Sophie Jamal, MD, FRCPC, Osteoporosis Research Fellow, Sunnybrook and Women's College Health Sciences Centre, Toronto, ON.

Osteoporosis, defined as a reduction in bone mass leading to an increased susceptibility to fracture with minimal trauma, affects 1.4 million Canadians.¹ Osteoporotic hip and vertebral fractures are major causes of disability and premature death. For example, the average length of stay in an acute care hospital after a hip fracture is three weeks, and one in four patients must remain in long-term care institutions for at least one year. Furthermore, patients with hip and vertebral fractures face a 20% increased risk of mortality.² Osteoporosis is also costly--in Canada, in 1993, the total expenditure for fractures was estimated to be 1.3 billion dollars.³ As the population of Canada ages, the impact of osteoporosis will increase. As such, health care providers should be aware of techniques to prevent fractures due to osteoporosis.

In addition to encouraging physical activity and ensuring adequate calcium and vitamin D intake, several medications can be used to prevent osteoporotic fractures. These drugs, which have been studied predominantly in postmenopausal women, include bisphosphonates, estrogen, selective estrogen receptor modulators and calcitonin. The evidence that supports the use of these agents to prevent bone loss and fractures in postmenopausal women is reviewed below.

M.D. Minden, M.D., Ph.D., FRCPC
Princess Margaret Hospital
University Health Network
Toronto, ON

Introduction
Leukemias are malignancies of the blood and bone marrow and are classified as either acute or chronic malignancies of the myeloid--red blood cell, granulocyte, platelet lineage--or lymphoid--T or B lymphocyte. In this article we will focus on acute myeloblastic leukemias (AML) and recent advances in their classification and therapy.

In the United States, approximately 10,100 cases of AML are diagnosed each year and the yearly mortality rate from this disease is approximately 6,900 individuals. The incidence of AML is low in children (<1/100,000) and increases with age, such that by the time a person reaches the age of 80 the incidence is approximately 15/100,000 (Figure 1).¹ Over 60% of patients are 55 years of age or older, making this a significant problem in the aging population.

AML develops as the result of genetic changes in hematopoietic stem cells of the bone marrow.² These changes block the ability of the cell to undergo normal differentiation resulting in a blast-like morphology. In some cases, the patient may have large numbers of circulating leukemic blast cells compromising blood flow to vital organs.

Julia Krestow, BSc, MSc

Brain cancer has long been known as one of the most difficult neoplasms to treat. Since the 1970's there has been little change in its management despite considerable laboratory progress in understanding brain tumour biology. Recently, however, advances in imaging techniques have begun to result in earlier and more accurate diagnosis.¹ Correct diagnosis combined with the standardized World Health Organization (WHO) classification system for tumours constitute the first step in a successful treatment strategy. The primary challenge and rate-determining step in brain cancer treatment is understanding the underlying tumour biology. This will determine tumour resistance to radiation and chemotherapy, tumour location and the degree of vascularity and abnormal vessel formation within a tumour. Together these comprise the main challenges of brain cancer treatment. Current research areas include Magnetic Resonance Imaging (MRI), which increa-ses surgical safety, new chemotherapeutics, such as, small molecule targeting drugs, which selectively kill tumour cells, and the still theoretical field of immunotherapy. Together these offer considerable hope to physicians, patients and their families even for the most malignant cancers generally found in older patients.

Pathology
Brain tumours are classified according to the tumour type and cell of origin. They are also classified as primary and secondary depending on the absence or presence of metastases.