Advantages of positron emission tomography (PET) with respect to computed tomography in the follow-up of lymphoma patients with abdominal presentation

Interim PET-results for prognosis in adults with Hodgkin lymphoma: a systematic review and meta-analysis of prognostic factor studies

BACKGROUND

Hodgkin lymphoma (HL) is one of the most common haematological malignancies in young adults and, with cure rates of 90%, has become curable for the majority of individuals. Positron emission tomography (PET) is an imaging tool used to monitor a tumour's metabolic activity, stage and progression. Interim PET during chemotherapy has been posited as a prognostic factor in individuals with HL to distinguish between those with a poor prognosis and those with a better prognosis. This distinction is important to inform decision-making on the clinical pathway of individuals with HL.

OBJECTIVES

To determine whether in previously untreated adults with HL receiving first-line therapy, interim PET scan results can distinguish between those with a poor prognosis and those with a better prognosis, and thereby predict survival outcomes in each group.

SEARCH METHODS

We searched MEDLINE, Embase, CENTRAL and conference proceedings up until April 2019. We also searched one trial registry (ClinicalTrials.gov).

SELECTION CRITERIA

We included retrospective and prospective studies evaluating interim PET scans in a minimum of 10 individuals with HL (all stages) undergoing first-line therapy. Interim PET was defined as conducted during therapy (after one, two, three or four treatment cycles). The minimum follow-up period was at least 12 months. We excluded studies if the trial design allowed treatment modification based on the interim PET scan results.

DATA COLLECTION AND ANALYSIS

We developed a data extraction form according to the Checklist for Critical Appraisal and Data Extraction for Systematic Reviews of Prediction Modelling Studies (CHARMS). Two teams of two review authors independently screened the studies, extracted data on overall survival (OS), progression-free survival (PFS) and PET-associated adverse events (AEs), assessed risk of bias (per outcome) according to the Quality in Prognosis Studies (QUIPS) tool, and assessed the certainty of the evidence (GRADE). We contacted investigators to obtain missing information and data.

MAIN RESULTS

Our literature search yielded 11,277 results. In total, we included 23 studies (99 references) with 7335 newly-diagnosed individuals with classic HL (all stages). Participants in 16 studies underwent (interim) PET combined with computed tomography (PET-CT), compared to PET only in the remaining seven studies. The standard chemotherapy regimen included ABVD (16) studies, compared to BEACOPP or other regimens (seven studies). Most studies (N = 21) conducted interim PET scans after two cycles (PET2) of chemotherapy, although PET1, PET3 and PET4 were also reported in some studies. In the meta-analyses, we used PET2 data if available as we wanted to ensure homogeneity between studies. In most studies interim PET scan results were evaluated according to the Deauville 5-point scale (N = 12). Eight studies were not included in meta-analyses due to missing information and/or data; results were reported narratively. For the remaining studies, we pooled the unadjusted hazard ratio (HR). The timing of the outcome measurement was after two or three years (the median follow-up time ranged from 22 to 65 months) in the pooled studies. Eight studies explored the independent prognostic ability of interim PET by adjusting for other established prognostic factors (e.g. disease stage, B symptoms). We did not pool the results because the multivariable analyses adjusted for a different set of factors in each study. Overall survival Twelve (out of 23) studies reported OS. Six of these were assessed as low risk of bias in all of the first four domains of QUIPS (study participation, study attrition, prognostic factor measurement and outcome measurement). The other six studies were assessed as unclear, moderate or high risk of bias in at least one of these four domains. Four studies were assessed as low risk, and eight studies as high risk of bias for the domain other prognostic factors (covariates). Nine studies were assessed as low risk, and three studies as high risk of bias for the domain 'statistical analysis and reporting'. We pooled nine studies with 1802 participants. Participants with HL who have a negative interim PET scan result probably have a large advantage in OS compared to those with a positive interim PET scan result (unadjusted HR 5.09, 95% confidence interval (CI) 2.64 to 9.81, I² = 44%, moderate-certainty evidence). In absolute values, this means that 900 out of 1000 participants with a negative interim PET scan result will probably survive longer than three years compared to 585 (95% CI 356 to 757) out of 1000 participants with a positive result. Adjusted results from two studies also indicate an independent prognostic value of interim PET scan results (moderate-certainty evidence). Progression-free survival Twenty-one studies reported PFS. Eleven out of 21 were assessed as low risk of bias in the first four domains. The remaining were assessed as unclear, moderate or high risk of bias in at least one of the four domains. Eleven studies were assessed as low risk, and ten studies as high risk of bias for the domain other prognostic factors (covariates). Eight studies were assessed as high risk, thirteen as low risk of bias for statistical analysis and reporting. We pooled 14 studies with 2079 participants. Participants who have a negative interim PET scan result may have an advantage in PFS compared to those with a positive interim PET scan result, but the evidence is very uncertain (unadjusted HR 4.90, 95% CI 3.47 to 6.90, I² = 45%, very low-certainty evidence). This means that 850 out of 1000 participants with a negative interim PET scan result may be progression-free longer than three years compared to 451 (95% CI 326 to 569) out of 1000 participants with a positive result. Adjusted results (not pooled) from eight studies also indicate that there may be an independent prognostic value of interim PET scan results (low-certainty evidence). PET-associated adverse events No study measured PET-associated AEs.

