Purpose: Mammography screening is expected to detect breast cancers at an earlier stage. Expected treatment costs in less severe cancers might be lower than in more severe cancers, due to reduced treatment intensity. Earlier detection increases life expectancy so less severe cancers might also lead to increased treatment costs compared to more severe cancers, due to a longer treatment period. The purpose of this study was to calculate treatment costs for breast cancer, exploring differences for similar TNM stages in different detection settings (screen detected cancers and non screen detected cancers).
Method: We collected data on resource use in hospitals for the period January 1st 2008 thru April 30th 2009 from the Norwegian Patient Registry (NPR) for women aged 50 to 69 who had been diagnosed with breast cancer in the period January 1st 1999 and December 31st 2008. As both treatment data and survival data were censored, expected treatment costs were calculated as a function of the mean cost and the survival probability t months after diagnosis by stage at diagnosis and detection setting. Cox proportional hazard models were used to calculate survival.
Result: Factors affecting survival were disability benefit, income, education, marital status, health region, detection setting, stage of breast cancer and age at detection. Preliminary results shows that patients with Ductal Carcinoma In Situ (DCIS) and cancers in stage I who were detected in screening, seams to receive initial treatment earlier compared to patients in similar stages with cancers detected outside of screening. Costs in the first ten years after diagnosis for TNM stage I cancers who were detected in screening and outside of screening, respectively, were $24585 and $46195. For stages II, III and IV, treatment costs for cancers detected in screening and outside of screening the first ten years were $55299 and $66794 (stage II), $49833 and $77722(stage III), and $71402 and $74138 (stage IV), respectively.
Conclusion: preliminary results shows that the cost of treating breast cancer diagnosed at screening tends to be lower for all stages compared to similarly staged cancers detected outside of screening. This might be due to several factors, such as interval cancers in the non screening group or that screening reveals less severe cancers within the TNM stages. This should explored more thoroughly.