A population-based study on the use of radiation therapy versus surveillance in early stage seminoma in Ontario
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ABSTRACT Background: Stage I Seminoma is treated with surgery followed with either adjuvant radiation therapy (RT) or a period of surveillance. Surveillance has emerged as a preferred management method, however there have been no randomized controlled trials comparing RT and surveillance. Aim: To describe the incidence, management, and outcome in early stage seminoma patients in Ontario over time. To examine the relationship between patient characteristics and post-operative management methods (adjuvant RT versus surveillance). To examine the relationship between post-operative management methods (adjuvant RT versus surveillance) and patient outcome. Hypothesis: The adoption of surveillance as a management option post-orchidectomy has increased over time with no resulting decrease in overall survival in an Ontario population. Material and Methods: We performed a retrospective population-based cohort study of patients with surgically resected seminoma in the Canadian province of Ontario between 1982-2004 using data from the Ontario Cancer Registry. The population was enriched for stage I by excluding patients with evidence of metastasis. Patients were divided into time cohorts of 4 -5 years in length. Multiple logistic regression was used to identify patient and system factors associated with the use of RT. Kaplan-Meier survival analysis was used to assess overall, cancer specific, and relapse free survival. Cox proportional hazards model was used to assess the effect of patient and system factors on patient survival. Results: Age-adjusted seminoma increased from 2.25 per 100,000 males in 1980-1981 to 2.94 per 100,000 males in 2004-2005. Adjuvant RT use in early stage seminoma patients has declined from 88.9% in 1983 to 32.2% in 2004. There has been no significant ii worsening of overall, cancer specific or relapse free survival between patients diagnosed in 1982-1986 and those in later years. Controlling for other factors in a Cox proportional hazards model, no significant change in overall survival was found over time. Conclusion: The incidence of seminoma has increased over time. Over the course of the study period, use of adjuvant RT has decreased. While controlling for other factors, there has been no significant decrease in overall survival. The decreasing use of adjuvant RT has not adversely affected these patient outcomes.