Tai Patricia, Yu Edward, Cserni Gábor, Vlastos Georges, Royce Melanie, Kunkler Ian, Vinh-Hung Vincent
University of Saskatchewan, Faculty of Medicine, Saskatoon, Canada.
BMC Cancer. 2005 May 17;5:48. doi: 10.1186/1471-2407-5-48.
The present commonly used five-year survival rates are not adequate to represent the statistical cure. In the present study, we established the minimum number of years required for follow-up to estimate statistical cure rate, by using a lognormal distribution of the survival time of those who died of their cancer. We introduced the term, threshold year, the follow-up time for patients dying from the specific cancer covers most of the survival data, leaving less than 2.25% uncovered. This is close enough to cure from that specific cancer.
Data from the Surveillance, Epidemiology and End Results (SEER) database were tested if the survival times of cancer patients who died of their disease followed the lognormal distribution using a minimum chi-square method. Patients diagnosed from 1973-1992 in the registries of Connecticut and Detroit were chosen so that a maximum of 27 years was allowed for follow-up to 1999. A total of 49 specific organ sites were tested. The parameters of those lognormal distributions were found for each cancer site. The cancer-specific survival rates at the threshold years were compared with the longest available Kaplan-Meier survival estimates.
The characteristics of the cancer-specific survival times of cancer patients who died of their disease from 42 cancer sites out of 49 sites were verified to follow different lognormal distributions. The threshold years validated for statistical cure varied for different cancer sites, from 2.6 years for pancreas cancer to 25.2 years for cancer of salivary gland. At the threshold year, the statistical cure rates estimated for 40 cancer sites were found to match the actuarial long-term survival rates estimated by the Kaplan-Meier method within six percentage points. For two cancer sites: breast and thyroid, the threshold years were so long that the cancer-specific survival rates could yet not be obtained because the SEER data do not provide sufficiently long follow-up.
The present study suggests a certain threshold year is required to wait before the statistical cure rate can be estimated for each cancer site. For some cancers, such as breast and thyroid, the 5- or 10-year survival rates inadequately reflect statistical cure rates, and highlight the need for long-term follow-up of these patients.
目前常用的五年生存率不足以代表统计学上的治愈情况。在本研究中，我们通过对死于癌症患者的生存时间采用对数正态分布，确定了估计统计学治愈率所需的最短随访年限。我们引入了“阈值年”这一术语，即死于特定癌症患者的随访时间涵盖了大部分生存数据，未覆盖的数据不到2.25%。这就足够接近从该特定癌症中治愈。
使用最小卡方方法检验监测、流行病学和最终结果（SEER）数据库中死于疾病的癌症患者的生存时间是否遵循对数正态分布。选择1973年至1992年在康涅狄格州和底特律登记处诊断的患者，以便到1999年最多可进行27年的随访。共测试了49个特定器官部位。针对每个癌症部位确定这些对数正态分布的参数。将阈值年时的癌症特异性生存率与最长可用的Kaplan-Meier生存估计值进行比较。
49个部位中42个癌症部位死于疾病的癌症患者的癌症特异性生存时间特征经证实遵循不同的对数正态分布。不同癌症部位经验证的统计学治愈阈值年各不相同，胰腺癌为2.6年，唾液腺癌为25.2年。在阈值年时，发现40个癌症部位估计的统计学治愈率与通过Kaplan-Meier方法估计的精算长期生存率相差在6个百分点以内。对于两个癌症部位：乳腺癌和甲状腺癌，阈值年过长，由于SEER数据未提供足够长的随访时间，尚未获得癌症特异性生存率。
本研究表明，对于每个癌症部位，需要等待一定的阈值年才能估计统计学治愈率。对于某些癌症，如乳腺癌和甲状腺癌，5年或10年生存率不能充分反映统计学治愈率，并突出了对这些患者进行长期随访的必要性。
