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R S Cox

Publications and source records attributed to R S Cox.

At least 55 records · Page 3Linked to original sources
PubMed1990

Development of total-skin electron therapy at two energies.

Total-Skin Electron Therapy (TSET) modalities have been developed at two energies on a Varian Clinac 1800. The physical criteria for the beams were determined mainly from the requirement of continuing the Stanford treatment technique, which was 12 Total-Skin Electron Therapy portals combined in six pairs. The penetration of the lower energy mode matches that previously obtained at Stanford on the Varian Clinac 10, (about 4 mm for the 80% isodose contour in the 12-field treatment). The penetration of the higher energy mode is about 8 mm at the 80% contour. The Total-Skin Electron Therapy modes necessarily use electrons produced by the two standard electron-beam modes of lowest energy, nominally 6 and 9 MeV. Measurements to verify the beam specifications were carried out with diodes, a variety of ionization chambers, and a specially constructed circular phantom for film dosimetry. Initially, the penetration of the Total-Skin Electron Therapy beams was too large to match our criteria, so two methods of reducing it were explored: (a) the energies of the electron beams produced by the machine were reduced (which also reduced the energies of the corresponding standard electron modes) and (b) a large polymethylmethacrylate degrader (2.4 m X 1.2 m) 1 cm thick was placed just in front of the patient plane. Acceptable Total-Skin Electron Therapy beams could be produced by either method and the latter was finally used. The use of the standard dose monitoring system for the Total-Skin Electron Therapy modes considerably simplifies the daily treatment delivery as well as the implementation. However, the need for reasonable dose rates at the treatment plane (3.5 meters beyond the isocenter) requires dose rates of 24 Gy/min at the isocenter. Nevertheless, it is possible to use the internal dose monitor provided the problems associated with high dose rates (recombination and amplifier saturation) are addressed. Solutions to these problems involved switching the primary and back-up dose monitors, increasing the collecting voltage on the ion chambers, and calibrating the dose monitor so that 1 unit = 1 cGy at the patient rather than at the isocenter.

Electrons↗
PubMed1990

Two or six hyperthermia treatments as an adjunct to radiation therapy yield similar tumor responses: results of a randomized trial.

From March 1984 to February 1988, 70 patients with 179 separate treatment fields containing superficially located (less than 3 cm from surface) recurrent or metastatic malignancies were stratified based on tumor size, histology, and prior radiation therapy and enrolled in prospective randomized trials comparing two versus six hyperthermia treatments as an adjunct to standardized courses of radiation therapy. A total of 165 fields completed the combined hyperthermia-radiation therapy protocols and were evaluable for response. No statistically significant differences were observed between the two treatment arms with respect to tumor location; histology; initial tumor volume; patient age and pretreatment performance status; extent of prior radiation therapy, chemotherapy, hormonal therapy, or immunotherapy; or concurrent radiation therapy. The means for all fields of the averaged minimum, maximum, and average measured intratumoral temperatures were 40.2 degrees C, 44.8 degrees C, 42.5 degrees C, respectively, and did not differ significantly between the fields randomized to two or six hyperthermia treatments. The treatment was well tolerated with an acceptable level of complications. At 3 weeks after completion of therapy, complete disappearance of all measurable tumor was noted in 52% of the fields, greater than or equal to 50% tumor reduction was noted in 7% of the fields, less than 50% tumor reduction was noted in 21% of the fields, and continuing regression (monotonic regression to less than 50% of initial volume) was noted in 20% of the fields. No significant differences were noted in tumor responses at 3 weeks for fields randomized to two versus six hyperthermia treatments (p = 0.89). Cox regression analyses were performed to identify pretreatment or treatment parameters that correlated with duration of local control. Tumor histology, concurrent radiation doses, and tumor volume all correlated with duration of local control. The mean of the minimum intratumoral temperatures (less than 41 degrees C vs. greater than or equal to 41 degrees C) was of borderline prognostic significance in the univariate analysis, and added to the power of the best three covariate model. Neither the actual number of hyperthermia treatments administered nor the hyperthermia protocol group (two versus six treatments) correlated with duration of local control. The development of thermotolerance is postulated to be, at least in part, responsible for limiting the effectiveness of multiple closely spaced hyperthermia treatments.

