The overall survival impact of prophylactic cranial irradiation in limited-stage small-cell lung cancer: a systematic review and meta-analysis

Prophylactic cranial irradiation for limited-stage small-cell lung cancer in the modern magnetic resonance imaging era may be omitted: a propensity score-matched analysis

We aimed to clarify whether prophylactic cranial irradiation (PCI) is associated with improved outcomes in limited-stage small-cell lung cancer (LS-SCLC) in the current era of magnetic resonance imaging (MRI). Data from patients with LS-SCLC who achieved a complete response to definitive chemoradiotherapy (CRT) at two medical centers were retrospectively reviewed. Propensity score-matching was performed in a 2:1 ratio to balance the baseline characteristics of the no-PCI and PCI groups. The endpoints were the incidence of brain metastasis (BM), neurological causes of death and overall survival (OS). Overall, 80% patients underwent head MRI during the initial staging and 75 patients (no-PCI, n = 50; PCI, n = 25) were matched. Their baseline characteristics were generally well-balanced except for age; patients in the no-PCI group tended to be older. The median follow-up period was 29 months. Although the incidence of BMs tended to be higher in the no-PCI group (1-year BM occurrence: 26% vs 17%, P = 0.22), the incidence of multiple BMs (defined as >4 metastases) was similar between groups (1-year multiple BMs occurrence: 8% vs 9%, P = 0.65). The 2-year neurological causes of death and OS rate did not significantly differ between the groups (6% and 9%; P = 0.85; and 70% and 79%; P = 0.36, respectively). The 1-year occurrence of multiple BMs did not increase, even without PCI, when modern imaging modalities were integrated into the initial diagnosis, suggesting that PCI could be omitted after CRT, if MRI was incorporated into the initial diagnosis and follow-up.

Implementing the optimized hippo-avoidance prophylactic cranial irradiation for limited-stage small cell lung cancer by tomotherapy and volumetric modulated arc therapy

BACKGROUND

Hippo-avoidance prophylactic cranial irradiation (HA-PCI) requires a hippocampal avoidance zone expanded from hippocampus to ensure dose fall-off and compensate for setup errors. Most studies recommend a 5-mm margin, while it could be optimized to a 2-mm expansion. Here, we showed the details of optimized HA-PCI for limited-stage small cell lung cancer (LS-SCLC).

METHODS

This cohort study reviewed patients with LS-SCLC receiving optimized HA-PCI from August 2014 to June 2020 in the National Cancer Center of China. The hippo-related dose parameters were summarized. The comparison of the Hopkins Verbal Learning Test-Revised (HVLT-R) scores in different time points was conducted. The Kaplan-Meier method was used to calculate the survival rates.

RESULTS

A total of 112 patients were included. The average doses of hippocampus and hippocampal avoidance zone were 6.80 Gy (IQR: 6.40-7.44) and 7.63 Gy (IQR: 7.14-8.39). No differences were observed in the two radiation techniques (tomotherapy [TOMO] vs. volumetric-modulated arc therapy [VMAT]). The decline of HVLT-R score remained in a low level and not significant in assessable patients (p = 0.095). With a median follow-up of 52 months (95% CI: 47.2-56.7), the 2-year overall survival and progression-free survival were 74.1% and 50.0%, respectively. Two intracranial recurrence lesions (2.3%) located <2 mm from the hippocampus.

CONCLUSIONS

Optimized HA-PCI could achieve similar dose limitation by TOMO and VMAT techniques with favorable efficacy and minor toxicity.

Re-examining prophylactic cranial irradiation in small cell lung cancer: a systematic review and meta-analysis

Background

Patients with small cell lung cancer (SCLC) are at high risk for brain metastases. Prophylactic cranial irradiation (PCI) is recommended in this population to reduce the incidence of brain metastases and prolong survival. We aimed to assesses the efficacy of PCI in this population in the era of routine brain imaging. To our knowledge, this is the first systematic review and meta-analysis to examine the use among patients who were radiographically confirmed not to have brain metastases after completion of first-line therapy.

