FEASIBILITY STUDY FOR USE OF BRUSH CYTOLOGY AS A COMPLEMENTARY METHODFOR DIAGNOSIS OF RECTAL-CANCER

Brush cytology has previously been described as a feasible method for accurately diagnosing colorectal cancer. PURPOSE: This study was desig ned: 1) to determine the sensitivity and specificity of brush cytology for the diagnosis of rectal cancer; 2) to prospectively assess the ex tent of interobserver variability with this technique; 3) to prospecti vely examine the cost impact of the addition of brush cytology as a ro utine method of confirming the diagnosis of rectal cancer. PATIENTS AN D METHODS: Three hundred fifty-seven patients who attended a rectal cl inic and who were found to have a lesion between January 1990 and Marc h 1996 were assessed. Each patient underwent rigid proctoscopy, follow ed by brush cytology and tissue biopsy. Results were compared with the final histologic diagnosis in each patient. The brushings from the la st 92 consecutive patients in this series were independently examined by four cytologists and a pathologist to determine the rate of interob server variability. RESULTS. Rectal adenocarcinoma was confirmed from surgically resected specimens in 303 patients. Brush cytology accurate ly diagnosed 278 of them. Of the remaining 25 patients, two had brushi ngs that were insufficient for diagnosis. There was one false-positive case. Forceps biopsy correctly identified cancer in 260 patients, wit h no false-positive interpretations. Brush cytology accurately identif ied 53 of 54 adenomas as being benign, and forceps biopsy correctly id entified all as benign. Sensitivity of brush cytology in this series w as 92 percent, with a specificity of 92 percent. Interobserver agreeme nt was 84 percent. Actual costs incurred with this method was an addit ional $17.00 per patient. CONCLUSIONS: Brush cytology can accurately d iagnose rectal cancer in a high proportion of patients. Interobserver variation is low and compares favorably with other forms of cytologic interpretation. The additional cost remains a concern but can be kept within acceptable proportion.