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.

Controversies in the Approach to Initial Therapy of Hodgkin Lymphoma

PURPOSE OF REVIEW

Availability of highly effective novel agents has altered the approach to initial therapy in patients with classical Hodgkin lymphoma (cHL). We will review controversies in the following areas: (1) the role of radiation in early unfavorable disease and the optimal treatment strategies for (2) advanced-stage disease and (3) elderly patients.

RECENT FINDINGS

Strategies incorporating brentuximab vedotin into frontline treatment of cHL yielded favorable results in non-randomized elderly studies and were compared to ABVD in advanced disease among adults. Meanwhile, four cycles of escalated BEACOPP yielded unprecedented favorable results for the treatment of advanced disease in the German Hodgkin Study Group 18 study. The addition of novel agents to conventional treatment strategies has the potential to improve outcomes in high-risk groups of patients while reducing toxicity. The role of radiation therapy remains in question but may see diminished use with the incorporation of more effective agents in the frontline setting.

Positron emission tomography-adapted therapy for first-line treatment in individuals with Hodgkin lymphoma

BACKGROUND

Hodgkin lymphoma (HL) is a B-cell lymphoma accounting for 10% to 15% of all lymphoma in industrialised countries. It has a bimodal age distribution with one peak around the age of 30 years and another after the age of 60 years. Although HL accounts for fewer than 1% of all neoplasms worldwide, it is considered to be one of the most common malignancies in young adults and, with cure rates of 90%, one of the most curable cancers worldwide. Current treatment options for HL comprise more- or less-intensified regimens of chemotherapy plus radiotherapy, depending on disease stage. [18F]-fluorodeoxy-D-glucose (FDG)-positron emission tomography (PET, also called PET scanning) is an imaging tool that can be used to illustrate a tumour's metabolic activity, stage and progression. Therefore, it could be used as a standard interim procedure during HL treatment, to help distinguish between individuals who are good or poor early responders to therapy. Subsequent therapy could then be de-escalated in PET-negative individuals (good responders) or escalated in those who are PET-positive (poor responders). It is currently unknown whether such response-adapted therapeutic strategies are of benefit to individuals in terms of overall and progression-free survival, and the incidence of long-term adverse events (AEs).

OBJECTIVES

To assess the effects of interim [18F]-FDG-PET imaging treatment modification in individuals with HL.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL; latest issue) and MEDLINE (from 1990 to September 2014) as well as conference proceedings (American Society of Hematology; American Society of Clinical Oncology; European Hematology Association; and International Symposium on Hodgkin Lymphoma) for studies. Two review authors independently screened search results.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) comparing FDG-PET-adapted therapy with non-adapted treatment in individuals with previously untreated HL of all stages and ages.

DATA COLLECTION AND ANALYSIS

Two review authors independently extracted data and assessed the quality of trials. As none of the included studies provided HRs for OS, we described risk ratios (RRs) for this outcome and did not pool the data. As an effect measure we used hazard ratios (HRs) for progression-free survival (PFS). We described RRs for the dichotomous data on AEs. We also calculated 95% confidence intervals (CIs).

MAIN RESULTS

Our search strategies led to 308 potentially relevant references. From these, we included three studies involving 1999 participants. We judged the overall potential risk of bias as moderate. The studies were reported as RCTs; blinding was not reported, but given the study design it is likely that there was no blinding. One study was published in abstract form only; hence, detailed assessment of the risk of bias was not possible.Two trials compared standard treatment (chemotherapy plus radiotherapy) with PET-adapted therapy (chemotherapy only) in individuals with early-stage HL and negative PET scans. The study design of the third trial was more complex. Participants with early-stage HL were divided into those with a favourable or unfavourable prognosis. They were then randomised to receive PET-adapted or standard treatment. Following a PET scan, participants were further divided into PET-positive and PET-negative groups. To date, data have been published for the PET-negative arms only, making it possible to perform a meta-analysis including all three trials.Of the 1999 participants included in the three trials only 1480 were analysed. The 519 excluded participants were either PET-positive, or were excluded because they did not match the inclusion criteria.One study reported no deaths. The other two studies reported two deaths in participants receiving PET-adapted therapy and two in participants receiving standard therapy (very-low-quality evidence). Progression-free survival was shorter in participants with PET-adapted therapy (without radiotherapy) than in those receiving standard treatment with radiotherapy (HR 2.38; 95% CI 1.62 to 3.50; P value < 0.0001). This difference was also apparent in comparisons of participants receiving no additional radiotherapy (PET-adapted therapy) versus radiotherapy (standard therapy) (HR 1.86; 95% CI 1.07 to 3.23; P value = 0.03) and in those receiving chemotherapy but no radiotherapy (PET-adapted therapy) versus standard radiotherapy (HR 3.00; 95% CI 1.75 to 5.14; P value < 0.0001) (moderate-quality evidence). Short-term AEs only were assessed in one trial, which showed no evidence of a difference between the treatment arms (RR 0.91; 95% CI 0.54 to 1.53; P value = 0.72) (very-low-quality evidence). No data on long-term AEs were reported in any of the trials.

AUTHORS' CONCLUSIONS

To date, no robust data on OS, response rate, TRM, QoL, or short- and long-term AEs are available. However, this systematic review found moderate-quality evidence that PFS was shorter in individuals with early-stage HL and a negative PET scan receiving chemotherapy only (PET-adapted therapy) than in those receiving additional radiotherapy (standard therapy). More RCTs with longer follow ups may lead to more precise results for AEs, TRM and QoL, and could evaluate whether this PFS advantage will translate into an overall survival benefit.It is still uncertain whether PET-positive individuals benefit from PET-based treatment adaptation and the effect of such an approach in those with advanced HL.