***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: Background The possible benefit for patients from follow‐up  examinations after curative surgery for colorectal cancer is unproven . The purpose of this study was to determine whether survival is improved by frequent follow‐up examinations BACKGROUND We tested the hypothesis that dietary intervention can inhibit the development of recurrent colorectal adenomas , which are precursors of most large-bowel cancers . METHODS We r and omly assigned 2079 men and women who were 35 years of age or older and who had had one or more histologically confirmed colorectal adenomas removed within six months before r and omization to one of two groups : an intervention group given intensive counseling and assigned to follow a diet that was low in fat ( 20 percent of total calories ) and high in fiber ( 18 g of dietary fiber per 1000 kcal ) and fruits and vegetables ( 3.5 servings per 1000 kcal ) , and a control group given a st and ard brochure on healthy eating and assigned to follow their usual diet . Subjects entered the study after undergoing complete colonoscopy and removal of adenomatous polyps ; they remained in the study for approximately four years , undergoing colonoscopy one and four years after r and omization . RESULTS A total of 1905 of the r and omized subjects ( 91.6 percent ) completed the study . Of the 958 subjects in the intervention group and the 947 in the control group who completed the study , 39.7 percent and 39.5 percent , respectively , had at least one recurrent adenoma ; the unadjusted risk ratio was 1.00 ( 95 percent confidence interval , 0.90 to 1.12 ) . Among subjects with recurrent adenomas , the mean ( + /-SE ) number of such lesions was 1.85+/-0.08 in the intervention group and 1.84+/-0.07 in the control group . The rate of recurrence of large adenomas ( with a maximal diameter of at least 1 cm ) and advanced adenomas ( defined as lesions that had a maximal diameter of at least 1 cm or at least 25 percent villous elements or evidence of high- grade dysplasia , including carcinoma ) did not differ significantly between the two groups . CONCLUSIONS Adopting a diet that is low in fat and high in fiber , fruits , and vegetables does not influence the risk of recurrence of colorectal adenomas PURPOSE To up date the 2000 American Society of Clinical Oncology guideline on colorectal cancer surveillance . RECOMMENDATIONS Based on results from three independently reported meta-analyses of r and omized controlled trials that compared low-intensity and high-intensity programs of colorectal cancer surveillance , and on recent analyses of data from major clinical trials in colon and rectal cancer , the Panel recommends annual computed tomography ( CT ) of the chest and abdomen for 3 years after primary therapy for patients who are at higher risk of recurrence and who could be c and i date s for curative-intent surgery ; pelvic CT scan for rectal cancer surveillance , especially for patients with several poor prognostic factors , including those who have not been treated with radiation  ; colonoscopy at 3 years after operative treatment , and , if results are normal , every 5 years thereafter ; flexible proctosigmoidoscopy [ corrected ] every 6 months for 5 years for rectal cancer patients who have not been treated with pelvic radiation  ; history and physical examination every 3 to 6 months for the first 3 years , every 6 months during years 4 and 5 , and subsequently at the discretion of the physician ; and carcinoembryonic antigen every 3 months postoperatively for at least 3 years after diagnosis , if the patient is a c and i date for surgery or systemic therapy .  Chest x-rays , CBCs , and liver function tests are not recommended , and molecular or cellular markers should not influence the surveillance strategy based on available evidence Objective . Guidelines for surveillance of patients with previous sporadic colorectal adenomas are based on retrospective long-term follow-up and prospect i ve short-term studies . The aim of the present studies was to compare relative risk ( RR ) of new neoplasia as well as complications , using different intervals between examinations in long-term surveillance . Material and methods . Between l98l and l991 , patients with pedunculated and small , flat and sessile adenomas were allocated at r and om to a 24 months ( group A ) or 48 months ( group B ) interval between surveillance colonoscopies  ( n=671 ) . Patients with flat and sessile adenomas greater than 5 mm in diameter were r and omized to intervals of 6 months ( group C ) or 12 months ( group D ) between l981 and 1987 ( n=73 ) . Finally , 200 patients with similar adenomas as in groups C and D were r and omized to 12 months ( group E ) or 24 months ( group F ) from 1988 to 2000 . The study ended in 2002 . Results . Advanced adenomas were