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Biomedical subjects

David McLeod

Publications and source records attributed to David McLeod.

15 recordsLinked to original sources

Caveat medicus: consequences of federal investigations of marketing activities of pharmaceutical suppliers of prostate cancer drugs.

In the course of recent health care fraud investigations against TAP Pharmaceuticals (Lake Forest, IL) and AstraZeneca International (London, United Kingdom), each pled guilty to one violation of the Prescription Drug Marketing Act, settled claims related to alleged violations of the False Claims Act without admitting guilt, and paid fines, settlements for liabilities, and reimbursements of dollar 850 million and dollar 355 million, respectively. In a unique aspect of these cases, federal investigators brought criminal charges against 14 TAP employees and investigated the billing practices of several urologists. These investigations resulted in guilty pleas from both urologists and industry employees relative to the Prescription Drug Marketing Act or the False Claims Act and probationary sentences with payments of fines and restitution to the government for urologists who cooperated with federal investigations. One uncooperative urologist was found guilty of violating the Federal False Claims Act and sentenced to 6 months of home arrest, excluded from Medicare for 5 years, required to provide 600 hours of free medical care to indigent patients and patients covered by Medicare or Medicaid, and paid fines and restitution to the government. The cases against TAP and AstraZeneca have been followed by federal and state investigations of allegedly illegal marketing practices of other pharmaceutical firms and have resulted in negotiated settlements of dollar 3.8 billion and dollar 71.5 million, respectively. Believing that an Average Wholesale Price-based reimbursement system was an important driving factor for these marketing activities, Medicare has shifted to an Average Sales Price-based reimbursement system. This is expected to greatly impact the practice of outpatient oncology nationwide.

Antineoplastic Agents↗

Predictors of prostate cancer-specific mortality after radical prostatectomy or radiation therapy.

PURPOSE: We evaluated predictors of prostate cancer-specific mortality (PCSM) after prostate-specific antigen (PSA) failure after radical prostatectomy (RP) or radiation therapy (RT). PATIENTS AND METHODS: A total of 1,159 men with clinically localized prostate cancer treated with RP (n = 498) or RT (n = 661) developed PSA failure, and they formed the study cohort. Competing risk regression analyses were used to evaluate whether previously identified predictors of time to metastasis, including post-treatment PSA doubling time (PSA-DT), Gleason score, and interval to PSA failure, could also predict time to PCSM after PSA failure. The cumulative incidence method was used to estimate PCSM after PSA failure. RESULTS: A post-RP PSA-DT of less than 3 months (hazard ratio [HR], 54.9; 95% CI, 16.7 to 180), a post-RT PSA-DT of less than 3 months (HR, 12.8; 95% CI, 7.0 to 23.1), and a biopsy Gleason score of 8 to 10 (HR, 6.1; 95% CI, 3.4 to 10.7) for patients treated with RT were significantly associated with PCSM. Post-RP estimated rates of PCSM 5 years after PSA failure were 31% (95% CI, 17% to 45%) v 1% (95% CI, 0% to 2%) for patients with PSA-DT of less than 3 months v > or = 3 months. Post-RT estimated rates of PCSM 5 years after PSA failure were 75% (95% CI, 59% to 92%) v 35% (95% CI, 24% to 47%) for patients with a biopsy Gleason score of > or = 8 v < or = 7, respectively, and PSA-DT of less than 3 months; these rates were 15% (95% CI, 0.8% to 28%) v 4% (95% CI, 1% to 6%), respectively, for patients with a PSA-DT > or = 3 months. CONCLUSION: Patients at high risk for PCSM after PSA failure can be identified based on post-RP PSA-DT or post-RT PSA-DT and biopsy Gleason score. These parameters may be useful in identifying patients for a randomized trial evaluating hormonal therapy with or without docetaxel.

Aged↗

Vaginal metastasis and thrombocytopenia from renal cell carcinoma.

