable survival benefit for patients with advanced PC receiving EndoTAG-1 in combination with gemcitabine and a favourable safety profile warranting further development of EndoTAG-1 in this indication.

[Table: see text]

Irinotecan in combination with 5-fluorouracil and folinic acid or with cisplatin in patients with advanced gastric or esophageal-gastric junction adenocarcinoma: results of a randomized phase II study

BACKGROUND

To identify the most effective of two combinations, irinotecan/5-fluorouracil (5-FU)/folinic acid (FA) and irinotecan/cisplatin, in the treatment of advanced gastric cancer, for investigation in a phase III trial.

PATIENTS AND METHODS

Patients were randomized to receive irinotecan [80 mg/m2 intravenously (i.v.)], FA (500 mg/m2 i.v.) and a 22-h infusion of 5-FU (2000 mg/m2 i.v.), weekly for 6 weeks with a 1-week rest, or irinotecan (200 mg/m2 i.v.) and cisplatin (60 mg/m2 i.v.), on day 1 for 3 weeks.

RESULTS

A total of 115 patients were eligible for analysis in the per-protocol population. The overall response rate in the irinotecan/5-FU/FA arm (n=59) was 42.4%, with a complete response rate of 5.1%. Corresponding figures for the irinotecan/cisplatin arm (n=56) were 32.1% and 1.8%, respectively. The median time to progression was 6.5 months (irinotecan/5-FU/FA) and 4.2 months (irinotecan/cisplatin) (P < 0.0001), with median survival times of 10.7 and 6.9 months, respectively (P=0.0018). The major toxicity was grade 3/4 neutropenia, which was more pronounced with irinotecan/cisplatin than with irinotecan/5-FU/FA (65.7% versus 27%). Diarrhea was the main grade 3/4 non-hematological toxicity with both irinotecan/5-FU/FA (27.0%) and irinotecan/cisplatin (18.1%).

CONCLUSIONS

Both combinations were active, with acceptable safety profiles. Irinotecan/5-FU/FA was selected as the most effective combination for investigation in a phase III trial in advanced gastric cancer.

[Radiation sensitivity testing and late neurological complications following radiosurgery for AVM: the use of SF2 from fibroblasts as a predictive factor]

PURPOSE

To identify SF2 as a prognostic factor of late complications from radiosurgery in patients treated for AVM.

PATIENTS AND METHODS

Five patients with AVM treated in three canadian institutions and who suffered clinically significant neurological sequelaes secondary to radiosurgery were identified. Their fibroblasts were cultured and their radiation sensitivity tested to determine the SF2 for each patient.

RESULTS

Patients who developed a neurological complication from radionecrosis, secondary to radiosurgery had an SF2 different than the two control patients with AVM and no complications and also from a group of five cancer patients without late radiation complications (P = 0.005).

CONCLUSION

Radiosurgery is an elective procedure. The identification of a subgroup of patients who are radiosensitive and at a higher risk of radiation induced complications can allow the treatment team to reduce the risk of such complications. SF2 as a new predictive factor should be incorporated in predictive models of risk from treatment of AVM by radiosurgery. This work needs to be confirmed in a larger cohort of patients.

Treatment planning aids in prostate cancer: friend or foe?

BACKGROUND

Rectal barium is commonly used as a treatment planning aid for prostate cancer to delineate the anterior rectal wall. Previous research at the Ottawa Regional Cancer Centre demonstrated that retrograde urethrography results in a systematic shift of the prostate. We postulated that rectal barium could also cause prostate motion.

PURPOSE

The study was designed to evaluate the effects of rectal barium on prostate position.

METHODS AND MATERIALS

Thirty patients with cT1-T3 prostate cancer were evaluated. Three fiducial markers were placed in the prostate. During simulation, baseline posterior-anterior and lateral films were taken. Repeat films were taken after rectal barium opacification. The prostate position (identified by the fiducials) relative to bony landmarks was compared before and after rectal barium. Films were analyzed using PIPsPro software.

