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Biomedical subjects

B H Pollock

Publications and source records attributed to B H Pollock.

At least 73 records · Page 4Linked to original sources
PubMed1993

Socioeconomic and demographic factors that predict where children receive cancer care in Florida.

Socioeconomic and demographic factors associated with type of facility (cancer center vs non-cancer center) at which a child with cancer is seen were identified to suggest interventions to increase access to state-of-the-art care. The 2268 children with cancer in Florida (1981-1986) were classified as ever having been seen or not having been seen at a cancer center. Patients referred from one type of facility to another were compared to those not referred. Nineteen percent of children with cancer were never seen at a cancer center. These children were likely to be older (15-19 years of age), have Hodgkin's disease or a brain tumor, reside in a county without a cancer center, or have higher median income. Interventions extending state-of-the-art cancer care beyond cancer centers should target (1) physicians treating adolescent-aged children and (2) patients for whom private insurance may serve as a barrier to referral and protocol therapy.

Adolescent↗
PubMed1993

Final attained height in patients successfully treated for childhood acute lymphoblastic leukemia.

We evaluated final adult height in 109 patients treated for childhood acute lymphoblastic leukemia on two multiarm Pediatric Oncology Group protocols between 1974 and 1981. Fifty-one patients received 2400 cGy cranial irradiation (XRT), and 58 patients received no XRT. All patients had no central nervous system involvement at diagnosis, achieved and maintained a complete response, entered puberty spontaneously, and had achieved final height. Height data were converted to standardized deviation scores. Mean age at diagnosis was 7.8 +/- 4.2 years. Distribution of heights at diagnosis was similar to that of the U.S. population. Relative to gender-specific heights for the population, female subjects in this study had lower attained heights than male subjects (p = 0.03). There was a monotonic trend of patients treated at an earlier age to have a reduction in final height (p = 0.057). Cranial irradiation was strongly associated with final height (mean standardized deviation score with XRT = -1.04 and without XRT = -0.14; p < 0.001). Final height was not associated with age at diagnosis, prognostic risk group, or Pediatric Oncology Group protocol. By multivariate analysis, only XRT and XRT x age were significantly associated with final height (p < 0.001 and p = 0.002, respectively). There was no significant gender effect. We conclude that XRT is significantly associated with reduced final adult height after treatment for childhood acute lymphoblastic leukemia. For survivors, therapy devoid of XRT does not appear to affect final height.

Adolescent↗
PubMed1992

The incidence of pediatric cancer in Florida, 1981 to 1986.

Incidence rates for pediatric (ages, 0 to 14 years) cancer in the state of Florida were produced for the period 1981 to 1986 and compared with national data to investigate variations in pediatric cancer incidence. Overall, Florida had an incidence rate of 12.77 per 100,000; this was not significantly higher than expected based on national rates (standardized incidence ratio, 1.0; 95% confidence interval, 0.9 to 1.0). Compared with national rates, whites residing in Florida had an increased rate of acute lymphocytic leukemia and decreased rate for soft tissue sarcomas (other than rhabdomyosarcoma), "other leukemias," and "other" cancers. Nonwhites residing in Florida had increased rates for soft tissue sarcomas (other than rhabdomyosarcoma) and decreased rates of "other" cancers. Boys in Florida had increased rates for retinoblastoma and acute lymphocytic leukemia and decreased rates for "other leukemias" and "other" cancers. Rates for girls were decreased for neuroblastoma and "other leukemias."

Adolescent↗
PubMed1992

Recurrence of cervical spine instability in rheumatoid arthritis following previous fusion: can disease progression be prevented by early surgery?

In a retrospective study, 110 patients with rheumatoid arthritis who had cervical spine fusion were evaluated for recurrence of cervical spine instability and resultant need for further surgery. Recurrence of cervical instability was correlated with initial radiographic abnormality, primary surgical procedure and interval between the 2 surgeries. There were 55 patients who had atlantoaxial subluxation (AAS) and required C1-C2 fusion as primary surgery. Three of these patients (5.5%) developed subaxial subluxation (SAS) and had a second procedure after a mean interval of 9 years. Twenty-two patients had AAS with superior migration of the odontoid (AAS-SMO) and had initial surgery of occiput-C3 fusion. Eight of these patients (36%) developed SAS and had a second surgery after a mean interval of 2.6 years. Of the 19 patients with primary radiographic deformity of SAS, one required further surgery for subluxation of an adjacent superior vertebra after a period of 6 years. Fourteen patients had combined deformity of AAS-SMO-SAS, and one required further surgery for SAS after an interval of 22 months. Recurrence of cervical instability following a previous fusion occurred in 15% of these 110 patients. It was seen in 5.5% of patients with initial deformity of AAS vs 36% of patients with AAS-SMO. No patients with C1-C2 fusion for AAS progressed to develop superior migration of the odontoid. We conclude that early C1-C2 fusion for AAS before development of SMO decreases the risk of further progression of cervical spine instability. The pattern of progression of cervical spine involvement, as discussed in the literature, is reviewed.

