By Megan Brooks
NEW YORK (Reuters Health) - A U.S. study looking at the natural history and growth parameters of small, low-risk papillary thyroid cancers (PTC) supports active surveillance as a management option, the researchers say.
Using serial measurements of tumor volume, they found that most tumors remain stable over several years of observation. They say serial measurements to define the rate of tumor growth may help in the early identification of tumors that will continue to grow and may inform the timing of surveillance imaging and therapeutic intervention.
The study, from Dr. R. Michael Tuttle of Memorial Sloan Kettering Cancer Center in New York and colleagues, was published August 31 online in JAMA Otolaryngology-Head and Neck Surgery.
“As the number of small, incidentally detected PTCs continues to increase, new approaches are needed to avoid over-treatment of tumors that would otherwise remain indolent and asymptomatic while identifying the small percentage of such tumors that will continue to grow,” the authors write. “Because PTCs appear to follow predictable growth kinetics under active surveillance, serial measurements of tumor volume hold significant promise in triaging patients to observation vs surgery.”
The researchers examined tumor volume kinetics (probability, rate, and magnitude) in 291 patients (75% women; mean age, 52) undergoing active surveillance for low-risk PTCs measuring 1.5 cm or less. Serial surveillance tumor measurements were obtained using ultrasonography.
During a median active surveillance period of 25 months, growth in tumor diameter of 3 mm or more was observed in 11 patients (3.8%), with a cumulative incidence of 2.5% at two years and 12.1% at five years.
No regional or distant metastases developed during observation. In all cases, 3-dimensional measurements of tumor volume allowed for earlier identification of growth, with a median of 8.2 months before increase in tumor diameter. An increase in tumor size was more likely in younger patients.
The kinetics of tumor volume growth followed “classic exponential growth patterns, indicating that growth can be accurately modeled,” the researchers report in their article.
“Our study shows that active surveillance can be effectively implemented in a U.S. population and that excellent results can be expected (just as had been previously shown by 2 centers in Japan),” Dr. Tuttle noted in an email to Reuters Health.
“We hope that patients and clinicians will become aware of this study so that they can be aware that depending on the specifics of an individual case, that immediate surgery may not be mandatory . . . but rather an observational management approach may be reasonable. Once patients and clinicians are aware and accepting that immediate surgery may not always be mandatory, they can begin to explore whether or not observation may be a reasonable alternative for their specific case,” he added.
Dr. Tuttle also noted that, at this point, the option of active surveillance is largely limited to a few major medical centers that have had an interest in this topic. “I don't think it has gained widespread use in the community yet, which is not surprising since the guidelines just changed in early 2016 to allow for active surveillance as a reasonable alternative to immediate surgery in very low risk papillary thyroid cancer. It usually takes several years for a new recommendation to be implemented in the community. So I expect active surveillance to become more widely accepted and practiced in the years to come.,” Dr. Tuttle said.
In an invited commentary, Dr. Joseph Scharpf from the Head and Neck Institute at the Cleveland Clinic in Ohio says this study provides “invaluable and much-needed support to implement active surveillance protocols in the United States. The authors acknowledged that the success of their active surveillance management program requires a highly specialized and skilled multidisciplinary team but also provide optimism that this approach could potentially be replicated outside of major centers.”
SOURCES: http://bit.ly/2gDOjh0 and http://bit.ly/2eIjKcK
JAMA Otolaryngol Head Neck Surg 2017.
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