215P - Prospective observational study to evaluate impact of metabolic tumor volume on baseline 18F FDG PET/CT and molecular markers on tumor response rate in patients with diffuse large B-cell lymphoma

Background

The prognostic impact of total metabolic tumor volume (TMTV) measured on pretreatment 18F-FDG PET/CT and its added value to molecular characteristics was investigated in patients with diffuse large B-cell lymphoma (DLBCL).

Methods

For 47 newly diagnosed patients with DLBCL treated with rituximab and CHOP/CHOP-like regimen, TMTV was computed using the 40% SUVmax thresholding method. Overexpression of BCL2, BCL6 and MYC was seen with the use of immunohistochemistry.

Results

Median follow-up was 14.1 months. Out of 47 patients, one patient died after 3 cycles of chemotherapy due to disease progression; the remaing 46 have completed 6 cycles of R-CHOP chemotherapy. Twenty-nine (61.7%) patients had a complete response (CR) to therapy. Using Spearman's correlation test, total metabolic tumor volume was positively and significantly correlated with tumor response, NCCN IPI and LDH levels. In the CR group mean TMTV was263.7 which is statistically lower than the mean TMTV in the non CR group that is 481.3 (p value – 0.006). For prediction of CR, the estimated optimal cutoff TMTV value was 215 cm3 with 0.83 sensitivity and 0.52 specificity done with the aid of receiver-operating characteristics (ROC) curve analysis. BCL2, BCL6 and MYC overexpression was seen in 35 (74.5%), 35 (74.5%) and 20 (42.6%) patients, respectively. Dual expression was seen in 5 (10.6%) and triple expression in 14 (29.8%) patients. It was found to be statistically insignificant with any of the clinical factors. In univariate analysis TMTV, LDH, response rate and NCCN IPI were found to be statistically significant in predicting progression-free survival, but in multivariate analysis none of the factors except response rate were shown to be independently predictive of progression-free survival.

Conclusions

In our study TMTV had an independent impact on response rate as well as on patient survival. Molecular analysis needs a study with long-term follow up with a large sample size to establish a significant relationship. TMTV with NCCN-IPI can be used in guiding treatment decisions, particularly in high-risk patients.

Clinical trial identification

Editorial acknowledgement

Legal entity responsible for the study

The authors.

Funding

Has not received any funding.

Disclosure

All authors have declared no conflicts of interest.