Given a passage with a context and an answer, construct a question on the basis of the information present in the passage. Construct the question in such a way that (i) it is unambiguous, (ii) it is answerable from the passage, (iii) its answer is unique (iv) it answer uses text phrases from the passage. Avoid creating questions that (i) can't be answered correctly without actually understanding the passage and (ii) uses the same words or phrases given in the passage.

Context: Age and certain pathologic features (ie, follicular histology, vascular invasion, and extracapsular extension) are reported to impact on prognosis in thyroid cancer, but the relationship between these two factors remains incompletely defined.', 'Clinical, pathologic, therapeutic, prognostic, and outcome data were retrospectively collected and compared among three groups of patients with thyroid cancer: group 1 (age 21 to 50), group 2 (age 51 to 70), and group 3 (age greater than 70).', 'There was a statistically significant age-related decrement in survival: 10-year survival was 92% in group 1, 77% in group 2, and 48% in group 3. Follicular histology, vascular invasion, and extracapsular extension were more frequently observed in group 3 versus group 2 and in group 2 versus group 1 (all differences statistically significant except for vascular invasion). Although survival was significantly less for group 3 versus group 2 versus group 1, only vascular invasion and extracapsular extension independently predicted outcome by multivariate analysis.
Answer: The prognostic importance of age in thyroid cancer may be due to the greater prevalence of pathologic risk factors in older patients.
Does age correlate with increased frequency of high risk factors in elderly patients with thyroid cancer?