Colorectal Cancer Following Negative Colonoscopy, Is 5-year Screening the Correct Interval to Recommend?

Steven K Nakao, MD, Iswanto Sucandy, MD, Steven Fassler, MD, Mark Zebley, MD, Soo Kim, MD. Abington Memorial Hospital


BACKGROUND: Despite the sensitivity of screening colonoscopy, polyps and cancers can still go undetected. With the polyp-to-cancer transformation cycle averaging 7-10 years, present guidelines recommend repeat colonoscopy within 10 years after negative screening. However, not all colorectal cancers follow this progression, and a 10-year interval may be too long for repeat surveillance. This study evaluates the incidence and pathology of colorectal cancers following a previous negative screening colonoscopy.


METHODS: Records of patients undergoing colorectal cancer resections at our institution were reviewed retrospectively. The patients were divided into two groups: Group 1, patients with a negative colonoscopy within 5 years; Group 2, patients without previous colonoscopy or with previous colonoscopy at intervals >5 years. Group 1 patients were evaluated by colonoscopy for anemia, diverticulitis, obstruction, and bleeding. Age, tumor location, operation performed and pathology findings were recorded. Chi2 was used for statistical analysis.


RESULTS: 233 patients were included in this study. Group 1 contained 43 patients with a mean age of 73 years (range: 35-94, median: 75,  M:18, F:25). Group 2 had 190 patients with a mean age of 68 years (range 19-91, median: 70, M:94, F:96). 18% of the study population had newly discovered colorectal cancer within 5 years. Both groups were subdivided by age: <50 years, 50-80 years, and >80 years (Table 1). No significant differences were found in the distribution of the T- and N-stages between the two groups, or between the two groups when the rate of lymphovascular invasion (19% vs 17%; p = 0.39) and perineural invasion (7% vs 11%; p = 0.58) were compared.


CONCLUSIONS: Within 5 years, 18% of our study population developed colorectal cancer. Most of these cancers were found within the 50-80 year age group, and were predominately located in the right colon and distally in the sigmoid and rectum. While distal cancers may be visualized by flexible sigmoidoscopy more proximal cancers will be missed, necessitating the need for colonoscopy. While staging was similar between the two groups, Group 1 cancers were not more aggressive despite having appeared within 5 years. Due to our incidence of colorectal cancer within a 5-year interval, a shorter period for routine colonoscopy may be necessary.

Table 1
  Group 1  Group 2 
 Number of PatientsLocationStageNumber of PatientsLocationStage
<502Right– 2(100%)
Stage I– 2(100%)
20Right– 6(30%)

Left– 3(15%)

Sigmoid– 4(20%)

Rectum– 7(35%)

Stage I– 6(30%)

Stage II– 4(20%)

Stage III– 10(50%)

50-8028Right– 11(39.3%)

Transverse– 1(3.6%)

Left– 2(7.1%)

Sigmoid– 7(25%)

Rectum– 6(21.4%)

Synchronous– 1(3.6%)

Stage I– 12(42.9%)

Stage II– 7(25%)

Stage III– 7(25%)

Stage IV– 2(7.1%)

133Right– 44(33%)

Transverse– 5(3.8%)

Left– 12(9%)

Sigmoid– 21(15.8%)

Rectum– 47(35.2%)

Synchronous– 4(3.6%)

Stage I– 45(33.9%)

Stage II– 7(35.3%)

Stage III– 39(29.3%)

Stage IV– 2(1.5%)

>8013Right– 9(69.2%)

Sigmoid– 1(7.7%)

Rectum– 3(23.1%)

Stage I– 4(30.8%)

Stage II– 4(30.8%)

Stage III– 5(38.4%)

37Right– 23(62.2%)

Left– 5(13.5%)

Sigmoid– 1(2.7%)

Rectum– 8(21.6%)

Stage I– 12(32.4%)

Stage II– 12(32.4%)

Stage III– 13(35.4%)

Total43  190  


Session Number: SS20 – Colorectal
Program Number: S117

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