Health-Related Quality of Life after Combined External Beam and Either High Dose Rate (HDR) or Low Dose Rate (LDR) Brachytherapy: Does the Rectal Dose from the LDR Brachytherapy Make a Difference?

PURPOSE/OBJECTIVE(S)

The recently reported randomized Phase III trial comparing health related quality of life (HRQOL) after combined external beam radiation therapy (EBRT) and either HDR or LDR brachytherapy (BT) found a significant decline in the EPIC Bowel domain HRQOL score at 24- 48 months after treatment in the LDR arm of the trial. As all patients in the trial received the same EBRT dose, and HDR rectal dose was strictly controlled to be <9.5 Gy to 1cc of rectal wall (RD1cc), we investigated whether the variable rectal dose from the LDR component of treatment was related to the decline in Bowel HRQOL for these patients.

MATERIALS/METHODS

A total of 195 men with upper tier intermediate or high-risk prostate cancer were assigned by a random number generator to receive either an HDR (15 Gy, n = 108) or LDR (110Gy, n = 87) brachytherapy boost combined with 46Gy/23 fractions EBRT. All LDR patients had 1 month post implant quality assurance using CT-MRI fusion. The Expanded Prostate Cancer Composite (EPIC) questionnaire was used to evaluate HRQOL at baseline, q3 mo for 1 year, q6mo for 3 yr and then annually. A multivariate linear regression model was used to investigate the dose-response relationship between EPIC bowel domain score at 24- 48 months and RD1cc.

RESULTS

With a median follow up of 48 months, the previous analysis confirmed the expected time course of acute bowel/urinary symptoms, with LDR showing more prolonged decline in HRQOL bowel domain at 3 and 6 months, but equivalence to HDR by 12 months. HRQOL urinary domain remained equivalent from 12-60 mo. The decline in the HRQOL bowel domain observed for LDR patients from 24-48 mo was analyzed for the 79 patients with sufficient data. The mean baseline HRQOL bowel domain score was 92 and fell on average to 85 at 24-48 mo. Mean RD1cc for the LDR patients was 82Gy (SD 22 Gy), with a maximum value of 129 Gy. In this range of rectal doses, a 20Gy increase in RD1cc, was associated on average with a 1.5-point decrease in EPIC HRQOL bowel domain score (p = 0.21).

CONCLUSION

The rectal dose received by the LDR patients showed a non-significant dose-response with the EPIC Bowel domain HRQOL score. This confirms the accepted rectal dose constraints for LDR brachytherapy but does not explain the observed decline in bowel scores from 24-48 months.

A phase III randomized trial comparing intermittent versus continuous androgen suppression for patients with PSA progression after radical therapy: NCIC CTG PR.7/SWOG JPR.7/CTSU JPR.7/UK Intercontinental Trial CRUKE/01/013

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Background: In men with PSA recurrence after radical radiotherapy (RRT), intermittent androgen suppression (IAS) has been suggested by phase II trials to improve quality of life (QoL) but effects on survival are unknown. In this Intergroup randomized phase III trial, we compared IAS vs continuous androgen deprivation (CAD) to test for non-inferiority of IAS with respect to overall survival (OS).

Methods: Eligible men had rising PSA > 3.0 ng/ml >1 year post RRT, either initial or salvage, for localized prostate cancer. Patients could receive up to 1 year of neo/adjuvant androgen deprivation therapy (ADT) completed >1 year prior. Stratification factors were time since RRT (>1-3 vs >3 years), initial PSA (<15 vs >15), prior radical prostatectomy and prior ADT. IAS was delivered for 8 months in each cycle with restart when PSA reached >10 ng/ml off treatment. Primary endpoint was OS; secondary endpoints included time to hormone refractory state (HR), QoL, cholesterol/HDL/LDL, duration of treatment/non-treatment intervals, time to testosterone and potency recovery. The independent DSMC recommended halting the trial after a planned interim analysis demonstrated that a pre-specified stopping boundary for non-inferiority was crossed.

Results: 1,386 patients were randomized to IAS (690) or CAD (696) arms. Arms were balanced for important baseline factors. Median follow up was 6.9 years. IAS patients completed a median of 2 x 8 month cycles (range: 1-9). 524 deaths were observed (268 on IAS vs 256 on CAD). Median OS was 8.8 vs 9.1 years on IAS and CAD arms, respectively (HR 1.02, 95%CI 0.86-1.21; p for non-inferiority [HR IAS vs CAD ≥ 1.25] = 0.009). The IAS arm had more disease related (122 vs 97) and fewer unrelated (134 vs 146) deaths. Time to HR was statistically significantly improved on the IAS arm (HR 0.80, 95%CI 0.67-0.98; p = 0.024). IAS patients had reduced hot flashes, but otherwise there was no evidence of differences in AEs, including myocardial events or osteoporotic fractures.

Conclusions: In men with PSA recurrence after RRT IAS, given as described herein, is non-inferior to CAD with respect to OS.

No significant financial relationships to disclose.

Use of a surgically derived nomogram to predict high likelihood of Gleason score upgrading for favorable-risk prostate cancer treated with permanent seed brachytherapy

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Background: Crook et al have reported a 7-year disease-free survival (DFS) of 95.2% in 1,111 men with prostate cancer treated with Iodine-125 permanent seed brachytherapy (BT) at Princess Margaret Hospital. Two nomograms have been developed that estimate the likelihood of Gleason score (GS) upgrading for patients with favorable risk prostate cancer undergoing radical prostatectomy (RP). The purpose of this project was to apply these nomograms to a cohort treated with BT.

Methods: Records were examined for all men receiving prostate BT in 2006-7. 217 had favorable risk disease. The likelihood of GS upgrading was predicted using RP-derived nomograms created by Kulkarni et al (PMH, 2007) and Budaus et al (2010). Clinical and pathologic information were available on 208 patients to allow completion of the Kulkarni nomogram, and on 193 patients for the Budaus nomogram.

Results: The median age of the BT cohort was 62 years (range 44–77), and the median PSA level 4.68 ng/ml. Clinical stage was T1 in 65%, and 47.6% had positive findings on transrectal ultrasound. Median prostate volume was 33.3 cc (15.0–72.3). Uro-pathology review was available for 93%. 84.1% had extended biopsies, with 40.9% showing prostatic intraepithelial neoplasia and 10.1% inflammation. The median % of positive cores was 25%, with a median maximum % involvement per core of 20%. Two men received androgen deprivation therapy for prostate downsizing. The median predicted likelihood of GS upgrading was 51.6% using the Kulkarni nomogram, and 43.6% using the Budaus nomogram. The median PSA after 3.2 years median follow-up is 0.18 ng/mL.

Conclusions: In a population of men with favorable risk prostate cancer treated with BT, the estimated likelihood of GS upgrading using two surgical nomograms was substantial. The study cohort was taken from a larger population of patients treated over 10 years for whom 7-year DFS is 95.2%. This suggests that permanent seed brachytherapy is a highly effective treatment option for patients with favorable risk disease despite unfavorable clinical and pathologic factors. Patients should not be discouraged from brachytherapy on the basis of a high likelihood of GS upgrading.

No significant financial relationships to disclose.

Comparative analysis of group II metabotropic glutamate receptor immunoreactivity in Brodmann's area 46 of the dorsolateral prefrontal cortex from patients with schizophrenia and normal subjects

Glutamate is the primary excitatory neurotransmitter in the mammalian central nervous system, and a key neurotransmitter in prefrontal cortical function. Converging lines of evidence implicate prefrontal cortical dysfunction in the neurobiology of schizophrenia. Thus, aberrant glutamate neurotransmission may underlie schizophrenia and other complex disorders of behavior. Group II metabotropic receptors (mGluRs) are important modulators of glutamatergic and non-glutamatergic neurotransmission. Moreover, in an animal model, an agonist for group II mGluRs has been shown to reverse the behavioral, locomotor, and cognitive effects of the psychotomimetic drug phencyclidine. Accordingly, group II mGluRs constitute attractive targets for the pharmacotherapeutics and study of schizophrenia. Using immunocytochemistry and Western immunoblotting, we compared the localization and levels of group II mGluRs in Brodmann's area 46 of the dorsolateral prefrontal cortex from patients with schizophrenia and normal subjects. Consistent with previous reports, we found that immunolabeling of group II mGluRs is prominent in Brodmann's area 46. The majority of labeling was present on axon terminals distributed in a lamina-specific fashion. No apparent difference in the cellular localization or laminar distribution of immunoreactive group II mGluRs was noted between the two diagnostic groups. Similarly, the levels of receptor immunoreactivity determined by quantitative Western immunoblotting were comparable between schizophrenic patients and normal subjects. We conclude that while the function of group II mGluRs in Brodmann's area 46 of dorsolateral prefrontal cortex may be altered in patients with schizophrenia, this is not evident at the level of protein expression using an antibody against mGluR2 and mGluR3.

Reliability of the lumbar flexion, lumbar extension, and passive straight leg raise test in normal populations embedded within a complete physical examination

STUDY DESIGN

The study measured the reliability of the passive straight leg raise (SLR) test and lumbar range of motion (LROM) tests measured as continuous variables embedded within a comprehensive physical examination.

OBJECTIVES

To determine the reliability of the SLR and LROM test scores when they are measured with a Cybex electronic inclinometer (Lumex, Inc., New York, NY) within a physical examination.

SUMMARY OF BACKGROUND DATA

Good published empirical reliability exists for the Cybex and for SLR and LROM tests when the measurements are taken in isolation from other physical examination procedures. Reliability of the Cybex for continuous SLR and LROM measurement within a physical examination has not been assessed, however.

