Conditional survival and hazards of death for peripheral T-cell lymphomas

Abstract

Typically, peripheral T-cell lymphoma (PTCLs) prognosis is estimated using overall survival before treatment. However, these estimates cannot show how prognosis evolves with the changing hazard rate over time. Patients (n = 650) with newly diagnosed PTCLs were enrolled retrospectively. After a median follow-up of 5.4 years, angioimmunoblastic T-cell lymphoma, peripheral T-cell lymphoma, not otherwise specified (PTCL, NOS) and NK/T cell lymphoma had initially lower 3-year conditional overall survival (COS3; i.e., the 3-year conditional overall survival was defined as the probability of surviving an additional 3 years) and higher hazards of death (26-44.3%). However, after 2 years, the COS3 increased and the death risk decreased over time, whereas anaplastic lymphoma kinase-positive anaplastic large-cell lymphoma constantly had a lower risk over time (0-19.5%). For patients with complete remission after initial treatment, prognosis varied by histological subtypes, with PTCL, NOS having a negative impact. Our data suggested that the risk stratification using the International Prognostic Index might not accurately predict the COS3 for survivors of PTCLs. The COS3 provided time-dependent prognostic information for PTCLs, representing a possible surrogate prognosis indicator for long-term survivors after systemic chemotherapy.

Keywords: T-cell; lymphoma; peripheral; prognosis; survival analysis.

Figure 1

Survival and conditional survival curves for patients with peripheral T-cell lymphomas (PTCLs). (A) The overall survival curves for the whole study and the cohort with PTCL excluded anaplastic lymphoma kinase positive anaplastic large-cell lymphoma (ALK+ALCL). (B) Three-year conditional and 3-year actuarial survival with error bars of 95% confidence intervals (CIs) for the whole study cohort. For example, the 3-year actuarial survival rate at 2 years was the 5-year survival rate estimated at baseline. All the actuarial survival rates were calculated at the time point of starting treatment. (C) Conditional survival curves for patients who have survived for 1 year, 2 years, 3 years, 4 years, and 5 years from the time of treatment are shown. (D) Smoothed hazard plots for the annual rate of death for PTCLs since treatment.

Figure 2

Conditional survival, actuarial survival, and annual hazards stratified by histologic subtypes for PTCLs. (A), (D), (G), (J), (M), and (P) presented the conditional survival curves for patients who have already survived a certain time for each subtype. (B), (E), (H), (K), (N), and (Q) showed the three-year conditional and 3-year actuarial survival with error bars of CIs. (C), (F), (I), (L), (O), and (R) demonstrated the smoothed hazard plots for the annual rate of death for each subtype. AITL: angioimmunoblastic T-cell lymphoma; ALK: anaplastic lymphoma kinase; ALCL: anaplastic large cell lymphoma; PTCL: peripheral T-cell lymphoma; NKTCL: NK/T cell lymphoma. PTCL, NOS: peripheral T-cell lymphoma, not otherwise specified.

Figure 3

(A) The overall survival curves were stratified into four groups by the International Prognostic Index (IPI). (B) Three-year conditional survival with error bars of 95% CIs for patients who have survived for 1 year, 2years, 3 years, 4 years, and 5 years from the time of treatment. (C) Smoothed hazard plots for the annual rate of death since treatment.

Figure 4

Risk-dependent conditional survival and annual hazard for patients with CR. (A) Overall survival curves for the patients who achieved or failed to obtain complete remission (CR) to initial chemotherapy. The overall survival rate was 75% and 31% at 5 years in the CR group and non-CR group, respectively. Survival comparison was made using the log-rank test. (B) Three-year conditional and 3-year actuarial survival with error bars of 95% confidence intervals (CIs) for the patients with CR. (C) Conditional survival curves for patients with CR who have survived for 1 year, 2 years, 3 years, 4 years, and 5 years from the time of treatment are shown. (D) Smoothed hazard plots for the annual rate of death for patients with CR since treatment.