Chapter 081. Principles of Cancer Treatment (Part 2) ppsx

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.. Efforts to treat the tumor and reduce its size can result in an in

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 (e.g., 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 cancer prevention surgery Counseling and education may not be enough to allay the fears of someone who has lost close family members to a malignancy

Diagnosis

The underlying principle in cancer diagnosis is to obtain as much tissue as safely possible Owing to tumor heterogeneity, pathologists are better able to make the diagnosis when they have more tissue to examine In addition to light-microscopic inspection of a tumor for pattern of growth, degree of cellular atypia, invasiveness, and morphologic features that aid in the differential diagnosis, sufficient tissue is of value in searching for genetic abnormalities and protein expression patterns, such as hormone receptor expression in breast cancers, that may aid in differential diagnosis or provide information about prognosis or likely

response to treatment Histologically similar tumors may have very different gene expression patterns when assessed by such techniques as microarray analysis using gene chips, with important differences in response to treatment Such testing requires that the tissue be handled properly (e.g., immunologic detection of proteins is more effective in fresh-frozen tissue rather than in formalin-fixed tissue) Coordination among the surgeon, pathologist, and primary care physician

is essential to ensure that the amount of information learned from the biopsy material is maximized

These goals are best met by an excisional biopsy in which the entire tumor

mass is removed with a small margin of normal tissue surrounding it If an

excisional biopsy cannot be performed, incisional biopsy is the procedure of

second choice A wedge of tissue is removed, and an effort is made to include the majority of the cross-sectional diameter of the tumor in the biopsy to minimize sampling error The biopsy techniques that involve cutting into tumor carry with

them a risk of facilitating the spread of the tumor Core-needle biopsy usually

obtains considerably less tissue, but this procedure often provides enough

information to plan a definitive surgical procedure Fine-needle aspiration

generally obtains only a suspension of cells from within a mass This procedure is minimally invasive, and if positive for cancer it may allow inception of systemic treatment when metastatic disease is evident, or it can provide a basis for planning

a more meticulous and extensive surgical procedure