METHODS

Forty-five participants were seen by one of two physician/physiotherapist teams. Participants were examined by both team members. The first examiner conducted the first tests and retested 1 week later (intrarater reliability). The second examined the participants the day after their first appointment (inter-rater reliability).

RESULTS

Only two scores showed substantial reliability (defined as r > or = 0.60). These scores were left (r = 0.81) and right (r = 0.79) SLR intrarater reliability. All other scores fell below the specified cutoff.

CONCLUSIONS

SLR and LROM scores used clinically are collected during comprehensive physical examinations. Most scores gathered under these conditions were not reliable. These findings have implications for the use of clinically derived SLR and LROM scores.

Commentary on the American Medical Association guides' lumbar impairment validity checks

STUDY DESIGN

The American Medical Association's (AMA) Guides to the Evaluation of Permanent Impairment range of motion-based (ROM) lumbar impairment model validity checks were reviewed. Published literature of lumbar ROM (LROM) testing also was reviewed for application of the AMA validity checking protocols.

OBJECTIVE

The utility and feasibility of use of the AMA Guides' ROM lumbar impairment ratings were examined.

SUMMARY OF BACKGROUND DATA

Although they appear to be essential components of the ROM model, few published studies report use of these validity checks. Of at least 22 reviewed studies of LROM testing, only six studies included at least three measurements (the bare minimum) of LROM. Furthermore, only two (9.1%) reported performance of the LROM validity check. Only one, however, reported the results.

METHODS

English language journals were searched on Medline using "region, lumbar," "range of motion," "validity of results," "observer variation," and "low back pain" as title and subject search terms. The study methodologies approximating the AMA Guides' specifications were included in the analysis.

RESULTS

Under normal conditions of ROM measurement, 33% of three consecutive lumbar flexion and 27% of three consecutive lumbar extension measurements failed the LROM validity check. In addition, across three different experimental sessions (each with more than three consecutive LROM measurements taken) only 15 participants (33%) had valid flexion scores and only 24 participants (53%) had valid extension scores across all three sessions.

CONCLUSION

Technical complications inherent in the ROM-based impairment-rating model render the validity checks difficult to perform satisfactorily and thus rarely used.

Analysis of the convergent and discriminant validity of published lumbar flexion, extension, and lateral flexion scores

STUDY DESIGN

Articles reflecting the convergent or discriminant validity of the lumbar range of motion tests were reviewed and compared. Mean scores and standard deviations for lumber range of motion from healthy control subjects were plotted against those from patients with low back injuries.

OBJECTIVE

To use published research to analyze the convergent and discriminant validity of lumbar range of motion tests for the characterization of low back pain and injury.

SUMMARY OF BACKGROUND DATA

Several publications have addressed lumbar range of motion validity. Individual studies suggest that the tests possess convergent validity, but that their discriminant validity is indeterminate.

METHODS

English-language journals were searched on Medline using "region," "lumbar," "range of motion," "validity of results," "observer variation," and "low back pain" as title and subject search terms. The study methods approximating the specifications of the American Medical Association Guides to the Evaluation of Permanent Impairment were included in the analysis.

RESULTS

Convergent validity research showed inconsistent relations between inclinometric and radiographic lumbar range of motion measurements. Some studies showed strong relation, whereas others showed essentially no relation between the two techniques. Correlations between lumbar range of motion scores and spinal disability and function were similarly inconclusive. Studies reporting mean scores and standard deviations for lumbar range of motion measurements showed a high degree of overlap between the scores of participants with low back injuries and those without such injuries.

CONCLUSIONS

Convergent and discriminant validities of the lumbar range of motion tests currently require further substantiation. Absolute lumbar range of motion scores may not be suitable as the sole determinants of low back pathology diagnosis. Implications for using the lumbar range of motion tests to characterize low back injuries in medicolegal situations are discussed.

Cholinergic systems and schizophrenia: primary pathology or epiphenomena?

Post mortem schizophrenia research has been driven first by the dopamine and then the glutamate hypotheses. These hypotheses posit primary pathology in pathways dependent upon dopamine or glutamate neurotransmission. Although the dopamine and glutamate hypotheses retain considerable theoretical strength, neurobiological findings of altered dopamine or glutamate activity in schizophrenia do not explain all features of this disorder. A more synthetic approach would suggest that focal pathological change in either the prefrontal cortex or mesial temporal lobe leads to neurochemical changes in multiple neurotransmitter systems. Despite the limited experimental evidence for abnormal cholinergic neurotransmission in psychiatric disorders, increased understanding of the role of acetylcholine in the human brain and its relationship to other neurotransmitter systems has led to a rapidly growing interest in the cholinergic system in schizophrenia. This review focuses on the basic anatomy of the mammalian cholinergic system, and its possible involvement in the neurobiology of schizophrenia. Summaries of cholinergic cell groups, projection pathways, and receptor systems, in the primate and human brain, are followed by a brief discussion of the functional correlations between aberrant cholinergic neurotransmission and the signs and symptoms of schizophrenia.

Low muscarinic receptor binding in prefrontal cortex from subjects with schizophrenia: a study of Brodmann's areas 8, 9, 10, and 46 and the effects of neuroleptic drug treatment

OBJECTIVE

Aberrant cholinergic inputs and synaptic neurotransmission in the prefrontal cortex induce cognitive impairment, which is a central feature of schizophrenia. Postsynaptic excitatory muscarinic cholinergic M(1) and M(4) receptors are the major cholinoceptive targets in the prefrontal cortex and hence may be involved in the pathology and/or pharmacotherapeutics of schizophrenia.

METHOD

Using quantitative autoradiography, the authors analyzed the binding of the M(1)/M(4) receptor selective antagonist [(3)H]pirenzepine in prefrontal cortex (Brodmann's areas 8, 9, 10, and 46) from schizophrenia patients who had (N=6) or had not (N=11) been treated with the anticholinergic agent benztropine mesylate and from normal comparison subjects (N=20). Moreover, preliminary studies of [(3)H]pirenzepine binding in rat frontal cortex following administration of antipsychotic drugs or benztropine mesylate were performed.

RESULTS

Relative to those of comparison subjects, the mean levels of [(3)H]pirenzepine binding were significantly lower in Brodmann's areas 9 and 46 of the schizophrenia patients not treated with benztropine mesylate (18% lower in Brodmann's area 9 and 21% lower in Brodmann's area 46) and in all four examined regions of the patients who had received benztropine (51%-64% lower). Antipsychotic or anticholinergic drugs tended to increase or have no effect on the density of [(3)H]pirenzepine-labeled receptors in rat frontal cortex.

CONCLUSIONS

Because M(1) and M(4) receptors are critical to the functions of prefrontal cortical acetylcholine, the present findings suggest a functional impairment in cholinergic neurotransmission in schizophrenia and the possibility that muscarinic receptors are involved in the pharmacotherapeutics of the disorder.

Intermittent androgen suppression for prostate cancer: Canadian Prospective Trial and related observations

The Canadian Prospective Trial of intermittent androgen suppression was a prototype therapeutic initiative started in 1995 for the management of patients in biochemical relapse after radiation for localized prostate cancer. An interim analysis has yielded several observations on the relations between baseline serum prostate specific antigen (PSA), nadir serum PSA, Gleason score, and time off-treatment. In a typical androgen-dependent tumor, the response of serum PSA to androgen withdrawal is biphasic, but with early tumor progression, plateauing of serum PSA is observed. Ligand-independent activation of the androgen receptor, a mechanism subserving the initiation of androgen independence, can be counteracted experimentally with decoy molecules and clinically with nonsteroidal antiandrogens. In some patients, it is possible to lengthen the off-treatment interval by inhibiting the enzyme 5 alpha-reductase, an effect that can be reinforced by lowering serum testosterone with an antigonadotropin. Serial measurements of serum PSA indicate that intermittent androgen suppression engenders a more diverse range of hormone-related responses than previously appreciated. These include: (1) repeated differentiation of tumor with recovery of apoptotic potential; (2) inhibition of tumor growth by rapid restoration of serum testosterone; and (3) restraint of tumor growth by subnormal levels of serum testosterone. These responses are aspects of regulation that should be taken into account when planning long-term treatment of prostate cancer with intermittent androgen suppression.

Combined physiological-anatomical approaches to study lateral inhibition

In the visual cortex, large basket cells form the cellular basis of long-range lateral inhibition. The present paper focuses on combinations of methods with which large basket cells can be studied in the context of extensive neuronal representations. In the first approach, the topographic relationship between large basket axons and known functional representations such as orientation, direction, and ocular dominance is analysed. Functional mapping is carried out using extracellular electrode recordings or optical imaging of intrinsic signals followed by 3-dimensional anatomical reconstruction of biocytin stained large basket cells in the same regions. In the second approach, the contribution of lateral inhibition to orientation and direction selectivity is assessed using the GABA inactivation paradigm and direct inhibitory projections from the inactivation to recording sites are demonstrated with biocytin staining and injections of [3H]nipecotic acid, a radioactive marker for GABAergic cells. The limitation of these approaches is that they can only be used in cortical regions which lie on the surface of the brain.

Decreased muscarinic receptor binding in subjects with schizophrenia: a study of the human hippocampal formation

BACKGROUND

Acetylcholine is important to hippocampal function, including the processes of learning and memory. Patients with schizophrenia show impaired learning and memory and hippocampal dysfunction. Thus, acetylcholinergic systems may be primarily or secondarily disrupted in the hippocampal formation of schizophrenic patients. The present study tested the hypothesis that [(3)H]pirenzepine-labeled muscarinic cholinergic receptor levels are altered in the hippocampal formation of patients with schizophrenia.