AUTHORS' CONCLUSIONS

This review provides moderate-certainty evidence that interim PET scan results predict OS, and very low-certainty evidence that interim PET scan results predict progression-free survival in treated individuals with HL. This evidence is primarily based on unadjusted data. More studies are needed to test the adjusted prognostic ability of interim PET against established prognostic factors.

Interim PET-results for prognosis in adults with Hodgkin lymphoma: a systematic review and meta-analysis of prognostic factor studies

BACKGROUND

Hodgkin lymphoma (HL) is one of the most common haematological malignancies in young adults and, with cure rates of 90%, has become curable for the majority of individuals. Positron emission tomography (PET) is an imaging tool used to monitor a tumour's metabolic activity, stage and progression. Interim PET during chemotherapy has been posited as a prognostic factor in individuals with HL to distinguish between those with a poor prognosis and those with a better prognosis. This distinction is important to inform decision-making on the clinical pathway of individuals with HL.

OBJECTIVES

To determine whether in previously untreated adults with HL receiving first-line therapy, interim PET scan results can distinguish between those with a poor prognosis and those with a better prognosis, and thereby predict survival outcomes in each group.

SEARCH METHODS

We searched MEDLINE, Embase, CENTRAL and conference proceedings up until April 2019. We also searched one trial registry (ClinicalTrials.gov).

SELECTION CRITERIA

We included retrospective and prospective studies evaluating interim PET scans in a minimum of 10 individuals with HL (all stages) undergoing first-line therapy. Interim PET was defined as conducted during therapy (after one, two, three or four treatment cycles). The minimum follow-up period was at least 12 months. We excluded studies if the trial design allowed treatment modification based on the interim PET scan results.

DATA COLLECTION AND ANALYSIS

We developed a data extraction form according to the Checklist for Critical Appraisal and Data Extraction for Systematic Reviews of Prediction Modelling Studies (CHARMS). Two teams of two review authors independently screened the studies, extracted data on overall survival (OS), progression-free survival (PFS) and PET-associated adverse events (AEs), assessed risk of bias (per outcome) according to the Quality in Prognosis Studies (QUIPS) tool, and assessed the certainty of the evidence (GRADE). We contacted investigators to obtain missing information and data.

