Methylation-specific PCR may pick up recurrent colorectal cancer in serum

Methylation-specific polymerase chain reaction targeting the p16 gene may be a sensitive noninvasive technique for the early detection of recurrent colorectal cancer in serum, Japanese researchers report in the July 1st edition of the International Journal of Cancer.

In an earlier study, Dr. Kenji Hibi from Nagoya University Graduate School of Medicine and colleagues found the p16 tumor suppressor gene to be silenced via hypermethylation of the promoter region in 47% of colorectal tumors studied. They found the same abnormality in 30% of corresponding serum samples. To see if this technique could be used to monitor for cancer recurrence, they examined p16 methylation using methylation-specific PCR in tumor DNA and serum from 45 patients with recurrent colorectal cancer.”Surprisingly,” Dr. Hibi and colleagues write, they detected tumor DNA in the serum of 31 (69%) of the patients. “No methylation was found in serum DNA of 50 patients with colorectal cancers whose corresponding tumor DNA had no methylation in p16 promoter,” the team reports. This study “proves for the first time that it is possible to detect recurrent colorectal cancers using methylation-specific PCR,” Dr. Hibi told Reuters Health. The technique was as sensitive as carcinoembryonic antigen (CEA) determination. When they combined methylation-specific PCR and CEA, the investigators were able to detect 84% of colorectal cancer recurrences using only the patient’s serum. “We have also tried to convert this assay to a quantitative format to measure circulating tumor DNA,” Dr. Hibi mentioned. “It would be interesting to study the variation in circulating tumor DNA levels in relation to cancer treatment and patient prognosis.”Additional studies are needed in surgically resected colorectal cancer patients who have yet to exhibit recurrent cancer, to assess the value of the technique in detecting early occult recurrence. “We hope that this method would be applied to noninvasively detect cancers widely and hopefully to save the lives of patients with this fatal disease,” Dr. Hibi said. (Source: Int J Cancer 2003;105:491-493: Reuters Health: Megan Rauscher: June 27, 2003: Oncolink)