A Comparison between Kaplan-Meier and Weighted Kaplan-Meier Methods of Five-Year Survival Estimation of Patients with Gastric Cancer
-
Ali Zare
,
Mahmood Mahmoodi
,
Kazem Mohammad
,
Hojjat Zeraati
,
Mostafa Hosseini
,
Kourosh Holakouie Naieni
Abstract
The 5-year survival rate is a good prognostic indicator for patients with Gastric cancer that is usually estimated based on Kaplan-Meier. In situations where censored observations are too many, this method produces biased estimations. This study aimed to compare estimations of Kaplan-Meier and Weighted Kaplan-Meier as an alternative method to deal with the problem of heavy-censoring. Data from 330 patients with Gastric cancer who had undergone surgery at Iran Cancer Institute from 1995- 1999 were analyzed. The Survival Time of these patients was determined after surgery, and the 5-year survival rate for these patients was evaluated based on Kaplan-Meier and Weighted Kaplan-Meier methods. A total of 239 (72.4%) patients passed away by the end of the study and 91(27.6%) patients were censored. The mean and median of survival time for these patients were 24.86±23.73 and 16.33 months, respectively. The one-year, two-year, three-year, four-year, and five-year survival rates of these patients with standard error estimation based on Kaplan-Meier were 0.66 (0.0264), 0.42 (0.0284), 0.31 (0.0274), 0.26 (0.0264) and 0.21 (0.0256) months, respectively. The estimations of Weighted Kaplan-Meier for these patients were 0.62 (0.0251), 0.35 (0.0237), 0.24 (0.0211), 0.17 (0.0172), and 0.10 (0.0125) months, consecutively. In cases where censoring assumption is not made, and the study has many censored observations, estimations obtained from the Kaplan-Meier are biased and are estimated higher than its real amount. But Weighted Kaplan-Meier decreases bias of survival probabilities by providing appropriate weights and presents more accurate understanding.
Gunderson LL, Sosin H. Adenocarcinoma of the stomach: areas of failure in a re-operation series (second or symptomatic look) clinicopathologic correlation and implications for adjuvant therapy. Int J RadiatOncol BiolPhys 1982;8(1):1-11.
Wisbeck WA, Becker EM, Russell AH. Adenocarcinoma of the stomach: Autopsy observations with therapeutic implications for the radiation oncologist. Radiother Oncol 1986;7(1):13-8.
Sadighi S, Mohagheghi M, Haddad P, et al. Life expectancy with perioperative chemotherapy and chemoradiotherapy for locally advanced gastric adenocarcinoma. Tehran Univ Med J 2008;66(9):664-9.
Japanese Gastric Cancer Association. Japanese gastric cancer treatment guidelines 2010 (ver. 3). Gastric Cancer 2011;14(2):113-23.
Young KD, Menegazzi JJ, Lewis RJ. Statistical methodology. Acad Emerg Med 1999;6(3):244-9.
Murray S. Using Weighted Kaplan‐Meier Statistics in Nonparametric Comparisons of Paired Censored Survival Outcomes. Biometrics 2001;57(2):361-8.
Zare A, Mahmoodi M. Modified Kaplan-Meier Estimator Based on Competing Risks for Heavy Censoring Data. Int J Statist Med Res 2013;2(4):297-304.
Jan B, Shah SWA, Shah S, et al. Weighted Kaplan Meier estimation of survival function in heavy censoring. Pak JStat 2005;21(1):55-63.
Jan B. Improved Inferences in the context of Survival/Failure Time [Dissertation]. Peshawar Univ., 2004.
Huang ML. A weighted estimation method for survival function. App Math Sci 2008;2(16):753-62.
Shafiq M, Shah S, Alamgir M. Modified Weighted Kaplan-Meier Estimator. Pak J Stat Operat Res 2007;3(1):39-44.
Ramadurai M, Ponnuraja C. Non-parametric estimation of the survival probability of children affected by TB meningitis. Int Refereed Res J 2011;II(2):216-27.
Ding YB, Chen GY, Xia JG, et al. Correlation of tumorpositive ratio and number of perigastric lymph nodes with prognosis of patients with surgically-removed gastric carcinoma. World J Gasrtroenterol 2004;10(2):182-5.
Thong-Ngam D, Tangkijvanich P, Mahachai V, et al. Current status of gastric cancer in Thai patients. J Med Assoc Thai 2001;84(4):475-82.
Schwarz RE, Zagala-Nevarez K. Recurrence patterns after radical gastrectomy for gastric cancer: prognostic factors and implications for postoperative adjuvant therapy. Ann Surg Oncol 2002;9(4):394-400.
Adachi Y, Tsuchihashi J, Shiraishi N, et al. AFP-producing gastric carcinoma: multivariate analysis of prognostic factors in 270 patients. Oncology 2003;65(2):95-101.
Triboulet J, Fabre S, Castel B, et al. Adenocarcinomas of the distal esophagus and cardia: Surgical management. Cancer Radither 2001;5(Suppl 1):90s-7s.
Wang CS, Hsieh CC, Chao TC, et al. Resectable gastric cancer: operative mortality and survival analysis. Chang Gung Med J 2002;25(4):216-27.
Zare A, Mahmoodi M, Mohammad K, Zeraati H, Hosseini M, Naieni KH. Survival Analysis of Patients with Gastric Cancer Undergoing Surgery at the Iran Cancer Institute: A Method Based on Multi-State Models. Asian Pacific journal of cancer prevention. 2013; 14(11):6369-73.
Zare A, Mahmoodi M, Mohammad K, Zeraati H, Hosseini M, Naieni KH. Factors Affecting the Survival of Patients with Gastric Cancer Under¬ gone Surgery at Iran Cancer Institute: Univariate and Multivariate Analyses. Iranian Journal of Public Health. 2014;43(6):800-8.
Klein JP, Moeschberger ML, editor. Survival analysis: techniques for censored and truncated data. 1st ed. New York, NY, USA: Springer; 2003: p. 92-104.
| Files | ||
| Issue | Vol 52, No 10 (2014) | |
| Section | Original Article(s) | |
| Keywords | ||
| Censoring Gastric Cancer Kaplan-Meier Survival Rate Weighted Kaplan-Meier | ||
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