MAIN RESULTS

Our literature search yielded 11,277 results. In total, we included 23 studies (99 references) with 7335 newly-diagnosed individuals with classic HL (all stages).Participants in 16 studies underwent (interim) PET combined with computed tomography (PET-CT), compared to PET only in the remaining seven studies. The standard chemotherapy regimen included ABVD (16) studies, compared to BEACOPP or other regimens (seven studies). Most studies (N = 21) conducted interim PET scans after two cycles (PET2) of chemotherapy, although PET1, PET3 and PET4 were also reported in some studies. In the meta-analyses, we used PET2 data if available as we wanted to ensure homogeneity between studies. In most studies interim PET scan results were evaluated according to the Deauville 5-point scale (N = 12).Eight studies were not included in meta-analyses due to missing information and/or data; results were reported narratively. For the remaining studies, we pooled the unadjusted hazard ratio (HR). The timing of the outcome measurement was after two or three years (the median follow-up time ranged from 22 to 65 months) in the pooled studies.Eight studies explored the independent prognostic ability of interim PET by adjusting for other established prognostic factors (e.g. disease stage, B symptoms). We did not pool the results because the multivariable analyses adjusted for a different set of factors in each study.Overall survivalTwelve (out of 23) studies reported OS. Six of these were assessed as low risk of bias in all of the first four domains of QUIPS (study participation, study attrition, prognostic factor measurement and outcome measurement). The other six studies were assessed as unclear, moderate or high risk of bias in at least one of these four domains. Nine studies were assessed as high risk, and three studies as moderate risk of bias for the domain study confounding. Eight studies were assessed as low risk, and four studies as high risk of bias for the domain statistical analysis and reporting.We pooled nine studies with 1802 participants. Participants with HL who have a negative interim PET scan result probably have a large advantage in OS compared to those with a positive interim PET scan result (unadjusted HR 5.09, 95% confidence interval (CI) 2.64 to 9.81, I² = 44%, moderate-certainty evidence). In absolute values, this means that 900 out of 1000 participants with a negative interim PET scan result will probably survive longer than three years compared to 585 (95% CI 356 to 757) out of 1000 participants with a positive result.Adjusted results from two studies also indicate an independent prognostic value of interim PET scan results (moderate-certainty evidence).Progression-free survival Twenty-one studies reported PFS. Eleven out of 21 were assessed as low risk of bias in the first four domains. The remaining were assessed as unclear, moderate or high risk of bias in at least one of the four domains. Eleven studies were assessed as high risk, nine studies as moderate risk and one study as low risk of bias for study confounding. Eight studies were assessed as high risk, three as moderate risk and nine as low risk of bias for statistical analysis and reporting.We pooled 14 studies with 2079 participants. Participants who have a negative interim PET scan result may have an advantage in PFS compared to those with a positive interim PET scan result, but the evidence is very uncertain (unadjusted HR 4.90, 95% CI 3.47 to 6.90, I² = 45%, very low-certainty evidence). This means that 850 out of 1000 participants with a negative interim PET scan result may be progression-free longer than three years compared to 451 (95% CI 326 to 569) out of 1000 participants with a positive result.Adjusted results (not pooled) from eight studies also indicate that there may be an independent prognostic value of interim PET scan results (low-certainty evidence).PET-associated adverse eventsNo study measured PET-associated AEs.

AUTHORS' CONCLUSIONS

This review provides moderate-certainty evidence that interim PET scan results predict OS, and very low-certainty evidence that interim PET scan results predict progression-free survival in treated individuals with HL. This evidence is primarily based on unadjusted data. More studies are needed to test the adjusted prognostic ability of interim PET against established prognostic factors.

Primary colorectal non-Hodgkin's lymphoma in a retropositive patient

A 43-year-old man known case of retropositive illness presented with abdomen pain of 15 days and loose stools for 10 days. Loose stools were foul smelling and blood stained. The patient was a known case of type 2 diabetes and retroviral illness on highly active antiretroviral therapy (HAART). General physical examination was normal. On examination an irregular mass was palpable in the right iliac fossa and right flank. The mass was hard in nature; irregular with restricted mobility. There was no palpable liver or spleen. CT of the abdomen and pelvis revealed a well-defined heterogeneously enhancing hypodense mass lesion measuring 16 × 11.7 × 12 cm involving the ileocaecal region and extending medially and inferiorly to sigmoid colon and rectum. A colonoscopy showed a proliferative highly vascular mass 15 cm from anal verge at the rectosigmoid junction. Histopathology revealed sheets of neoplastic lymphoid cells in rectal wall suggestive of non-Hodgkins lymphoma.

Strikingly high false positivity of surveillance FDG-PET/CT scanning among patients with diffuse large cell lymphoma in the rituximab era

