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. 2011 Oct 11:11:438.
doi: 10.1186/1471-2407-11-438.

Survival endpoints in colorectal cancer and the effect of second primary other cancer on disease free survival

Helgi Birgisson  1 , Ulrik Wallin, Lars Holmberg, Bengt Glimelius
Affiliations

Survival endpoints in colorectal cancer and the effect of second primary other cancer on disease free survival

Helgi Birgisson et al. BMC Cancer. .

Abstract

Background: In cancer research the selection and definitions of survival endpoints are important and yet they are not used consistently. The aim of this study was to compare different survival endpoints in patients with primary colorectal cancer (CRC) and to understand the effect of second primary other cancer on disease-free survival (DFS) calculations.

Methods: A population-based cohort of 415 patients with CRC, 332 of whom were treated with curative intention between the years 2000-2003, was analysed. Events such as locoregional recurrence, distant metastases, second primary cancers, death, cause of death and loss to follow-up were recorded. Different survival endpoints, including DFS, overall survival, cancer-specific survival, relapse-free survival, time to treatment failure and time to recurrence were compared and DFS was calculated with and without inclusion of second primary other cancers.

Results: The events that occurred most often in patients treated with curative intention were non-cancer-related death (n = 74), distant metastases (n = 66) and death from CRC (n = 59). DFS was the survival endpoint with most events (n = 170) followed by overall survival (n = 144) and relapse-free survival (n = 139). Fewer events were seen for time to treatment failure (n = 80), time to recurrence (n = 68) and cancer-specific survival (n = 59). Second primary other cancer occurred in 26 patients and its inclusion as an event in DFS calculations had a detrimental effect on the survival. The DFS for patients with stage I-III disease was 62% after 5 years if second primary other cancer was not included as an event, compared with 58% if it was. However, the difference was larger for stage II (68 vs 60%) than for stage III (49 vs 47%).

Conclusions: The inclusion of second primary other cancer as an endpoint in DFS analyses significantly alters the DFS for patients with CRC. Researchers and journals must clearly define survival endpoints in all trial protocols and published manuscripts.

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Figures

Figure 1
Figure 1
Comparison of different survival endpoints in patients treated with curative intention for colorectal cancer, disease stages I-III (n = 332). CSS: cancer specific survival; TTR: time to recurrence; TTF = time to treatment failure; OS: overall survival; RFS: relapse-free survival; DFS: disease-free survival.
Figure 2
Figure 2
Comparison of different survival endpoints in patients treated with curative intention for colorectal cancer, disease stage I (n = 57). CSS: cancer specific survival; TTR: time to recurrence; TTF = time to treatment failure; OS: overall survival; RFS: relapse-free survival; DFS: disease-free survival.
Figure 3
Figure 3
Comparison of different survival endpoints in patients treated with curative intention for colorectal cancer, disease stage II (n = 149). CSS: cancer specific survival; TTR: time to recurrence; TTF = time to treatment failure; OS: overall survival; RFS: relapse-free survival; DFS: disease-free survival.
Figure 4
Figure 4
Comparison of different survival endpoints in patients treated with curative intention for colorectal cancer, disease stage III (n = 122). CSS: cancer specific survival; TTR: time to recurrence; TTF = time to treatment failure; OS: overall survival; RFS: relapse-free survival; DFS: disease-free survival.
Figure 5
Figure 5
Comparison of two different definitions of disease-free survival (DFS) in patients curatively treated for colorectal cancer stages I-III (n = 332). For DFSa only second primary same cancer was included as an event and second primary other cancer was ignored. For DFSb all second primary cancers were counted as an event. The cumulative proportion with standard deviations at 3, 5 and 7 years are given.
Figure 6
Figure 6
Comparison of two different definitions of disease-free survival (DFS) in patients curatively treated for colorectal cancer stage stage II (n = 149) and III (n = 122). For DFSa only second primary same cancer was included as an event and second primary other cancer was ignored. For DFSb all second primary cancers were counted as an event. The cumulative proportion with standard deviations at 3, 5 and 7 years are given.
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