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Featured researches published by David K. Ahn.


International Journal of Radiation Oncology Biology Physics | 1992

Highly anaplastic astrocytoma: A review of 357 patients treated between 1977 and 1989☆

Michael D. Prados; Philip H. Gutin; Theodore L. Phillips; William M. Wara; David A. Larson; Penny K. Sneed; Richard L. Davis; David K. Ahn; Kathleen R. Lamborn; Charles B. Wilson

Between May 1977 and August 1989, 357 patients (199 male, 158 female; median age 40 years) with highly anaplastic astrocytomas other than glioblastoma multiforme were treated according to any of several protocols used in studies by the University of California, San Francisco, and the Northern California Oncology Group. The data evaluated were age, Karnofsky Performance Score, survival, time to tumor progression, therapy, and the effect of treatment at the time of progression. The records of 219 patients were taken from the University of California database, and those of the other 138 were taken from the Northern California Oncology Group computer files. Their median Karnofsky Performance Score was 90% (range 40-100%), the overall median survival was projected as 170.9 weeks, and the median time to first tumor progression was 127.3 weeks. The median survival time measured after the first progression was 41.3 weeks. Age and Karnofsky Performance Score had a significant influence on survival and on time to the first tumor progression, whereas extent of surgery and the use of interstitial brachytherapy in the initial therapy did not. We conclude that these patients can expect a median survival of over 3 years, that young age and high Karnofsky Performance Score have a positive influence on survival, and that salvage therapies can extend survival after the onset of tumor progression for nearly a year. Although it did not lengthen survival when used in initial therapy, interstitial brachytherapy used at the time of tumor progression was associated with increased survival.


International Journal of Radiation Oncology Biology Physics | 1991

Evaluation of bromodeoxyuridine in glioblastoma multiforme: A A Northern California cancer center phase II study

Theodore L. Phillips; Victor A. Levin; David K. Ahn; Philip H. Gutin; Richard L. Davis; Charles B. Wilson; Michael D. Prados; William M. Wara; M.S. Flam

In a study activated in 1983 and closed in 1987, the Brain Tumor Research Center of the University of California and the Northern California Cancer Center evaluated the effect of bromodeoxyuridine in the treatment of glioblastoma multiforme. A total of 160 patients were evaluable of 173 entered. Patients were to receive a bromodeoxyuridine infusion of 0.8 g/m2 daily over 24 hours for 4 days of each of 6 weeks of radiotherapy directed to the tumor plus a margin delivering a total of 60 Gy. Eligibility requirements included Karnofsky performance status greater than or equal to 70, biopsy or resection and central pathology review by one of the authors. Following radiotherapy patients were to receive chemotherapy with procarbazine, CCNU, and vincristine for 1 year. Median survival was 55.7 weeks and time to failure, 34.5 weeks for the evaluable group of 160 patients. In a univariate analysis the variables that influence survival and time to failure were: age, Karnofsky performance status, bromodeoxyuridine dose and the delivery of at least one procarbazine, CCNU, and vincristine cycle following radiotherapy. In multivariate analysis, age, Karnofsky performance status, and bromodeoxyuridine dose remain significant for time to failure; age and Karnofsky performance status remain significant for survival.


International Journal of Radiation Oncology Biology Physics | 1990

Long-term results of helium ion irradiation of uveal melanoma

David E. Linstadt; Joseph R. Castro; Devron H. Char; Mary Decker; David K. Ahn; Paula Petti; Valerie Nowakowski; Jeanne M. Quivey; Theodore L. Phillips

Between 1978 and 1988, 307 patients with uveal melanoma were irradiated using helium ions at Lawrence Berkeley Laboratory. The length of follow-up ranged from 1-115 months (median 42 months). The 5-year actuarial treatment results were: local control rate, 96.8%, determinate survival rate, 81%, freedom from distant metastases, 76%, eye retention rate, 83%, and risk of developing neovascular glaucoma, 36%. Long-term vision outcome was analyzed in 81 patients with a minimum follow-up of 5 years. Forty-seven percent of patients retained vision of 20/200 or better. The median change in vision was a loss of four lines on the standard eye chart. Thirty-eight percent of patients had visual acuity either improve or remain within two lines of their pretreatment vision. A multivariate analysis identified tumor size as the only independently significant risk factor affecting survival, development of neovascular glaucoma, or the risk of enucleation; no risk factor correlated with local recurrence. Tumor size, tumor-fovea distance, and pretreatment visual acuity were independently significant risk factors influencing vision outcome. These results confirm that helium ion irradiation is an effective treatment for uveal melanoma which combines high rates of local control, survival, and eye retention with a substantial likelihood of long-term vision preservation.


