Possibility of a Risk-Adapted Treatment Strategy for Untreated Aggressive Adult T-Cell Leukemia-Lymphoma (ATL) Based on the ATL Prognostic Index: A Supplementary Analysis of the JCOG9801 Study

Introduction

The JCOG9801 study, a randomized phase III trial of the Japan Clinical Oncology Group (JCOG), compared CHOP every two weeks (CHOP-14) with VCAP-AMP-VECP (mLSG15) for patients with untreated aggressive adult T-cell leukemia-lymphoma (ATL) [J Clin Oncol 2007;25:5458-64]. Based on a higher complete response (CR) rate and marginally better overall survival (OS), we concluded that mLSG15 could be a sufficiently effective regimen at the expense of higher toxicity profiles. However, there was an insufficient mLSG15 effect among patients with an Eastern Cooperative Oncology Group performance status (ECOG PS) of 0 or those aged ≥56 years, suggesting that mLSG15 is not always a definitive treatment for all patients with aggressive ATL.

Thus, identifying patients who should receive mLSG15 is essential. We aimed to conduct a supplementary analysis of patients enrolled in the JCOG9801 study using the ATL prognostic index (ATL-PI) that has been recently advocated for acute- and lymphoma-types of ATL [J Clin Oncol 2012;30:1635-40].

Methods

We adopted the "age-adjusted" ATL-PI that was established for ATL patients aged ≤70 years as patients aged between 15 and 69 years were eligible in the JCOG9801 study. Having eliminated "age", this index comprised 4 factors, namely Ann Arbor stage (III or IV), ECOG PS (>1), serum albumin (<3.5 g/dL), and soluble interleukin-2 receptor (sIL-2R; >20,000 U/mL). We excluded patients lacking any factors of the age-adjusted ATL-PI and those with unfavorable chronic type based on the age-adjusted ATL-PI model from patients enrolled in JCOG9801. Subsequently, we categorized the remaining patients into three groups, namely low, intermediate, and high risk, and compared mLSG15 and CHOP-14 in terms of OS, treatment CR rate, and toxicity in each risk group.

Results

Of 118 enrolled JCOG9801 patients, we included 105 patients in this supplementary analysis based on the above criteria, of which 51 and 54 were treated with mLSG15 and CHOP-14, respectively. According to the age-adjusted ATL-PI, these patients were classified as follows: low (n=44, 41.9%), intermediate (n=54, 51.4%), and high (n=7, 6.7%) risks. Regarding patient characteristics, between the two treatment arms, there were no remarkable differences in age, sex, ECOG PS, ATL subtypes, Ann Arbor stage, presence of B symptoms, presence of bulky mass (≥5 cm), and serum albumin, serum calcium, and sIL-2R levels. The mLSG15 arm included 21 (41.2%), 25 (49.0%), and 5 (9.8%) patients in the low-, intermediate-, and high-risk groups, respectively, whereas the CHOP-14 arm included 23 (42.6%), 29 (53.7%), and 2 (3.7%) patients, respectively. We excluded the high-risk group from our analysis due to the small number of patients. mLSG15 did not show any superior trend for OS compared to CHOP-14 in the low-risk group (hazard ratio [HR]: 0.957; 95% confidence interval [CI]: 0.491-1.868) (Figure A). In contrast, in the intermediate-risk group, better prognosis for OS was observed with mLSG15 (HR: 1.538; 95% CI: 0.841-2.811) than with CHOP-14 (Figure B). Similarly, the CR rate, including the unconfirmed CR rate, did not differ between both arms of the low-risk group (mLSG15 vs. CHOP-14, 47.6% vs. 43.5%), while in the intermediate-risk group, mLSG15 showed a higher CR rate than CHOP-14 (44.0% vs. 13.8%). Regarding toxicity profiles, grade 4 thrombocytopenia was more frequently observed in the mLSG15 arm of both risk groups than in the CHOP-14 arm (66.7% vs. 4.5% in the low-risk group; 68.0% vs. 24.1% in the intermediate-risk group only). There was a higher incidence of grade 4 neutropenia in the mLSG15 arm than in the CHOP-14 arm (100.0% vs. 75.9%) only in the intermediate-risk group. All three treatment-related deaths were documented in the mLSG15 arm of the intermediate-risk group.

Conclusions

Given the very poor prognosis of ATL, our findings suggest that despite higher toxicities, mLSG15 is more suitable for the intermediate-risk group of age-adjusted ATL-PI, whereas its benefits appear modest in the low-risk group. This supplementary analysis is exploratory; therefore, a further prospective study of aggressive ATL is necessary to confirm these results.

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