METHODS

We have used quantitative autoradiography to measure [(3)H]pirenzepine binding to M(1) and M(4) receptors in the hippocampal formation from 15 schizophrenic and 18 nonschizophrenic subjects.

RESULTS

The mean density of [(3)H]pirenzepine binding was reduced in all regions studied, including the dentate gyrus, subdivisions of Ammon's Horn (CA1-CA4), subiculum, and the parahippocampal gyrus, of the schizophrenic cohort. Moreover, unlike controls, there was no significant variation between the mean levels of [(3)H]pirenzepine binding across the subregions of the hippocampal formation from schizophrenic subjects.

CONCLUSIONS

These findings provide support for a possible involvement of the muscarinic cholinergic system in the pathology and/or treatment of schizophrenia.

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.

Muscarinic1 and 2 receptor mRNA in the human caudate-putamen: no change in m1 mRNA in schizophrenia

Studies using tissue obtained at autopsy suggest that changes in cholinergic neurons could be important in the pathology of schizophrenia.1-4 We have previously reported a decrease in [3H]pirenzepine binding5 and [3H]AF-DX 384 binding6 to caudate-putamen (CP) from subjects who had schizophrenia. Under the conditions chosen, [3H]pirenzepine would predominately bind to muscarinic1 (M1) and muscarinic4 (M4) receptors,7whereas [3H]AF-DX 384 would mainly bind to muscarinic2 (M2) and M4 receptors.8 Given the relative concentrations of M1, M2 and M4 receptors in the human CP and the magnitude of the decreases in radioligand binding in schizophrenia, our results most likely reflected a change in the density of M1 and M2 receptors in the CP from the schizophrenic subjects. In situ hybridisation has now been used to determine levels of m1 and m2 mRNA in CP from 14 schizophrenic and 16 control subjects previously used for radioligand binding. m2 mRNA in the CP from the schizophrenic and control subjects was below the sensitivity of in situhybridisation. There was no difference in the levels of m1 mRNA in CP from schizophrenic and control subjects (mean +/- SEM: 103 +/- 16 vs106 +/- 17 fmol [35S]oligonucleotide probe g-1estimated tissue equivalents, P = 0.91). In conclusion, data from our radioligand binding studies show decreases in [3H]pirenzepine binding that are likely to reflect a decrease in the density of M1 receptors in CP from schizophrenic subjects. Our data in this study show the absence of a concomitant change in mRNA coding for that receptor.

The binding of [3H]AF-DX 384 is reduced in the caudate-putamen of subjects with schizophrenia

Clinical studies of cholinergic pharmacotherapy, together with the putative role of the muscarinic receptor system in the neurophysiology of human behavior, support a possible muscarinic cholinergic involvement in schizophrenia. The present study has measured the density of [3H]AF-DX 384 labelled receptors (muscarinic M2 and M4) in the caudate-putamen, obtained at autopsy, from 19 subjects who had schizophrenia, and 20 subjects who did not have schizophrenia. [3H]AF-DX 384 binding was reduced in caudate-putamen from schizophrenic subjects (104 +/- 10.3 vs 145 +/- 901 fmol mg(-1) TE; mean +/- s.e.; p = 0.007). Preliminary analysis of patient drug data as well as rat studies suggest that the reduced [3H]AF-DX 384 binding in caudate-putamen of schizophrenic subjects is not wholly due to antipsychotic drug treatment, or anticholinergic medication for the treatment of extrapyramidal effects. These data suggest that the muscarinic cholinergic system may be involved in the pathology of schizophrenia.

Intermittent androgen suppression in the management of prostate cancer

OBJECTIVES

Intermittent androgen suppression (IAS) has been suggested as a means of attenuating the androgen deprivation syndrome in men with incurable prostate cancer. Laboratory data suggest that intermittent therapy may prolong the duration of androgen dependence.

METHODS

Since October 1993, 54 patients have entered a Phase II protocol consisting of 8 months of total androgen blockade (TAB) using leuprolide (Lupron) depot and nilutamide (Anandron) followed by an off-treatment interval of variable length. Eleven patients had biopsy-proven local failure after radiotherapy, 4 had biochemical failure, 24 had distant metastases (fewer than six axial sites on bone scan), 11 had combined local and distant failure, and 4 were treated as primary management for nodal disease. Mean prostate-specific antigen (PSA) at entry was 37 ng/mL (range 3.8 to 196). After 8 months of TAB, hormonal therapy was discontinued for those patients whose PSA was less than 4.0 ng/mL and stable or decreasing and was resumed (cycle 2) when PSA increased to greater than 10 ng/mL.

RESULTS

As of April 1 998, mean follow-up was 33 months (range 14 to 53). Patients have completed at least one, and up to five treatment cycles. The mean time to nadir PSA in cycle 1 was 20 weeks, and the mean time off was 35 weeks (31 weeks for those with metastatic disease versus 39 for local or biochemical failure). In cycle 2, the mean time to PSA nadir was 17 weeks, and the mean time off was 30 weeks (28 weeks for metastatic disease and 38 weeks for local or biochemical failure). In cycle 3, the time to PSA nadir was 19 weeks. Full testosterone data are available for 40 patients in cycle 1. Normal levels were achieved during the off-treatment interval in 73% by a mean of 18 weeks (median 9). Testosterone normalization in cycle 2 was achieved in 71% at a mean time of 17 weeks (median 14).

CONCLUSIONS

TAB can be used intermittently, and appears to be more appropriate for patients with local or biochemical failure. Testosterone recovery is not universal in the off-treatment intervals. IAS needs to be investigated in a randomized trial to determine the effect on overall survival and quality of life.

Percent free prostate-specific antigen after radiotherapy for prostate cancer

OBJECTIVES

The range of "normal" prostate-specific antigen (PSA) values compatible with cure following radiotherapy (RT) for prostate cancer (PCa) has yet to be established. Various thresholds, ranging from 0.5 to 4.0 ng/mL are used to define biochemical disease-free status. Because the proportion of free PSA is lower in men with PCa, the ratio of free PSA to total PSA could theoretically be useful in determining cancer-free status after RT.

METHODS

One hundred two men treated with standard external beam RT from October 1988 to October 1994 (median dose, 66 Gy) were chosen for measurement of percent free PSA because they had a routine follow-up visit in November or December of 1996. All patients had undergone systematic transrectal ultrasound-guided biopsies after RT. Biopsies were negative in 66 patients, positive in 21, and indeterminate in 15 (rare, degenerated cancer cells with no evidence of proliferation by immunohistochemical stains). Stage distribution was T1b, 8; T1c, 9; T2a, 25; T2b/c, 40; and T3, 20. Median follow-up is 40 months.

RESULTS

Total serum PSA ranged from 0. 1 to 10.0 ng/mL. Because the mean (+/-SD) percent free PSA for patients with negative (n = 66) and indeterminate (n = 15) biopsies were 29% +/- 18% and 25% +/- 7%, respectively (P = 0.13), these were combined. The mean (+/-SD) percent free PSA for those with positive biopsies (n = 21) was 15% +/- 8% and was significantly different from those with negative or indeterminate biopsies (P < 0.001). Patients with negative or indeterminate biopsies were grouped according to their total PSA as 0.1 to 0.5 ng/mL (n = 33), 0.6 to 1.0 ng/mL (n = 23), 1.1 to 2.0 ng/mL (n = 17), and greater than 2.0 ng/mL (n = 7). The mean percent free PSAs were 34%, 28%, 21%, and 12%, respectively.

CONCLUSIONS

Percent free PSA may be a useful adjunct in diagnosing recurrent PCa after RT. The ratio is significantly different in patients of known biopsy status, distinguishing a group with positive biopsies from those with negative. However, there is overlap in individual values, and because patients with negative biopsies after RT may have subclinical distant disease, more follow-up is necessary before percent free PSA can be incorporated into a definition of biochemical disease-free status. Percent free PSA may be most useful for PSA from 0.6 to 2.0 ng/mL, where failure is common, but not universal.

Evidence for a contribution of lateral inhibition to orientation tuning and direction selectivity in cat visual cortex: reversible inactivation of functionally characterized sites combined with neuroanatomical tracing techniques

We have previously reported that cells in cat areas 17 and 18 can show increases in response to non-optimal orientations or directions, commensurate with a loss of inhibition, during inactivation of laterally remote, visuotopically corresponding sites by iontophoresis of gamma-aminobutyric acid (GABA). We now present anatomical evidence for inhibitory projections from inactivation sites to recording sites where 'disinhibitory' effects were elicited. We made microinjections of [3H]-nipecotic acid, which selectively exploits the GABA re-uptake mechanism, < 100 microm from recording sites where cells had shown either an increase in response to non-optimal orientations during inactivation of a cross-orientation site (n = 2) or an increase in response to the non-preferred direction during inactivation of an iso-orientation site with opposite direction preference (n = 5). Retrogradely labelled GABAergic neurons were detected autoradiographically and their distribution was reconstructed from series of horizontal sections. In every case, radiolabelled cells were found in the vicinity of the inactivation site (three to six within 150 microm). The injection and inactivation sites were located in layers II/III-IV and their horizontal separation ranged from 400 to 560 microm. In another experiment, iontophoresis of biocytin at an inactivation site in layer III labelled two large basket cells with terminals in close proximity to cross-orientation recording sites in layers II/III where disinhibitory effects on orientation tuning had been elicited. We argue that the inactivation of inhibitory projections from inactivation to recording sites made a major contribution to the observed effects by reducing the strength of inhibition during non-optimal stimulation in recurrently connected excitatory neurons presynaptic to a recorded cell. The results provide further evidence that cortical orientation tuning and direction selectivity are sharpened, respectively, by cross-orientation inhibition and iso-orientation inhibition between cells with opposite direction preferences.