Methods

In this systematic review and meta-analysis, cohort studies and controlled trials reporting on the use of PCI for patients SCLC were identified in EMBASE, MEDLINE, CENTRAL, and grey literature sources. The literature search was conducted on November 12, 2023. Summary data were extracted. Random-effects meta-analyses pooled hazard ratios (HR) for the primary outcome of overall survival between PCI and no intervention groups. This study is registered with the Open Science Framework, DOI:10.17605/OSF.IO/BC359, and PROSPERO, CRD42021249466.

Findings

Of 4318 identified records, 223 were eligible for inclusion. 109 reported on overall survival in formats amenable to meta-analysis; PCI was associated with longer survival in all patients with SCLC (HR 0.59; 95% CI, 0.55-0.63; p < 0.001; n = 56,770 patients), patients with limited stage disease (HR 0.60; 95% CI, 0.55-0.65; p < 0.001; n = 78 studies; n = 27,137 patients), and patients with extensive stage disease (HR 0.59; 95% CI, 0.51-0.70; p < 0.001; n = 28 studies; n = 26,467 patients). Between-study heterogeneity was significant when pooled amongst all studies (I2 = 73.6%; 95% CI 68.4%-77.9%). Subgroup analysis did not reveal sources of heterogeneity. In a subgroup analysis on studies that used magnetic resonance imaging to exclude presence of brain metastases at restaging among all patients, overall survival did not differ significantly between patients who did or did not receive PCI (HR 0.74; 95% CI, 0.52-1.05; p = 0.08; n = 9 studies; n = 1384 patients).

Interpretation

Our findings suggested that administration of PCI is associated with a survival benefit, but not when considering studies that radiographically confirmed absence of brain metastases, suggesting that the survival benefit conferred by PCI might be therapeutic rather than prophylactic.

Funding

No funding.

Progress in radiotherapy for small-cell lung cancer

Small-cell lung cancer (SCLC) is a highly aggressive neuroendocrine tumor that is prone to spread extensively. Compared to non-small-cell lung cancer (NSCLC), SCLC treatment progresses slowly. Although SCLC is highly sensitive to chemotherapy during the initial treatment, most patients still experience resistance and recurrence after receiving chemotherapy. A meta-analysis demonstrated that thoracic radiotherapy (TRT) improves overall survival in SCLC. The results of the CALGB and CONVERT trials provide evidence for the efficacy of once-daily high-dose TRT. TRT at 60 Gy administered twice daily significantly improved survival without increasing toxicity. The long-standing debate over the optimal timing of radiotherapy has not been fully resolved. SBRT has excellent local control rates and is a safe and effective treatment option for patients with stage I or II SCLC. Prophylactic cranial irradiation (PCI) is used to reduce treatment-related neurotoxicity to the extent that there has been a recent discussion on whether magnetic resonance imaging (MRI) monitoring can replace PCI. Radiotherapy combined with immunotherapy significantly improves the survival rate of patients with NSCLC; however, its clinical effectiveness has not been systematically explored in patients with SCLC. Therefore, we summarize the evolving therapeutic strategies, (TRT for limited stage-SCLC and consolidative TRT for extensive stage-SCLC) and improved radiotherapy techniques (role of SBRT in stage I or II node-negative SCLC, progress of PCI, and stereotactic radiosurgery), and discuss the possibilities and prospects of radiotherapy combined with immunotherapy for SCLC.

Factors associated with overall survival, progression-free survival and toxicity in patients with small cell lung cancer and thoracic irradiation in a clinical real-world setting

BACKGROUND

Small-cell lung cancer (SCLC) is a malignant tumor known for its poor prognosis. In addition to chemotherapy and immunotherapy irradiation plays a big role especially in inoperability. This study evaluated prognostic factors in patients with SCLC, receiving chemotherapy and thoracic irradiation, that may affect overall survival (OS), progression-free survival (PFS) and toxicity.