BACKGROUND: Vaginal cancer represents approximately 1-2% of genital tract malignancies. Most cases represent metastasis from the cervix, endometrium, or colon. Metastasis of renal cell carcinoma to the vagina is extremely rare. CASE: A 58-year-old female presented with a bleeding vaginal lesion. Laboratory studies revealed severe thrombocytopenia, and radiological studies revealed a left renal mass; excision was consistent with metastatic renal cell carcinoma. A subsequent nephrectomy confirmed renal cell carcinoma. Postoperatively, the patient underwent immunotherapy and the thrombocytopenia resolved. CONCLUSION: We report the first case of metastatic renal cell carcinoma presenting as a vaginal metastasis with thrombocytopenia as a paraneoplastic manifestation. Renal cell carcinoma must be in the differential diagnosis of a clear cell neoplasm in a postmenopausal woman, particularly with systemic symptoms suggestive of a paraneoplastic syndrome.

Carcinoma, Renal Cell↗

Age-related changes on the surface of vitreous collagen fibrils.

PURPOSE: To determine whether aging vitreous collagen fibrils undergo ultrastructural changes that might underlie vitreous liquefaction and posterior vitreous detachment. METHODS: Vitreous collagen fibrils from 21 human subjects (age range, 3-89 years) and from bovine eyes were isolated on electron microscopy grids. Cupromeronic blue labeling in the presence of 0.3 M MgCl(2) and immunogold labeling for collagen types II and IX were analyzed by transmission electron microscopy. RESULTS: Aging was associated with marked changes on the surface of human vitreous collagen fibrils, including an exponential loss of type IX collagen along with its chondroitin sulfate side-chains (half-life, 11 years) and a fourfold increase in the exposure of type II collagen. CONCLUSIONS: Despite being a minor component of vitreous collagen fibrils, type IX collagen, probably by virtue of its chondroitin sulfate side-chains, shields type II collagen from exposure on the fibril surface. With aging, this shielding diminishes, resulting in the surface exposure of "sticky" type II collagen and thus predisposing the vitreous collagen fibrils to fusion. These changes could underlie vitreous liquefaction and weakening of vitreoretinal adhesion.

Adolescent↗

Abnormalities of the vitreoretinal interface caused by dysregulated Hedgehog signaling during retinal development.

Mutations in Patched (PTCH), encoding the Hedgehog (Hh) receptor, underlie Basal Cell Naevus syndrome (BCNS) and, in addition to tumor predisposition, are associated with a wide range of 'patterning' defects. The basis for the underlying patterning problems in Hh-dependent tissues in BCNS and their long-term consequences on tissue homeostasis are, however, not known. Hh signaling is required for normal growth and organization of the mammalian retina and we show that PtchlacZ+/- mice exhibit vitreoretinal abnormalities resembling those found in BCNS patients. The retinas of PtchlacZ+/- mice exhibit abnormal cell cycle regulation, which culminates in photoreceptor dysplasia and Müller cell-derived gliosis. In BCNS, the intraretinal glial response results in epiretinal membrane (ERM) formation, a proliferative and contractile response on the retinal surface. ERMs are a cause of significant visual loss in the general, especially elderly, population. We hypothesize that alteration of Müller cell Hh signaling may play a role in the pathogenesis of such age-related 'idiopathic' ERMs.

Animals↗

Age-dependent changes in the basal retinovitreous adhesion.

PURPOSE: To determine the width of the posterior vitreous base in human eyes of different ages and to clarify the nature of the postoral retinovitreous adhesion that underlies the development of juxtabasal retinal tears and retinal detachment after posterior vitreous detachment (PVD). METHODS: The posterior limit of the vitreous base was delineated with indocyanine green after mechanical peeling of the postbasal vitreous cortex from the retina in 58 pairs of donor eyes. The area of residual retinovitreous adhesion was measured by image analysis. Scanning electron microscopy was performed on the undersurface (or retinal aspect) of the inner limiting lamina (ILL) after trypsin digestion of the peripheral retina. RESULTS: An age-dependent increase in the anteroposterior dimension of the posterior vitreous base was revealed that became progressively wider in eyes of male donors than in those of female donors and in the nasal half compared with the temporal half of the globe. Ultrastructural studies showed progressive invasion of the innermost peripheral retina by bundles of collagen fibrils, initially in the form of characteristic braids splaying out beneath the ILL and eventually as a dense sublaminar mat in the elderly. The collagen fibrils penetrated the ILL through localized defects and intertwined with those in the basal gel. CONCLUSIONS: With aging, the posterior border of the vitreous base migrates posteriorly so that an annular band of firm adhesion eventually straddles the ora serrata eccentrically. Intraretinal synthesis of collagen fibrils, their penetration of the ILL, and their splicing with cortical vitreous fibrils, underlie the slowly evolving retinovitreous adhesion.