Use of strontium-89 in endocrine-refractory prostate cancer metastatic to bone. Provincial Genitourinary Cancer Disease Site Group

GUIDELINE QUESTION

What is the role of strontium-89 in effective palliative care of patients with stage D endocrine-refractory prostate cancer and multiple sites of painful bone metastases?

OBJECTIVE

To make recommendations about the routine use of 89Sr in this clinical setting.

OUTCOMES

Effective palliation is the primary outcome of interest. Patient survival and toxic effects of treatment are also considered.

PERSPECTIVE (VALUES)

Evidence was selected and reviewed by 3 members of the Genitourinary Cancer Disease Site Group (Genitourinary Cancer DSG) of the Cancer Care Ontario Practice Guidelines Initiative. Earlier drafts of the guideline were circulated and reviewed by members of the DSG. The Genitourinary Cancer DSG comprises medical oncologists, radiation oncologists, urologists, a pathologist and a community representative. Guideline approval requires input from community representatives.

QUALITY OF EVIDENCE

Three randomized controlled trials (RCTs) were available for evaluation. Two compared 89Sr with placebo, and one RCT compared 89Sr with conventional radiation (either hemibody or involved-field radiotherapy, as determined before randomization).

BENEFITS

One of the 2 studies comparing 89Sr with placebo demonstrated the palliative efficacy of the intervention (p < 0.01); the other showed no benefit. The third study, comparing 89Sr with conventional radiation, concluded that all treatments provided equally effective pain relief and that improvement was sustained for at least 3 months in similar proportions of patients. The difference in the median duration of patient survival between groups in this study was neither clinically nor statistically significant.

HARMS

The use of 89Sr may cause bone marrow suppression, but clinically significant sequelae are uncommon. The use of 89Sr may preclude further systemic chemotherapy or eligibility for clinical trials of systemic therapy. Symptoms other than those due to bone marrow suppression are rare.

PRACTICE GUIDELINE

89Sr is recommended for use in patients with endocrine-refractory prostate cancer who have multiple uncontrolled painful sites of bone metastases on both sides of the diaphragm not adequately controlled with conventional analgesic therapy, and in whom the use of multiple single fields of external beam radiation is not possible. 89Sr has proven to be efficacious in the palliation of hormone-refractory painful bone metastases from prostate cancer. It has not been shown to lengthen the average duration of patient survival. There is limited evidence on the relative efficacy of 89Sr compared with wide-field radiotherapy. 89Sr is the treatment of choice given all the following specific indications: Established diagnosis of prostate cancer metastatic to bone. Metastatic disease refractory to hormone therapy. Progressive sites of pain poorly controlled with conventional narcotics. Painful sites of disease on both sides of the diaphragm (otherwise, hemibody radiotherapy is equally efficacious). Patient or tumour factors (number of involved sites, location of involved sites or level of pain control) that are relative contraindications to the use of multiple single fields of radiation as an alternative. No evidence of impending spinal cord compression. Adequate bone marrow reserve. Evidence from a diagnostic bone scan of radionuclide concentration in painful bone lesions. PRACTICE GUIDELINE DATE: Nov. 23, 1997. Part 2.

GUIDELINE QUESTION

What is the role of 89Sr in effective palliative care of patients with stage D hormone-refractory prostate cancer receiving involved-field radiotherapy for isolated painful bone metastases?

OBJECTIVE

To make recommendations about the routine use of 89Sr in this clinical setting.

OUTCOMES

Effective palliation is the primary outcome of interest. Patient survival and toxic effects of treatment are also considered.

PERSPECTIVE (VALUES)

As described in preceding abstract (Part 1).

QUALITY OF EVIDENCE

One RCT was available for evaluati

Serum prostate-specific antigen profile following radiotherapy for prostate cancer: implications for patterns of failure and definition of cure

OBJECTIVES

A reference range of prostate-specific antigen (PSA) values compatible with cure following radiotherapy (RT) for prostate cancer (PCa) has yet to be established. Various thresholds, as low as 0.5 ng/mL, have been used to define biochemical disease-free status. We report PSA profiles in 118 patients who were systematically biopsied following standard RT, with a minimum 4-year follow-up.

METHODS

One hundred eighteen patients were treated with standard external beam RT from May 1987 to October 1991, and were followed prospectively with transrectal ultrasound (TRUS)-guided biopsies and measurement of serum PSA levels. Stage distribution was as follows: T1b: 25 patients, T2a: 27 patients, T2b/c: 42 patients, T3: 23 patients, T4: 1 patient. Median follow-up for patients without clinical failure is 68 months (range 48 to 108). Treatment failures were categorized as biochemical (biochemical failure [chemF]: PSA level of 2.0 ng/mL or more and greater than 1 ng/mL over nadir), local (local failure [LF]: positive biopsy and PSA level greater than 2.0), and distant failure (DF).

RESULTS

PCa recurred in 55% of patients: 38% LF (n = 45; 30 isolated and 15 with DF), 25% DF (n = 30; 15 isolated and 15 with LF), and 4% chemF (n = 5). Mean PSA nadir was 0.4 for patients with no evidence of disease (NED) and occurred at 33 months, 3.2 for LF at 17 months, 7.7 for DF at 12 months, and 1.4 for chemF at 24 months. After reaching the nadir, PSA in patients with recurrence followed first-order kinetics, rising exponentially over time. The mean PSA doubling time was 12.6 months for LF, 5.2 months for DF, and 21.8 months for chemF (P = 0.004). At last follow-up, the median PSA for patients without evidence of disease is 0.5 ng/mL. Four such patients had PSA values that rose to between 1 and 2 ng/mL for 5 to 38 months, but these eventually fell again to less than 1 ng/mL. Three patients had PSA values between 2 and 3 ng/mL, but 2 now have decreasing levels and the third has a rising level. All patients whose PSA levels rose to greater than 3 ng/mL exhibited a persistently rising pattern and ultimate tumor recurrence.

CONCLUSIONS

There is a range of PSA values following RT for PCa that is compatible with cure. A definition of biochemical disease-free status at any absolute threshold of PSA level less than 3 ng/mL will overdiagnose failure in a significant proportion of patients. Patients with a PSA level between 1.5 and 3 ng/mL should be observed until there is unequivocal evidence of disease recurrence. In the absence of known biopsy status, PSA doubling time can be a useful indicator of whether failure is local or distant.

Radiotherapy for localized prostate carcinoma. The correlation of pretreatment prostate specific antigen and nadir prostate specific antigen with outcome as assessed by systematic biopsy and serum prostate specific antigen

BACKGROUND

The objective of this study was to correlate the failure pattern of localized prostate carcinoma after radiotherapy (RT) with pretreatment (preTx) PSA and post-RT nadir PSA, using systematic biopsies and serum PSA in the assessment of outcome.

METHODS

From January 1990 to February 1994, 207 patients treated with external beam RT were followed prospectively with systematic transrectal ultrasound-guided biopsies and measurements of serum PSA levels. Three hundred forty-three biopsies were performed, with 4-7 samples taken per session. The distribution of T classification was as follows: 19 patients had T1b, 15 had T1c, 34 had T2a, 79 had T2b/c, 53 had T3, and 7 had T4. Median follow-up was 36 months (range, 12-70 months). Failures were categorized as biochemical (chemF) (PSA > 2.0 ng/mL and > 1 ng/ mL over nadir), local (LF) (positive biopsy and PSA > 2), and distant (DF). The Cox proportional hazards model was used for multivariate analysis (MVA).

RESULTS

Overall, failures were seen in 68 of 207 patients: 20 LF, 24 DF, 7 LF + DF, and 17 chemF. In univariate analysis, failures correlated significantly with preTx PSA, post-RT nadir PSA, T classification, and Gleason's score (GS). The total failure rate was 12% for T1b, T1c, and T2a; 39% for T2b and T2c; and 60% for T3 and T4 (P < 0.0001). By evaluation with preTx PSA, at 36 months the total failure rate was 3% for preTx PSA < or = 5 ng/mL 16% for 5.1-10 ng/mL, 32% for 10.1-15 ng/mL, 42% for 15.1-20 ng/mL, 63% for 20.1-50 ng/mL, and 88% for > 50 ng/mL (P < 0.0001). By evaluation with post-RT nadir PSA, at 36 months the total failure rate was 4% for nadir PSA < or = 0.5 ng/ mL, 26% for 0.6-1 ng/mL, 33% for 1.1-2 ng/mL, and 92% for > 2 ng/mL (P < 0.0001). In MVA, nadir PSA (P < 0.0001) and T classification (P < 0.0005) were independent predictors for any failure. LF occurred in 13% of patients (27 of 207). For these 27 patients, the categorization of T classification was: T1b/T1c/T2a, 7%; T2b/T2c, 16%; and T3/T4, 15% (P = not significant). In MVA, only nadir PSA (P = 0.0004) predicted for LF. DF occurred in 15% of patients (31 of 207). In MVA, nadir PSA (P < 0.0001) and T classification (P < 0.0001) predicted for DF, with pretreatment PSA of borderline significance (P < 0.05). To assess preTx predictors of outcome, post-RT nadir PSA was removed from the model. PreTx PSA then became the dominant variable to predict any failure (P < 0.0001), LF (P = 0.05), chemF (P = 0.0001), and DF (P < 0.003), while T classification also predicted for any failure (P = 0.03), chemF (P = 0.05), and DF (P < 0.0001).

CONCLUSIONS

Systematic prostate biopsies, performed as part of the rigorous followup of prostate carcinoma after RT, define the patterns of failure and confirm the prognostic value of preTx PSA, post-RT nadir PSA, and T classification. Prior to treatment, preTx PSA is the overwhelming independent predictor of failure, but it is surpassed by post-RT nadir PSA when this is added to the model.

