Updating Perspectives on Meta-Analyses in the Field of Radiation Oncology

Local Treatment of Hepatocellular Carcinoma with Oligometastases: A Systematic Review and Meta-Analysis

Although recent studies have shown favorable results after local treatment for oligometastases, the clinical decision of applying local treatment for oligometastatic hepatocellular carcinoma (HCC) remains controversial. This meta-analysis aimed to investigate the benefits of local treatment for HCC oligometastases. Pubmed, Embase, Medline, and the Cochrane library were searched for studies until 1 May 2022. Clinical studies involving at least five cases of HCC oligometsatases treated with local modalities were included. The primary endpoint was overall survival (OS). The benefit of local treatment was assessed as the pooled odds ratio (OR) among comparative series, and the pooled OS percentile was calculated from all studies including patients treated with local treatment. Complications of grade ≥ 3 were assessed subjectively. A total of 10 studies involving 527 patients were included. Radiotherapy and radiofrequency ablation (RFA) were mainly performed (six and five studies) as local modalities treating oligometastases. Pooled OR of comparative series favored the use of local treatment (4.664, 95% confidence interval [CI]: 2.595-8.380, p < 0.001, I²: ~0.0%). Including all cohorts with patients who underwent local treatment, pooled rates of 1-year OS were 71.8% (95% CI: 59.0-81.9; I² = 81.5%), and pooled 2-year OS were 43.3% (95% CI: 29.1-59.6; I² = 85.4%). Except for temporal or pre-existing toxicities, grade ≤ 3 complications were reported less than 10% in most studies, although common toxicities include pneumothorax and hematologic deficiency after RFA and radiotherapy, respectively. Grade 5 toxicity has not yet been reported. This systematic review supports the application of local treatment for treating HCC oligometastases.

Role of Local Treatment for Oligometastasis: A Comparability-Based Meta-Analysis

PURPOSE

We intend to investigate the oncological efficacy and feasibility of local consolidative therapy (LCT) through a meta-analysis method.

MATERIALS AND METHODS

Four databases including PubMed, MEDLINE, Embase, and Cochrane library were searched. Target studies are controlled trials comparing outcomes of LCT versus a control group. Primary endpoints are overall survival (OS) and progression-free survival (PFS).

RESULTS

A total of 54 studies involving 7,242 patients were included. Pooled analyses showed that the LCT arm could achieve improved OS with pooled odds ratio of 2.896 (95% confidence interval [CI], 2.377 to 3.528; p < 0.001). Regarding PFS, pooled analyses showed pooled odds ratio of 3.045 (95% CI, 2.356 to 3.937; p < 0.001) in favor of the LCT arm. In the subgroup analyses including the studies with reliable comparability (e.g. randomized studies or intentionally matched studies without significant favorable prognosticator in LCT arms), pooled odds ratio was 2.548 (95% CI, 1.808 to 3.591; p < 0.001) favoring the LCT arm regarding OS. Regarding PFS, pooled OR was 2.656 (95% CI, 1.713 to 4.120; p < 0.001) which also favored the LCT arm. Subgroup analyses limited to the randomized controlled trials (RCT) were also performed and pooled odds ratios on OS and PFS were 1.535 (95% CI, 1.082 to 2.177; p=0.016) and 1.668 (95% CI, 1.187 to 2.344; p=0.003). The rates of grade ≥ 3 complications related to LCT was mostly low (< 10%) and not significantly higher compared to the control arm.

CONCLUSION

Pooled analyses results of all included studies, selected studies with reliable comparability, and RCT's demonstrated the survival benefit of LCT. These consistent results suggest that LCT was beneficial to the patients with oligometastasis.

Comparison of radiofrequency ablation and ablative external radiotherapy for the treatment of intrahepatic malignancies: A hybrid meta-analysis

Background & Aims

Radiofrequency ablation (RFA) and ablative external beam radiotherapy (ablative RT) are commonly used to treat small intrahepatic malignancies. We meta-analysed oncologic outcomes and systematically reviewed the clinical consideration of tumour location and size.

