Gompertzian tumor growth. The growth fraction of a tumor declines exponentially over time (top). The growth rate of a tumor peaks before it is clinically detectable (middle). Tumor size increases slowly, goes through an exponential phase, and slows again as the tumor reaches the size at which limitation of nutrients or auto- or host regulatory influences can occur. The maximum growth rate occurs at 1/e, the point at which the tumor is about 37% of its maximum size (marked with an X). Tumor becomes detectable at a burden of about 109 (1 cm3) cells and kills the patient at a tumor. | Chapter 081. Principles of Cancer Treatment Part 2 Figure 81-1 Gompertzian tumor growth. The growth fraction of a tumor declines exponentially over time top . The growth rate of a tumor peaks before it is clinically detectable middle . Tumor size increases slowly goes through an exponential phase and slows again as the tumor reaches the size at which limitation of nutrients or auto- or host regulatory influences can occur. The maximum growth rate occurs at 1 e the point at which the tumor is about 37 of its maximum size marked with an X . Tumor becomes detectable at a burden of about 109 1 cm3 cells and kills the patient at a tumor cell burden of about 1012 1 kg . Efforts to treat the tumor and reduce its size can result in an increase in the growth fraction and an increase in growth rate. Principles of Cancer Surgery Surgery is used in cancer prevention diagnosis staging treatment for both localized and metastatic disease palliation and rehabilitation. Prophylaxis Cancer can be prevented by surgery in people who have premalignant lesions resected . premalignant lesions of skin colon cervix and in those who are at increased risk of cancer from either an underlying disease colectomy in those with pancolonic involvement with ulcerative colitis the presence of genetic lesions colectomy for familial polyposis thyroidectomy for multiple endocrine neoplasia type 2 bilateral mastectomy or oophorectomy for familial breast or ovarian cancer syndromes or a developmental anomaly orchiectomy in those with an undescended testis . In some cases prophylactic surgery is more radical than the surgical procedures used to treat the cancer after it develops. The assessment of risk involves many factors and should be undertaken with care before advising a patient to undergo such a major procedure. For breast cancer prevention many experts use a 20 risk of developing breast cancer over the next 5 years as a threshold. However patient fears play a major role in defining candidates for