RESULTS

The rectal barium procedure resulted in a significant displacement of the prostate in the anterior and superior direction. The mean displacement of the prostate measured on the lateral films was 3.8 mm (SD: 4.4 mm) in the superior direction and 3.0 mm (SD: 3.1) in the anterior direction.

CONCLUSIONS

Rectal barium opacification results in a systematic shift of the prostate. This error could result in a geographic miss of the target; therefore, alternate methods of normal tissue definition should be used.

Severe normal tissue complication correlates with increased in vitro fibroblast radiosensitivity in radical prostate radiotherapy: a case report

The radiation responses of fibroblasts taken from four patients undergoing radiotherapy for prostate cancer were evaluated in vitro. One patient exhibited a severe normal tissue late reaction after radiotherapy, and the fibroblasts from this patient also showed increased radiosensitivity. The other three patients exhibited a normal clinical response, and their fibroblast response in vitro was also considered normal when compared with previously published data from our laboratory. When cells were allowed to repair potentially lethal damage (PLDR), the differences between cell lines were reduced; therefore, a deficiency in PLDR did not cause the differences in radiosensitivity. Fractionated radiation resulted in elevated survival due to repair of sublethal damage (SLDR), and the differences in radiosensitivity were increased. In addition, the survival curves displayed an upward bending nature, indicative of an adaptive response. Thus, adaptive response and ability to modify it may play an important role in fractionated radiotherapy. Int. J. Cancer (Radiat. Oncol. Invest.) 90, 336-342 (2000).

A prospective comparison of three systems of patient immobilization for prostate radiotherapy

PURPOSE

The study compared the setup reliability of 3 patient immobilization systems, a rubber leg cushion, the alpha cradle, and the thermoplastic Hipfix device, in 77 patients with cT1-T3, N0, M0 prostate cancer receiving conformal radiotherapy.

METHODS AND MATERIALS

Port films were analyzed and compared to simulation films to estimate the setup errors in the three coordinate axes (anterior-posterior, cranial-caudal, medial-lateral). A total vector error was calculated from these shifts.

RESULTS

The Hipfix was found significantly superior to the other two devices in reducing mean setup errors in all axes (p < 0.005). The average field-positioning error with the Hipfix ranged from 1.9 mm to 2.6 mm for all axes, whereas the deviation for the other two systems ranged from 2.7 to 3. 4 mm. Errors greater than 10 mm were virtually eliminated with the Hipfix system. There was a reduction in the mean total vector error in the alpha cradle and Hipfix patient cohorts over time, reflecting improved efficacy as a result of experience.

CONCLUSION

There was a significant difference in the performance of each immobilization device. The Hipfix was consistently more reliable in reducing setup errors than the other devices.

Respiratory-induced prostate motion: quantification and characterization

PURPOSE

The precise localization of the prostate is critical for dose-escalated conformal radiotherapy. This study identifies and characterizes a potential cause of inaccurate prostatic localization-respiratory-induced movement.

METHODS AND MATERIALS

Prostate movement during respiration was measured fluoroscopically using implanted gold fiducial markers. Twenty sequential patients with CT(1)-T(3) N(0) M(0) prostate carcinoma were evaluated prone, immobilized in customized thermoplastic shells. A second 20 patients were evaluated both prone (with and without their thermoplastic shells) and supine (without their shells).

RESULTS

When the patients were immobilized prone in thermoplastic shells, the prostate moved synchronously with respiration. In the study the prostate was displaced a mean distance of 3.3 +/- 1.8 (SD) mm (range, 1-10.2 mm), with 23% (9/40) of the displacements being 4 mm or greater. The respiratory-associated prostate movement decreased significantly when the thermoplastic shells were removed.

CONCLUSION

Significant prostate movement can be induced by respiration when patients are immobilized in thermoplastic shells. This movement presumably is related to transmitted intraabdominal pressure within the confined space of the shells. Careful attention to the details of immobilization and to the possibility of respiratory-induced prostate movements is important when employing small field margins in prostatic radiotherapy.