International Journal of Radiation Oncology Biology Physics | 1992

Charged particle radiotherapy of paraspinal tumors.

Valerie Nowakowski; Joseph R. Castro; Paula Petti; J.M. Collier; Inder K. Daftari; David K. Ahn; Grant E. Gauger; Philip H. Gutin; David E. Linstadt; Theodore L. Phillips

Between 1976 and 1987, 52 patients with tumors adjacent to and/or involving the cervical, thoracic, or lumbar spinal cord were treated with charged particles at the University of California Lawrence Berkeley Laboratory. The histologies included chordoma and chondrosarcoma (24 pts), other bone and soft tissue sarcoma (14 pts), and metastatic or unusual histology tumors (14 pts). Radiation doses ranged from 29 to 80 Gray-equivalent (GyE), with a median dose of 70 GyE. Twenty-one patients received a portion of their treatment with photons. Median followup was 28 months. For 36 previously untreated patients, local control was achieved in 21/36 patients and the 3-year actuarial survival was 61%. Of 16 patients treated for recurrent disease, 7/16 were locally controlled and the 3-year actuarial survival was 51%. For patients treated for chordoma and chondrosarcoma, probability of local control was influenced by tumor volume (less than 100 cc or greater than 150 cc) and whether disease was recurrent or previously untreated. Complications occurred in 6/52 patients, including one spinal cord injury, one cauda equina and one brachial plexus injury, and three instances of skin or subcutaneous fibrosis. Charged particle radiotherapy can safely deliver high tumor doses to paraspinal tumors with good local control.


International Journal of Radiation Oncology Biology Physics | 1989

CILIARY BODY MELANOMA TREATED WITH HELIUM PARTICLE IRRADIATION

Mary Decker; Joseph R. Castro; David E. Linstadt; Devron H. Char; Paula L. Petti; Jeanne M. Quivey; David K. Ahn

Melanoma involving the ciliary body is a rare tumor which carries a poor prognosis when compared to all uveal melanoma. We have treated 54 patients with ciliary body melanoma using helium ions from 1978 to 1985. Because of the high rate of metastatic disease, the 5-year disease specific survival rate is only 59% despite a 5-year local control rate of 98%. The greatest diameter of the tumor was predictive of loss of vision and enucleation (p = .05, p = .04, respectively). Multivariate analysis showed that the greatest diameter of the tumor was the most important predictor of death from metastases. The incidence of neovascular glaucoma at 5 years is 43%. The 5-year actuarial rate of enucleation is 26%. Enucleation was done for pain and/or neovascular glaucoma. Univariate analysis showed treatment volume to be a statistically significant predictor for the development of neovascular glaucoma (p = .0017) and enucleation (p = .0078). Seventy percent of neovascular glaucoma occurred in patients with treatment volume greater than 5.5 cc. Seventy-four percent occurred in patients with an initial ultrasound height greater than 9.2 mm. Using this information, patients at high risk for neovascular glaucoma could be considered for prophylactic treatment with panretinal photocoagulation.


Epidemiology | 1995

Cutaneous melanoma in women. V. Characteristics of those who tan and those who burn when exposed to summer sun.

Rosemary D. Cress; Elizabeth A. Holly; David K. Ahn

We studied 338 Caucasian women with superficial spreading melanoma (hereafter called melanoma) and 872 control subjects ages 25–59 years and compared characteristics of women who reported that they tanned with sun exposure with those who reported that they burned. The purpose of the study was to investigate how skin type, as measured by tendency to burn or tan, modified the effect of other melanoma risk factors. There was a clear relation between tendency to burn and prevalence of red hair, light complexion, freckles, and history of sunburns during elementary school and high school. Host factors such as light complexion and increased number of self-assessed large nevi elevated risk of melanoma among women of all skin types. Increased risk for melanoma associated with frequent sunburns during childhood and adolescence was most pronounced for women who burned and then tanned; risk was not substantially elevated for women who burned without tanning. Women who had a history of sunburns had an increased melanoma risk even if they reported tanning.


