[Study of colorectal metachronous neoplastic lesions]

To analyse the frequency and characteristics of metachronous neoplastic lesions, carcinomas and adenomas, following resection of colorectal cancer.

We reviewed 382 patients subjected to RCC operations and followed up through complete colonoscopies in two hospitals in our province. We analysed the metachronous lesions registered, evaluating their localisation, time of diagnosis, histology, number and size. We studied the frequency of early adenomas (12 months), comparing their size with the rest of the lesions.

The average follow-up was 48 months (12-112), with 2.74+/-1.47 colonoscopies/case. We diagnosed 7 metachronous cancers (1.8%), 4 of them in stage I. The average time until their diagnosis was 24 months (13-54). We registered metachronous adenomas in 162 cases (42.4%), without differences between the two hospitals: 42.1% vs. 43.8% (p=0.88). Six point three percent of the patients presented advanced adenomas. In 164 cases where the control was carried out after 12 months, the incidence of adenomas was 24%. In the majority of cases, the adenomas were sole (60.8%) and smaller than 5 mm (68.5%). In 55.5% of the cases with polyps, some had a proximal localisation. Diagnosis was made on the 1st exploration (56.2%), the 2nd (27.8%) or the 3rd (9%). Average time until diagnosis was 21 months (12-112) for simple adenoma and 35 (12-112) for advanced adenoma.

Our follow up made it possible to apply a theoretically curative treatment in the majority of the metachronous carcinomas diagnosed. The high incidence of adenomas and the frequent proximal localisation make a follow up with complete colonoscopies necessary, which must be started one year after the operation and can become less strict following three consecutive explorations without polyps.