الفهرس 
ANATOMYOnly 14 pages are availabe for public view
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Abstract
Colorectal cancer represents a major public health problem, especially in developed countries. As such, it has attracted the efforts of researchers from a wide variety of disciplines, including epidemiologists, molecular biologists, nutritionists, gastroenterologists, prevention experts, surgeons, radiation therapists, nurses, medical oncologists, and outcomes researchers. This study present some of the exciting information that has been generated about this common malignancy.
While The most reliable prognostic factor identified to date in colorectal cancer is the staging of disease at the time that treatment is initiated, other prognostic factors are still of value in prognosis of colorectal cancers like presentation at time of treatment [bleeding, obstruction, perforation and age etc...] presence of lymphatic invasion, vascular invasion and neural invasion, character of invasive margin and tumor type.
Recently, VEGF has appeared to be of value as a prognostic factor. Over expression of VEGF may be useful in predicting distant metastasis in node negative colorectal cancers.
Immune response to primary tumor including lymphocytes infiltration and local inflammatory reaction have prognostic importance for survival in colorectal cancers.
Also the study of molecular markers has enormously advanced our understanding of the development and treatment of colorectal cancer. Molecular markers have the potential to revolutionize the way such cancers are treated. Some of the areas of intensive research currently are thymidylate synthase, dihydropyrimidine dehydrogenase (DPD), and the presence of microsatellite instability.
These prognostic factors not only for research purpose but mainly for surgeon to make the best decision to improve survival and outcome of colorectal cancers patients, while Surgery is the only curative modality for localized colorectal cancer (stage I-III) and potentially provides the only curative option for patients with limited metastatic disease in liver and/or lung (stage IV disease) The introduction of novel agents targeted to specific molecular features of cancer cells promises more options and marked improvements in efficacy for treatment of colorectal cancer these include Bevacizumab, cetuximab and panitumumab.
The issues surrounding the treatment of distal rectal cancer are many, but from a patient’s perspective the main concerns are: “Am I going to lose my anus? Do I have to wear a bag for the rest of my life?” and this should be the surgeons perspective also that how far we as surgeons can save patient’s anus and keep the colostomy bag away from patient’s dreams [nightmares] without affecting patient survival. This is mainly based on oncologic consideration, surgeon factor and functional outcome In turn, these factors are dependent on many variables, including the initial presentation and location of the tumor, the presence of metastatic disease, the tumor response to neoadjuvant chemoradiation, the surgeon’s technical expertise and judgment, the patient’s body habitus, the intraoperative findings, the patient’s comorbidities and physiologic age, the overall performance status of the patient, and baseline anorectal function.
Recommendations for management of low rectal tumours as a challenge for surgeons to preserve sphincter and anus without affecting survival rate:
While surgery is the main treatment for rectal cancer radiochemotherapy will often be given before or after surgery and are promising tools in improving survival.
• Superficial cancers (stage I rectal cancer):
o Polypectomy.
o Local excision.
o Transanal endoscopic microsurgery.
o Local transanal full thickness resection.
• Stage I and most of stage II, III.
o Low anterior resection.
o Proctectomy with coloanal anastomosis and mesorectal excision.
Decision to preserve anus is determined by 3 factors:
• Oncological considerations.
• Technical feasibility.
• Functional outcome.
In turn it depends on many variables:
o Initial presentation.
o Location of the tumor.
o Presence of metastatic disease.
o Tumor response to neoadjuvant chemoradiation.
o Surgeon’s technical expertise.
o Comorbidities.
In the past 5cm of distal margin was advocated, now distal margin of 2cm is accepted and doesn’t affect survival or local tumor control. So, 6cm from anal verge is for complete resection and anal sphincter preservation.
In case of tumor lies less than 6cm from anal verge with internal sphincter invasion a complete resection of rectum including sphincter with total mesorectal excision and coloanal anastomosis is advised where continence is maintained by levator ani in 60% of patients.
• One centimeter margin is adequate for small cancer without adverse histological features.
• A complete pathological response to preoperative chemoradiation is associated with improved survival in patient undergoing total mesorectal excision, in those patients few millimeter of tissue beyond the tumor scar may be sufficient. In such cases advanced surgical techniques, such as intersphincteric dissection through abdominal and transanal approach don’t affect survival.
• Abdominoperineal resection is indicated only if:
o Involvement of anorectal.
o No response to chemoradiation.
o Poorly differentiated tumor.
In turn, preoperative assessment of patient with low rectal tumor, should includes pathological examination of tumor and assessment of local invasion of surrounding tissue and sphincters which are best done by MRI, endoanal ultrasound and endoanal MRI. Together with oncologist consultation for possibility of preoperative chemoradiation and assessment of the response of tumor to the adjuvant therapy.