Adult↗
PubMed1990

Reduction of spinal metastases after preemptive irradiation in prostatic cancer.

For this study, 136 patients treated at Stanford University Hospital for prostatic cancer between 1971 and 1980 were selected for review. The patients had received no prior therapy, and had no evidence of bone metastases at time of radiation treatment based on radiographic studies and bone scan. Of this group, 71 patients received extended-field irradiation (paraaortic and pelvic fields), and 65 patients received pelvic irradiation. The pelvic field was treated to 50 Gy and the paraaortic field received 45 Gy to 60 Gy. All patients subsequently underwent routine follow-up examinations and studies at Stanford University Hospital: 1,513 follow-up X rays, bone scans, and CT-scans were analyzed for site-specific recurrence. The follow-up ranged from 14 months to 16 yrs from the time of initial treatment, with a mean follow-up of 7 yrs. Lower extremities and ribs were found to be the most common sites of bone metastases. Irradiation of the lumbar spine to a dose of 35 to 60 Gy, coincidental to irradiation of the paraaortic lymph nodes prevented or delayed the development of lumbar spine metastases. The potential mechanism and clinical implications are discussed.

Bone Neoplasms↗
PubMed1990

Prostate specific antigen after irradiation for prostatic carcinoma.

The clinical significance of serum prostate specific antigen after primary irradiation for adenocarcinoma of the prostate is uncertain. Between September 1986 and December 1987 serial prostate specific antigen values were determined in 43 patients before and after definitive radiation therapy. The study group included 6 patients with stage T0d, 10 with stage T1, 11 with stage T2 and 16 with stage T3 disease, with a mean pre-treatment prostate specific antigen level of 49.2 +/- 10.8. For all patients the first post-treatment prostate specific antigen level was less than the pre-treatment level. One patient failed locally with recurrent prostatic cancer that invaded the rectum. The 6 patients who failed with symptomatic metastases had an increasing prostate specific antigen level 2 to 7 months before detection of recurrence. Based on the absolute value and trend of the prostate specific antigen, patients were described as being at high, intermediate or low risk for distant metastases. Of 9 high, 6 intermediate and 28 low risk patients 4 (44%), 2 (33%) and 0 (0%) have experienced recurrent disease (p = 0.0025). We conclude that serial post-irradiation prostate specific antigen values may be useful in the early identification of patients at risk for treatment failure.

Adenocarcinoma↗
PubMed1990

Radiation therapy for localized prostate cancer. Justification by long-term follow-up.

In the series presented here, survival patterns at 15 years after radiotherapy for patients with clinical stage A carcinoma of the prostate did not deviate significantly from those of an age-matched peer group. For patients with clinical stage B disease (nodular disease that did not exceed involvement of one lateral lobe), survival was only 5% less at 15 years than for the age-matched group of California men. This was in spite of the fact that the lymph node status and the true incidence of capsular penetration were unknown. Moreover, the patients were not stratified by histopathologic grade or by either acid phosphatase or prostate-specific antigen values. If one were to restrict the patients to those with intermediate and low Gleason scores, normal acid phosphatase, and low prostate-specific antigen values, it is likely that there would have been no difference between the survival of those with prostatic cancer and their age-matched peers. As one deviates from these conservative selection criteria and includes patients with more advanced stages, the likelihood of achieving 15-year survival diminishes. With radiation treatment, however, patients whose disease, by clinical examination, extends beyond the prostate and who seem too advanced for radical prostatectomy still may have a 20 per cent to 30 per cent chance of 15-year survival.

Adult↗
PubMed1989

The influence of initial hemoglobin and blood pressure levels on results of radiation therapy for carcinoma of the prostate.

A group of 914 patients with carcinoma of the prostate treated by definitive radiotherapy at Stanford between 1956 and 1985 was studied. Of these, the initial hemoglobin level was recorded in 656 cases and the initial blood pressure in 760 cases. End-points studied in actuarial analyses were survival, disease-specific survival, local control, freedom from distant relapse, and occurrence of late intestinal complications. Although the anemic group (Hb less than 13.5 g/dl) was correlated negatively with survival (p = 0.02), there was no correlation with disease-specific survival or local control. The conclusion was that anemia per se did not affect the outcome of radiation therapy. A pulse pressure greater than or equal to 60 mm Hg was significantly correlated with worse survival (p = 0.01) and local control (p = 0.04), but no correlation was found between systolic and diastolic blood pressure and the end-points measured. Neither anemia nor hypertension were significantly correlated with late intestinal complications.

