Limited clinical benefit for surveillance PET-CT scanning in patients with histologically transformed lymphoma in complete metabolic remission following primary therapy

To develop guidelines for performing and interpreting positron emission tomography (PET) imaging for treatment assessment in patients with lymphoma both in clinical practice and in clinical trials. An International Harmonization Project (IHP) was convened to discuss standardization of clinical trial parameters in lymphoma. An imaging subcommittee developed consensus recommendations based on published PET literature and the collective expertise of its members in the use of PET in lymphoma. Only recommendations subsequently endorsed by all IHP subcommittees were adopted. PET after completion of therapy should be performed at least 3 weeks, and preferably at 6 to 8 weeks, after chemotherapy or chemoimmunotherapy, and 8 to 12 weeks after radiation or chemoradiotherapy. Visual assessment alone is adequate for interpreting PET findings as positive or negative when assessing response after completion of therapy. Mediastinal blood pool activity is recommended as the reference background activity to define PET positivity for a residual mass > or = 2 cm in greatest transverse diameter, regardless of its location. A smaller residual mass or a normal sized lymph node (ie, < or = 1 x 1 cm in diameter) should be considered positive if its activity is above that of the surrounding background. Specific criteria for defining PET positivity in the liver, spleen, lung, and bone marrow are also proposed. Use of attenuation-corrected PET is strongly encouraged. Use of PET for treatment monitoring during a course of therapy should only be done in a clinical trial or as part of a prospective registry.

To assess the incidence and predictive factors for development of transformed lymphoma in a population-based series of patients with follicular lymphoma (FL). The Lymphoid Cancer Database was used to identify patients with FL diagnosed and treated in the province of British Columbia, Canada. Transformed lymphoma was defined as the development of aggressive non-Hodgkin's lymphoma (NHL) in patients with FL. Factors present at the time of initial diagnosis of indolent NHL and at transformation were analyzed for their impact on risk of transformation and subsequent outcome. Between 1986 and 2001, 600 patients with newly diagnosed FL met the inclusion criteria. With a median follow-up of 109 months (range, 10 to 244), 170 (28%) developed transformation, 107 (63%) based on biopsy confirmation. The annual risk of transformation was 3% continuously through 15 years. A multivariate analysis of clinical factors at diagnosis identified advanced stage as the only predictor of future transformation. The median post-transformation survival was 1.7 years. The 5-year survival was superior for patients with limited extent transformation compared with those with advanced cases (66% v 19%, P < .0001). Patients with transformation based on clinical versus histological criteria had an identical median survival of 1.8 years (P = .2). The annual risk of transformation of FL is 3% continuing without plateau beyond 15 years. Advanced stage at diagnosis is predictive of future transformation. Clinically diagnosed transformation has an equal impact on outcome as biopsy proven transformation.

To study the clinical significance of transformation to diffuse large B-cell lymphoma (DLBCL) in patients with follicular lymphoma (FL). From 1972 to 1999, 325 patients were diagnosed with FL at St Bartholomew's Hospital (London, United Kingdom). With a median follow-up of 15 years, progression occurred in 186 patients and biopsy-proven transformation in 88 of the 325. The overall repeat biopsy rate was 70%. The risk of histologic transformation (HT) by 10 years was 28%, HT not yet having been observed after 16.2 years. The risk was higher in patients with advanced stage (P = .02), high-risk Follicular Lymphoma International Prognostic Index (FLIPI; P = .01), and International Prognostic Index (IPI; P = .04) scores at diagnosis. Expectant management (as opposed to treatment being initiated at diagnosis) also predicted for a higher risk of HT (P = .008). Older age (P = .005), low hemoglobin level (P = .03), high lactate dehydrogenase (P < .0001), and high-risk FLIPI (P = .01) or IPI (P = .003) score at the time of first recurrence were associated with the diagnosis of HT in a biopsy performed at that time. The median survival from transformation was 1.2 years. Patients with HT had a shorter overall survival (P < .0001) and a shorter survival from progression (P < .0001) than did those in whom it was not diagnosed. Advanced stage and high-risk FLIPI and IPI scores at diagnosis correlate with an increased risk of HT. This event strongly influences the outcome of patients with FL by shortening their survival. There may be a subgroup of patients in whom HT does not occur.