GABA-induced inactivation of functionally characterized sites in cat striate cortex: effects on orientation tuning and direction selectivity

Microiontophoresis of gamma-aminobutyric acid (GABA) was used to reversibly inactivate small sites of defined orientation/direction specificity in layers II-IV of cat area 17 while single cells were recorded in the same area at a horizontal distance of approximately 350-700 microns. We compared the effect of inactivating iso-orientation sites (where orientation preference was within 22.5 deg) and cross-orientation sites (where it differed by 45-90 deg) on orientation tuning and directionality. The influence of iso-orientation inactivation was tested in 33 cells, seven of which were subjected to alternate inactivation of two iso-orientation sites with opposite direction preference. Of the resulting 40 inactivations, only two (5%) caused significant changes in orientation tuning, whereas 26 (65%) elicited effects on directionality: namely, an increase or a decrease in response to a cell's preferred direction when its direction preference was the same as that at an inactivation site, and an increase in response to a cell's nonpreferred direction when its direction preference was opposite that at an inactivation site. It is argued that the decreases in response to the preferred direction reflected a reduction in the strength of intracortical iso-orientation excitatory connections, while the increases in response were due to the loss of iso-orientation inhibition. Of 35 cells subjected to cross-orientation inactivation, only six (17%) showed an effect on directionality, whereas 21 (60%) showed significant broadening of orientation tuning, with an increase in mean tuning width at half-height of 126%. The effects on orientation tuning were due to increases in response to nonoptimal orientations. Changes in directionality also resulted from increased responses (to preferred or nonpreferred directions) and were always accompanied by broadening of tuning. Thus, the effects of cross-orientation inactivation were presumably due to the loss of a cross-orientation inhibitory input that contributes mainly to orientation tuning by suppressing responses to nonoptimal orientations. Differential effects of iso-orientation and cross-orientation inactivation could be elicited in the same cell or in different cells from the same inactivation site. The results suggest the involvement of three different intracortical processes in the generation of orientation tuning and direction selectivity in area 17: (1) suppression of responses to nonoptimal orientations and directions as a result of cross-orientation inhibition and iso-orientation inhibition between cells with opposite direction preferences; (2) amplification of responses to optimal stimuli via iso-orientation excitatory connections; and (3) regulation of cortical amplification via iso-orientation inhibition.

Evaluation of radiation effect, tumor differentiation, and prostate specific antigen staining in sequential prostate biopsies after external beam radiotherapy for patients with prostate carcinoma

BACKGROUND

Sequential systematic biopsies after radiotherapy (RT) for prostate carcinoma were evaluated with respect to radiation effect, tumor differentiation, and prostate specific antigen (PSA) staining, and these histopathologic parameters were correlated with local outcome.

METHODS

Since 1990, transrectal ultrasound-guided biopsies have been used to follow patients with localized prostate carcinoma after radical external RT at the General Hospital division of the Ottawa Regional Cancer Centre. Eighty-nine patients with residual tumor in 1 or more biopsies at 10-78 months of follow-up were selected for review. All patients had undergone biopsy on more than one occasion. The 198 biopsies were stained for PSA, high molecular weight keratin, and proliferative cell nuclear antigen (PCNA). Therapy effect was graded by nuclear and cytoplasmic changes.

RESULTS

Of these 89 selected patients, 25 progressed to local failure (LF), 38 had delayed tumor clearance, and 26 remained biopsy positive without local or biochemical progression. In the 24- and 36-month biopsies, RT effect correlated with mean nadir serum PSA (Grade 4-6 RT effect: 0.7 ng/mL; Grade 0-3 RT effect: 1.3 ng/mL [P = 0.01]) and with local outcome (Grade 0-2 RT effect: 55% LF; Grade 3-4 RT effect: 30% LF; and Grade 5-6 RT effect: 0% LF [P = 0.003]). Of tumors with minimal RT effect, 61% were PCNA positive, compared with 34% for moderate and 17% for marked RT effect (P < 0.001). Adjacent areas within biopsies showed varied RT effect in 27 patients, of whom 41% had local failure, compared with 18% of patients with uniform RT effect (P = 0.03). Gleason score was assigned only if RT effect was minimal (36 patients/59 biopsies); 74% had the same Gleason score (+/-1) as the original, whereas 23% were 2 points lower. Only 1 biopsy lost PSA staining completely and 10% stained faintly, whereas 34% stained moderately and 55% strongly.

CONCLUSIONS

PSA staining is apparently retained in residual tumor after RT, despite obvious RT effect. RT effect correlates with serum PSA nadir, PCNA staining, and local outcome. Varied RT effect is commonly observed in biopsies, and correlates with local failure. There is no convincing evidence for tumor dedifferentiation after RT.

GABA-induced inactivation of functionally characterized sites in cat visual cortex (area 18): effects on direction selectivity

1. Microiontophoresis of gamma-aminobutyric acid was used to reversibly inactivate small sites of defined orientation and direction specificity at a horizontal distance of 400-700 microns from single cells recorded in cat area 18. There was extensive or complete overlap between the receptive fields of cells at the recording and inactivation sites. A cell's directionality index [DI: 1 - (response to nonpreferred direction/response to preferred direction)], the response to the preferred direction, and orientation tuning width (measured at half the maximum response) were compared before and during inactivation of either iso-orientation sites (where the orientation preference was within 22.5 degrees) or cross-orientation sites (where it differed by 45-90 degrees). 2. During iso-orientation inactivation, 40 (73%) of 55 cells showed a significant (> 0.20) change in DI; the mean change in DI for these cells was 0.59. An additional cell showed a marked increase in response to the preferred direction that did not result in a change in DI. With one exception, the effects occurred in the absence of a significant (> 25%) change in orientation tuning width. 3. In most cases, the results were broadly predictable in the sense that iso-orientation inactivation predominantly affected a cell's response to the direction of motion of an optimally oriented bar that was closest to the preferred direction at the inactivation site: viz., a decrease in response to the preferred direction and an increase in response to the preferred or nonpreferred direction. 4. It is argued that the decreases in response were due to a reduction in the strength of intracortical iso-orientation excitatory connections made primarily between cells with similar direction preferences, whereas the increases in response involved a loss of iso-orientation inhibition. 5. In cases where remote inactivation caused an increase in response to the nonpreferred direction, comparable effects could be elicited when a mask left exposed only the excitatory subregion of the receptive field in S cells or the most responsive part of the excitatory discharge region in C cells. This implies extensive or complete spatial overlap between the profiles of excitation and inhibition in a cell's nonpreferred direction. 6. During cross-orientation inactivation, a significant change in DI was seen in only 14 (19%) of 73 cells and, with one exception, these changes were accompanied by increases in response to non-optimal orientations and significant broadening of orientation tuning. The effects of cross-orientation inactivation on directionality were presumably due to the loss of cross-orientation inhibition, which contributes primarily to orientation tuning. 7. Inactivation of the same site could cause an increase in response to the nonpreferred direction in cells recorded at iso-orientation sites and an increase in response to nonoptimal orientations and broadening of orientation tuning in cells recorded at cross-orientation sites. This is consistent with the notion that a single inhibitory neuron can contribute to the directionality or orientation tuning of different target cells depending on their location in the orientation map. 8. The results provide evidence for a major contribution of intrinsic mechanisms to the orientation tuning and direction selectivity of cells in cat area 18. It is proposed that two different intracortical processes are involved in the enhancement of orientation and direction selectivity: 1) suppression of responses to nonoptimal orientations and directions as a result of cross-orientation inhibition and iso-orientation inhibition; and 2) facilitation of responses to optimal orientations/directions via iso-orientation excitatory connections.

The density of muscarinic M1 receptors is decreased in the caudate-putamen of subjects with schizophrenia

Changes in cholinergic neurons have been implicated in the pathology of schizophrenia. Clozapine, an atypical anti-psychotic drug, has been shown to bind with high affinity to the muscarinic1 (M1) receptor suggesting this receptor could be involved in the therapeutic efficacy of the drug. Because of this we measured the density of M1 receptors in the caudate-putamen, obtained at autopsy, from 19 schizophrenic subjects and 19 non-schizophrenic subjects. The density of M1 receptors was decreased in the caudate-putamen from the schizophrenic subjects (181 +/- 20 vs 287 +/- 10 fmol mg-1 TE; mean +/- s.e.m.; P < 0.001). Furthermore, preliminary studies would not suggest that the change in the density of M1 receptors in the tissue from the schizophrenic subjects had resulted from drug treatment prior to death. These data raise the possibility that changes in muscarinic receptors may be involved in the pathology of schizophrenia.

Prostate motion during standard radiotherapy as assessed by fiducial markers

From November 1993 to August 1994, 55 patients with localized prostate carcinoma had three gold seeds placed in the prostate under transrectal ultrasound guidance prior to the start of radiotherapy in order to track prostate motion. Patients had a planning CT scan before initial simulation and again at about 40 Gy, just prior to simulation of a field reduction. Seed position relative to fixed bony landmarks (pubic symphysis and both ischial tuberosities) was digitized from each pair of orthogonal films from the initial and boost simulation using the Nucletron brachytherapy planning system. Vector analysis was performed to rule out the possibility of independent seed migration within the prostate between the time of initial and boost simulation. Prostate motion was seen in the posterior (mean: 0.56 cm; SD: 0.41 cm) and inferior directions (mean: 0.59 cm; SD: 0.45 cm). The base of the prostate was displaced more than 1 cm posteriorly in 30% of patients and in 11% in the inferior direction. Prostate position is related to rectal and bladder filling. Distension of these organs displaces the prostate in an anterosuperior direction, with lesser degrees of filling allowing the prostate to move posteriorly and inferiorly. Conformal therapy planning must take this motion into consideration. Changes in prostate position of this magnitude preclude the use of standard margins.

