Is contrast material needed after treatment of malignant lymphoma in positron emission tomography/computed tomography?

The value of intravenous contrast medium in PSMA PET/CT imaging in patients with biochemical recurrence of prostate cancer

PURPOSE

To investigate the added value of diagnostic abdominal contrast-enhanced computed tomography (ceCT) in Ga-68 PSMA PET/CT in prostate cancer patients with biochemical recurrence (BCR).

METHODS

Eighty-two consecutive patients (median age, 69 years; range, 45-86 years) with BCR underwent Ga-68 PSMA PET/CT with low-dose nonenhanced (ne) whole-body CT and diagnostic ceCT. Imaging results were retrospectively reviewed by two readers (R1, R2) for diagnostic certainty, local recurrence, lymph node metastasis (LNM) and bone metastasis. Interobserver agreement was assessed. Histopathology served as reference standard in 7, imaging and clinical follow-up in 65 and clinical follow-up alone in 10 patients.

RESULTS

Certain local recurrence, LNM and bone metastasis diagnoses increased substantially from ceCT (R1: 5%/18%/32%; R2: 37%/50%/82%) to nePET/CT (R1: 78%/87%/93%; R2: 81%/87%/95%) for both readers, but the difference between nePET/CT and cePET/CT (R1: 77%/96%/92%; R2: 89%/94%/96%) was marginal. Interobserver agreement was minimal with ceCT (Krippendorff's alpha: 0.04-0.26), substantial with nePET/CT (0.60-0.86) and best with cePET/CT (0.76-0.86). The areas under the receiver operating characteristic curve (AUCs) for local recurrence for R1/R2 were 0.60/0.65 for ceCT, 0.81/0.79 for nePET/CT and 0.81/0.82 for cePET/CT. AUCs for LNMs for R1/R2 were 0.67/0.77 for ceCT, 0.91/0.82 for nePET/CT and 0.92/0.87 for cePET/CT. AUCs for BMs for R1/R2 were 0.60/0.53 for ceCT, 0.93/0.84 for nePET/CT and 0.93/0.86 for cePET/CT.

CONCLUSION

Diagnostic abdominal ceCT increases the diagnostic certainty and interobserver agreement in Ga-68 PSMA PET/CT in BCR of prostate cancer. The diagnostic performance of cePET/CT is significantly better than ceCT alone but not nePET/CT.

Limited benefit of additional contrast-enhanced CT to end-of-treatment PET/CT evaluation in patients with follicular lymphoma

Despite follicular lymphoma (FL) is frequently characterized by a moderate increase of glucose metabolism, PET/CT examinations provides valuable information for staging and response assessment of the disease. The aim of the study was to assess and compare the diagnostic performance of PET/ldCT and PET/ceCT, respectively, in evaluating FL patients at the end of treatment. Fifty FL consecutive patients who underwent end-of-therapy PET/CT with both ldCT and ceCT were analyzed. Two blinded observers independently assessed PET/ldCT and PET/ceCT applying the Deauville score (DS) and Lugano classification criteria. PET imaging obtained after the end-of-treatment (EoT) was classified as showing PET and ce-CT matched response (concordant imaging group, CIG) or PET and ce-CT unmatched response (discordant imaging group, DIG). Relapse rate and Event-Free Survival (EFS) were compared between CIG and DIG patients. Overall, no differences in metabolic response classification were observed between PET/ldCT and PET/ceCT. In 13 (26%) patients PET/ceCT identified additional FDG-negative nodal lesions in mesenteric, retroperitoneal and iliac regions. However, in all cases, final DS remained unchanged and the additional results did not modify the following therapeutic decision. Among patients, who obtained complete metabolic response a comparable rate of relapse was registered in DIG 3/13 (23%) and CIG subgroups 5/20 (25%) [p = 0.899]. In all 3 DIG cohort patients who relapsed the recurrent disease involved also, but not exclusively, PET negative lymph nodes detected by ceCT. In overall population metabolic response defined by PET/ldCT predicted EFS [76% (group of patients with metabolic response) vs 35% (group of patients with residual disease), p = 0.0013] significantly better than ceCT-Based response assessment [75% (group of patients with complete response) vs 53% (group of patients with residual disease), p = 0.06]. Our study demonstrates a negligible diagnostic and predictive value of ceCT performed in addition to standard ¹⁸FDG PET/ldCT for EoT response evaluation in FLs. PET/ldCT should be performed as first-line imaging procedure, also in patients with prevalent abdominal and pelvic involvement, limiting the acquisition of ceCT in selected cases. This tailored approach would contribute to avoid useless radiation exposure and preserve renal function of patients.

Role of multimodality imaging in the diagnosis of lymphoproliferative malignancies and hematologic disorders of the kidneys

Lymphoproliferative and hematologic disorders of the kidney may present with focal or diffuse renal parenchymal involvement in clinical practice. Radiologic findings of lymphoproliferative and hematologic disorders of the kidney may mimick primary neoplastic and inflammatory disorders of the kidney. All cross-sectional imaging modalities including ultrasonography, computed tomography, and magnetic resonance imaging may be used in the diagnosis of these diseases. Percutaneous biopsy may be used in problematic cases for definitive diagnosis.

