Biology of Disease

the patient does not require a colostomy bag. Patients with rectal cancer may
be given radiation treatment after surgery to reduce the risk of the tumor
recurring locally. Radiation therapy may also be used in the palliative care of
late stage metastatic cancer. Chemotherapy, 5-FU and leucovorin is sometimes
offered postsurgery to patients with a Dukes B, and usually to those with
Dukes C cancer. Chemotherapy of metastatic colorectal cancer uses 5-FU,
leucovorin and irinotecan (CPT11). Combined oxaliplatin and 5FU treatment
may also be used. Patients successfully treated for colorectal cancer should
be regularly checked for several years after surgery to detect any recurrence
of the tumor.

Leukemias

Leukemias are tumors of bone marrow cells that give rise to the blood cells
and platelets (Chapter 13). Leukemias were historically classified according
to the speed of onset and progression, with those of sudden onset and rapid
progression termed acute leukemias, while those that develop slowly over
months and years are called chronic leukemias. The current classification
is based on specific typing of the blood cells, although the terms acute and
chronic are still used. The main types of leukemias encountered clinically
are acute myeloblastic and chronic myelogenous leukemias and acute
lymphoblastic and chronic lymphocytic leukemias. Another rarer leukemia is
hairy cell leukemia named according to the microscopic ‘hair-like’ appearance
of the plasma membrane.

Most leukemias are characterized by symptoms such as excessive bleeding
of the gums and nose, bruising, fatigue, breathlessness and increased
susceptibility to infections. These are due to inadequate production of
erythrocytes, platelets and lymphocytes owing to the abnormal proliferation
of leukemic cells in the bone marrow. Blood and bone marrow films may show
immature blast cells (Figures 17.36). Treatments for leukemia may involve
chemotherapy, radiation therapy and stem cell transplantation (Chapter 6).

Chronic myelogenous leukemia

Chronic myelogenous leukemia (CML) is a rare disorder that affects
approximately 500 people annually in the UK and accounts for between
7 and 15% of all leukemias. Patients are usually adults between the ages
of 40 and 60 years. The disease is caused by malignant transformation of a
myeloid stem cell which would normally give rise to the polymorphonuclear
leukocytes, monocytes, basophils, erythrocytes and megakaryocytes. The
clonal proliferation of a myeloid stem cell results in the accumulation of

SPECIFIC TYPES OF CANCERS

CZhhVg6]bZY!BVjgZZc9Vlhdc!8]g^hHb^i]:YLddY *%,

Dukes

system

Description Proportion

of patients

diagnosed/%

Prognosis (5-year

survival as %)

Dukes A cancer confined to innermost lining of

colon/rectum

10 80

Dukes B cancer grown into muscle layer of wall

of colon/rectum

35 60–70

Dukes C cancer spread to lymph nodes

surrounding the colon/rectum

25 30–60

Dukes D cancer has metastasized to other parts

of the body

30 15 (survival at 2 years

after diagnosis)

Table 17.11Classification of colorectal cancers

A)

B)

Figure 17.36Blast cells, indicated by arrows,

in (A) the bone marrow and (B) the blood of a

patient with leukemia.