Management and outcome of glottic cancer: A population-based comparison between Ontario, Canada and the SEER areas of the United States

Objective: We compared treatment practice and outcome in glottic cancer in Ontario, Canada to that in the Surveillance, Epidemiology and End Results ( SEER) program areas in the United States to determine whether the Ontario e mphasis on the use of delayed combined therapy was associated with similar survival and better laryngectomy-free survival than the U.S. approach, whic h emphasizes greater use of surgery. Methods: Electronic, clinical, and hospital data were linked to cancer regi stry data. The study groups compared on survival comprised all patients dia gnosed from 1982 to the end of 1991 in Ontario (2324 patients) and in the S EER areas (5715 patients). Comparisons on initial treatment, laryngectomy r ates, and laryngectomy-free survival were limited to subsets of these study populations due to data availability. Initial treatment data were provided by the SEER registries in the U.S. and by the cancer clinic and hospitaliz ation data in Ontario. Information about laryngectomies performed subsequen t to initial treatment was available from Medicare hospitalization data in the U.S. and from Canadian Institute for Health Information hospitalization data in Ontario. Results: Although radiotherapy was the most common initial treatment in bot h areas, it was used more often in Ontario (84.4% versus 63.2% in the U.S. [p < 0.001]). Relative survival was not statistically different with a rela tive risk comparing SEER to Ontario of 1.09, 95% confidence interval (CI) ( 0.93, 1.29). Laryngectomy rates were similar with a relative risk of 1.01, 95% CI (0.67, 1.52), and it follows from the survival and laryngectomy rate comparisons that the laryngectomy-free survival was not statistically diff erent (p = .95). Conclusions: There are large differences in the management of glottic cance r between the U.S. and Ontario and no corresponding differences in survival or laryngectomy-free survival. This work highlights a need for more clinic al investigation into the relative merits of differing management policies in glottic cancer.