By Mary Jo Lechowicz, MD
2009-12-08
The usefulness of positron emission
tomography (PET) scanning in hematologic malignancies depends on disease type,
timing, the experience of the person reading the images, and scanner type. This
year’s annual meeting includes a number of presentations that focus on interim
use of PET scans in patients with non-Hodgkin lymphoma. Sunday and Monday’s
oral and poster sessions covered some of the controversy over PET scans.
A French group’s abstract (#98),
presented by Dr. Violaine Safar, described a large prospective study of 112
patients with diffuse large B-cell lymphoma (DLBCL). PET scans were done after
two cycles of anthracycline- and rituximab-based therapy, (R-CHOP21 or a
dose-dense regimen [R-ACVBP or R-CHOP14]. The median follow-up was 38 months
for living patients. Ten of 70 (14%) PET(-) patients showed progression, versus
22 of 42 (52%) PET(+) patients. The estimated five-year progression-free
survival (PFS) was 81 percent for PET(-) and 47 percent for PET(+) patients, a
highly significant difference. Prognostic value of interim PET was significant
in terms of PFS with all treatments. The estimated five-year overall survival
(OS) was 88 percent for PET(-) and 62 percent for PET(+) patients.
Meanwhile, an Italian group found
interim 18-FDG-PET/computed tomography (PET) failed to predict outcome in
patients with DLBCL treated with rituximab and CHOP (abstract #99). There was a correlation between interim PET
(PET-2) results and complete response (CR) rates. CR was 96 percent in
PET-2-negative patients compared to 74 percent in PET-2-positive patients
(p=.004). The median follow-up for patients was 18 months and PFS was 78
percent in both arms. PET-2 did not correlate with PFS (p=.198). However,
end-of-treatment PET (PET-3) strongly predicted PFS (p=.015). While PET-2 did
not predict PFS, LDH (p=.005) and International Prognostic Index (IPI) 0-2
versus 3-5 (p<.001) were confirmed as independent predictors of progression.
Early results of the German PETAL
trial (PET-guided therapy of Aggressive non-Hodgkin Lymphomas) were presented
during Sunday night’s poster session (#2695). The PETAL trial is for patients
with newly diagnosed aggressive non-Hodgkin lymphomas and a positive PET scan
before starting any lymphoma-directed therapy. Interim-PET is done after two
cycles of the CHOP protocol administered at a 14-day interval. Precautions were
taken to minimize the risk of false-positive interim-PET results by controlling
the timing of the PET, use of growth factor support after the second cycle, and
quantitative standard uptake value (SUV)-based assessment as described in an
article published in the Journal of Nuclear Medicine (Lin et al. 2007;
48:1626-32). Two hundred and sixty-six patients have been studied to date, and
the maximum SUV at staging and SUV reduction after two cycles of (R-) CHOP were
independent of the IPI.
Additional PET abstracts continue to be presented throughout
the meeting. The role of interim PET scanning in determining treatment outcomes
continues to be muddy … not unlike the possible results of kissing a frog in a
recent animated movie set in New
Orleans. Stay tuned to see how both of these stories
conclude.
Dr. Lechowicz indicated no relevant conflicts of
interest.
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