Predictive Value of Interim ¹⁸f-FDG PET-CT Scans on Diffuse Large B-Cell Lymphoma Treated with R-CHOP: A Prospective Study of Chinese Southwest Oncology Group (CSWOG)

Purpose

¹⁸F-FDG PET-CT has been widely used for pre-treatment staging and post-treatment response assessment in diffuse large B cell lymphoma (DLBCL), but the predictive value of interim PET-CT remained controversial and most of studies were retrospective.

Patients and Methods

Newly-diagnosed DLBCL patients treated with R-CHOP regimen were included in our prospective study to evaluate the predictive value of interim PET-CT. All patients were evaluated with PET-CT scans before treatment and after every 2 cycles of R-CHOP. PET-CT positivity or negativity was related to survival using Kaplan-Meier analysis.

Results

From Feb 2008 to Jan 2013, 149 patients were included. After 2 cycles of R-CHOP, the PET-CT evaluation showed CR in 82 patients. Among the remaining 67 non-CR patients, 31 achieved CR after 4 cycles. At the end of treatment, PET-CT evaluation showed CR in 121, PR in 21, SD in 3 and PD in 4 patients. With a median follow-up of 20.6 months (range 1.5-60.5 months), patients with negative PET-2 (PET-CT scan after 2 cycles) had a superior 2-year PFS than those with positive PET-2 (86.6% vs. 67.0%, p=0.019) and a tendency of superior 2-year OS without statistical differences (91.9% vs. 85.2%, p=0.330). The 2-year PFS and OS for negative PET-4 (PET-CT scan after 4 cycles) compared with positive PET-4 group were 84.8% vs. 51.9% (p=0.001) and 93.1% vs. 73.0% (p=0.027) respectively. PET-CT scans were interpreted using the International Harmonization Project (IHP) criteria above. The second analysis applying the Five-Point Scale (5PS) criteria showed that 2-year PFS for score 1-2 (uptake＜mediastinum), score 3 (mediastinum＜uptake≤liver) and score 4-5 (uptake＞liver) group were 86.6%, 75.8% and 71.0% according to PET-2, and 84.9%, 50.0% and 52.7% according to PET-4. PFS of score 3 group was not significant different from the other two groups in PET-2 (both P＞0.05), but significantly inferior to score 1-2 group (p=0.046) and similar to score 4-5 group (p=0.767) in PET-4. In the multivariate analysis, only PET-4 (95%CI, 1.07-5.44) and IPI score (95%CI, 1.53-10.06) remained independent predictive factors for PFS.

Conclusion

PET-CT after 4 cycles of R-CHOP in patients with DLBCL is highly predictive of PFS and should be considered in clinical practice.

(Clinical Trail Registration Number: CTR-TRC-11001687)