Effects of urethrography on prostate position: considerations for radiotherapy treatment planning of prostate carcinoma

PURPOSE

Retrograde urethrography is commonly used to define the prostate apex at simulation. This study evaluated the hypothesis that urethrography causes prostate displacement, resulting in an error in treatment planning.

METHODS AND MATERIALS

Forty-five patients with carcinoma of the prostate were evaluated. Gold seeds were placed in the apex, posterior wall, and base of the gland. In the first 20 patients, the position of the seed-defined apex was compared at simulation (with urethrogram) and on day 1 of treatment (without urethrogram). In the second cohort of 25 patients, the effects of urethrography on prostate position were evaluated directly at simulation by comparing the position of apex pre- and post-urethrography. An analysis was performed to estimate the possible impact of urethrogram-induced prostate motion on target coverage.

RESULTS

The mean superior displacement in the first and second cohort was 5.2 mm and 6.8 mm, respectively (combined mean shift 6.1 mm). With a 10-mm field margin below the tip of the urethrogram cone, 56% of patients in this study would have inadequate planning target volume (PTV) coverage.

CONCLUSION

Retrograde urethrography causes a significant superior shift of the prostate. Strict reliance on urethrography in determining the inferior field margin could result in inadequate treatment.

Maintenance treatment with medroxyprogesterone acetate in patients with advanced breast cancer responding to chemotherapy: results of a randomized trial. Essen Breast Cancer Study Group

The purpose of this randomized phase III trial was to study whether medroxyprogesterone acetate (MPA) maintenance treatment prolongs the time to progression in advanced breast cancer patients responding to an induction chemotherapy. Patients with progressive advanced breast cancer previously untreated with anthracylines and progestins were given epirubicin (30 mg/m2) and ifosfamide (2 g/m2) on days 1 and 8 at 3-weekly intervals. Patients without disease progression after 6 cycles of chemotherapy were randomly assigned to receive, until progression, either no treatment or MPA at a daily total dose of 500 mg. Ninety patients were randomized: 46 to the MPA arm and 44 to the observation arm. Median time to progression was longer in the MPA arm: 4.9 months versus 3.7 months in the intent-to-treat analysis (p = 0.02), and 4.9 months versus 3.0 months in the secondary efficacy analysis (p = 0.012). Seven patients were removed from MPA due to side effects. The changes in patient-rated quality of life scores were similar in both groups. The median length of survival from randomization was 17.4 months for patients receiving MPA and 18.3 months for patients randomized to observation (p = 0.39). In conclusion, in patients with advanced breast cancer achieving remission or non-progression with 6 cycles of epirubicin and ifosfamide chemotherapy, MPA maintenance treatment led to a significant, though modest, prolongation of the time to progression without affecting overall survival of the study patients.

Epirubicin and ifosfamide in metastatic breast cancer

In a randomized, phase II trial, we evaluated the effectiveness of continued chemotherapy with epirubicin/ ifosfamide versus unmaintained treatment interruption in advanced metastatic breast cancer. Three hundred fifty-seven patients were enrolled and 331 were evaluable for response. Complete response was achieved in 25 patients (8%) and partial response in 121 patients (37%). Pretreatment status correlated significantly with response (complete and partial response). While 54% of unpretreated patients responded, only 42% of the patients responded who had been pretreated with adjuvant chemotherapy and 33% who had been pretreated in the metastatic stage of disease; 69 patients (21%) had disease progression. Of 11 patients pretreated in both the adjuvant and metastatic setting, only two responded. Toxicity of treatment was mild, with leukopenia being the treatment-limiting factor. Thrombocyte levels were not altered significantly by treatment. Thus, there seems to be room for dose escalation using granulocyte colony-stimulating factor. There was no considerable cardiotoxicity, central nervous system toxicity, or cystitis observed. The low rate of cardiotoxicity appeared to be related to dose fractionation of epirubicin. After randomization of patients to treatment interruption versus continuation of chemotherapy, a longer relapse-free survival was observed for patients who continued chemotherapy (mean relapse-free survival, 2+ months); however, this did not translate into prolonged survival. The cumulative scores of toxicity and quality of life parameters showed increasing superiority for treatment interruption. Therefore, a strategy of treatment until maximum response and subsequent treatment interruption seems to be superior to treatment continuation.