Methods

PubMed, Medline, Embase, and Cochrane Library databases were searched on February 24, 2022. Studies comparing RFA and ablative RT, providing one of the endpoints (local control or survival), and encompassing ≥5 patients in each arm were included.

Results

Twenty-one studies involving 4,638 patients were included. Regarding survival, the odds ratio (OR) was 1.204 (p = 0.194, favouring RFA, not statistically significant) among all studies, 1.253 (p = 0.153) among hepatocellular carcinoma (HCC) studies, and 1.002 (p = 0.996) among colorectal cancer metastasis studies. Regarding local control, the OR was 0.458 (p <0.001, favouring ablative RT) among all studies, 0.452 (p <0.001) among HCC studies, favouring the ablative RT arm, and 0.649 (p = 0.484) among colorectal cancer metastasis studies. Pooled 1- and 2-year survival rates for HCC studies were 91.8% and 77.7% after RFA, and 89.0% and 76.0% after ablative RT, respectively; and for metastasis studies were 88.2% and 66.4% after RFA and 82.7% and 60.6% after RT, respectively. Literature analysis suggests that ablative RT can be more effective than RFA for tumours larger than 2-3 cm or for specific sublocations in the liver (e.g. subphrenic or perivascular sites), with moderate quality of evidence (reference to the grading system of the American Society for Radiation Oncology Primary Liver Cancer Clinical Guidelines). The pooled grade ≥3 complication rates were 2.9% and 2.8% in the RFA and ablative RT arms, respectively (p = 0.952).

Conclusions

Our study shows that ablative RT can yield oncologic outcomes similar to RFA, and suggests that it can be more effective for the treatment of tumours in locations where RFA is difficult to perform or for large-sized tumours.

Systematic Review Registration

This study was registered with PROSPERO (Protocol No: CRD42022332997).

Impact and implications

Radiofrequency ablation (RFA) and ablative radiotherapy (RT) are non-surgical modalities for the treatment of small intrahepatic malignancies. Ablative RT showed oncologic outcomes at least similar to those of RFA, and was more effective at specific locations (e.g. perivascular or subphrenic locations).

Clinical efficacy and safety of external radiotherapy combined with sorafenib in the treatment of hepatocellular carcinoma: a systematic review and meta-analysis

INTRODUCTION AND OBJECTIVES

Both external radiotherapy and sorafenib are promising treatments for hepatocellular carcinoma (HCC). Nevertheless, the combined treatment of external radiotherapy and sorafenib has not been widely applied clinically due to potentially adverse effects. This meta-analysis aimed to evaluate the clinical efficacy and safety of external radiotherapy combined with sorafenib in the treatment of HCC.

METHODS

Pubmed, MEDLINE, EMBASE, Cochrane Library, and Web of Science databases were searched. The primary and secondary observation endpoints were the end of survival and incidence of adverse events, respectively. 11 studies involving 664 patients were included in this meta-analysis.

RESULTS

The results demonstrated that median overall survival (mOS) and median progression-free survival (mPFS) of the external radiotherapy combined with sorafenib (RS) group were 19.45 months and 8.20 months. The one- and two-year survival rates were 0.65 (95%CI: 0.55-0.76) and 0.40 (95%CI: 0.24-0.56). The incidence of adverse events was 0.34 (95%CI: 0.25-0.44).

CONCLUSIONS

The findings demonstrated that the survival of the RS group was significantly improved and few severe adverse events were observed. Hence, it can be concluded that external radiotherapy combined with sorafenib is a safe, effective, and promising therapeutic option for HCC.

Radiotherapy for bone metastases of hepatocellular carcinoma: a hybrid systematic review with meta-analyses

INTRODUCTION

External beam radiation therapy (EBRT) is commonly used as a palliative treatment for bone metastases of hepatocellular carcinoma (HCC). We planned a hybrid systematic review that meta-analyzed the efficacy and feasibility of EBRT and reviewed the literature to answer specific clinical questions.