Aged↗
PubMed1991

Improved treatment results in boys with overt testicular relapse during or shortly after initial therapy for acute lymphoblastic leukemia. A Pediatric Oncology group study.

Boys with acute lymphoblastic leukemia (ALL) who have overt testicular relapse (OTR) during initial continuation chemotherapy or within 6 months thereafter have poor outcomes, with long-term survival similar to patients with marrow relapse during treatment. In April 1983, the Pediatric Oncology Group (POG) adopted for these patients an intensive treatment protocol (POG 8303) consisting of a four-drug systemic reinduction (prednisone, vincristine, daunorubicin, and asparaginase), a brief intensive consolidation phase with teniposide and cytarabine, and a 2-year program of continuation chemotherapy with weekly rotating drug pairs (vincristine/cyclophosphamide and teniposide/cytarabine) with or without (by randomization) four-drug reinforcement pulses every 16 weeks. Bilateral testicular radiation (2600 cGy) was administered during reinduction, and intrathecal chemoprophylaxis was given every 4 to 6 weeks. Among 38 eligible study patients with OTR, 5 had prior or concominant extramedullary relapse in other sites. The median duration of complete remission before OTR was 27 months (range, 10 to 42 months). All 38 patients achieved clinical remission after reinduction. Three patients withdrew while in remission, 22 had another relapse (12 marrow, 5 central nervous system (CNS), 2 testicular, 1 retroperitoneal, 1 prostate, and 1 eye), and 13 (34%) remain in complete remission from 32+ to 74+ months after OTR (median, 53+ months). Eighteen patients had their therapy electively discontinued, and five relapses occurred thereafter. These results are superior to those observed in patients with first marrow relapse treated with the same protocol. Approximately one third of patients with OTR treated with POG protocol 8303 exhibit prolonged second remissions with the potential for cure.

Adolescent↗
PubMed1991

Increased T lymphocytes bearing the gamma-delta T cell receptor in subjects at high risk for insulin dependent diabetes.

The effector mechanisms responsible for autoimmune beta cell destruction in insulin dependent (type 1) diabetes (IDD) remain elusive. In order to investigate whether T lymphocytes bearing the gamma-delta T cell receptor (gamma delta+ T cells) could be involved in this process, we measured percentages of peripheral blood gamma delta+ T cells in IDD patients, relatives of IDD probands and controls. High levels of gamma delta+ T cells strongly differentiated 23 relatives at high risk for IDD on the basis of positive islet cell autoantibodies (ICA positive relatives) from 59 controls (P = 0.0013), whereas 26 ICA negative relatives, 14 recent-onset and nine long term IDD patients could not be distinguished from controls on the basis of percentages of gamma delta+ T cells. These data suggest that increased levels of circulating gamma delta+ T cells correlate with the ongoing autoimmune process in pancreatic islets of subjects at high risk for IDD and may thus represent an additional marker for the development of the disease.

Adolescent↗
PubMed1991

Interval between symptom onset and diagnosis of pediatric solid tumors.

Lag time (the interval between symptom onset and diagnosis) was described for 2665 children with lymphoma or a solid tumor who participated in Pediatric Oncology Group therapeutic protocols from 1982 until 1988. Median lag time ranged from 21 days for neuroblastoma to 72 days for Ewing sarcoma. Significant differences in lag time were found among diagnostic groups (p less than 0.001), even after adjustment for age, gender, and race. Age was significantly associated with lag time for all diagnoses (p less than 0.05) except Hodgkin disease. Girls had increased lag times for non-Hodgkin lymphoma (p = 0.02) but decreased lag times for Ewing sarcoma (p = 0.02). Differences in lag time related to race were significant only for children with osteosarcoma (p = 0.02), for which white children had longer lag times. Type of tumor and age were strongly associated with lag time. Within diagnostic groups, age, gender, and race failed to explain more than 16% of the variance in lag time, suggesting that other factors may play more prominent roles. Further study is necessary to identify these factors and to assess the relationship between lag time, stage of disease at diagnosis, and prognosis, especially before designing early-detection interventions for childhood cancer.