Adhesiveness↗

Multisampling suprathreshold perimetry: a comparison with conventional suprathreshold and full-threshold strategies by computer simulation.

PURPOSE: To compare a multisampling suprathreshold strategy with conventional suprathreshold and full-threshold strategies in detecting localized visual field defects and in quantifying the area of loss. METHODS: Probability theory was applied to examine various suprathreshold pass criteria (i.e., the number of stimuli that have to be seen for a test location to be classified as normal). A suprathreshold strategy that requires three seen or three missed stimuli per test location (multisampling suprathreshold) was selected for further investigation. Simulation was used to determine how the multisampling suprathreshold, conventional suprathreshold, and full-threshold strategies detect localized field loss. To determine the systematic error and variability in estimates of loss area, artificial fields were generated with clustered defects (0-25 field locations with 8- and 16-dB loss) and, for each condition, the number of test locations classified as defective (suprathreshold strategies) and with pattern deviation probability less than 5% (full-threshold strategy), was derived from 1000 simulated test results. RESULTS: The full-threshold and multisampling suprathreshold strategies had similar sensitivity to field loss. Both detected defects earlier than the conventional suprathreshold strategy. The pattern deviation probability analyses of full-threshold results underestimated the area of field loss. The conventional suprathreshold perimetry also underestimated the defect area. With multisampling suprathreshold perimetry, the estimates of defect area were less variable and exhibited lower systematic error. CONCLUSIONS: Multisampling suprathreshold paradigms may be a powerful alternative to other strategies of visual field testing. Clinical trials are needed to verify these findings.

Computer Simulation↗

Neoadjuvant androgen ablation before radical prostatectomy in cT2bNxMo prostate cancer: 5-year results.

PURPOSE: In the initial report of the Lupron Depot Neoadjuvant Prostate Cancer Study Group patients who received 3 months of androgen deprivation had a significant decrease in the positive margin rate. We monitored these patients for 5 years and to our knowledge present the longest followup of any neoadjuvant trial. MATERIALS AND METHODS: A multi-institutional prospective randomized trial was performed between February 1992 and April 1994 involving patients with stage cT2b prostate cancer, including 138 who received 3 months of leuprolide plus flutamide before radical prostatectomy and 144 who underwent radical prostatectomy only. Patients were followed every 6 months with serum prostate specific antigen (PSA) testing for 5 years. Biochemical recurrence was defined as PSA greater than 0.4 ng./ml. RESULTS: At 5 years there was no difference in the biochemical recurrence rate. PSA was less than 0.4 ng./ml. in 64.8% of the patients in the neoadjuvant androgen ablation plus prostatectomy and 67.6% in the prostatectomy only group (p = 0.663). CONCLUSIONS: Although 3 months of androgen deprivation before radical prostatectomy resulted in an apparently significant decrease in positive surgical margins, a 5-year followup does not indicate any difference in the recurrence rate. Until studies document improvement in biochemical or clinical recurrence with longer periods of treatment, induction androgen deprivation before radical prostatectomy is not indicated.

Androgen Antagonists↗

Response time as a discriminator between true- and false-positive responses in suprathreshold perimetry.

PURPOSE: To report on differences between the latency distributions of responses to stimuli and to false-positive catch trials in suprathreshold perimetry. To describe an algorithm for defining response time windows and to report on its performance in discriminating between true- and false-positive responses on the basis of response time (RT). METHODS: A sample of 435 largely inexperienced patients underwent suprathreshold visual field examination on a perimeter that was modified to record RTs. Data were analyzed from 60,500 responses to suprathreshold stimuli and from 523 false-positive responses to catch trials. RESULTS: False-positive responses had much more variable latencies than responses to suprathreshold stimuli. An algorithm defining RT windows on the basis of z-transformed individual latency samples correctly identified more than 70% of false-positive responses to catch trials, whereas fewer than 3% of responses to suprathreshold stimuli were classified as false-positive responses. CONCLUSIONS: Latency analysis can be used to detect a substantial proportion of false-positive responses in suprathreshold perimetry. Rejection of such responses may increase the reliability of visual field screening by reducing variability and bias in a small but clinically important proportion of patients.

Adolescent↗