Predictive value (PV) of surveillance fluorodeoxyglucose positron emission tomography (FDG-PET) in patients with diffuse large B-cell lymphoma (DLBCL) treated with chemotherapy-rituximab (R) versus chemotherapy only, remains unclear. The aim of the current study was to compare the performance of surveillance PET in DLBCL patients receiving CHOP (cyclophosphamide, hydroxydaunorubicin hydrochloride, vincristine, and prednisone) alone versus CHOP-R. Institutional database was retrospectively searched for adults with newly diagnosed DLBCL, receiving CHOP or CHOP-R, who achieved complete remission and underwent surveillance PETs. Follow-up (FU) PET was considered positive for recurrence in case of an uptake unrelated to physiological or known benign process. Results were confirmed by biopsy, imaging and clinical FU. One hundred nineteen patients, 35 receiving CHOP and 84 CHOP-R, who underwent 422 FU-PETs, were analyzed. At a median PET-FU of 3.4 years, 31 patients relapsed (17 vs. 14, respectively; P = 0.02). PET detected all relapses, with no false-negative studies. Specificity and positive PV (PPV) were significantly lower for patients receiving CHOP-R vs. CHOP (84% vs. 87%, P = 0.023; 23% vs. 74%, P < 0.0001), reflecting a higher false-positive (FP) rate in subjects receiving CHOP-R (77% vs. 26%, P < 0.001). In the latter group, FP-rate remained persistently high up to 3 years post-therapy. Multivariate analysis confirmed rituximab to be the most significant predictor for FP-PET. In conclusion, routine surveillance FDG-PET is not recommended in DLBCL treated with rituximab; strict criteria identifying patients in whom FU-PET is beneficial are required.

Colorectal lymphoma

Extranodal lymphomas account for a third of all cases of non-Hodgkin lymphoma with the gastrointestinal tract being the most common extranodal site. The most common location is the stomach followed by the small intestine, colon and rectum. Colorectal lymphomas are rare and comprise 10-20% of all gastrointestinal lymphomas and only 1% of all colorectal malignancies. Presenting symptoms include abdominal pain, weight loss, and anorexia. Diagnosis depends on the clinical setting with elective cases being diagnosed with colonoscopy and emergent cases being diagnosed in the operating room. Colonic lymphomas are frequently located proximal to the hepatic flexure. Management depends on the aggressiveness of the lymphoma subtype. Indolent tumors, which are resistant to standard chemotherapeutic regimens, are treated with surgical resection. Aggressive lymphoma subtypes are managed with chemotherapy and surgery with late-stage disease patients being referred to clinical trials.

PET/CT for the staging and follow-up of patients with malignancies

Positron emission tomography (PET) and computed tomography (CT) complement each other's strengths in integrated PET/CT. PET is a highly sensitive modality to depict the whole-body distribution of positron-emitting biomarkers indicating tumour metabolic activity. However, conventional PET imaging is lacking detailed anatomical information to precisely localise pathologic findings. CT imaging can readily provide the required morphological data. Thus, integrated PET/CT represents an efficient tool for whole-body staging and functional assessment within one examination. Due to developments in system technology PET/CT devices are continually gaining spatial resolution and imaging speed. Whole-body imaging from the head to the upper thighs is accomplished in less than 20 min. Spatial resolution approaches 2-4mm. Most PET/CT studies in oncology are performed with (18)F-labelled fluoro-deoxy-D-glucose (FDG). FDG is a glucose analogue that is taken up and trapped within viable cells. An increased glycolytic activity is a characteristic in many types of cancers resulting in avid accumulation of FDG. These tumours excel as "hot spots" in FDG-PET/CT imaging. FDG-PET/CT proved to be of high diagnostic value in staging and restaging of different malignant diseases, such as colorectal cancer, lung cancer, breast cancer, head and neck cancer, malignant lymphomas, and many more. The standard whole-body coverage simplifies staging and speeds up decision processes to determine appropriate therapeutic strategies. Further development and implementation of new PET-tracers in clinical routine will continually increase the number of PET/CT indications. This promotes PET/CT as the imaging modality of choice for working-up of the most common tumour entities as well as some of the rare malignancies.

Role of [18F]Fluorodeoxyglucose Positron Emission Tomography Scan in the Follow-Up of Lymphoma

Purpose

In lymphoma, [18F]fluorodeoxyglucose positron emission tomography (FDG-PET) is routinely used for initial staging, early evaluation of treatment response, and identification of disease relapse. However, there are no prospective studies investigating the value of serial FDG-PET over time in patients in complete remission.

Patients and Methods

All patients with lymphoma who achieved the first complete remission were prospectively enrolled onto the study and scheduled for serial FDG-PET scans at 6, 12, 18, and 24 months; further scans were then carried out on an annual basis. Overall, the population included 421 patients (160 patients with Hodgkin's lymphoma [HL], 183 patients with aggressive non-Hodgkin's lymphoma [NHL], and 78 patients with indolent follicular NHL). All patients had a regular follow-up evaluation, including complete clinical and laboratory evaluation, and final assessment of any suspect FDG-PET findings using other imaging procedures (computed tomography [CT] scan) and/or biopsy and/or clinical evolution. FDG-PET findings were reported as positive for relapse, inconclusive (when equivocal), or negative for relapse.

