Estimating a Hazard Function for Each of Four Items of Adverse Event Induced by the Anti-cancer Drug TS-1
10.3820/jjpe1996.11.9
- Author:
Akira FUKUSHIMA
;
Wataru KASHIWAGI
;
Masaki SANO
;
Chikuma HAMADA
;
Isao YOSHIMURA
- Publication Type:Journal Article
- Keywords:
adverse event;
hazard function;
interval censoring;
log-logistic model;
clinical laboratory test
- From:Japanese Journal of Pharmacoepidemiology
2006;11(1):9-21
- CountryJapan
- Language:English
-
Abstract:
Background : The safety of newly approved drugs must be assessed using postmarketing surveillance data. One of the difficulties in assessing the hazard rates of adverse events induced by the anti-cancer drug TS-1 was that the time to event was not exactly identified due to the interval censoring. Most patients were outpatients who underwent clinical laboratory tests almost periodically at 1- or 2-week intervals and therefore, the occurrence of an adverse event was confirmed at the time of testing days after the event occurrence.
Objective : The purpose of this study was to propose a new model of hazard functions for each of 4 items of adverse event induced by TS-1 using post-marketing surveillance data considering the interval censoring.
Methods : The data obtained from 3, 294 patients with gastric cancer who received an initial 4-week course of therapy with TS-1 administered orally twice a day, followed by a 4-week second course with a 2-week no-treatment period after the initial course, were used to estimate hazard functions. Four items of adverse event--hemoglobin level (HB), white blood cell (WBC), neutrophil (NEUT) and platelet counts (PLT) --were graded, respectively, using the criteria established by the Japan Society of Clinical Oncology. Slip-mixed log-logistic and slip-mixed Weibull models were proposed as candidate models for estimating hazard functions. The goodness of fit of the two candidate models was evaluated by applying them to the above-mentioned data. The hazard functions for each of 4 items were assessed using the model with the better fit.
Results : The initial occurrence of adverse event was shown to follow the slip-mixed log-logistic model for each of 4 items. Although most events occurred early on in the initial course of therapy, a small peak in HB was also observed in the second course, while no such peak appeared for the other items.