Anemia↗
PubMed1988

Risk of second cancers after treatment for Hodgkin's disease.

We estimated the risk of second cancers among 1507 patients with Hodgkin's disease treated at Stanford University Medical Center since 1968. Eight-three second cancers occurred more than one year after diagnosis, as compared with 15.9 expected on the basis of rates in the general population (relative risk, 5.2; 95 percent confidence interval, 4.2 to 6.5). The mean (+/- SE) 15-year actuarial risk of all second cancers was 17.6 +/- 3.1 percent, of which 13.2 +/- 3.1 percent was due to solid tumors. The risk of leukemia appeared to reach a plateau level of 3.3 +/- 0.6 percent at 10 years, whereas non-Hodgkin's lymphoma continued to increase, to 1.6 +/- 0.7 percent by the end of the follow-up period. The risk of solid tumors did not vary significantly according to treatment category, with the array of neoplasms resembling that previously observed in populations exposed to radiation and in immunosuppressed groups. The risk of leukemia, although elevated after radiation therapy alone (relative risk, 11; 95 percent confidence interval, 1.2 to 38), was much higher after either adjuvant chemotherapy (relative risk, 117; 95 percent confidence interval, 69 to 185) or chemotherapy alone (relative risk, 130; 95 percent confidence interval, 26 to 380). These data suggest that the risk of solid tumors after therapy for Hodgkin's disease continues to increase with time.

Adolescent↗
PubMed1988

Brachytherapy.

Explore the source record for details and available documents.

Antineoplastic Agents↗
PubMed1988

Astrocytoma in children: 14 years' experience at Stanford University Medical Center.

Between January 1, 1971 and December 31, 1984, 50 children (31 males, 19 females) ages 3 1/2 months to 18 years with primary CNS astrocytoma were seen in the Department of Therapeutic Radiology, Stanford University Medical Center. The actuarial survival and freedom from relapse (FFR) for the treated group is 46%, with a median follow-up of 7.2 years and a maximum follow-up of 14 years. The majority of relapses occurred within the first 2 years of diagnosis, and all relapses occurred at or adjacent to the initial site of tumor. Multivariate analysis revealed that factors correlated with poor survival are high histologic grade (including presence of necrosis) and primary tumor in the brain stem, while the only important prognostic factor associated with an adverse FFR is high histologic grade. Age, sex, degree of surgical resection, and total radiation dose to the tumor are not correlated with outcome. Patients with high-grade tumor were selected to receive whole brain irradiation and/or adjuvant chemotherapy; therefore, the findings of apparent poor prognosis associated with whole brain irradiation and adjuvant chemotherapy actually reflect patient selection. Current therapy is adequate for only half of children with astrocytoma. Thus, continued development of innovative therapies is indicated, particularly for those children with adverse prognostic factors.

Adolescent↗
PubMed1988

Status of radiation treatment of prostate cancer at Stanford University.

Over 900 patients have been treated with radiation therapy in the 30-year Stanford prostate study. Overall survival, i.e., scoring death due to all causes, was 45%, 35%, 33%, 20%, and 10% for Stanford stages T0, T1, T2, T3, and T4 (nominal stages A, B1, B2, C) at 15 years; lymph node status was unknown. Disease-specific survival at 15 years was 85%, 64%, 45%, 33%, and 15%, respectively, for the same patients. In 141 patients with restricted nodular disease (lymph node status unknown) equal to or less than one-half of one lobe involved (stage B1), the 15-year overall survival was 50% and identical to the expected survival of an age-matched cohort of males. Potency was preserved in 86% of the patients at 15 months posttreatment, and 50% of the patients maintained erectile potency for 7 years posttherapy. Other sequelae and complications are analyzed. The incidence of second neoplasms did not exceed expectations for an age-matched population.