Routine prostate biopsies following radiotherapy for prostate cancer: results for 226 patients

OBJECTIVES

To determine the time course of histologic resolution of prostate cancer following radiotherapy (RT) and to correlate biopsy results with clinical outcome.

METHODS

Since July 1990, all patients treated with radical external beam RT for prostate cancer at the General Division of the Ottawa Regional Cancer Centre have had systematic transrectal ultrasound (TRUS) and TRUS-guided biopsies beginning 12 months after RT and then every 6 months until negative or until clinical failure. Thus, 226 patients have had 375 TRUS with four to seven specimens per examination. Stage distribution was T1b: 32, T1c: 11, T2a: 45, T2b: 82, T3: 50, and T4: 6. Median follow-up was 33 months.

RESULTS

Biopsy results were negative in 69.5% of patients by 30 months of follow-up. Thirty-two (14%) had local failure (T1b: 12.5%, T1c: 0%, T2a: 11%, T2b: 15%, T3: 18%, T4: 33%). Seven (3%) had chemical failure, and 47 (21%) had biopsy-only failure. Median follow-up for the biopsy-only failure group is only 19.5 months and mean prostate-specific antigen (PSA) is 1.0 ng/mL. Thirty-nine patients, initially with biopsy-only failure, have converted to negative biopsies at a median of 26 months. Nadir PSA for patients with local failure was 3.9 ng/mL at 14 months versus 0.7 ng/mL at 23 months for those without failure. Patients with late conversion to negative biopsy results had a later nadir PSA of 1.3 ng/mL at 27.3 months.

CONCLUSIONS

Routine prostate biopsy specimens after RT in an unselected population show tumor clearance that is in agreement with long-term clinical follow-up, although tumor may take more than 30 months to resolve. Nadir PSA can be used to predict outcome.

Velocity invariance of preferred axis of motion for single spot stimuli in simple cells of cat striate cortex

Directional tuning for motion of a long bar and a spot was compared quantitatively over a wide range of velocities in 23 simple cells of cat striate cortex whose "on" and "off" receptive field subregions had been mapped with optimally oriented, stationary flash-presented bars. Tuning curves were derived using stimuli whose polarity of contrast was appropriate for the dominant receptive field subregion of each cell (i.e. light stimuli for on-subregions and dark stimuli for off-subregions); stimulus sweep was centred accurately on the centre of that subregion. Bar stimuli were of optimal width, and spot diameter was equal to the width of the bars. In all simple cells, preferred axis of motion for a long bar was invariant with velocity, being orthogonal to preferred orientation, as assessed with a stationary flash-presented bar. In 20 of 23 simple cells, preferred axis for spot motion was approximately orthogonal to that for bar motion (i.e., parallel to preferred orientation) at all velocities tested, including those just above threshold for spot stimuli. However, tuning for the spot became sharper as velocity was increased, due to an increase in response to the spot moving along the preferred axis and a decrease in response to spot motion along other axes, including the preferred axis for the bar. Both preferred and upper cut-off velocity were consistently higher for spot than for bar motion. The remaining 3 simple cells showed no response to spot motion at any velocity, and their preferred axis of motion for the shortest bar which evoked a consistent response was the same as the long bar.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of intersource spacing on local control and complications in brachytherapy of mobile tongue and floor of mouth

From 1971 to 1988, 133 T1 and 141 T2 biopsy-proven squamous cell carcinomas of mobile tongue and floor of mouth were definitively managed by Iridium-192. Implantations were performed using either guide gutters or afterloading plastic catheters. The prescribed dose at the reference isodose (85% of the basal dose rate, Paris system) was 60-70 Gy. Total dose was not adjusted to dose rate or tumor volume. Results of the 274 implants have been analysed to look for a possible influence of intersource spacing on local control and necrosis. Follow up for patients free of local recurrence is 1-180 months with median of 35 months. The 274 tumors were divided into two groups according to intersource spacing: 9-14 mm (n = 204), and 15-20 mm (n = 70). At 5 years, the estimated local control (Kaplan Meier) was 86% and 76%; respectively (p = 0.13); the necrosis rate was 33% and 46%, respectively (p = 0.04). Multivariate analysis shows that dose and activity of wires were significantly related to local control, while only tumor site was predictive of necrosis; there was a non-statistically significant relationship between intersource spacing of wires and local control (p = 0.055). When considering only patients with oral tongue cancers, necrosis was significantly related to activity of wires (p = 0.013), and there was a non-significant trend to a relationship between necrosis and intersource spacing (p = 0.066) and tumor diameter (p = 0.065). For patients with floor of mouth cancer, none of these factors was significantly related to necrosis.(ABSTRACT TRUNCATED AT 250 WORDS)

GABA-induced inactivation of functionally characterized sites in cat visual cortex (area 18): effects on orientation tuning

Microiontophoresis of the inhibitory transmitter GABA was used to reversibly inactivate small sites of defined orientation specificity at a horizontal distance of some 600 microns from single cells recorded in area 18 of cat visual cortex, and the effects on orientation tuning were studied. The receptive fields of cells at the recording and inactivation sites overlapped extensively. During the inactivation of sites where the orientation preference differed by 45 degrees or more from that of a recorded cell ("cross-orientation" sites), 65% of 54 cells tested showed significant broadening of orientation tuning, with a mean increase in tuning width (measured at half the maximum response) of 93%, and an almost fourfold increase in the relative response to the orientation orthogonal to the optimum, compared with the response to the optimum; four cells essentially lost their orientation tuning. Broadening of tuning reflected an increase in response to nonoptimal orientations and was reversible upon termination of GABA application. The effects on orientation tuning typically peaked within 10-15 min of the onset of GABA iontophoresis with 50-100 nA ejecting currents, and could not be replicated by inactivating sites where the orientation preference was similar to that of a recorded cell; when the orientation preference at the inactivation sites was within 22.5 degrees of that of a recorded cell ("iso-orientation" sites), only 3 of 22 cells showed significant broadening of tuning, and in these cases, the effects were relatively weak (mean increase in tuning width of 39% and a negligible change in the relative response to the orientation orthogonal to the optimum). The effect of inactivating "iso-orientation" sites consisted primarily in an increase in response magnitude. The difference in the magnitude of the effects on orientation tuning elicited by inactivating "cross-orientation" and "iso-orientation" sites was highly statistically significant. Additionally, inactivation of "cross-orientation" or "iso-orientation" sites elicited differential effects on orientation tuning in 10 of the 13 cells in which direct comparisons were made. It is argued that the observed broadening of tuning was due to the loss of a "cross-orientation" inhibitory input, which normally sharpens orientation tuning by suppressing responses to nonoptimal orientations.

The neurophysiological correlates of colour and brightness contrast in lateral geniculate neurons. I. Population analysis

The colour of an object is changed by surround colours so that the perceived colour is shifted in a direction complementary to the surround colour. To investigate the physiological mechanism underlying this phenomenon, we recorded from 260 neurons in the parvo-cellular lateral geniculate nucleus (P-LGN) of anaesthetized monkeys (Macaca fascicularis), and measured their responses to 1.0-2.0 degrees diameter spots of equiluminant light of various spectral composition, centered over their receptive field (spectral response function, SRF). Five classes of colour opponent neurons and two groups of light inhibited cells were distinguished following the classification proposed by Creutzfeldt et al. (1979). In each cell we repeated the SRF measurement while an outer surround (inner diameter 5 degrees, outer diameter 20 degrees) was continuously illuminated with blue (452 nm) or red (664 nm) light of the same luminance as the center spots. The 1.0-1.5 degree gap between the center and the surround was illuminated with a dim white background light (0.5-1cd/m2). During blue surround illumination, neurons with an excitatory input from S- or M-cones (narrow- and wide-band/short-wavelength sensitive cells, NS- and WS-cells, respectively) showed a strong attenuation of responses to blue and green center spots, while their maintained discharge rate (MDR) increased. During red surround illumination the on-minus-off-responses of NS- and WS-cells showed a clear increment. L-cone excited WL-cells (wide-band/long-wavelength sensitive) showed a decrement of on-responses to red, yellow and green center spots during red surround illumination and, in the majority, also an increment of MDR. The response attenuation of narrow-band/long-wave-length sensitive (NL)-cells was more variable, but their on-minus-off-responses were also clearly reduced in the average during red surrounds. Blue surround illumination affected WL-cell responses little and less consistently than those of NL-cells, but often broadened the SRF also in the WL-cells towards shorter wavelengths. The M-cone excited and S-cone suppressed WM-cells were strongly suppressed by blue but only little affected by red surround illumination. The changes of spectral responsiveness came out clearly in the group averages of the different cell classes, but showed some variation between individual cells in each group. The zero-crossing wavelengths derived from on-minus-off-responses were also characteristically shifted towards wavelengths complementary to those of the surround.(ABSTRACT TRUNCATED AT 400 WORDS)

Effect of dose rate on local control and complications in definitive irradiation of T1-2 squamous cell carcinomas of mobile tongue and floor of mouth with interstitial iridium-192

