Incidence and Natural History of Hepatic Metastases from Rectal Cancer

Rectal cancer represents 39% of all colonic cancer in western countries, and its incidence and mortality is lower only than breast cancer in women and lung cancer in men.

During the natural history of the disease about 50-60% of patients will develop liver metastases: in 20% these are isolated to the liver, whereas 80% are associated with other sites. The identified risk factors for the development of hepatic metastases in rectal cancer are the rectal tumour stage, the presence of microscopic venous invasion and the histotype of

Table 1. Extrahepatic disease by site


Frequency (%)





Lymph nodes








primary tumour (Table 1) [2]. Among various histo-types, the mucinous histotype has the highest risk of developing liver metastasis.

Hepatic metastases may be divided into synchronous, in 15-20% of patients, and metachronous, in 50% of patients. Metastases are synchronous when they are recognised during the diagnosis of primitive tumour and metachronous when they are diagnosed during follow-up of the primitive tumour. It is possible that microscopic metastases already exist at the time of the diagnosis of the primitive tumour and are not diagnosed at the time of the rectum resection surgery.

These considerations could explain the lack of homogeneity in the literature regarding the time limit to define the synchronous or metachronous metastases. Headrick and Miller [3] proposed a cutoff time of 3 months between the diagnosis of the primitive tumour and the appearance of the metastasis. Within 3 months of rectal cancer diagnosis, the metastasis is defined as synchronous; after 3 months the metastasis is defined as metachronous.

Many studies in the 1970s and the 1980s reported the natural history of patients with liver metastases without any treatment. In these patients survival is very low: 10-20% 3-year survival, with few patients surviving more than 5 years and an extremely variable mean survival, ranging from 3 to 24 months [4].

In these patients survival is related to the extent of the hepatic involvement, with 1-year survival of 60% for patients with single metastasis, 27% for patients with multiple metastases localised to one lobe or to one hepatic segment and 5.7% for patients with massive hepatic involvement. Patients with single metastasis have mean survival of 25 months and a 3-year survival of 20%. The potential resectability of metastases may also affect survival: 1-, 3- and 5-year survival for patients with non-treated but potentially resectable metastases is 77%, 23% and 8%, respectively, whereas for patients with non-resectable metastases it is 15% after 1 year, with no patients surviving more than 3 years [5].

On the contrary, patients submitted to hepatic resection have good results, with 5-year survival ranging from 26 to 45%, with low surgical morbidity and mortality lower than 3%. Unfortunately, only 10-20% of patients suffering from hepatic metastases from colorectal cancer can be submitted to hepatic resection.

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