How reliable is genetic blood testing for HNPCC?

My father had colon cancer in 2004, I in 2003 and my younger sister in 2002, at ages 83, 58 and 51 respectively, all stage 2 colon cancer, operated on detection. Genetic blood tests confirmed the presence of Hereditary non-polyposis colorectal cancer (HNPCC). Please guide in what precautions and surveillance I need to take for my children. How reliable is genetic blood testing for children and which are the best centers for testing?

Doctors Answers (1)

Harsha Vittal, M.D.
Answered on: 3/23/2012

The genetic test is quite reliable and you and your family should discuss this with a geneticist. Here are the guidelines, but you need to have a close communication with your gastroenterologist and oncologist. Annual colonoscopy starting between the ages of 20 and 25 years, or 10 years, prior to the earliest age of colon cancer diagnosis in the family (whichever comes first). In families with MSH6 mutations, screening can start at age 30 since the onset of colon cancer is later in these families. Annual screening for endometrial cancer with endometrial biopsy and ovarian cancer with CA 125 and transvaginal ultrasound beginning at age 30 to 35 years, or 5 to 10 years earlier than the earliest age of first diagnosis of these cancers in the family (whichever is earlier). Discussion of prophylactic hysterectomy and salpingo-oophorectomy at the end of childbearing years. Annual urinalysis beginning at age 25 to 35 years. Annual skin surveillance. Periodic upper endoscopy.