Low-Dose PET/CT and Full-Dose Contrast-Enhanced CT at the Initial Staging of Localized Diffuse Large B-Cell Lymphomas

Computed tomography (CT) has been used as the reference imaging technique for the initial staging of diffuse large B-cell lymphoma until recent days, when the introduction of positron emission tomography (PET)/CT imaging as a hybrid technique has become of routine use. However, the performance of both examinations is still common. The aim of this work was to compare the findings between low-dose 2-deoxy-2-(¹⁸F)fluoro-d-glucose (¹⁸F-FDG) PET/CT and full-dose contrast-enhanced CT (ceCT) in 28 patients with localized diffuse large B-cell lymphoma according to PET/CT findings, in order to avoid the performance of ceCT. For each technique, a comparison in the number of nodal and extranodal involved regions was performed. PET/CT showed more lesions than ceCT in both nodal (41 vs. 36) and extranodal localizations (16 vs. 15). Disease staging according to both techniques was concordant in 22 patients (79%) and discordant in 6 patients (21%), changing treatment management in 3 patients (11%). PET/CT determined a better staging and therapeutic approach, making the performance of an additional ceCT unnecessary.

PET scan integration in lymphoma management

SUMMARY Despite a marked improvement in lymphoma treatment outcome, current prognostic models, relying on a pretreatment set of static clinical variables, appear unable to support a risk-adapted therapeutic strategy. On the other hand, functional imaging with 18F-fluoro-2-deoxy-D-glucose (FDG)-PET proved to be a reliable tool to dynamically assess tumor FDG uptake changes during and after treatment. In this article we aim to review the prognostic value of FDG-PET in all the stages of Hodgkin’s and non-Hodgkin’s lymphoma management, without the intent to address the diagnostic value of PET or to replace available consensus guidelines. In particular we focused on two critical issues: the cost–effectiveness of PET in the overall strategy of lymphoma diagnosis and treatment; and ongoing clinical trials adopting an interim PET-based strategy to modulate treatment intensity based on PET results. Finally, new trends in multimodality imaging, as well as in new radiopharmaceutical tracers, are briefly reviewed.

Role of [18F]-FDG-PET/MDCT in evaluating early response in patients with Hodgkin's lymphoma

PURPOSE

The authors evaluated the prognostic role of 18-fluoro-fluorodeoxyglucose positron emission tomography/multidetector computed tomography ([(18)F]-FDG PET/MDCT) in treating patients with Hodgkin's lymphoma (HL).

MATERIALS AND METHODS

We retrospectively evaluated 132 patients with HL studied with PET/MDCT before the start of chemotherapy (CTX) for staging purposes and again after two CTX cycles with [doxorubicin (Adriblastin), bleomycin, vinblastine, dacarbazine (ABVD_] (interim PET/MDCT), at least 30 days after the end of the last CTX cycle and/or 3 months after the end of radiotherapy, if delivered (final PET-MDCT).

RESULTS

Interim PET-MDCT was negative in 104/132 patients (79%), and their final PET-MDCT showed complete remission in 102/104 (98%) of cases, with disease recurrence/persistence in two (2%). In the remaining 28 (21%) patients, interim PET-MDCT revealed an early response in 68% of cases and chemoresistance with disease progression in 32% of cases; in these 28 patients, final PET-MDCT showed a lack of response to treatment in 43% of cases (43%) and complete remission in 57% of cases. Statistical analysis of these data showed that interim PET-MDCT had a negative predictive value of 98% and a positive predictive value of 42%, with values of sensitivity, specificity and diagnostic accuracy of 85.7%, 86.4% and 86.4%, respectively.

CONCLUSIONS

Interim PET-MDCT has a reliable prognostic role in diagnosis and treatment of patients with HL, as it helps predict which patients are more likely to achieve a complete response at the end of treatment. PET/MDCT may also lead to a change in treatment, with reduced treatment-related toxic effects and significantly reduced total costs.

Positron emission tomography/computed tomography surveillance in patients with Hodgkin lymphoma in first remission has a low positive predictive value and high costs

BACKGROUND

The value of performing post-therapy routine surveillance imaging in patients with Hodgkin lymphoma is controversial. This study evaluates the utility of positron emission tomography/computed tomography using 2-[18F]fluoro-2-deoxyglucose for this purpose and in situations with suspected lymphoma relapse.

DESIGN AND METHODS

We conducted a multicenter retrospective study. Patients with newly diagnosed Hodgkin lymphoma achieving at least a partial remission on first-line therapy were eligible if they received positron emission tomography/computed tomography surveillance during follow-up. Two types of imaging surveillance were analyzed: "routine" when patients showed no signs of relapse at referral to positron emission tomography/computed tomography, and "clinically indicated" when recurrence was suspected.

RESULTS

A total of 211 routine and 88 clinically indicated positron emission tomography/computed tomography studies were performed in 161 patients. In ten of 22 patients with recurrence of Hodgkin lymphoma, routine imaging surveillance was the primary tool for the diagnosis of the relapse. Extranodal disease, interim positron emission tomography-positive lesions and positron emission tomography activity at response evaluation were all associated with a positron emission tomography/computed tomography-diagnosed preclinical relapse. The true positive rates of routine and clinically indicated imaging were 5% and 13%, respectively (P = 0.02). The overall positive predictive value and negative predictive value of positron emission tomography/computed tomography were 28% and 100%, respectively. The estimated cost per routine imaging diagnosed relapse was US$ 50,778.

CONCLUSIONS

Negative positron emission tomography/computed tomography reliably rules out a relapse. The high false positive rate is, however, an important limitation and a confirmatory biopsy is mandatory for the diagnosis of a relapse. With no proven survival benefit for patients with a pre-clinically diagnosed relapse, the high costs and low positive predictive value make positron emission tomography/computed tomography unsuitable for routine surveillance of patients with Hodgkin lymphoma.