Results

PET enabled documentation of lymphoma relapse in 41 cases at 6 months, in 30 cases at 12 months, in 26 cases at 18 months, in 10 cases at 24 months, and in 11 cases at more than 36 months. All 36 patients with inconclusive positive PET underwent biopsy; only 12 (33%) of 36 patients had a concomitant suggestion of positivity on CT. A lymphoma relapse was diagnosed in 24 (66%) of 36 patients.

Conclusion

Our results confirm FDG-PET as a valid tool for follow-up of patients with HL and NHL. In patients with inconclusive positive results, histologic confirmation plays an important role in identifying true relapse.

Imaging of pediatric lymphomas

Hodgkin lymphoma (HL) and non-Hodgkin lymphoma (NHL) represent 10% to 15% of all malignancies occurring in children younger than 20 years of age. Advances in cross-sectional imaging and the availability of positron emission tomography (PET) and PET-CT have had a major impact on imaging and management of pediatric patients. This article reviews the clinical features of lymphoma, focusing on the spectrum of imaging findings seen in diagnosis, staging, and follow-up of HL and NHL. Pediatric NHL has four major histologic subtypes: Burkitt lymphoma, diffuse large B-cell lymphoma, anaplastic large cell lymphoma, and lymphoblastic lymphoma. The most important subtype of HL is nodular sclerosis.

PET and PET/CT in management of the lymphomas

Within recent years, F-18 fluorodeoxyglucose (FDG) PET has become the most important nuclear medicine and radiology imaging modality in the management of lymphoma. FDG-PET detects more disease sites and involved organs than conventional staging procedures, including CT, and has a large influence on staging. FDG-PET performed during and after therapy seems to provide considerable prognostic information. The impact on patient outcome is not clear, however, because no controlled trials have yet been conducted and follow-up periods are generally short.

2-[18F]fluoro-2-deoxyglucose positron-emission tomography in staging, response evaluation, and treatment planning of lymphomas

2-[18F]fluoro-2-deoxyglucose positron-emission tomography (FDG-PET) is used increasingly in the clinical management of lymphomas. With regard to staging, FDG-PET is more sensitive and specific than conventional staging methods in FDG avid lymphomas (ie, Hodgkin lymphoma and most aggressive non-Hodgkin lymphomas). Despite methodological problems, in particular the lack of a valid reference test, FDG-PET is approved and generally used for this purpose. With regard to response evaluation, FDG-PET at the end of treatment seems to aid considerably in differentiating between residual masses with or without residual lymphoma. Hence, new revised response criteria have been proposed, incorporating the result of FDG-PET at the end of treatment. An early interim FDG-PET scan after 1 to 3 cycles of chemotherapy is a very strong predictor of outcome, and trials are now in progress testing treatment modifications on this basis. With regard to treatment planning, in the context of combined-modality therapy, radiotherapy for lymphomas is moving toward more conformal techniques reducing the irradiated volume to include only the macroscopic lymphoma. In this situation, accurate imaging is essential, and FDG-PET coregistered with the planning computed tomography (CT) scan is used increasingly. The availability of PET/CT scanners suited for virtual simulation has aided this process. However, clinical data evaluating this technique are at present sparse.

The role of FDG PET in the management of lymphoma: what is the evidence base?

[18F]Fluorodeoxyglucose positron emission tomography (18F-FDG PET) is playing an increasing role in the management of both Hodgkin and non-Hodgkin lymphoma, offering potential advantages in the accuracy of disease assessment at a number of points in the management pathway. This review evaluates the current level of confidence in the use of PET technology in (1) initial staging, (2) the assessment of early response to chemotherapy, (3) the assessment of residual masses at completion of initial treatment, (4) follow-up, and (5) radiotherapy planning.

[Post-treatment surveillance for potentially curable malignancies]

Through an enormous research effort over the past five decades and especially due to early screening, an increasing number of cancers are potentially curable. Patients expand immeasurable energy in adhering to treatment plans and supportive care. Unfortunately, nothing prepares them for the anxiety that often comes with completion of therapy. More importantly, physicians are not properly equipped with data from controlled trials to define appropriate post-treatment surveillance, data with which they could educate patients and allay their fears. The goal of post-treatment surveillance is to enable the early detection of relapses and thus enhance the possibility of subsequent cure. Accordingly special follow-up is appropriate only for patients who can receive a second-line therapy. Clinical trials support conservative, rather than aggressive, surveillance to detect curable local relapse of breast tumors and potentially surgically curable metastases (mainly in the liver) of colon cancer. For germ-cell tumors, second-line treatments are potentially curative in nearly all instances. Follow-up for other cancers depends on patients' anxiety levels and on the costs of surveillance.

