D

Dennis A. Johnston

Louisiana State University

Publishes on Prostate Cancer Treatment and Research, Prostate Cancer Diagnosis and Treatment, Bladder and Urothelial Cancer Treatments. 238 papers and 12.2k citations.

238Publications
12.2kTotal Citations

Is this you? Claim your profile.

Add your photo, update your bio, and get notified when your ranking changes.

Top publicationsby citations

A COMPARATIVE ANALYSIS OF SEXTANT AND AN EXTENDED 11-CORE MULTISITE DIRECTED BIOPSY STRATEGY
R. Joseph Babaian, Ants Toi, Kazumi Kamoi et al.|The Journal of Urology|2000
Cited by 455

PURPOSE: The 3 tumor locations unsampled by conventional sextant biopsies that have been identified on composite 3-dimensional reconstruction of 180 radical prostatectomy specimens are the anterior transition zone, midline peripheral zone and inferior portions of the anterior horn in the peripheral zone. We evaluated an 11-core multisite directed biopsy scheme incorporating these alternate areas and conventional sextant biopsies in 362 patients from 2 institutions. MATERIALS AND METHODS: Patients without a prior diagnosis of cancer underwent ultrasound guided 11-core biopsies which included conventional sextant and 3 alternate sites. All specimens were separated for specific location identification. Biopsy was performed in 183 patients at MD Anderson Cancer Center (group 1) and in 179 at Toronto General Hospital (group 2). All group 2 and 54% of group 1 patients (98 of 183) had a prior biopsy negative for cancer. RESULTS: Median prostate specific antigen was higher in group 2 than in group 1 patients (11.5 versus 9.5 ng./ml., p = 0.016). Overall a 33% increase (36 of 110 patients) in cancer detection was observed when biopsy technique included the alternate areas (p = 0.0021). The anterior horn was the most frequently positive biopsy site followed by the transition zone and midline sites. The 11-core technique had significantly better cancer detection rates when digital rectal examination and transrectal ultrasound were normal, and in men with serum prostate specific antigen between 4.1 and 10 ng./ml. CONCLUSIONS: Biopsies of the alternate sites suggested by our simulation studies are feasible and reproducible. This new strategy significantly enhanced (p = 0.0075) prostate cancer detection compared to conventional sextant biopsies in men undergoing a repeat procedure.

Sensitivity to genotoxic effects of bleomycin in humans: Possible relationship to environmental carcinogenesis
Tsai‐Ching Hsu, Dennis A. Johnston, Lorraine M. Cherry et al.|International Journal of Cancer|1989
Cited by 315

Responses to the genotoxic effect of bleomycin in lymphocytes of blood cultures, expressed as the average number of chromatid breaks per cell (b/c), varied from less than 0.20 to more than 2.00 in 335 normal individuals. More than 11% of the subjects tested showed a b/c rate above 1.00 and more than 22% showed a b/c rate above 0.80. These individuals are considered sensitive to this radiomimetic drug. The distributional profile of bleomycin responses of the control individuals appears to be representative of the normal human population. In patients with cancers of the colon (83), upper aerodigestive tract (head/neck) (77), and lung (71), the frequencies of subjects in the hypersensitive class were found to be between 40 and 50%, and the response profiles were distinctly different from those of the control population. On the other hand, in a group of elderly cigarette smokers, who exhibited no symptoms of lung cancer, the bleomycin sensitivity profile was significantly skewed toward the more resistant stratum, with only one hypersensitive case among 56 individuals tested (1.78%). The sensitivity profile of patients with breast cancer (82) was similar to that of the control population. Our data suggest that: (1) mutagen sensitivity may play an important role in carcinogenesis of organs and tissues that have direct contact with the external environment (respiratory, digestive, and integumentary systems); (2) it appears to have no significant influence on carcinogenesis of tissues that are not directly exposed to the environment (e.g., breast, brain); and (3) it also has little impact on carcinogenesis in individuals with a hereditary predisposition to cancer (e.g., retinoblastoma, Gardner's syndrome). Development of more effective and precise test systems for carcinogen sensitivity is highly desirable for identification of persons at risk.

Marfan Syndrome
Cited by 311

BACKGROUND: Development of surgical therapy for aortic aneurysms and dissections has led to treatment of the life-threatening cardiovascular complications associated with Marfan syndrome. The present study determines the effect of surgical therapy on the life expectancy of patients with Marfan syndrome and the clinical course of these patients after aortic aneurysm repair. METHODS AND RESULTS: Medical records were reviewed on 192 patients with Marfan syndrome who underwent aortic aneurysm repair during the past 26 years; 103 patients were interviewed, and complete preoperative and postoperative medical information was obtained. Survival curves were generated, and data were analyzed. The median cumulative probability of survival was 61 years, significantly increased compared with the median survival of 47 years for patients with Marfan syndrome determined 30 years ago (P < .0006). The majority of patients (53%) had second surgeries to repair subsequent aneurysms or dissections at other sites, the vast majority of which involved the aorta. The most common pattern of aneurysm repair was proximal ascending aortic aneurysm repair, followed by descending thoracic aneurysm surgery. The following variables predicted patients requiring second vascular surgeries: presence of acute or chronic dissection at the time of the first surgery, hypertension after the first surgery, and a history of smoking. CONCLUSIONS: The life expectancy of patients with Marfan syndrome undergoing surgical repair of aortic aneurysms has improved and is consistent with increased survival. After initial repair of an ascending aortic aneurysm, a significant number of patients have subsequent surgeries at other sites throughout the aorta, indicating Marfan syndrome is a disease involving the entire aorta. Patients who had a dissection at the time of the first aortic surgery were more likely to require subsequent aortic surgery than were patients who underwent prophylactic composite graft repair of an aortic aneurysm.

Effect of Radiation-Induced Xerostomia on Human Oral Microflora
Lee R. Brown, Samuel Dreizen, Sandra Handler et al.|Journal of Dental Research|1975
Cited by 301

A longitudinal study was performed to assess the effects of radiation-induced xerostomia on the human oral microflora. Pronounced microbial population shifts were found in each of five intraoral sites tested. Cariogenic microorganisms gained prominence at the expense of noncariogenic microorganisms in concert with the saliva shutdown. These changes occurred before the onset of clinical caries irrespective of whether or not a topical fluoride gel was used as a caries preventive.