International Journal of Radiation Oncology Biology Physics | 1991

Rapidly alternating radiotherapy and high dose cisplatin chemotherapy in stage IIIB non-small cell lung cancer: Results of a phase I/II study

David R. Gandara; Frank H. Valone; Edith A. Perez; Albert B. Deisseroth; Mack Roach; David K. Ahn; Theodore L. Phillips

Alternating radiotherapy and chemotherapy increases tumor cure rates in some animal models with reduced normal tissue damage compared to sequential use of these modalities. To test this concept in non-small cell lung cancer, 23 patients with predominantly Stage IIIB disease were treated on a Northern California Oncology Group pilot study of alternating radiotherapy and high dose cisplatin. Radiotherapy consisted of 6000 cGy delivered in three separate 10-day courses of 200 cGy/fraction/day during weeks 1 and 2, 5 and 6, and 9 and 10. High dose cisplatin, 100 mg/m2 in 3% saline, was administered on weeks 3 and 4, 7 and 8, 11 and 12, and 15 and 16. The response rate in 22 eligible patients is 73% (16/22) with four complete responses and 12 partial responses. Feasibility of this approach is demonstrated by 20/22 patients completing radiotherapy and a median of 2.5 courses of chemotherapy administered. Median survival time is 14.2 months (range 2-40+ months). One- and 2-year survival rates are 64% (14/22) and 41% (9/22), respectively. Hematologic, renal, and radiation-related toxicities were significant but manageable. We conclude that rapid alternation of radiotherapy and a high dose intensity cisplatin regimen is feasible in Stage IIIB non-small cell lung cancer, with a high response rate and acceptable toxicity. The long-term impact on local control and survival remains unclear, although preliminary survival data are encouraging in this poor prognosis population. Further studies of this concept are warranted.


Journal of Neuro-oncology | 1994

The prognostic implications of histologic classification and bromodeoxyuridine labeling index of mixed gliomas

Margaret R. Wacker; Takao Hoshino; David K. Ahn; Richard L. Davis; Michael D. Prados

SummaryTo clarify the biological and clinical behavior and prognosis of mixed gliomas, 47 patients underwent intraoperative bromodeoxyuridine (BrdU) labeling studies. The mean age was 27.8 years at symptom onset and 31.8 years at labeling (median, 36 years). Forty-five tumors were supratentorial, 30 were frontal, and two were cerebellar; 16 were recurrent at labeling. The median labeling index (LI) was 1% (range,<1 to 15.1%). Forty-six tumors had oligodendroglial and astrocytic elements, and one had astrocytic and ependymal elements. The median LI was 4.4% in recurrent tumors and <1% in primary tumors. A higher BrdU LI correlated with an increased risk of recurrence and a shorter time to recurrence. During a median follow-up of 16 months, four patients died; each had a BrdU LI≥4.4%. The median time to recurrence was 4.5 months for tumors with BrdU LIs >5% but was not reached for tumors with LIs <5% (p< 0.003). The histologic grade of the oligodendroglial component correlated with the median time to recurrence (8 months for Smith Grade C tumors, not reached for Smith Grade B tumors; p<0.05); there were too few cases to evaluate the median times to recurrence of Smith Grade A and Grade D tumors. The median time to recurrence was not reached for any astrocytic grade, and there were no significant differences in the Kaplan-Meier survival curves. These findings suggest that the BrdU LI and the grade of the oligodendroglial component of mixed gliomas have prognostic significance.


American Journal of Epidemiology | 1992

Ewing's Bone Sarcoma, Paternal Occupational Exposure, and Other Factors

Elizabeth A. Holly; Diana A. Aston; David K. Ahn; Jennifer J. Kristiansen


International Journal of Radiation Oncology Biology Physics | 1992

Thermoradiotherapy of recurrent malignant brain tumors

Penny K. Sneed; Philip H. Gutin; Paul R. Stauffer; Theodore L. Phillips; Michael D. Prados; Keith A. Weaver; Stuart Suen; Sharon Lamb; Brigid Ham; David K. Ahn; Kathleen R. Lamborn; David A. Larson; William M. Wara

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Philip H. Gutin

Memorial Sloan Kettering Cancer Center

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