Tokyo, Oct. 2 (Jiji Press)--A study led by Japan's National Cancer Center has shown that there are many cases in which colon cancer spreading to the liver seemed to have disappeared in post-drug treatment imaging tests, but actually had not been eradicated. Liver metastases from colon cancer can shrink after treatment and disappear on magnetic resonance imaging and computed tomography scans. In such cases, cancer cells only visible under a microscope may still remain, leading to differing clinical opinions on whether affected parts should be removed. The latest study, whose results were announced on Tuesday, showed that 62.5 pct of such cancers were confirmed to have disappeared, as the imaging tests had shown. On the other hand, 37.5 pct were of cases in which such cancers appeared to have disappeared in imaging tests, but had actually either survived or later came back. The study was conducted by an international team, which examined 233 patients with cases of liver metastases from colon cancer that were deemed at one point by doctors to be difficult to remove. The team mainly analyzed cases of patients whose hepatic lesions were deemed to have disappeared after drug treatment and subsequently underwent surgery. The team checked through pathological tests whether there were any cancer cells from removed parts of 45 patients who were told that their hepatic lesions had disappeared in CT and MRI scans. For unresected areas, the team kept track of signs of recurrence through the imaging tests for two years. "It is important that we create a meticulous surgical plan and carefully observe (patients') condition, with the possibility in mind that cancer cells can still exist even though imaging tests show that they appear to have disappeared," said Kozo Kataoka, a member of the team and a Hyogo Medical University doctor. END [Copyright The Jiji Press, Ltd.]