From 1971 to 1988, 134 T1 and 145 T2 biopsy-proven squamous cell carcinomas of mobile tongue and floor of mouth were definitively managed by iridium-192. Implantations were performed using either guide gutters or afterloading plastic catheters. The prescribed dose at the reference isodose (85% of the basal dose rate, Paris system) was 60-70 Gy. Total dose was not adjusted to dose rate or tumor volume. Results of the 279 implants have been analysed to look for a possible influence of dose rate on local control and necrosis. Follow-up patients free of local recurrence is 1-180 months with average of 51 months. The 279 tumors were divided in four groups according to dose and dose rate: greater than or equal to 62.5 Gy and greater than or equal to 0.5 Gy/h (n = 130), greater than or equal to 62.5 Gy and less than 0.5 Gy/h (n = 36), less than 62.5 Gy and greater than or equal to 0.5 Gy/h (n = 81), less than 62.5 Gy and less than 0.5 Gy/h (n = 32). The four groups were comparable according to age, sex, tumor diameter and macroscopic aspect. At 5 years, the estimated local control (Kaplan Meier) was 93, 87, 79 and 52%, respectively (dose adjusted to dose rate: p less than 0.001, dose rate adjusted to dose: p less than 0.01, Log-rank); the necrosis rate was 44, 24, 37 and 5%, respectively (dose adjusted to dose rate: p = 0.08, dose rate adjusted to dose: p less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Influence of GABA-induced remote inactivation on the orientation tuning of cells in area 18 of feline visual cortex: a comparison with area 17

We have investigated the effect of iontophoretically applying the inhibitory transmitter gamma-aminobutyric acid (GABA) through four pipettes, each located at a horizontal distance of some 500-600 microns from the recording site, on the orientation tuning of cells in areas 17 and 18 of the cat visual cortex for moving the stationary flash-presented bar stimuli. Forty-five of 74 cells tested in area 18 (61%) showed a significant (greater than 25%) increase in orientation tuning width (at half the maximum response) during GABA application, which reflected an increase in response to non-optimal orientations. The mean orientation tuning width of these cells increased by 79%, and the ratio of responses to the orientation orthogonal to the optimum and to the optimum increased from 0.16 to 0.46. The results were similar to those from area 17, in which 36 of 54 cells (66%) showed significant broadening of orientation tuning during GABA application, with a 90% increase in mean tuning width and an increase in the relative response to the orientation orthogonal to the optimum from 0.17 to 0.42. The distributions of cells in areas 17 and 18 with respect to the magnitude of GABA-induced effects on orientation tuning width were not significantly different (mean increase in tuning width: area 17, 102%; area 18, 87%). Although most cells were tested only with moving bars, comparable effects of remote GABA application on orientation tuning were observed when stationary flash-presented bars were used. Of 11 cells thus tested in area 18, seven showed significantly broader tuning during GABA application, with a 132% increase in mean tuning width. In some 25% of cells in each area which showed a significant effect of GABA application on orientation tuning the response to at least one non-optimal orientation exceeded, during GABA application, the response to the previous optimum. There was essentially no correlation between the changes in orientation tuning and changes in the level of spontaneous activity or in the response to the optimum orientation during GABA application. Thus, an increase in the general excitability of recorded cells or the loss of an unspecific inhibitory input cannot account for the effects of GABA application on orientation tuning. Remote GABA application presumably inactivated cells with different preferred orientations from that of the recorded cell. It is thus argued that the observed broadening of orientation tuning during GABA application reflected the loss of an inhibitory input tuned to non-optimal orientations.(ABSTRACT TRUNCATED AT 400 WORDS)

Iridium 192 implantation of T1 and T2 carcinomas of the mobile tongue

Between 1970 and 1986, 166 patients with T1 or T2 epidermoid carcinomas of the mobile tongue were treated by iridium 192 implantation (70 T1N0, 83 T2N0, 13 T1-2 N1-3). Five-year actuarial survival was 52% for T1N0, 44% for T2aN0, and 8% for or T1-2 N1-3. Cause specific survivals were 90%, 71%, and 46%, respectively. Local control was 87% for both T1N0 and T2N0, and 69% for T1-2 N1-3. Seven of 23 failures were salvaged by surgery, increasing local control to 96% for T1 and 90% for T2. Thirty-six patients developed a minor or moderate necrosis (16% T1, 28% T2). Half of these involved bone but only five required surgical intervention. Both local control (LC) and necrosis (nec) increased with increasing dose but improvement beyond 65 Gy is minimal (less than or equal to 60 Gy: LC = 78% nec = 13%; 65 Gy: LC = 90% nec = 29%; greater than or equal to 70 Gy: LC = 94% nec = 23%). For N0 patients, neck management consisted of surveillance (n = 78), elective neck dissection followed with external irradiation for pathologically positive nodes (n = 72), or irradiation (n = 3). Clinically positive nodes (13 patients) were managed by either neck dissection followed by external irradiation if pathologically positive (n = 10) or irradiation alone (n = 3). Regional control was 79% for N0 patients, improving to 88% after surgical salvage, and was 9/13 for N1-3 patients. We recommend that T1 and T2 carcinomas of the mobile tongue be treated by iridium 192 implantation to deliver 65 Gy. Mandibular necrosis should be reduced by using an intra-oral lead-lined dental mold.

Directional tuning of cells in area 18 of the feline visual cortex for visual noise, bar and spot stimuli: a comparison with area 17

Directional tuning for visual noise, bar and single spot stimuli was compared over a wide range of velocities in cells from areas 17 and 18 of the visual cortex in lightly-anaesthetized cats. In each area, S-cells were predominantly insensitive to motion of a field of visual noise. C-cells were more sensitive to noise motion than B-cells, but showed heterogeneity in noise sensitivity, which was associated with other response properties: strongly noise-sensitive C-cells had relatively high spontaneous activity and broad directional tuning, and were predominantly direction-selective and binocularly-driven. Frequently, directional tuning for noise was unimodal at low velocity, but became progressively more bimodal as velocity was increased: a trough of depressed response corresponding to the peak in tuning for the bar separated two progressively more widely disparate preferred directions. In area 18, cells with velocity tuned (VT) functions for bar motion developed bimodal tuning for noise well below the optimum velocity for bar or for noise motion, while velocity high-pass (VHP) cells became progressively more bimodally tuned for noise over a wide range of velocities, in parallel with a steep increase in response to bar and noise motion. A high proportion of VT and VHP cells was bimodally tuned for noise at all velocities, one VHP cell showing two discrete lobes of tuning for noise below the threshold velocity for bar motion. Among cells which remained unimodally tuned for noise, VT and VHP cells in area 18 had radically dissimilar preferred directions for noise and bar motion at all velocities. With the exception of VHP cells, velocity bandpass was higher for noise than for bar motion. These results, together with other novel observations on the modality of tuning for noise in preferred and opposite directions of motion, demonstrate that bimodality of tuning for noise cannot simply be an effect of upper cut-off velocity for bar motion (Movshon et al. 1980; Orban 1984). It is argued that the trough between the lobes of tuning arises through laterally-directed inhibitory convergence from superficial- and deep-layer, large basket cells. In 40% of noise-sensitive cells, tuning for bar motion was broader on the flank closest to the preferred direction for noise and for a moving sport, while some 25% of cells showed variations in tuning for bar motion with velocity, which were associated with velocity-dependent changes in tuning for noise.(ABSTRACT TRUNCATED AT 400 WORDS)

GABA-induced remote inactivation reveals cross-orientation inhibition in the cat striate cortex

We investigated the contributions of lateral intracortical connections to the orientation tuning of area 17 cells using micro-iontophoresis of the inhibitory transmitter gamma-aminobutyric acid (GABA) to inactivate small cortical sites in the vicinity of a recorded cell. GABA was ejected from an array of micropipettes each with an average horizontal distance of 500 microns from the recording site. Of 54 cells tested, 33 showed a reduction and 3 a loss of orientation selectivity due to an increase in responses to non-optimal orientations during GABA inactivation. The response to the optimal orientation remained constant in more than half of the cells and increased or decreased in others. Given that a complete cycle of orientations occupies a tangential distance of 1000 microns, the observed broadening of orientation tuning is presumably due to GABA-mediated inactivation of inhibitory interneurones with different preferred orientations from those of their target cell.

Modulatory influences of a moving visual noise background on bar-evoked responses of cells in area 18 of the feline visual cortex

The modulatory influence of a synchronously moving visual noise background on responsiveness to an optimally-oriented moving bar stimulus was investigated in visual cortical area 18 of the lightly-anaesthetized cat. The bar and noise background were swept along the axis orthogonal to bar orientation, with the same phase, velocity and amplitude of motion. Cells which were insensitive to motion of visual noise per se or weakly responsive to individual 'grains' in the noise sample showed suppression of bar-evoked responses by simultaneous motion of the noise background. Percent suppression declined with increase in bar length, over a range which could exceed the maximum estimate of receptive field length. The decline in percent suppression was non-linear, becoming progressively flatter in slope as bar length was increased until an asymptotic value was reached; observations on end-stopped cells and on end-free cells with restricted length summation verified that percent suppression was related specifically to the length of the comparison bar and not to the strength of response it evoked. Percent suppression and the extent over which it declined with increase in bar length were comparable for preferred and opposite directions of bar motion even in cells with radically different length-response functions in the two directions, including end-stopped cells with direction-selective end-zones. In contrast to end-inhibition, which was maximal at or near the preferred velocity for a bar of optimal length, percent suppression by motion of the noise background was essentially velocity-invariant; in velocity tuned and velocity high-pass cells, background motion reduced the slope(s) of the velocity-response function, implying that the suppressive action of moving noise backgrounds is divisive rather than subtractive. It is argued that the suppression derives predominantly from an axo-somatic noise-sensitive inhibitory input from superficial- and deep-layer, large basket cells in orientation 'columns' at some distance from those of their target cells.