Adolescent↗
PubMed1991

Recombinant interferon alfa given before and in combination with standard chemotherapy in children with acute lymphoblastic leukemia in first marrow relapse: a Pediatric Oncology Group pilot study.

Recombinant interferon alfa (rIFN-alpha) was given to 31 children with acute lymphoblastic leukemia (ALL) in first on-therapy marrow relapse as the sole treatment (30 megaunits/m2/d intravenously x 10 days) before standard four-drug reinduction and during multiagent continuation therapy (30 megaunits/m2 subcutaneously x 3 consecutive days every 3 weeks). After 10 days of rIFN-alpha, there were two partial remissions (PRs); seven additional patients had either greater than or equal to 25% reduction in the percentage of marrow blast cells or hypoplastic marrow. Two patients had progressive disease with an increase in leukocyte counts. All patients experienced influenza-like symptoms, and there were isolated instances of severe abdominal pain and personality change. Dose-limiting toxicity comprised grade III/IV transaminase elevation (two patients) and syncope with personality change (one patient). Twenty-three of 31 children (74%) subsequently achieved marrow remission using standard agents. One patient was taken off study during teniposide (VM-26) and cytarabine (ara-C) consolidation due to toxicity. Continuation therapy including rIFN-alpha pulse was well tolerated in the remaining children; only one patient required rIFN-alpha dosage reduction (for CNS toxicity). rIFN-alpha toxicity did not necessitate reductions in doses of standard chemotherapy agents or significant delays in therapy. Five patients remain in remission at 26+ to 36+ months; 13 patients relapsed in marrow, one in the meninges (7 months), and one in meninges, mediastinum, and lymph nodes (2 months). Two children were removed from study for marrow transplant. In summary, high-dose rIFN-alpha alone had a modest antileukemic effect. In contrast to the clinical experience with combined rIFN-alpha and chemotherapy in adults, rIFN-alpha given in a pulse-like manner throughout continuation therapy did not compromise the intensity of the standard chemotherapy regimen.

Adolescent↗
PubMed1990

Teniposide (VM-26) and continuous infusion cytosine arabinoside for initial induction failure in childhood acute lymphoblastic leukemia. A Pediatric Oncology Group pilot study.

Twenty-six evaluable children with newly diagnosed acute lymphoblastic leukemia (ALL) who failed to achieve initial remission after receiving two to seven drugs for at least a 4-week period were given teniposide (VM-26) and continuous infusion cytosine arabinoside (Ara-C). Twenty-two received 150 mg/m2 of VM-26 on days 1 and 2 with 100 mg/2 of Ara-C as a continuous infusion on days 1 through 5; a second shortened course was given on day 14 to eight patients who had evidence of some antileukemic effect or were clinically judged able to tolerate a second course. The last four patients received three daily doses of VM-26 and a 7-day infusion of Ara-C at the same daily dosages. Twelve (48%) achieved complete remission (CR) of ALL. There was a trend toward decreasing response rates with an increasing number of drugs used in the initial induction regimen, i.e., five CR among seven patients with a prior two-drug induction attempt, six CR among 14 patients with a prior three- to four-drug induction attempt, and one CR among four patients with a prior five- to seven-drug induction attempt (P = 0.14). Ten of 17 non-T-cell patients and two of nine T-cell patients achieved remission (P = 0.10). The median time required to achieve a complete remission from the initiation of treatment was 26 days (range, 14-72 days). This period was shorter in those who required one course compared with those who required two induction courses, i.e., 25 days median vs. 44 days median. Toxicity was significant and due mainly to marrow aplasia and infection; one patient had severe prolonged VM-26-induced hypotension. Of the 12 patients entering remission, two were removed for marrow transplant and one was removed due to parental request. In the remaining nine patients, median remission duration was only 2 months (range, 1-18 months). All nine patients relapsed in the marrow. Among the entire group of 26 patients, only one patient is alive and a long-term event-free survivor (after allogeneic marrow transplant). Due to the current use of more aggressive initial induction regimens and the extremely poor prognosis in children who fail to achieve initial remission, more intensive regimens of continuation therapy or alternative therapies, such as bone marrow transplant, should be considered.

Adolescent↗
PubMed1988

Comparative accuracy of clinical tests for diagnosis and prognosis of coronary artery disease.