METHODS

The PubMed, Medline, Embase, and Cochrane Library databases were searched through 1 December 2021. Primary endpoints were overall survival (OS) and response rate (RR). Secondary endpoints were comparative data, including treatment response and survival related to dose escalation, number of metastases, and fractionation scheme. Formal pooled analyses were performed on the primary endpoints, and the secondary endpoints were systematically reviewed. Complications were also reviewed.

RESULTS

Nineteen studies involving 1613 patients with HCC and bone metastases were included. The median OS was 6 months (range: 3-13 months). The pooled one-year OS was 23.1% (95% confidence interval [CI]: 18.4-28.6); pooled pain RR was 81.5% (95% CI: 76.4-85.7) and of pain complete remission was 26.5% (95% CI: 21.7-32.0). Pain response might be related to dose escalation, considering the moderate consistency of results and plausibility, with a low-quality grade of evidence^†. Considering the indeterminate results, we cannot suggest that dose escalation is correlated with OS. The oligometastasis status might be related to better OS, considering the high consistency of results and plausibility with low to moderate quality of evidence. Hypofractionated EBRT might yield comparable efficacy to conventional EBRT, with a low-quality grade of evidence. There were few complications of grade ≥3, except for hematologic complications, which ranged from 11.5to 34%.

CONCLUSION

EBRT is an efficient and feasible palliative option. Clinical consideration of hematologic complications is necessary. Future studies are needed to increase the quality of evidence for actual clinical questions. ^†Reference to a system of the American Society for Radiation Oncology primary liver cancer clinical guidelines.

Benefit of adjuvant radiotherapy for gallbladder cancer: a comparability-based meta-analysis

BACKGROUND AND PURPOSE

The benefits of adjuvant radiotherapy (ART) in gallbladder cancer (GBC) treatment remain inconclusive owing to the rarity of GBC and lack of randomized studies.

METHODS

PubMed, Medline, Embase, and Cochrane Library were systematically searched until March 2021. The primary endpoint was overall survival (OS). Comparative clinical studies that reported survival outcomes in GBC patients treated with or without ART were included. The comparability of each study was assessed by considering all possible clinical indicators (group 2: ART arm with poor clinical profile; group 1: ART arm with statistically similar profile or no evidence of having inferior clinical factors compared to non-ART arm).

RESULTS

Twenty-one studies involving 6876 GBC patients were reviewed. In pooled analyses of OS, the odds ratio (OR) was 1.26 (p = 0.111) neither favoring ART or non-ART arms. In subgroup analyses considering comparability, the OR significantly favored the ART arm (1.92, p = 0.008) among comparability group 1 studies, whereas it was 1.03 (p = 0.865) in comparability group 2 studies. The pooled rate of 5-year OS in the ART vs. non-ART arms was 44.9% vs. 20.9% in group 1 and 34.1% vs. 40.0% in group 2. With ART, significant reduction in locoregional recurrence (OR 0.21, p = 0.001) but not in distant metastasis (OR 1.32, p = 0.332) was noted.

CONCLUSION

ART not only showed benefits in patients with a similar clinical profile to those treated without ART but also yielded comparable survival in patients with an inferior clinical profile. Our results suggest the more active application of ART in GBC treatment.

PROTOCOL REGISTRATION

This study is registered in PROSPERO (CRD42021240624, available at: https://www.crd.york.ac.uk/ ).

Comparison of External Beam Radiation Therapy Modalities for Hepatocellular Carcinoma With Macrovascular Invasion: A Meta-Analysis and Systematic Review

Purpose

We performed a systematic review and meta-analysis to compare external beam radiation therapy modalities for hepatocellular carcinoma (HCC) with macrovascular invasion (MVI).

Methods

Studies were selected from online databases from the date of inception to November 2021. The outcomes of interest were overall survival (OS), objective response rate (ORR), and local control rate (LCR).