equally as frequent in group A and group B , but colorectal cancer ( CRC ) was found significantly more often in group B ( RR = 6.2 ( 1.0–117.4 ) ) . Severe complications occurred in 4 patients in group A and 2 patients in group B. Advanced new adenomas tended to be more frequent in group D than in C ( p=0.08 ) , but only one CRC was detected and this was in group C. There was no significant difference in the risk of CRC between the E and F groups , but the two cancers in group E were both early stage , in contrast to those in group F. Severe complications were seen in one patient in group E and also in group F. Conclusions . The results suggest that 2-year intervals should be used between colonoscopies in patients with previous pedunculated adenomas and small , flat and sessile adenomas , whereas larger , flat and sessile adenomas may need intervals of 1 year BACKGROUND & AIMS Colonoscopic polypectomy is considered effective for preventing colorectal cancer ( CRC ) , but the incidence of cancer in patients under colonoscopic surveillance has rarely been investigated . We determined the incidence of CRC in patients under colonoscopic surveillance  and examined the circumstances and risk factors for CRC and adenoma with high- grade dysplasia . METHODS Patients were drawn from 3 adenoma chemoprevention trials . All underwent baseline colonoscopy with removal of at least one adenoma and were deemed free of remaining lesions . We identified patients subsequently diagnosed with invasive cancer or adenoma with high- grade dysplasia . The timing , location , and outcome of all cases of cancer and high- grade dysplasia identified are described and risks associated with their development explored . RESULTS CRC was diagnosed in 19 of the 2915 patients over a mean follow-up of 3.7 years ( incidence , 1.74 cancers/1000 person-years ) . The cancers were located in all regions of the colon ; 10 were at or proximal to the hepatic flexure . Although most of the cancers ( 84 % ) were of early stage , 2 participants died of CRC . Seven patients were diagnosed with adenoma with high- grade dysplasia during follow-up . Older patients and those with a history of more adenomas were at higher risk of being diagnosed with invasive cancer or adenoma with high- grade dysplasia . CONCLUSIONS CRC is diagnosed in a clinical ly important proportion of patients following complete colonoscopy and polypectomy . More precise and representative estimates of CRC incidence and death among patients undergoing surveillance examinations are needed OBJECTIVE To determine whether an intensified follow-up of patients with colorectal cancer can lead to improved reresectability and a better long-term survival . DESIGN A prospect i ve r and omized trial of 106 patients . SETTING Oulu University Hospital , a referral center in northern Finl and . PATIENTS A total of 106 consecutive patients who underwent radical resection for colorectal cancer , 54 of whom were r and omized into a conventional follow-up group and 52 into an intensified follow-up group .  MAIN OUTCOME MEASURES After a 5-year follow-up , the time of detection of recurrence , the recurrence rates , the first method showing recurrence , the mode of recurrence , reresectability , and survival were compared between the groups . RESULTS The recurrences were identified earlier in the intensified follow-up group than in the conventional follow-up group ( mean + /- SD , 10 + /- 5 months vs 15 + /- 10 months ) . The overall recurrence rate was 41 % , with 39 % in the conventional group and 42 % in the intensified group . Carcinoembryonic antigen determination was the most common method showing recurrence in both groups . Endoscopy and ultrasound were beneficial in the intensified follow-up group , but computed tomography failed to improve the diagnostics . The mode of recurrence did not differ between the groups . Radical resections were performed on 19 % ( 8/43 ) of the patients , 14 % ( 3/21 ) in the conventional group and 22 % ( 5/22 ) in the intensified group . The cumulative 5-year survival was 54 % in the conventional group and 59 % in the intensified group . CONCLUSION Earlier detection of recurrent colorectal cancer by intensified follow-up does not lead to either significantly increased reresectability or improved 5-year survival Context Patients who have had colorectal cancer can develop second primary colorectal cancer .  The American Cancer Society recommends that surveillance colonoscopy be performed 1 year after surgery , then every 3 to 5 years if results are negative . This surveillance strategy is unproven . Contribution This study documented an incidence rate of 274 cases of second primary colon cancer per 100 000 person-years after surgery with curative intent and 5-fluorouracil-based chemotherapy .  