People with papillary thyroid cancer that hasn't spread beyond the thyroid gland appear to have good outcomes regardless of whether or not they are treated, new research shows.

Papillary thyroid cancer is the most common type of thyroid cancer. Among more than 35,000 people with "localized" papillary thyroid cancer who underwent immediate surgery to remove half or all of their thyroid gland, researchers found that 99 percent were still alive 20 years later. For the 440 patients who didn't undergo immediate treatment, 97 percent were still alive after 20 years.

As the numbers show, surgery is the mainstay of treatment for localized thyroid cancer, with just a handful of patients — 1.2 percent in all in the current study — not being treated.

But the findings suggest that in many cases surgery may not be necessary, Dr. Louise Davies of the Department of Veterans Affairs Medical Center in White River Junction, Vermont, one of the study's authors, told Reuters Health.

But in an editorial accompanying the study in the Archives of Otolaryngology — Head and Neck Surgery, Drs. Erich M. Sturgis and Steven I. Sherman of the University of Texas M.D. Anderson Cancer Center in Houston argue that observation "should only be cautiously considered in the most carefully selected cases."

In 2006, Davies and her colleague Dr. H. Gilbert Welch reported a sharp rise in thyroid cancer diagnoses over the previous 15 years, without a corresponding increase in deaths. This is because new diagnostic technology has identified many cancers in people who don't have symptoms; 87 percent of the new tumors identified were less than 2 centimeters across, meaning they likely couldn't have been felt by a patient or doctor.

In the current study using National Cancer Institute registries, Davis and Welch identified 35,663 cases of localized papillary thyroid cancer diagnosed between 1973 and 2005, including 440 people who did not undergo immediate treatment.

Among people who were treated immediately, 161 — or less than a half percent — died of thyroid cancer over an average of about 7.6 years. For the non-treated individuals, there were 6 thyroid cancer deaths (about 1.4 percent) over an average of 6 years.

The 20-year survival rate from cancer was estimated to be 97 percent for those who went without treatment and 99 percent for those who did receive treatment.

There are four types of thyroid cancer in all, Davies noted; the two most deadly types make up just 2 percent of all cancers. And people who develop this type of disease usually are aware that something is wrong, she added. The more serious types of thyroid cancer "don't just sort of sneak up on you. They cause symptoms. They make it difficult to breathe or talk, they change your voice, you feel something in your neck and it feels hard."

And certain groups of people are at risk of more serious forms of thyroid cancer, Davies added: men, people younger than 20, people over 70, people who have symptoms, and people who have had radiation to the head and neck area in the past.

If a doctor identifies a localized tumor in your thyroid gland, the researcher said, people can choose to have it biopsied, or they can opt for having another imaging test in six months to a year.

The new findings, Davies said, "make me feel much more comfortable advising patients that we don't need to do a biopsy right now."

In three to five percent of cases, Davies added, people have serious complications of thyroid surgery such as loss of function of the parathyroid gland (which necessitates taking multiple doses of calcium throughout the day) or loss of function in the vocal cords. People who have their entire thyroid gland removed, she added, will also need to take a thyroid hormone pill every day.

In their editorial, Sturgis and Sherman agree that observation without immediate treatment is appropriate for some patients, including those with other major health problems or small, recurrent tumors. But "inadequate initial evaluation and/or treatment" also carries risks, they add.

"We as individual clinicians must keep the individual patient's best interest at the center of our decision making, whether it be operating on, observing, or referring the patient," Sturgis and Sherman wrote.