Lateral electron equilibrium and electron contamination in measurements of head-scatter factors using miniphantoms and brass caps

The head-scatter factor (Sh) can be measured with a narrow miniphantom or a metal cap provided it is completely covered by the photon beam and its lateral size is thick enough to prevent electron contamination contributions. The effects of lateral electron equilibrium (LEE) and electron contamination on the Sh values were studied. The EGS4 Monte Carlo technique was used to calculate the minimum beam radii (rLEE) required to achieve complete LEE for photon beams ranging from 60Co to 24 MV. The measurement shows that the error introduced to the Sh value due to lateral electron disequilibrium is negligible. The radii of the miniphantoms or the sidewall thicknesses of the caps can be reduced below rLEE provided they are thick enough to prevent the effect of electron contamination.

Asymmetric arc technique for posterior pharyngeal wall and retropharyngeal space tumors

PURPOSE

Tumors of the posterior pharyngeal wall and nasopharyngeal cancer with retropharyngeal extension can partly encircle the cervical vertebrae. Treating the patient within spinal cord tolerance can cause a geographic miss. A simple technique has been developed to avoid this problem.

METHODS AND MATERIALS

The standard fields for posterior pharyngeal wall and nasopharyngeal tumors are used up to 36-40 Gy. A planning computed tomography (CT) scan is taken during the second or third week of treatment with the patient fitted in a new shell ensuring that the cord is straight and parallel to the treatment couch. The asymmetric arc technique consists of two posterior arcs with closure of one jaw beyond the central axis. Each arc delivers the total dose to each ipsilateral side, while the median region of the U-shaped volume is treated by the summation of both arcs.

RESULTS

We have treated 10 patients using asymmetric arcs in the last 3 years. This technique proved to be a versatile way of treating targets wrapped around the spine. The technique allows better individualization for target volume irregularities than the partial rotation with a central bar.

A translating-bed technique for total-body irradiation

Total-body irradiation (TBI) is a therapy modality that is being used with increasing frequency, in conjunction with chemotherapy, for patients undergoing bone-marrow transplantation. At the Ottawa Regional Cancer Centre a technique has been developed for the delivery of TBI to patients prior to bone-marrow transplantation. In this technique patients are treated on a mobile couch at approximately 195 cm SSD with a field size of 66.5 cm wide by 57 cm long. A computer-controlled stepping motor drives the patient couch at a user-selectable speed. The total dose delivered to the patient is a function of couch velocity, field size and patient separation. Treatment times are of the order of 10 min for each of the anterior and posterior fields for a 400 cGy fraction. It has been found that the conventional central axis tissue maximum ratio (TMR) and percentage depth dose (PDD) functions are not appropriate for describing dose delivered during dynamic treatment. To this end we have developed dynamic TMR and PDD functions. Extensive measurements have been performed in an anthropomorphic water phantom to determine the dose distributions in three dimensions and the efficacy of polymethyl methacrylate (PMMA) beam spoilers as a replacement for anterior and lateral bolus. It has been found that 2.4 cm PMMA spoilers do provide full skin dose and negate the requirement for lateral bolus. This TBI procedure is simple, rapid and appears to be well tolerated by the patients. 55 patients have been treated since the introduction of this technique in 1991.

A safe method of analysis for mechanical damage in spherical radioactive sources used in remote afterloading brachytherapy devices

The examination of brachytherapy sources in a quality assurance program can result in significant exposure to staff. Even though exposure may be within prescribed limits attempts should be made to reduce such exposure to as low as reasonably achievable (ALARA concept). In this report, a system that can be used to examine small spherical radiation sources while minimizing exposure to staff is described.

