WEBVTT HAPPENING AND WHETHER IT COULD BE A CANCER CLUSTER. KEVIN: YOUR THYROID IS RIGHT HERE. IT FIRST ATTACKS THE GLAND AND THEN SPREADS TO OTHER AREAS. IN PARTS OF NORTHERN CALIFORNIA, DOCTORS ARE NOT DISCOVERING IT UNTIL IT HAS ALREADY SPREAD AND THAT COULD HAVE DEVASTATING CONSEQUENCES. WHEN SUSAN IS NOT MANAGI HER CLOTHING STORE, SHE IS MANAGING HER THYROID MEDICATION. SHE HAS HAD THYROI CANCER TWICE NOW. SHE HAD TO HAVE HER GLAND REMOVED, LEAVING A SCAR AND CONSTANT REMINDER. >> I LOOK IT AS A BATTLE SCARRED. I TAKE A PRIMARY HELL WHICH IS GREAT. IT IS AWESOME THERE IS A PILL -- A THYROID PILL WHICH IS GREAT. IT IS AWESOME THERE IS A PILL. >> LIFE DEFINITELY CHANGED. REPORTER: WE TALKED TO HER IN HER NEW HOME. SHE HAS HAD TO HAVE HER LYMPH NODES TAKEN OUT A INDOOR IODINE TREATMENTS. >> I WORRY. THAT THEY MIGHT NOT HAVE GOTTEN IT ALL OR IT WILL SPREAD AGAIN. REPORTER: HER HUSBAND HAS BEEN DIAGNOSED, TOO. THE ONE THING ALL THREE HAVE IN COMMON, THEY HAVE LIVED FOR YEARS IN GOLD COUNTRY. HE USED TO BE POLICE CHIEF IN SUTTER CREEK. RESEARCHERS FOUND THE TRICOUNTY AREA HAS A HIGHER RATE OF ADVANCED THYROID CANCER THAN ANYWHERE ELSE IN CALIFORNIA. >> I TEND TO THINK SOMETHING IS GOING ON BUT I DO NOT KNOW WHAT. REPORTER: THEY WONDER IF IT IS TIED TO THIS SPOT IN FRONT OF THEIR OLD HOME. THERE USED TO BE A MINE ACCESS. THEY LANDSCAPED TO PROTECT KIDS AND PETS. >> THEN SOMEONE BROUGHT UP, MAYBE RADON GAS. WHICH IS ONE OF THOSE RADIOACTIVE RISK FACTORS. MAYBE THAT IS WHAT CAUSED IT. REPORTER: THE DOCTOR TREATS PATIENTS. SHE STARTED RESEARCHING. >> IF WE CAN CATCH IT EARLIER , THAT IS BETTER. THAT IS PROMPTING ME TO LOOK INTO THIS. REPORTER: SHE USED DATA FROM THE CANCER REGISTRY. SHE DISCOVERED'S EIGH WHITE, 35% OF PEOPLE WERE ALREADY IN THE ADVANCED STAGE. THAT IS SIGNIFICANTLY HIGHER THAN THE NATIONAL AVERAGE. AND THE ALPINE AND CALAVERAS COUNTY AREA, MORE THAN HALF WERE ADVANCED, THE HIGHEST IN THE STATE. SUTTER COUNTY WAS ALSO AT THE TOP OF THE LIST. THE ONLY KNOWN ENVIRONMENTAL RISK FACTOR IS RADIATION. RESEARCHERS SAY THAT DOES NOT FULLY EXPLAIN WHAT IS HAPPENING. WHERE THE RATES ARE SO HIGH. THE DATA RAISES OTHER QUESTIONS. >> ARE THEY PROGRESSING MORE QUICKLY? WHAT WE DON'T KNOW IS WHEN THE CANCER STARTED. REPORTER: SHE SAYS WHAT MAY HAVE CAUSED IT MIGHT HAVE HAPPENED LONG AGO. >> IT MAY BE 20 YEARS TO DEVELOP THE CANCER. YOU NEED TO SEE WHAT THE RESIDENTIAL HISTORY IS GOING BACKWARDS. REPORTER: SHE SAID SHE WANTS TO LOOK AT OTHER FACTORS INCLUDING PESTICIDES. SHE SAYS THE DATA SHOULD SERVE AS A WAKE-UP CALL. >> SEE YOUR DOCTOR REGULARLY. I THICKET IT IS IMPORTANT, JUST IN GENERAL. REPORTER: IT IS SOMETHING THAT CANCER SURVIVORS URGE OTHERS TO DO. >> MAKE SURE YOUR DOCTOR IS LISTENING TO YOU. IT IS IMPORTANT. REPORTER: IT COULD MEAN THE DIFFERENCE BETWEEN LIFE OR DE ATH. SHE SAYS THE NEXT ROUND OF RESEARCH WILL INCLUDE REACHING OUT TO MORE PATIENTS.