Use of FDG-PET to monitor response to chemotherapy and radiotherapy in patients with lymphomas

Lymphoma is a heterogeneous group of diseases with many curable subtypes. Primary treatment cures a significant proportion of, but not all, patients. Patients not achieving a complete remission with primary treatment, or those who relapse later, have a second chance of cure with high-dose chemotherapy and haematopoietic stem cell transplantation. Response assessment is therefore crucial in the management of lymphomas. FDG-PET has an emerging role in assessing response, both at the end of and during treatment. This article will review the current published evidence and offer some suggestions on future directions from a clinician's viewpoint.

Early positron emission tomography (PET) restaging: a predictive final response in Hodgkin's disease patients

BACKGROUND

It is important to distinguish between responders to standard treatment and non-responders Hodgkin's disease (HD) patients.

PATIENTS AND METHODS

Between June 2003-September 2004, in our institute, 40 newly-diagnosed patients with advanced stage HD were consecutively treated with ABVD chemotherapy for six cycles. All these patients underwent staging/restaging: computed tomography (CT) and positron emission tomography (PET) at time 0, PET after two cycles, CT and PET after four and six cycles.

RESULTS

After two cycles (PET-2), the PET was negative in 28/40 (70%), positive in 8/40 (20%), and minimal residual uptake (MRU) was present in the remaining four (10%) patients. After treatment, among eight patients who were PET-2+, seven showed refractory disease and one had relapse after 3 months. All four patients with MRU at the PET-2 became PET- during the further four cycles and, after treatment, three were in complete response (CR) and one relapsed after 5 months. All 28 PET negative patients at the PET-2 remained PET negative and all of them were in CR after treatment.

CONCLUSIONS

The PET use for early (after two cycles) response assessment in HD patients is a significant step forward and has the potential to help physicians make crucial decisions about further treatment.

A metaanalysis of 18F-2-deoxy-2-fluoro-D-glucose positron emission tomography in the staging and restaging of patients with lymphoma

BACKGROUND

In recent years, the use of positron emission tomography (PET) has become widespread for the staging and follow-up of several malignancies. In the current study, the authors conducted a metaanalysis of the published literature to evaluate the diagnostic performance of 18F-2-deoxy-2-fluoro-D-glucose PET (FDG-PET) in the staging of patients with lymphoma.

METHODS

The authors conducted a systematic MEDLINE search of articles published between January 1995 and June 2004. Studies that evaluated FDG-PET with a dedicated camera and that reported sufficient data to permit the calculation of sensitivity and specificity were included in the analysis. Two reviewers independently reviewed the eligibility of the studies and abstracted data (sample population; characteristics of FDG-PET; and the number of true-positive results, true-negative results, false-positive results, and false-negative results). The authors estimated the pooled sensitivity, false-positive rate, and maximum joint sensitivity and specificity.

RESULTS

Twenty studies were eligible for the metaanalysis. Fourteen studies included patient-based data, comprising a sample size of 854 subjects, and 7 studies included lesion-based data, totaling 3658 lesions. Among those studies with patient-based data, the median sensitivity was 90.3% and the median specificity was 91.1%. The pooled sensitivity was 90.9% (95% confidence interval [95% CI], 88.0-93.4) and the pooled false-positive rate was 10.3% (95% CI, 7.4-13.8). The maximum joint sensitivity and specificity was 87.8% (95% CI, 85.0-90.7). The pooled sensitivity and false-positive rate appeared to be higher in patients with Hodgkin disease compared with those with non-Hodgkin lymphoma.

CONCLUSIONS

The results of the current study indicate that FDG-PET is a valuable tool for the staging and restaging of patients with lymphoma; showing a high positivity and specifity. Clinicians may consider adding FDG-PET to the staging workup of patients with lymphoma.

