Chapter 25 Prognostic factors in neoplasia
The predicted clinical outcome for a patient with a particular disease is referred to as their prognosis and depends on the nature of the disease process and the general medical condition of the patient. The prognosis of all diseases is based upon our understanding of their pathophysiology and our experience of clinical outcomes in previous patients. A prognosis can be expressed in several ways, such as the likelihood of disease recurrence or progression, the average period of disease-free survival or the overall likelihood of survival for a certain time period.
The accuracy with which a prognosis can be calculated varies considerably between diseases. Medical interventions (i.e. treatments) may be considered successful if they improve the patient’s prognosis, although some treatments are designed to be purely supportive in nature, ameliorating distressing symptoms such as severe pain but not necessarily altering the course of the disease. The latter may apply to patients with incurable conditions, which may be neoplastic (e.g. widespread cancer) or non-neoplastic (e.g. motor neuron disease) in nature.
Malignant tumours most commonly cause death through the development of metastases within vital organs such as the brain and liver. Therefore, although the primary tumour may result in distressing symptoms, treatment of malignant tumours always aims to reduce the risk of metastasis occurring or to reduce the size of established metastases. Malignant tumours may also cause death through extensive local growth and infiltration of adjacent tissues. Oesophageal carcinomas often cause dysphagia (difficulty swallowing) by obstructing the oesophageal lumen, and this contributes to the severe weight loss characteristic of this disease. Colonic carcinomas may cause bowel obstruction or perforation, with peritonitis. Lung cancers not uncommonly grow into the walls of major mediastinal blood vessels such as the aorta with massive ensuing haemoptysis (coughing up blood). Cerebral gliomas almost never metastasize beyond the central nervous system (although they may widely disseminate within the brain and spinal cord) but result in damage to the cardiovascular and respiratory centres within the brainstem, either by direct infiltration or through secondary effects of raised intracranial pressure.
Benign tumours cannot metastasize but may still unusually cause death by compression of vital adjacent structures. Even a small benign tumour within or next to the brainstem (e.g. a meningioma) may lead to death through damage to the cardiovascular or respiratory centres.
The prognosis of a neoplastic disease is dependent upon characteristics of the tumour and the ‘host’ (the patient) (Table 3.25.1). Pathological factors in prognosis include: