Zahl P H
Section of Medical Statistics, University of Oslo, Blindern, Norway.
Stat Med. 1997 Jul 30;16(14):1573-85. doi: 10.1002/(sici)1097-0258(19970730)16:14<1573::aid-sim585>3.0.co;2-q.
Long-term excess hazards for cancer survival sometimes tend to zero or become negative even though we expect them to be positive. This may be explained by selection at diagnosis; individuals with certain cancers may have an increased risk of dying of other diseases in general. Then comparing with population mortality rates is not correct. Alternatively, we may have a continuous selection of the most robust individuals after diagnosis. When there are unobserved heterogeneity, and those with highest risk of dying of cancer also have the highest risk of dying of other diseases, this will cause selection after diagnosis. This may be modelled by multivariate frailty variables, and a corrected excess hazard may be estimated. In two examples, these corrected excess hazards give a better estimate when comparing to the cause-specific cancer mortality. Actually, this study questions the usefulness of long-term excess hazard rates.
癌症生存的长期超额风险有时趋于零甚至变为负数，尽管我们预期它们是正数。这可能可以通过诊断时的选择来解释；某些癌症患者总体上死于其他疾病的风险可能会增加。那么与人群死亡率进行比较是不正确的。或者，在诊断后我们可能会持续选择最健壮的个体。当存在未观察到的异质性，且死于癌症风险最高的人死于其他疾病的风险也最高时，这将导致诊断后的选择。这可以通过多变量脆弱性变量进行建模，并可以估计校正后的超额风险。在两个例子中，与特定病因的癌症死亡率相比，这些校正后的超额风险给出了更好的估计。实际上，这项研究对长期超额风险率的有用性提出了质疑。