Lymphoma: Diagnosis, staging, natural history, and treatment strategies

Non-Hodgkin's lymphoma (NHL) is not a single disease, but a group of closely related B- and T-cell cancers of the lymphatic system. The incidence of NHL is rising, particularly in the countries of the industrialized world. The increased incidence is poorly understood, but several risk factors have been postulated to be associated with NHL, including: exposure to chemicals, viral infections, organ transplantation and blood transfusion, family history, and lifestyle factors. Precise staging of NHL is a prerequisite for the selection of a suitable therapeutic regimen and influences the likelihood of its success. Staging of lymphoma is traditionally conducted using tumor biopsy, imaging (X-ray, computerized tomography [CT], magnetic resonance imaging, lymphangiogram, gallium scan using 67 Ga citrate single photon emission CT [ 67 Ga-SPECT], or positron emission tomography), blood tests, bone marrow examination, and examination of cerebrospinal fluid. CT is the most commonly used imaging technique, but several studies indicate that other techniques, such as 67 Ga-SPECT, are more sensitive and better predictors of response. Low- and high-grade lymphomas differ markedly in prognosis and response to treatment. The management of NHL has been characterized by the increasing recognition that distinct subgroups of NHL respond differently to various therapeutic approaches. In follicular lymphoma (FL), a successful approach has been to combine fludarabine with mitoxantrone (FM), resulting in an overall response rate of 89% (67% complete remission). In an ongoing phase III trial in patients with untreated, advanced, low-grade follicular lymphoma, FM was compared with CHOP (cyclophosphamide/doxorubicin/vincristine/prednisone) with or without rituximab. Patients previously treated with FM achieved a significantly better complete remission rate (67% v 38%; P = .0013) and a better molecular remission (36% v 20%; P = .049) than patients previously treated with CHOP. Following rituximab treatment, 88% of patients who had received FM achieved clinical and molecular remission compared with 70% who had received CHOP. Strategies using various chemotherapy combinations, including innovative agents such as 90 Y-ibritumomab tiuxetan, show promise in the treatment of NHL, particularly indolent NHL, and hopefully will lead to an improvement in prognosis.

Predictive role of positron emission tomography (PET) in the outcome of lymphoma patients

An extensive analysis of the reliability of positron emission tomography (PET) after induction treatment in patients with Hodgkin's disease (HD) or aggressive non-Hodgkin's lymphoma (NHL). In all, 75 untreated patients with HD (n=41) or aggressive NHL (n=34) were studied with both PET and CT scans following standard chemotherapy induction therapy (ABVD or MACOP-B) with/without radiotherapy. Histopathological analysis was performed when considered necessary. After treatment, four out of five (80%) patients who were PET⁺/CT⁻ relapsed, as compared with zero out of 29 patients in the PET⁻/CT⁻ subset. Among the 41 CT⁺ patients, 10 out of 11 (91%) who were PET⁺ relapsed, as compared with 0 out of 30 who were PET⁻. The actuarial relapse-free survival (RFS) rates were 9 and 100% in the PET⁺ and PET⁻ subsets, respectively (P=0.00001). All five patients who were PET⁺/CT⁻ underwent a lymph node biopsy: in four (80%) cases, persistent lymphoma and was confirmed at histopathological examination. Two HD patients who were PET⁻/CT⁺ (with large residual masses in the mediastinum or lung) were submitted to biopsy, which in both cases revealed only fibrosis. In HD and aggressive NHL patients, PET positivity after induction treatment is highly predictive for the presence of residual disease, with significant differences being observable in terms of RFS. PET negativity at restaging strongly suggests the absence of active disease; histopathological verification is important in patients who show PET positivity.

FDG-PET in the clinical management of Hodgkin lymphoma

Positron emission tomography (PET) is a molecular functional imaging technique that provides qualitative and quantitative information about the localization and activity of pathophysiological processes. The most commonly used tracer for oncological purposes is 2-[18F]fluoro-2-deoxy-d-glucose (FDG). FDG-PET has within recent years become the most important nuclear medicine imaging modality in the management of lymphoma. This review summarizes the data published so far concerning the value of FDG-PET in staging, treatment monitoring, therapy planning, and follow-up of Hodgkin lymphoma (HL). FDG-PET detects more disease sites and involved organs than conventional staging procedures including computerized tomography (CT) and has a large influence on staging. FDG-PET during and after therapy appears to provide considerable prognostic information. However, the impact on patient outcome is not clear since no controlled trials are conducted and follow-up periods are generally short. The value of dual-modality PET/CT and its potential role in the radiotherapy planning is discussed.