Results

Forty-four studies (n = 3730) were selected from 1050 articles. The pooled 1-year OS were 60.9%, 45.3%, and 44.9 for particle radiotherapy (PRT) group, conventional radiotherapy (CRT), and stereotactic body radiotherapy (SBRT) group, respectively; p = 0.005 and 0.002 for PRT vs. CRT and SBRT, respectively. Both the PRT group and the SBRT group have the advantage over the CRT group in the pooled ORR. The PRT group showed significantly higher than the CRT group (p = 0.007) in LCR. For combination therapy, CRT plus transarterial chemoembolization can prolong survival than CRT alone (p = 0.006 for 1-year OS; p = 0.014 for 2-year OS). Among grade ≥ 3 complications, the most frequent type of toxicity in CRT, SBRT, PRT group was hematological toxicity, hepatotoxicity, dermatological toxicity, respectively.

Conclusions

Among patients with HCC with MVI, the 1-year OS and the 2-year OS were both higher in the PRT group than in the CRT, SBRT groups. The ORR was similar between the PRT and SBRT groups. The combination therapy based on radiotherapy is expectable. PRT is associated with less complications than photon radiotherapy.

Salvage External Beam Radiotherapy after Incomplete Transarterial Chemoembolization for Hepatocellular Carcinoma: A Meta-Analysis and Systematic Review

Background and objective: Although transarterial chemoembolization (TACE) has been the commonest local modality for hepatocellular carcinoma (HCC), incomplete repsonse occurs especially for tumors with a large size or difficult tumor accessment. The present meta-analysis assessed the efficacy and feasibility of external beam radiotherapy (EBRT) as a salvage modality after incomplete TACE. Materials and Methods: We systematically searched the PubMed, Embase, Medline, and Cochrane databases. The primary endpoint was overall survival (OS), and the secondary endpoints included the response ratem toxicity of grade 3, and local control. Results: Twelve studies involving 757 patients were included; the median of portal vein thrombosis rate was 25%, and the pooled median of tumor size was 5.8 cm. The median prescribed dose ranged from 37.3 to 150 Gy (pooled median: 54 Gy in *EQD2). The pooled one- and two-year OS rates were 72.3% (95% confidence interval (CI): 60.2-81.9%) and 50.5% (95% CI: 35.6-65.4%), respectively; the pooled response and local control rates were 72.2% (95% CI: 65.4-78.1%) and 86.6 (95% CI: 80.1-91.2%) respectively. The pooled rates of grade ≥3 gastrointestinal toxicity, radiation-induced liver disease, hepatotoxicity, and hematotoxicity were 4.1%, 3.5%, 5.7%, and 4.9%, respectively. Local control was not correlated with intrahepatic (p = 0.6341) or extrahepatic recurrences (p = 0.8529) on meta-regression analyses. Conclusion: EBRT was feasible and efficient in regard to tumor response and control; after incomplete TACE. Out-field recurrence, despite favorable local control, necessitates the combination of EBRT with systemic treatments. *Equivalent dose in 2 Gy per fraction scheme.

Stepwise-Hierarchical Pooled Analysis for Synergistic Interpretation of Meta-analyses Involving Randomized and Observational Studies: Methodology Development

Background

The necessity of including observational studies in meta-analyses has been discussed in the literature, but a synergistic analysis method for combining randomized and observational studies has not been reported. Observational studies differ in validity depending on the degree of the confounders’ influence. Combining interpretations may be challenging, especially if the statistical directions are similar but the magnitude of the pooled results are different between randomized and observational studies (the ”gray zone”).

Objective

To overcome these hindrances, in this study, we aim to introduce a logical method for clinical interpretation of randomized and observational studies.

Methods

We designed a stepwise-hierarchical pooled analysis method to analyze both distribution trends and individual pooled results by dividing the included studies into at least three stages (eg, all studies, balanced studies, and randomized studies).

Results

According to the model, the validity of a hypothesis is mostly based on the pooled results of randomized studies (the highest stage). Ascending patterns in which effect size and statistical significance increase gradually with stage strengthen the validity of the hypothesis; in this case, the effect size of the observational studies is lower than that of the true effect (eg, because of the uncontrolled effect of negative confounders). Descending patterns in which decreasing effect size and statistical significance gradually weaken the validity of the hypothesis suggest that the effect size and statistical significance of the observational studies is larger than the true effect (eg, because of researchers’ bias).