On the spatial resolution of clinical thermometers

In this work the spatial resolution of type T (copper-Constantan) and type K (Chromel-Alumel) multipoint thermocouple thermometers was investigated. For clinical use, thermocouples are usually inserted within catheters to provide easy access, reproducibility, and a sterile environment. The effect of several types of catheter on the ability of these thermometers to accurately resolve thermal gradients was studied. The influence of the number of wire pairs within the multipoint thermometer was also investigated. A mathematical model has been developed to determine the spatial resolving power of these thermometers. Results indicate that type K thermocouples are generally superior to type T and the use of catheters plays a significant role in spatial resolution. Moreover, the use of mineral oil as a thermal coupling agent between the catheter and the thermometer was also found to have some effect.

Effects of gold and silver backings on the dose rate around an 125I seed

Measurements of the effect of either gold or silver backing on the dose rate around an 125I seed were performed using a Therados RFA7 dosimetry system and a small diode detector which was 2.5 mm in diameter and 0.06 mm thick. It was found that the presence of the gold or silver backing modifies the diode response on the side of the 125I seed away from the backing. The effect depends on the backing material and the distance from the seed. There is a small increase close to the gold backing but a decrease further away. This decrease at distances greater than 10 mm from the seed is uniformly 10%, the same as found when the seed is backed by air. There is an increase of up to 25% observed with silver backing the seed and this increase remains significant more than 30 mm from the seed. When the response increases, the results are hard to interpret quantitatively because of variations in the diode response per unit dose with photon energy and extreme sensitivity to geometric changes. Nonetheless, except for the increase at close distances with the gold, the results are in agreement with EGS4 Monte Carlo photon transport simulations which are for a simplified geometry and account for x-ray fluorescence from the K-shell. Furthermore, the increase in the gold-backed case is qualitatively explained by Williamson's Monte Carlo calculations which take into account the L-shell fluorescent x-rays from gold.

Efficacy of dichlorvos, fenbendazole, and ivermectin in swine with induced intestinal nematode infections

Anthelmintic efficacies of dichlorvos, fenbendazole, and ivermectin were compared in specific-pathogen-free crossbred weanling pigs inoculated with Ascaris suum, Trichuris suis, and Oesophagostomum dentatum. On postinoculation day (PID) 50, 24 pigs in each treatment group were treated orally with 43 mg of dichlorvos/kg of body weight, 3 X 3 mg of fenbendazole/kg, or 300 micrograms of ivermectin/kg, SC. Twenty-four pigs were not treated. On posttreatment day 7 (PID 57), 12 pigs from each treatment group (phase I) were slaughtered, and the anthelmintic efficacy of each treatment was determined. Efficacies against A suum, T suis, and O dentatum, respectively, were: dichlorvos, 100%, 99.9%, and 100%; fenbendazole, 100%, 99.8%, and 100%; and ivermectin, 98.7%, 53.9%, and 87.6%. Weight gains and feed conversions of the remaining pigs were monitored until they reached market weight (phase II). The average weight gains (kg) and feed conversions (kg of feed/kg of gain) at posttreatment day 81 (PID 131), respectively, were: 73.6 and 3.44 for nontreated controls, 78.9 and 3.31 for dichlorvos-treated pigs, 72.1 and 3.36 for fenbendazole-treated pigs, and 74 and 3.48 for ivermectin-treated pigs. Differences in average weight gains and feed conversions were not significant (P greater than 0.05).

Antiparasitic agents. 6. Synthesis and anthelmintic activities of novel isothiocyanatophenyl-1,2,4-oxadiazoles

The syntheses and anthelmintic activities of 31 3- and 5-(isothiocyanatophenyl)-1,2,4-oxadiazoles are reported. In the primary anthelmintic screen, 3-(4-isothiocyanatophenyl)-1,2,4-oxadiazole (39) showed 100% nematocidal activity and 3-(2-furanyl)-5-(4-isothiocyanatophenyl)-1,2,4-oxadiazole (63), 3-(2-furanyl)-5-(2-chloro-4-isothiocyanatophenyl)-1,2,4-oxadiazole (64), and 3-(2-furanyl)-5-(4-chloro-3-isothiocyanatophenyl)-1,2,4-oxadiazole (66) showed 100% taeniacidal activity when administered orally to mice. The two most active members of this series, 39 and 63, were active against the gastrointestinal nematodes of sheep at 100 mg/kg. In addition, 39 was also found to be active against hookworms in dogs at a single, oral dose of 200 mg/kg.