The discriminant accuracy of 14 variables derived from clinical evaluation, cardiac fluoroscopy, exercise electrocardiography, thallium scintigraphy and radionuclide angiography was assessed with respect to the diagnosis of angiographic coronary artery disease (CAD) among 607 patients undergoing coronary angiography, and with respect to the prognosis of subsequent cardiac death or nonfatal infarction among 4,104 patients followed for 1 year after testing. Discriminant accuracy (quantified in terms of the area under a receiver-operating characteristic curve for each variable) ranged from 50 to 73% for diagnosis, and from 54 to 77% for prognosis. Although there was a great deal of variability from test to test, variables representing direct or indirect manifestations of myocardial ischemia tended to correlate better with prognosis. Thus, variables derived from radionuclide angiography and thallium scintigraphy tended to have more prognostic accuracy than diagnostic accuracy, while fluoroscopy tended to have more diagnostic accuracy than prognostic accuracy. The pattern associated with clinical evaluation and exercise electrocardiography was less discernable. Accordingly, the accuracy of noninvasive tests with respect to diagnosis and prognosis of CAD should be separately determined based on individual empiric observation.

Adult↗
PubMed1987

Incremental prognostic power of clinical history, exercise electrocardiography and myocardial perfusion scintigraphy in suspected coronary artery disease.

The incremental ability of a clinical history, exercise electrocardiography (ECG) and myocardial perfusion scintigraphy to identify coronary events in the year after testing was assessed in 1,659 patients with symptoms suggestive of coronary artery disease (CAD), 74 of whom suffered a coronary event in the year after testing. Prognostic power was quantified in terms of the area under receiver operating characteristic curves derived from logistic regression. In 1,451 patients with normal rest ECG findings, a clinical history alone provided the most prognostic power (area = 72%). This improved significantly (by 5%) only when both tests were analyzed. In contrast, clinical history had significantly less prognostic power in the 208 patients with abnormal rest ECG findings (area = 58%), but each test then provided a significant incremental improvement in these patients (by 14% for each). A strategic model was thereby developed for prognostic assessment that recognizes the incremental power of these tests in specific patient groups as well as their overall accuracy and monetary cost. This strategy stratified individual patient risk for subsequent coronary events over a full order of magnitude (from 2 to 22%) at a 64% reduction in the cost of testing compared to performing both stress tests in all patients.

Aged↗
PubMed1987

Clinician decisions and computers.

The clinician's decisions are subject to numerous distorting influences. Computer decision aids can help avoid these distortions by placing the clinician's limited personal experience into broader perspective through comparison with a larger repository of clinically relevant information; by making explicit the assumptions implied by his or her decisions; and by alerting the clinician whenever the decisions made do not appear consistent with these assumptions, with the available information or with the conventional rules of logic. Practical standards of performance with respect to the development, validation and clinical application of these decision aids are still in evolution, however, and a variety of ethical and legal issues have yet to be addressed. Despite the promise of computer decision aids, it remains to be seen whether their diffusion into medical practice will improve the quality and cost of health care.

Algorithms↗
PubMed1986

A model for assessing the sensitivity and specificity of tests subject to selection bias. Application to exercise radionuclide ventriculography for diagnosis of coronary artery disease.

A probabilistic model was developed which allows one to estimate sensitivity and specificity of diagnostic tests for coronary artery disease without reference to angiography. The feasibility of the model was evaluated first in a series of computer simulations, and the model was then applied to the assessment of ejection fraction in 933 patients without prior myocardial infarction who underwent exercise radionuclide ventriculography. In 196 patients who were referred to angiography, the conventional abnormal ejection fraction criterion--an absolute rise of less than 0.05 with exercise--had a sensitivity of 79% and a specificity of 68% when referenced to coronary angiography. In 737 patients who were not referred for angiography and who were analyzed instead by our probabilistic model, sensitivity was 63% (p = 0.004 compared to that in the 119 angiographically diseases patients) and specificity was 79% (p = 0.036 compared to that in the 77 angiographic normals). Both the higher sensitivity and lower specificity in the catheterized patients are consistent with a preferential referral of positive test responders to angiography, and of negative test responders away from angiography. The distortion of test sensitivity and specificity which results from this selection bias can be circumvented by substituting a probabilistic estimate of disease for conventional angiographic ascertainment.

Adult↗
PubMed1986

Extent and severity of myocardial hypoperfusion as predictors of prognosis in patients with suspected coronary artery disease.