Conclusions

We recommend using the stepwise-hierarchical pooled analysis approach for meta-analyses involving randomized and observational studies.

Adjuvant Radiotherapy for Extrahepatic Cholangiocarcinoma: A Quality Assessment-Based Meta-Analysis

INTRODUCTION

The benefits of adjuvant radiotherapy (ART) for extrahepatic cholangiocarcinoma are uncertain largely because existing publications lack clear comparisons between ART and non-ART arms.

METHODS

PubMed, Medline, Embase, and the Cochrane library were systematically searched until December 2020. The primary endpoint was overall survival (OS). Sensitivity analysis was performed for studies with reliable comparability (i.e., no favorable prognosticators in the ART arm that could skew the data).

RESULTS

Twenty-three studies involving 1,731 patients with extrahepatic cholangiocarcinoma were reviewed. The overall median of all median prescribed doses was 50.4 Gy; brachytherapy or an intraoperative boost of 10-21 Gy was applied in 5 studies. The pooled 1-, 3-, and 5-year OS rates in the non-ART and ART arms were 69.2% versus 81.0%, p = 0.035; 34.3% versus 44.7%, p = 0.025; 25.6% versus 31.7%, p = 0.115, respectively. The corresponding pooled locoregional recurrence rates were 52.1% versus 34.9% (p = 0.014). The pooled rate of grade ≥3 gastrointestinal complications was 9.8%. Sensitivity analysis performed on 14 eligible studies showed that the ART arms had a lower pooled R0 rate (36.8% vs. 63.2%, p = 0.02) and a higher rate of positive lymph nodes (47.4% vs. 34.9%, p = 0.08). The pooled 1-, 3-, and 5-year OS rates in the non-ART versus ART arms of the selected studies were 78.2% versus 84.9%, p = 0.143; 38.5% versus 49.2%, p = 0.026; and 27.8% versus 34.5%, p = 0.11, respectively.

CONCLUSIONS

ART was shown to improve OS in all studies and in those selected for their reliable comparability.

Is the Concurrent Use of Sorafenib and External Radiotherapy Feasible for Advanced Hepatocellular Carcinoma? A Meta-Analysis

We evaluate the feasibility of a concurrent application of sorafenib and external beam radiation therapy (EBRT) for advanced hepatocellular carcinoma (HCC). PubMed, Embase, Medline, and Cochrane Library were searched up to 9 April 2021. The primary endpoint was grade ≥3 complications, and the secondary endpoint was overall survival (OS). Subgroup analyses were performed for studies with the EBRT targets, intrahepatic vs. non-intrahepatic lesions (e.g., extrahepatic metastases or malignant vessel involvement only). Eleven studies involving 512 patients were included in this meta-analysis. Pooled rates of gastrointestinal, hepatologic, hematologic, and dermatologic grade ≥3 toxicities were 8.1% (95% confidence interval (CI): 4.8-13.5, I2 = ~0%), 12.9% (95% CI: 7.1-22.1, I2 = 22.4%), 9.1% (95% CI: 3.8-20.3, I2 = 51.3%), and 6.8% (95% CI: 3.8-11.7, I2 = ~0%), respectively. Pooled grade ≥3 hepatologic and hematologic toxicity rates were lower in studies targeting non-intrahepatic lesions than those targeting intrahepatic lesions (hepatologic: 3.3% vs. 17.1%, p = 0.041; hematologic: 3.3% vs. 16.0%, p = 0.078). Gastrointestinal and dermatologic grade ≥3 complications were not significantly different between the subgroups. Regarding OS, concurrent treatment was more beneficial than non-concurrent treatment (odds ratio: 3.3, 95% CI: 1.3-8.59, p = 0.015). One study reported a case of lethal toxicity due to tumor rupture and gastrointestinal bleeding. Concurrent treatment can be considered and applied to target metastatic lesions or local vessel involvement. Intrahepatic lesions should be treated cautiously by considering the target size and hepatic reserve.