Prognostic Value of Early 18fluorodeoxyglucose PET Scan in Patients with Diffuse Large B Cell Lymphoma Treated with Rituximab Plus CHOP or High-Dose CHOP.

The results of ¹⁸Fluorodeoxyglucose – Positron Emission Tomography scan (PET) performed early during treatment (after 1 – 3 courses of chemotherapy) have been shown to predict outcome in aggressive lymphoma (Jerusalem, Haematologica 2000; Spaepen, Ann Oncol 2002; Haioun, Blood 2005). However, studies on early PET have been performed mostly in patients (pts.) treated without Rituximab. Our goal was to explore if the powerful predictive value of early PET was also observed in pts. treated with Rituximab-chemotherapy combinations. Seventy-three pts. with diffuse large B-cell lymphoma from 2 institutions were treated with R-CHOP (n=47) or R-high-dose CHOP (R-ACVBP, n=26) and were evaluated by PET after the two first cycles. PETs were interpreted on the basis of visual assessment. PET results were not taken into account to guide the treatment strategy after the 2 first cycles, which was solely based upon the results of conventional response assessment. Among responders, 16 young poor-risk pts. received planned consolidative high-dose therapy with autotransplant, while the others received immunochemotherapy based consolidation. Median age was 63 years (range 26–79) and 68% pts. were male. Baseline characteristics were as follows: Advanced Stage (Ann Arbor III–IV) 75%; Elevated LDH 62%; Poor performance status (ECOG 2–4) 32%. The International Prognostic Index was as follows: Low risk 27%, Low-intermediate 21%, Intermediate-high 21%, High risk 31%. PET was performed after a median of 15 days following the second cycle. Forty-nine pts. had a negative PET, while 24 were positive. With a median follow-up of 49 months, 11/49 (22%) PET negative pts. showed an event (progression or death) after a median delay of 13 months, while this was the case in 14/24 (58%) PET-positive patients after a median of 8 months. The estimated 5 year event free survival rates were 75% (95% CI: 63%–88%) for PET negative pts. and 41% (95% CI: 22%–61%) (log-rank test, p=0.001). Regarding overall survival, the estimated 5 year rates were 85% (95% CI: 78%–95%) and 53% (95% CI: 34%–74%) (log-rank test, p=0.005) in PET negative and PET positive pts., respectively. The same differences were found at 4 years when analysing separately pts. treated with R-CHOP and R-ACVBP (except for a non significant difference in OS in R-ACVBP pts.). In conclusion, we confirm the strong prognostic value of PET after 2 cycles in pts. treated with Rituximab combined to chemotherapy. Prospective studies (including a GELA study) are ongoing to evaluate the potential interest of tailoring treatment strategy to the results of early PET.