Adult↗
PubMed1987

Selecting initial therapy for prostate cancer. Radiation therapy perspective.

External-beam irradiation of prostatic cancer was introduced at Stanford in 1956. The program has sought to determine the following: whether prostatic carcinoma can be cured by external beam radiation therapy, with what frequency this can be accomplished, which patients are best suited for irradiation, and what technique best accomplishes the irradiation. This report deals with differences and similarities between radiation therapy and surgery, and emphasizes the selection of patients for irradiation.

Actuarial Analysis↗
PubMed1987

Extracutaneous mycosis fungoides.

The clinical course of 40 patients with histologically documented extracutaneous mycosis fungoides (ECMF) was reviewed. Thirty one patients had documentation of nodal disease only (Stage IVA). Nine patients had histologic evidence of visceral involvement (Stage IVB). A wide variety of topical, regional and/or systemic therapies were used in the management of these patients. The median survival for the entire group was 14.5 months. Eleven patients (28%) obtained a complete response (CR) and had a median survival of 21 months as compared with 8 months among 29 patients not obtaining a CR. One patient is without evidence of disease (NED) at 10 years. Multiple prognostic factors were examined with respect to survival. Prognostic factors found to be significant at the P = 0.05 level included ECMF at presentation of skin disease (versus at the time of relapse), the ability to achieve a CR, and management incorporating the use of topical therapy, especially electron beam treatment. Tabulation of all trials of chemotherapy either at diagnosis of ECMF or subsequently revealed that cyclophosphamide, vincristine and prednisone (CVP) and cyclophosphamide, vincristine, prednisone, and bleomycin (COP-Bleo) were the most effective chemotherapeutic combinations. In a multivariate analysis with survival as the endpoint, the best model consisted of only two covariates: ECMF at presentation of skin disease, and the use of topical therapy. Other covariates found not to be significant at the P = 0.05 level included age, gender, clinical extent of cutaneous and extracutaneous disease, Stage IVA versus Stage IVB disease, the presence of Sezary cells in the peripheral blood smear, and management incorporating the use of systemic therapy.

Adult↗
PubMed1987

Relationship between the neurotoxicity of the hypoxic cell radiosensitizer SR 2508 and the pharmacokinetic profile.

Complete pharmacological data from 71 patients treated on the phase I trial of SR 2508 were analyzed to see if the dose-limiting toxicity of peripheral neuropathy is related to the individual patient's pharmacokinetic profile. In a retrospective analysis, the risk of toxicity was best predicted by using the bivariate model of total drug exposure and the time over which the treatment course was given. Drug exposure [area under the curve (AUC)] for a single treatment was calculated by the integral over time of the serum concentration of SR 2508. Since the AUC was constant during the course of a patient's treatment, the total drug exposure (total-AUC) was estimated by the product of the AUC times the number of drug administrations. While the clinical efficacy of hypoxic cell sensitizers remains to be proven, SR 2508 is better tolerated than its predecessors, misonidazole and desmethylmisonidazole, as three times the amount of SR 2508 can be given. If this model is confirmed in the current phase II and III trials, the probability of developing neuropathy would be predictable for an individual patient from measurements made at the time of the first drug dose, allowing for the adjustment of drug schedule to avoid all but minor toxicity.

Dose-Response Relationship, Drug↗
PubMed1987

Minimal long-term cardiopulmonary dysfunction following treatment for Hodgkin's disease.