The incidence of second cancer was higher than the incidence of first colorectal cancer in the general population , despite surveillance . Caution s This study suggests that surveillance may need to be more vigilant than currently recommended . However , more data are needed to decide how often to do surveillance colonoscopy . The Editors Colorectal cancer is a major public health problem , with more than 130 000 new cases thought to have occurred in the United States in 2001 . Patients who have had colon cancer are at risk for second primary colon cancer , but the extent of this risk is unclear . The incidence and rate of development of second primary tumors have implication s for appropriate surveillance of the colon after diagnosis of colorectal cancer . After first primary colon cancer is diagnosed , resection with curative intent is possible in approximately 75 % of patients because the disease is limited to the bowel or to regional lymph nodes . The st and ard of care for patients with stage II or stage III disease is surgical resection , followed by adjuvant therapy for stage III disease . After surgery and adjuvant chemotherapy , patients frequently undergo some form of surveillance . Computed tomography of the abdomen , chest radiography , and measurement of carcinoembryonic antigen have been used to detect distant metastatic disease , although no convincing data show that these tests are cost-effective or improve survival ( 1 ) . Colonoscopy or barium enema combined with flexible sigmoidoscopy has been used to survey for second primary colorectal cancer . Surveillance for second primary colorectal cancer serves two purpose s : removal of premalignant polyps and early detection of malignancy . Most colorectal cancer is the product of slow , orderly progression from normal cells to malignancy . Surveillance with endoscopy and polypectomy has been shown to prevent colon cancer ( 2 , 3 ) . The most convincing data for this intervention come from the National Polyp Study , which found that in patients with adenomatous polyps , colonoscopic surveillance significantly decreased the incidence of colorectal carcinoma ( 3 ) . The National Polyp Study also examined the question of how frequently to perform colonoscopic surveillance by comparing two surveillance strategies in patients who had recently had adenomas removed by colonoscopy ( 4 ) . The study showed that repeated colonoscopy 3 years after colonoscopy and polypectomy in patients with adenomatous polyps was equivalent to more frequent surveillance . The authors conceded , however , that more frequent follow-up colonoscopy may be needed in patients with a history of colorectal cancer because they may have different biological characteristics and natural history . Current guidelines for surveillance of patients with a history of colon cancer are at least partially based on data from the National Polyp Study . The American Gastroenterological Association and the American Cancer Society recommend complete examination of the colon within 1 year of resection ; if findings on this or on complete preoperative examination are normal , examination should be repeated in 3 years and then , if findings are again normal , every 5 years ( 5 ) . In addition to finding new second primary tumors , surveillance within 1 year of colon cancer surgery may detect previously undetected polyps or synchronous tumors . Recent recommendations from the American Society of Clinical Oncology call for perioperative colonoscopy followed by colonoscopy every 3 to 5 years ( 1 ) . However , deciding whether to extrapolate surveillance recommendations for patients with polyps to patients with a history of colon cancer requires a better underst and ing of the absolute and relative risk for second colorectal cancer in such patients . In the general population , the best estimates of the risk ratio for second primary colorectal cancer compared with first primary colorectal cancer have ranged from 1.5 to 3.0 ( 6 , 7 ) . The studies that have addressed this issue have had several deficiencies : incomplete follow-up , incomplete reporting of new cases , reporting of cumulative incidence rates ( which do not consider length of follow-up ) , unknown surveillance practice s in the study sample , arbitrary time cut 
    Output:
    
Despite the lack of evidence to support or refute any survival benefit for follow-up colonoscopy after curative-intent CRC resection , surveillance colonoscopy is recommended by most guidelines .
For surveillance after CRC resection , it considered colonoscopy appropriate 1 year after resection .
Colonoscopy is recommended as a first-choice procedure for surveillance after polypectomy by all published guidelines and by the EPAGE II criteria .
Despite the limitations of the published studies , colonoscopy is also recommended by most of the guidelines and by EPAGE II criteria for surveillance after curative-intent CRC resection