Interstitial iridium 192 for cutaneous carcinoma of the external nose

Several implantation techniques useful for nasal skin carcinoma have been developed at the Henri Mondor Hospital in Créteil, France and are described in detail. Iridium 192 wires, 0.3 mm in diameter, are afterloaded into either supple plastic tubes or rigid needles implanted according to the rules of the Paris system. Dosimetry is performed by computer, based on either direct measurements of active lengths and spacing, orthogonal films or a tomogram oriented in the central plane of the implant. According to a recent review by the European Curietherapy Group of 468 implants, the optimal dose is 60 Gy. The overall failure rate was 2.6%. Indications for implantation and choice of technique, based on tumor size, site, and gross morphology are discussed.

Visual resolution of macaque retinal ganglion cells

1. The visual resolving ability of different types of macaque retinal ganglion cells was estimated at different retinal eccentricities, by measuring the amplitude of modulated responses to black-white gratings of spatial frequencies near the resolution limit for each cell. 2. The resolving ability of tonic, spectrally opponent ganglion cells was usually similar to that of phasic, non-opponent ganglion cells at similar eccentricities, except that at eccentricities greater than 10 deg some tonic ganglion cells with remarkably high resolution (up to ca. 15 cycles/deg) were found. Our cell sample was limited within the central 2 deg of the visual field, however. 3. Only a small proportion of phasic ganglion cells showed an increase of mean firing level to gratings near the resolution limit. The maintained firing of tonic ganglion cells was higher than that of phasic ganglion cells. 4. With red-black or green-black gratings, the resolution of phasic ganglion cells was unaffected. For red or green on-centre ganglion cells, a marked deterioration of resolving ability occurred when the grating was of a colour to which a cell responded poorly (green-black gratings for red on-centre cells, and red-black gratings for green on-centre cells). A slight improvement in resolving ability occurred when the grating was of an excitatory colour. 5. For a sub-sample of cells, we compared resolution limit with centre size as determined from area-threshold curves. For both phasic and tonic ganglion cells, resolution limit (the period length just resolved) was about half the centre diameter, as is the case for cat ganglion cells. This implies that the centre sizes of phasic and tonic monkey ganglion cells are similar at most eccentricities. 6. We attempt to relate these results to primate retinal anatomy and visual resolution, determined behaviourally.

Thresholds to chromatic spots of cells in the macaque geniculate nucleus as compared to detection sensitivity in man

1. The relation between wavelength and psychophysical threshold for chromatic spots on a white background provides evidence for the existence of chromatic channels in the primate visual system. To find the physiological substrate of this task, we compared increment thresholds of different cell types in the macaque lateral geniculate nucleus with human psychophysical thresholds to the same stimuli, using two spot sizes, 4 and 0.4 deg. 2. At different wavelengths, different opponent cell classes in the parvocellular layers of the nucleus were most sensitive, so that at long wavelengths (greater than 600 nm) red on-centre cells were most sensitive, while at short wavelengths (less than 500 nm) S-cone, blue on-centre cells were most sensitive, from 500 to about 550 nm green on-centre cells being most sensitive. A rare cell type with inhibition from S-cones was most sensitive at about 570 nm, although its maximum contrast increment sensitivity was poor compared with that of other cell types. Variation in strength of cone opponency caused a considerable range in threshold in each of the opponent cell classes of the parvocellular layers. 3. On- and off-centre cells from the magnocellular layers were more sensitive than opponent cells to white and yellow spots (as is the case with achromatic gratings). 4. With different wavelengths and spot sizes, the most sensitive cells found approached (to within 0.1-0.3 log units) human psychophysical sensitivity, suggesting that the most sensitive cells available may underlie detection. 5. Measurements of psychophysical chromatic discrimination thresholds, both with nearly monochromatic spots and with spots of differing saturation (purity), support this hypothesis. When magnocellular cell sensitivity corresponded to psychophysical threshold, a suprathreshold stimulus, capable of activating opponent cells, was required for chromatic discrimination.

Dosimetric methods in the optimization of radiotherapy for carcinoma of the uterine cervix

Pelvic failures and late radiation sequelae were analyzed using the dosimetric parameters of ICRU Report 38 for 338 patients with Stage I-III carcinoma of the uterine cervix treated by radiation alone and followed for a minimum of 2 years. The pelvic recurrence rates were: Stage IB 5.1% (N = 118, 1% pelvis alone), Stage IIA 15.1% (N = 53, 9.4% pelvis alone), Stage IIB 15.8% (N = 76, 9.2% pelvis alone) and Stage IIIB 28.9% (N = 76, 17.1% pelvis alone). For Stages I and II pelvic failure was unrelated to cumulated lateral parametrial dose (CDPW) or reference volumes, but for Stage IIIB was higher for CDPW above 65 Gy. Overall complication rates were: grade 3-10.1% and grade 2-18.1% but were much lower for 176 patients treated with stem and ovoids (S + O: grade 3-5.7%, grade 2-15.7%) than for 43 receiving vaginal cylinders (grade 3-37.2%, grade 2-28%). Grade 3 rectal complications associated with cylinders were related to a maximal vaginal application over 1.50 cGy X m2 of total reference air kerma (or 2080 mgh) and cumulated rectal reference doses (CDRref) above 75 Gy. For the S + O group, grade 2 and 3 rectal complications increased with increasing reference volumes (hwt and HWT) and showed dose thresholds for CDRref and CDRmean (grade 3: 75 Gy). Prospective use of zones of risk defined graphically on a dose-volume plot (CDRref vs HWT) has reduced our severe complication rate without reducing local control. This technique requires individualization of patient therapy, rapid access to computerized dosimetry and the establishment of center- and applicator-specific risks of complications.

Reference volume, milligram-hours and external irradiation for the Fletcher applicator

The ICRU Report 38 recommends the use of reference point doses and reference volumes for the reporting of intracavitary gynecologic therapy. The reference volume enclosed by the 60 Gy isodose for intracavitary therapy alone (which can be represented by hwt) and for combined external and intracavitary therapy (HWT) has no conceptual counterpart in the standard intracavitary systems. We report the relationship of the reference volumes (hwt and HWT) to milligram-hours (mgh) radium equivalent and to dose of external irradiation (XRT) for the Fletcher system. HWT and hwt are directly proportional to mgh, the proportionality constant depending on XRT but not appreciably on moderate changes in source geometry. HWT increases slowly with increasing XRT to about 30 Gy, then increases dramatically with even small increases in XRT. The reasons for this behavior and the possible clinical significance are discussed.

Dose-volume analysis and the prevention of radiation sequelae in cervical cancer

We report a 9 year (1975-1983) experience of treatment of carcinoma of the uterine cervix by radiation alone. Computerized dosimetry conforming to the ICRU 38 recommendations was performed for all 348 patients analyzed. Late sequelae were graded as mild (grade 1), moderate (grade 2) and severe (grade 3). The overall rates were grade 3: 9.8%, grade 2: 18%, and grade 1: 19.5%. Of the moderate to severe sequelae, 48% were rectal, 15% rectosigmoid and 21% urinary. The complication rate was highly dependent on the type of intracavitary applicator: lowest for patients treated by two insertions of a standard Fletcher-Suit applicator (grade 3: 5.4%, grade 2: 14.4%) and highest for those receiving uterine stem plus vaginal line sources (grade 3: 29.5%, grade 2: 26%). For 183 patients treated with stem and standard ovoids, moderate and severe rectal and bladder sequelae were analyzed according to critical organ reference doses and reference treatment volumes as defined by ICRU 38, with the addition of a mean rectal dose. Zones of low, moderate and high risk could be defined on dose-volume plots using these parameters. Modification of treatment plans at the Cancer Institute G. F. Leclerc (CGFL) of Dijon according to these concepts produced a reduction in moderate and severe sequelae (grade 3: 14.4-3.4%) without a concurrent increase in pelvic failures. Although the zones of risk proposed can be used directly only with standard Fletcher-Suit applicators and comparable computer dosimetry, the concept can be applied to other systems.

Neuronal responses to borders with and without luminance gradients in cat visual cortex and dorsal lateral geniculate nucleus

We investigated responses of neurones in cortical areas 17 and 18 and in the dorsal lateral geniculate nucleus (dLGN) of the cat to a phase shift in a moving line pattern forming a border without a luminance gradient ("subjective contour"). In both areas 17 and 18, S cells and B cells respond only slightly or not at all along the phase shift while C cells respond strongly. The response of C cells is strongest for line patterns with medium line separation and decreases with smaller and larger separation. In the dLGN the relative magnitude of neuronal responses along a phase shift is similar to that of C cells. However, C cells respond uniformly along the entire phase shift, whereas geniculate cells merely respond to individual line ends along the phase shift. In addition we compared responses along a phase shift and those to a luminance gradient formed by a dotted line whose dots were separated by the same distance as the line ends along the phase shift. S cells and B cells respond preferentially to dotted lines whereas C cells and geniculate cells respond equally well along both phase shifts and dotted lines. Possible explanations for these results in terms of receptive field structure and differences in inhibitory input to the cells are discussed. Differential neurone responses may account for the perceptual distinctness of the contours with and without luminance gradients.

Visceral anatomy of the Amphisbaenia

Study of the visceral anatomy of 41 specimens of amphisbaenians representing 13 genera shows that they share a very distinct structure which differs from that found in either snakes or typical lizards. The left lung is large while the right is rudimentary or absent (unique); the kidneys are freely suspended in the coelom by a mesentery (unique); the spleen is usually embedded in the anterior end of the pancreas (as in snakes); the gall bladder lies in a notch in the liver, and the kidneys lie opposite each other (as in lizards). The distinctness of this pattern supports the recognition of the Amphisbaenia as a separate suborder of the Squamata.