UNLABELLED: We studied the long term cardiopulmonary function, at rest and during exercise, of 57 patients who were at least 1 year (mean 5 years) post-treatment for Hodgkin's disease. To establish the maximum degree of dysfunction we studied 40 patients who had extensive intrathoracic disease treated with radiotherapy alone (Exten-X; n = 20) or combined modality therapy (Exten-XC; n = 20). Patients without intrathoracic disease given either prophylactic mantle therapy (Proph-X, n = 10) or no chest irradiation ( CONTROL: n = 7) were used as controls. An abnormal electrocardiogram, by virtue of a conduction defect, was observed in seven patients, six in the Exten-X or Exten-XC groups. Borderline abnormalities including ST-T changes, prolonged QT interval, or axis deviation occurred in 14 patients distributed evenly throughout the groups. Resting mean pulmonary function test values were normal in all treatment groups. Exercise tolerance, as indicated by peak oxygen consumption (VO2), was significantly lower for the Exten-XC group compared to Proph-X (p less than 0.01). However, the mean value of VO2 for group Exten-XC was only 15% below that predicted. Of the 12 patients with abnormally low VO2 (greater than 20% below their predicted value), 11 were in the Exten-X or Exten-XC group with no difference between the two groups. Patients who received radiotherapy to at least one lung field, using either the thin lung block technique or open field irradiation, had significantly lower exercise tolerance than those treated with full thickness blocks (p less than 0.05). Despite these abnormalities only a single patient complained of marked dyspnea. We conclude that extensive treatment to the mantle field, especially when followed by chemotherapy in patients with extensive intrathoracic Hodgkin's disease, can result in minimal cardiopulmonary dysfunction in approximately one-third of patients.

Adolescent↗
PubMed1987

Solitary plasmacytoma of bone: treatment, progression, and survival.

Twenty patients with solitary plasmacytoma of bone were treated by radiation therapy. Local control was achieved in 19 and most patients developed systemic myeloma. To evaluate disease progression, 65 patients, including 45 from published series, were analyzed. Younger patients seemed less likely to progress (P = .06), but other clinical characteristics including site of involvement and paraprotein status did not influence progression. After dissemination, patients had a clinical course similar to patients with stage I myeloma, with a median survival of 47 months. Overall, patients with solitary plasmacytoma of bone had an indolent course of disease, with a median survival of 10.7 years and a 5-, 10-, and 20-year survival of 75%, 52%, and 37%, respectively.

Adult↗
PubMed1986

Neurologic dysfunction in patients treated for small cell carcinoma of the lung: a clinical and radiological study.

The neurologic dysfunction in 7 patients treated for small cell carcinoma (SCC) of the lung by combination chemotherapy and prophylactic brain irradiation was evaluated. The disease appeared to be a diffuse encephalopathy frequently affecting the higher cortical functions. Five out of seven patients had progressive dysfunction leading to death in 1 to 26 months; one patient had stabilization of symptoms followed by death in 21 months, probably from the neurologic disease as well as SCC; one patient's symptoms improved. The clinical course of the neurologic disorder seemed different from the known reactions to brain irradiation and from the other neurologic syndromes associated with lung cancer. The relative contributions of cranial irradiation and treatment with chemotherapeutic agents in producing the neurotoxicity are not known. Computed tomographic (CT) brain scans done after the onset of symptoms did not show any focal signs or necrosis. However, there was a suggestion of progressive increase in intracranial fluid volume on the scans. The incidence of the disorder, 10.2% among a group of 49 patients, suggests the need for prospective studies to evaluate the problem.

Adult↗
PubMed1986

Treatment of lymphoblastic lymphoma in adults.

Forty-four adult patients with lymphoblastic lymphoma (LBL) were treated according to one of two protocols. Both included (1) induction with cyclophosphamide, doxorubicin, vincristine, prednisone, and L-asparaginase; (2) CNS prophylaxis; and (3) maintenance therapy with methotrexate (MTX) and 6-mercaptopurine. In the second protocol, CNS prophylaxis began earlier than in the first protocol and included cranial irradiation and intrathecal (IT) MTX rather than simultaneous high-dose systemic and IT MTX. The overall response rate was 100% (95% complete). With a 26-month median follow-up, the 1-and 3-year actuarial freedom from relapse (FFR) for the composite patient group was 70% and 56%, respectively. The incidence of CNS relapse was reduced from 31% in the first protocol to 3% in the second protocol (P = .04, Gehan). Patients can be assigned retrospectively to low (n = 19) and high (n = 25) risk prognostic groups, as indicated by a multivariate analysis of pretreatment prognostic factors. High-risk is defined by Ann Arbor stage IV disease with bone marrow or CNS involvement or initial serum lactate dehydrogenase (LDH) concentration of greater than 300 IU/L (normal, less than 200). FFR of low- and high-risk groups at 5 years are 94% and 19%, respectively (P = .0006). Low-risk patients are highly curable using this approach to adult LBL. More intensive treatment for high-risk patients is warranted.

Adult↗