Antiparasitic agents. 5. Synthesis and anthelmintic activities of novel 2-heteroaromatic-substituted isothiocyanatobenzoxazoles and benzothiazoles

The synthesis and antiparasitic properties of 22 isothiocyanato-2-pyridinylbenzoxazoles and benzothiazoles are described; the preparation and anthelmintic activities of 14 isothiocyanato-2-thienyl-, -furyl-, and -pyrrolylbenzoxazoles are outlined. In mice experimentally infected with Nematospiroides dubius (nematode) and Hymenolepis nana (tapeworm), three derivatives, i.e., 5-isothiocyanato-2-(2-furyl)benzoxazole (34), 5-isothiocyanato-2-(5-methyl-2-furyl)benzoxazole (35), and 5-isothiocyanato-2-(1-methyl-1H-2-pyrroly)benzoxazole (37), show 100% nematocidal activity and two, i.e., 5- and 6-isothiocyanato-2-(3-pyridinyl)benzoxazole (5) and 5- and 6-isothiocyanato-2-(3-pyridinyl)benzthiazole (21), show 10% taeniacidal activity at 0.2% in the diet. Two derivatives (5 and 21) show good nematocidal activity in sheep. Maximum activity requires 3-pyridinyl derivatives for both the benzoxazole and benzothiazole series.

Antiparasitic agents. 3. Synthesis and anthelmintic activities of novel 2-pyridinyl-5-isothiocyanatobenzimidazoles

The preparation and anthelmintic activities of a series of 2-pyridinyl-5-isothiocyanatobenzimidazoles are described. In the primary oral mouse screen, six derivatives showed 100% taeniacidal activity at 0.2% in diet. The most active member in this series, 1c, is potentially an effective gastrointestinal nematocide in sheep at 50 mg/kg po.

Critical evaluation of taeniacidal antibiotic S15-1 (SQ 21, 704) for removal of natural tapeworm infections in dogs and cats

The new taeniacidal antibiotic S15-1 (SQ 21,704) was evaluated against naturally occuring infections of Taenia pisiformis in 53 dogs, Dipylidium caninum in 35 dogs, T taeniaformis in 18 cats, and D caninum in 33 cats. It all instances, the compound was administered in gelatine capsules in a single oral dose. The doses tested were between and 200 mg/kg of body weight in dogs and between 15 and 45 mg/kg in cats. In dogs, doses of 25 mg/kg and greater were 100% effective against T pisiformis, whereas a dose of 50 mg/kg was necessary to clear D caninum. In cats, a single oral dose of 22.5 mg/kg was 100% efficacious against T taeniaeformis, and a single dose of 45 mg/kg (the largest dose tested) clearly seven of eight cats of D caninum. The efficacy was limited to tapeworms only; there was no efficacy against nematodes. The antibiotic was well tolerated by both species with no drug-related vomiting or other side-effects observed.

Anticoccidial activity of lonomycin (SQ 12,525) in chicks

Lonomycin (TM-481, SQ 12,525) at various concentrations in the feed was tested in controlled battery experiments against laboratory strains of single and mixed Eimeria species infections. The experimental results indicated that lonomycin at doses of .003125, .00625, or .0125% demonstrated a high degree of anticoccidial activity by preventing or reducing mortality, reducing fecal dropping scores, and allowing for normal or near-normal weight gains against single and mixed infections of 5 major pathogenic species, E. acervulina, E. brunetti, E. maxima, E. necatrix, and E. tenella. Lonomycin, at these same dosages, was highly effective against a recent field isolate obtained from a flock previously fed monensin. These studies involving 7 trials totaling 1,680 broiler chicks, have demonstrated that lonomycin at levels of .003125 to .0125% (dependent on species of Eimeria) in the feed is an effective aid in the control of avian coccidiosis in broiler chickens.