Maroufizadeh Saman, Hajizadeh Ebrahim, Baghestani Ahmad Reza, Fatemi Seyed Reza
Department of Biostatistics, Faculty of Medical Science, Tarbiat Modares University, Tehran, Iran.
Asian Pac J Cancer Prev. 2011;12(7):1697-702.
Gastric cancer is the second leading cause of cancer death worldwide and is the most common type of cancer in Iran. The objective of this paper is to apply the additive hazards models to the study of survival of patients with gastric cancer and to compare results obtained by the additive hazards models and the Cox model.
We retrospectively studied 213 patients with gastric cancer who were registered in one referral cancer registry center in Tehran, Iran. Age at diagnosis, sex, presence of metastasis, tumor size, histology type, lymph node metastasis, and pathologic stages were entered into analysis using the Cox model and additive hazard models. To visualize a covariate effect over time, the estimated cumulative regression function by the Aalen's model is examined.
The five-year survival rate and the median life expectancy in the studied patients were 14.6% and 29.6 months, respectively. Multivariate Cox and Additive hazards models analysis identified that age at diagnosis, tumor size and pathologic stage were independent prognostic factors for the survival of patients with gastric cancer (P<0.05). Moreover, pathologic stage has a late or delayed effect according to the Aalen's plot. Other clinicopathological characteristics were not statistically significant (P<0.05).
Since Cox and additive models give different aspects of the association between risk factors and the study outcome, it seems desirable to use together to give a more comprehensive understanding of data. Our results also suggest that early detection of patients at younger age and in primary stages is important to increase survival of patients with gastric cancer.
胃癌是全球癌症死亡的第二大主要原因，也是伊朗最常见的癌症类型。本文的目的是将相加风险模型应用于胃癌患者生存情况的研究，并比较相加风险模型和Cox模型所得结果。
我们回顾性研究了在伊朗德黑兰一家转诊癌症登记中心登记的213例胃癌患者。使用Cox模型和相加风险模型对诊断时的年龄、性别、转移情况、肿瘤大小、组织学类型、淋巴结转移和病理分期进行分析。为了直观呈现协变量随时间的效应，我们考察了Aalen模型估计的累积回归函数。
研究患者的五年生存率和中位预期寿命分别为14.6%和29.6个月。多变量Cox模型和相加风险模型分析确定，诊断时的年龄、肿瘤大小和病理分期是胃癌患者生存的独立预后因素（P<0.05）。此外，根据Aalen图，病理分期具有晚期或延迟效应。其他临床病理特征无统计学意义（P<0.05）。
由于Cox模型和相加模型给出了风险因素与研究结果之间关联的不同方面，因此似乎有必要一起使用以更全面地理解数据。我们的结果还表明，早期发现年龄较小且处于初级阶段的患者对于提高胃癌患者的生存率很重要。