The ability of exercise-induced myocardial hypoperfusion on thallium scintigraphy to predict coronary events was assessed in 1,689 patients with symptoms suggestive of coronary artery disease but without prior myocardial infarction or coronary artery bypass surgery. A total of 74 patients had a coronary event in the year after testing (12 cardiac deaths, 20 nonfatal infarctions and 42 referrals for bypass surgery more than 60 days after testing). Stepwise logistic regression identified only three independent predictors: the number of myocardial regions with reversible hypoperfusion (an index of the extent of hypoperfusion), the maximal magnitude of hypoperfusion (an index of the severity of hypoperfusion) and the achieved heart rate (an index of exercise performance). Both extent and severity were exponentially correlated with event rate (r greater than 0.97 and p less than 0.01 for each), whereas achieved heart rate was linearly correlated with event rate (r = 0.79 and p less than 0.05). On the basis of these data, a prognostic model was defined that employs extent and severity as stress-dependent orthogonal variables. Using this model, the predicted coronary event rate ranged over two orders of magnitude--from a low of 0.4% in patients able to exercise adequately without developing severe and extensive hypoperfusion at a low heart rate (less than 85% of their maximal predicted heart rate). Extent and severity of myocardial hypoperfusion, therefore, are important independent variables of prognosis in patients with suspected coronary artery disease.

Aged↗
PubMed1985

A format for integrating the interpretation of exercise ejection fraction and wall motion and its application in identifying equivocal responses.

The conventional interpretation of ejection fraction change with exercise may be limited because it does not consider the rest value, define equivocal responses or integrate wall motion data reproducibly. Thus, a format was developed for combined interpretation of rest and exercise radionuclide ejection fraction and wall motion by reviewing the reported data for the exercise responses of patients without prior myocardial infarction. The ejection fraction data of 202 normal patients and of 259 patients with coronary artery disease were first fitted to beta distributions. The true positive and false positive rates for coronary disease for each combination of rest and exercise ejection fraction were then determined directly from these distributions. A given rest/exercise ejection fraction combination was "normal" if the false positive rate was greater than the true positive rate, or "abnormal" if the true positive rate was greater than the false positive rate, and "equivocal" when the rates were similar (within a 50% confidence interval). This analytic format, which predicted an inverse relation between rest ejection fraction and the change required with exercise, was then validated prospectively in 854 patients without myocardial infarction (557 with and 297 without angiographic coronary artery disease). Using the conventional criterion of an abnormal test result (less than 0.05 absolute rise in ejection fraction with exercise or a wall motion abnormality), sensitivity was 85 +/- 2% and specificity only 42 +/- 3%. The statistical format had a sensitivity of 70 +/- 2% and specificity of 70 +/- 3%, resulting in a twofold increase in information content. This format has at least two advantages over conventional interpretation: 1) it provides an explicit definition of equivocal responses; and 2) it reproducibly integrates discordant ejection fraction and wall motion responses and allows for the combined analysis of other nonscintigraphic observations, such as age and sex.

Adult↗
PubMed1983

Computer-assisted diagnosis in the noninvasive evaluation of patients with suspected coronary artery disease.

A microcomputer program called CADENZA, which employs Bayes' theorem to analyze and report the results of various clinical descriptors and noninvasive tests relative to the diagnosis of coronary artery disease, was evaluated in 1,097 consecutive patients without previous myocardial infarction. With this program, each patient was characterized by a probability for coronary artery disease, based on Framingham risk factor analysis, symptom characterization, electrocardiographic stress testing, cardiokymography, cardiac fluoroscopy, thallium perfusion scintigraphy and technetium equilibrium-gated blood pool scintigraphy. A total of 11,808 probability estimates derived from various combinations of the available observations were analyzed: 2,180 in 170 patients undergoing coronary angiography and 9,628 in 969 patients who completed a 1 year follow-up for coronary events. The predicted probability of disease correlated linearly with observed angiographic prevalence in the 170 patients who subsequently had coronary angiography (prevalence = [0.001 +/- 0.011] + [0.966 +/- 0.019] X probability). The difference between probability and prevalence averaged 3.1%, and the magnitude of this correlation was not affected by the type or amount of data analyzed. The prevalence of multivessel disease in these patients increased as a monotonic function of disease probability. Below a probability of 25%, single vessel disease was slightly more common than multivessel disease. Above a probability of 75%, multivessel disease predominated. In the 969 patients followed up for 1 year from the date of testing, the incidence of cardiac death and nonfatal infarction increased as a cubic function of disease probability (from approximately 0 to 8% per year for each). Above a probability of 90%, however, the standard deviation for predicting these events was wide. These data indicate that Bayes' theorem in general--and CADENZA in particular--is an accurate, clinically applicable means for quantifying the prevalence of angiographic coronary artery disease, the risk of multivessel disease and the incidence of morbid coronary events in the year after testing.

Coronary Angiography↗