الفهرس 
Chapter 1 (Colorectal cancer)Only 14 pages are availabe for public view
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Abstract
Colorectal cancer (CRC) is a term used for cancer that starts in the
colon or the rectum. CRC incidence and mortality rates vary markedly
around the world. However, rates are substantially higher in males than in
females, representing the third most commonly diagnosed cancer in males
and the second in females.
The importance of screening tools to identify early stage CRC is
acknowledged worldwide. Colonoscopy is currently considered to be the
gold standard for CRC screening. However, it is estimated that many
individuals over 50 years of age have refused to undergo this test due to
the invasiveness of the procedure.
Screening with established tumor markers for gastrointestinal
cancers, such as CEA or CA19-9, has limited efficiency because of
erratic detection and increased levels in benign disorders.
Circulating cell free DNA (ccf-DNA) is a double-stranded
molecule of low molecular weight which, although mainly fragmented in
70-200 base pairs (bp), also has pieces up to 21 kilobases in length. ccf-
DNA can be found in healthy persons, persons with non-malignant
diseases, as well as persons with various malignancies.
In healthy individuals, apoptosis and necrosis of lymphocytes and
other nucleated cells are mainly involved in the release of circulating
nucleic acids into the blood. Apoptosis leads to DNA degradation in
which chromosomal DNA is first cleaved into large fragments (50-300
kb) and then into multiples of nucleosomal units (180-200 bp).
While in cancer patients, ccf-DNA most likely result from tumor
necrosis, but other suggested mechanisms include lysis of circulating
Summary and Conclusion
124
cancer cells or of micro-metastases, or due to active release. Necrosis
generates a spectrum of DNA fragments with different strand lengths,
mostly large DNA fragments, because of random and incomplete
digestion of genomic DNA by DNases.
DNA integrity that potentially mirrors the relation between the
necrotic and overall cell death rate, can be defined as the ratio of the
concentrations of longer DNA fragments (ALU 247) to shorter DNA
fragments (ALU 115). The integrity index is increased at the early stages
of CRC and is a promising molecular biomarker for detecting CRC.
The current study was carried out by cooperation between Medical
Biochemistry, General Surgery & Clinical Oncology and Nuclear
Medicine Departments, Faculty of Medicine, Menoufia University.
The aim of this study was to study whether the concentrations and
integrity index of circulating cell free DNA (ccf-DNA) in serum can be
used as a diagnostic biomarker for colorectal cancer (CRC) patients. This
study involved 80 individuals, 40 CRC patients, 20 patients with benign
diseases in colon and rectum and 20 healthy persons served as controls.
Full history and clinical examination were made to every subject.
Laboratory investigations were also carried out to all individuals
including analysis of CA19-9 level by ELISA technique and ccf-DNA
through detection of long (247 bp) and short (115 bp) DNA fragments in
serum by real-time quantitative PCR by amplifying the ALU repeats
(ALU-qPCR).
The results of the present study can be summerized as follows:
A significantly higher level of serum CA 19-9 concentrations were
observed in CRC patients and patients with benign diseases in
comparison to control group.
Summary and Conclusion
125
A significantly higher level of serum ALU 115 and ALU 247
concentrations were observed in CRC patients and patients with
benign diseases in comparison to control group.
Significantly higher levels of DNA integrity (ALU247/115) were
observed in CRC patients and patients with benign diseases in
comparison to control group.
There was significant statistical difference among studied CRC
patients in tumor stage and size as regards ALU 247 serum levels.
There was significant statistical difference among studied CRC
patients in tumor stage and size as regards DNA integrity
(ALU247/115).
There was significant negative correlation between ALU 115
serum levels and each of the size of tumor and the invasiveness of
the primary tumor (T stage).
There was significant positive correlation between ALU 115 serum
levels and the grade of tumor.
There was significant negative correlation between DNA integrity
(ALU247/115) and the invasiveness of the primary tumor (T
stage).
There was significant positive correlation between DNA integrity
(ALU247/115) and each of size of tumor and the number of local
and regional lymph nodes containing metastatic cancer (N stage).
There was significant positive correlation between CA19-9 serum
levels and each of the invasiveness of the primary tumor (T stage)
and distant metastasis (M stage).
Summary and Conclusion
126
The diagnostic accuracy for distinguishing primary CRC patients
from normal controls by ALU 115 serum levels was (85%), with
sensitivity (83%) , specificity (90%), positive predictive value
(96%) and negative predictive value (64%) at cut off point of 426
ng/ml.
The diagnostic accuracy for distinguishing primary CRC patients
from normal controls by ALU 247 serum levels was (93%), with
sensitivity (93%), specificity (90%), positive predictive value
(97%) and negative predictive value (82%) at cut off point of 135
ng/ml.
The diagnostic accuracy for distinguishing primary CRC patients
from normal controls by DNA integrity (ALU247/115) was (61%),
with sensitivity (75%), specificity (20%), positive predictive value
(74%) and negative predictive value (21%) at cut off point of 0.42.