The effect of aging on the utilization of chemotherapy for metastatic breast cancer: a population-based study.

Older women (i.e., > or = 65 years of age) receive less adjuvant chemotherapy than younger women, in part because chemotherapy has been less effective in postmenopausal than premenopausal women in clinical trials. Metastatic breast cancer, however, does not respond differently to chemotherapy by age. Therefore, to evaluate further the effect of age on chemotherapy utilization, we conducted a population-based study of the treatment of metastatic breast cancer. Patients (n = 132) were identified by cross-tabulating death certificates from 1984 to 1991 with breast cancer cases in the Washington County Cancer Registry. Treatment information was obtained from the Tumor Registry of the Washington Country Hospital and Hospital medical records. Forty patients (74%) < 65 years old received chemotherapy compared to 11 (42%) 65-74 and 6 (12%) > or = 75 (p < 0.0001). Adjusting for other medical conditions and whether or not the patient saw a medical oncologist, there was still a significant effect of age in patients > or = 75 (p < 0.001) and a trend (p = 0.17) for patients 65-74. The different patterns of chemotherapy utilization were not associated with survival differences. Radiation therapy was also utilized significantly less frequently in older than younger patients, but the age effect was not as pronounced as with chemotherapy. There was no age effect on the utilization of hormonal therapy. Less frequent utilization of chemotherapy in older patients is probably caused by a combination of patient and physician factors and may result in less effective palliation for older patients.

Clinical experience with erythropoietin in continuous ambulatory peritoneal dialysis.

The purpose of this project was to determine a safe and effective Epogen (EPO) subcutaneous administration schedule for patients who were on continuous ambulatory peritoneal dialysis. To comply with the manufacturer's recommendation to enter a vial only once, a dosing regimen had to be established that used a standard dose of 2,000 or 4,000 units. The goal was to determine the frequency of administration that would achieve and maintain the target hematocrit. Twenty-six patients participated. The starting dose of 4,000 units was administered either two or three times per week. An average 8.3% point increase in hematocrit was seen in 8 weeks. When the target hematocrit of 33% to 35% was reached, the dose and or frequency of administration was decreased. Maintenance doses were established at 2,000 or 4,000 units weekly or biweekly. We were able to meet and maintain the target hematocrit by using 2,000 or 4,000 units per dose and adjusting the frequency.

Effects of simulated altitude on O2 transport in dogs.

The effects of exposure to simulated altitude on skeletal muscle and on the cardiocirculatory system rhave been studied on awake, conscious, dogs (16-39 kg) at rest and during moderate treadmill exercise at 15% incline. Measurements were obtained in Denver at a PB of 635 mm Hg and after 3 weeks of continuous exposure to a PB of 435 mm Hg using a hypobaric chamber. At both levels of PB the dogs showed marked panting, associated with pulmonary hyperventilation and low PaCO2's (28 mm Hg at 635 and 17 mm Hg at 435 mm Hg). Resting VO2's were high (12.4 and 11.4 ml/min-kg) reflecting the high respiratory outputs. [Hb] and Hct increased significantly after 3 weeks at 435 mm Hg with a 4 mm Hg decrease in P50. Q, HR, SV and systemic blood pressures were normal in both normoxic and hypoxic animals, at rest as well as during exercise. Arterial and mixed venous PO2's decreased in the hypoxic dogs (82 to 56 and 42 to 36 mm Hg, respectively) but arterial O2 content, arterial-venous O2 content difference and systemic O2 transport remained unchanged. Capillary density in the sternothyroid muscle doubled (617 to 1245 cap/mm2) after 3 weeks at a PB of 435, whereas the average muscle fiber diameter decreased about 30%. Calculations indicate that the PO2 in the 'lethal corner' of the muscle fiber is relatively higher in the hypoxic animal because of the decrease in fiber size and intercapillary distances.

Capillary density of skeletal muscle in Andean dogs.

High capillary density and small muscle fiber diameters were found in the sternothyroid muscle of dogs native to 4350 m. The number of capillaries per square millimeter was three times greater while the diameter was less than half of those obtained in the same muscle of normoxic dogs. These findings suggest that tissular adaptative mechanisms are important in the process of acclimatization to hypoxia, contributing to the maintenance of adequate levels of PO2 in the tissue in the presence of hypoxemia.