FROM JOURNAL OF CLINICAL ONCOLOGY
The total metabolic tumor volume, as quantified on PET scanning at the time that follicular lymphoma is diagnosed, is a strong independent predictor of treatment response and patient outcome, according to a report published online in Journal of Clinical Oncology.
Until now, no study has specifically examined the prognostic possibilities of PET-derived total metabolic tumor volume (TMTV) for this malignancy, either on its own or in combination with any of several existing prognostic indices. Those tools use a variety of surrogates to estimate tumor burden. Now that PET is recommended at diagnosis for all cases of follicular lymphoma and anatomic CT data are also available, it is much easier to estimate total tumor burden than it was when those indices were developed, said Michel Meignan, MD, PhD, of Hôpital Henri Mondor, Crétiel (France) and his associates.
It is crucial to identify patients likely to have a poor response to standard treatment, both to spare them the considerable adverse effects of that treatment and to select them for alternative first-line approaches. Even though patient survival has improved markedly during the past decade with the introduction of combined treatment using rituximab plus chemotherapy, approximately 20% of patients still show disease progression within 2 years, and the 5-year overall survival is only 50%, the investigators noted.
To assess the prognostic value of TMTV as assessed by PET, they pooled data from three multicenter prospective studies involving 185 patients with either a high tumor burden or advanced-stage follicular lymphoma. These participants were followed for a median of 63.5 months at 56 medical centers in France, Belgium, Australia, and Italy.
A TMTV threshold of 510 cm3 was found to have the optimal sensitivity (0.46), specificity (0.83), positive predictive value (0.67), and negative predictive value (0.67) for predicting both progression-free and overall survival. The 30% of patients who had a TMTV greater than that cutoff point had markedly inferior 5-year progression-free survival (less than 3 years), while the 70% who had a smaller TMTV had median progression-free survival of more than 6 years, Dr. Meignan and his associates said (J Clin Oncol. 2016 Aug 22. doi:10.1200/JCO.2016.66.9440).
Combining TMTV with other prognostic measures improved predictions even further. Patients who had both a high TMTV and an intermediate to high score on the Follicular Lymphoma International Prognostic Index 2 showed extremely poor outcomes, with a median progression-free survival of only 19 months. “This population can no longer be characterized as having an indolent lymphoma,” the investigators said.
No sponsor or funding source was cited for this study. Dr. Meignan reported receiving fees for travel and expenses from Roche; his associates reported ties to numerous industry sources.
