Trends in treatment costs for localized prostate cancer: the healthy screenee effect.

OBJECTIVE: We sought to obtain estimates of trends in initial treatment costs during the prostate-specific antigen (PSA) era that account for the changing patient case-mix associated with screening.
SUBJECTS: We used reimbursement claims for Medicare-eligible subjects diagnosed with nonmetastatic prostate cancer between 1991 and 1999. Patients were grouped by initial treatment, with 17,846 receiving radical prostatectomy (RP), 25,933 receiving external beam radiotherapy (XRT), and 4525 receiving brachytherapy (BT).
METHODS: Cancer-attributable costs were computed by subtracting noncancer costs from total Medicare reimbursements among newly diagnosed cancer patients. Noncancer costs were estimated in 2 ways: (1) average costs among age-matched, cancer-free control subjects (control method) and (2) projections based on claims from subjects before diagnosis (prediagnosis method). Adjusted annual percent change in cancer-attributable costs was calculated using multivariate generalized linear models.
RESULTS: Noncancer costs increased at a much lower rate among men prior to diagnosis (3.8% annually) than among the general Medicare population (10.9%). The 2 approaches yielded different results; RP costs declined by 2.4% annually (prediagnosis method) versus 6.2% (control method); XRT costs declined by 1.5% versus 5.8%; and BT costs declined by 4.1% versus 8.3%.
CONCLUSIONS: Because of self-selection of PSA screening, men diagnosed with prostate cancer today are now healthier overall than men in the general population and are considerably healthier than men diagnosed previously. Estimates of cancer-attributable costs that do not account for this healthy selection effect are likely to be biased. Declines in cancer-attributable treatment costs are evident even after accounting for a healthy screenee effect, suggesting that there has been a real reduction in cancer treatment costs.