METHODS

Patients with limited disease (LD) SCLC (n = 57) and extensive disease (ED) SCLC (n = 69) who received thoracic radiotherapy were analyzed retrospectively. The prognostic factors sex, age, Karnofsky performance status (KPS), tumor-, nodal-stage and timepoint of start of irradiation in relation to the first cycle of chemotherapy were evaluated. Start of irradiation was stratified as early ([Formula: see text] 2 cycles of chemotherapy), late (3 or 4 cycles) and very late ([Formula: see text] 5 cycles). Results were analyzed by Cox univariate and multivariate as well as logistic regression analysis.

RESULTS

The median OS of LD-SCLC patients was 23.7 months in early, and 22.0 months in late start of irradiation. In very late start, median OS was not reached. PFS was 11.8, 15.2 and 47.9 months, respectively. In patients with ED-SCLC OS was 4.3 months in early, 13.0 months in late and 12.2 months in very late start of irradiation. PFS was 6.7, 13.0 and 12.2 months, respectively. Prognosis of patients with LD- or ED-SCLC receiving late or very late start of irradiation was significantly prolonged in OS and PFS compared to an early start (p < 0.05). KPS [Formula: see text] 80 shows a significant increase of OS and PFS in ED-SCLC. Female sex and smaller mean lung dose were associated with lower risk of toxicity.

CONCLUSION

Late or very late start of irradiation is a prognosis-enhancing factor in LD-SCLC and ED-SCLC for OS and PFS. KPS [Formula: see text] 80 increases prognosis of OS and PFS in ED-SCLC as well. Toxicity is less common in female sex and patients with low mean lung dose in LD-SCLC.

Prophylactic cranial irradiation in small cell lung cancer: an update

PURPOSE OF REVIEW

The current review presents recent updates in the seminal literature of research on prophylactic cranial irradiation (PCI) in small cell lung cancer (SCLC).

RECENT FINDINGS

Brain MRI restaging before the administration of PCI reveals a substantial proportion of brain metastasis in baseline brain metastasis free extensive-stage SCLC (ES-SCLC) and limited-stage SCLC (LS-SCLC). Posthoc analyses from the CASPIAN and IMpower133 trials revealed decreases in brain metastasis rates in ES-SCLC treated with chemoimmunotherapy relative to the brain metastasis rates in ES-SCLC treated with chemotherapy alone. A recent meta-analysis of literature published after the landmark 1999 Auperin meta-analysis confirmed the survival benefit of PCI in LS-SCLC patients. A recent study employing PET before and after PCI demonstrated that hippocampal avoidance -PCI (HA-PCI) preserved the metabolic activity of the hippocampi compared with regular PCI. Two phase III trials evaluating neurocognitive functions after HA-PCI versus PCI have yielded conflicting results. Ongoing clinical trials (MAVERICK, PRIMALung, NRG CC003, NCT04535739, NCT04829708 and NCT03514849) regarding PCI versus MRI surveillance and HA-PCI versus PCI were also discussed.

SUMMARY

Currently, the indications for PCI in SCLC are under question in the modern MRI era. Result from prospective phase III, MRI staged and MRI monitored RCTs are expected to elucidate the role of PCI in LS-SCLC and ES-SCLC. Preliminary results indicated that adding immunotherapy to chemotherapy may reduce brain metastasis rate in SCLC. Further data to this aspect are warranted to determine the role of PCI in the immuno-chemotherapy era. The future direction for PCI should be the comprehensive integration of personalized patient selection, HA-PCI utilization and potential employment of other neurocognitive preservation strategies.

An Overview of the Role of Radiotherapy in the Treatment of Small Cell Lung Cancer - A Mainstay of Treatment or a Modality in Decline?

AIMS

Small cell lung cancer (SCLC) accounts for about 15% of all lung cancers. Chemotherapy, immunotherapy and radiotherapy all play important roles in the management of SCLC. The aim of this study was to provide a comprehensive overview of the role and evidence of radiotherapy in the cure and palliation of SCLC.

MATERIALS AND METHODS

The search strategy included a search of the PubMed database, hand searches, reference lists of relevant review articles and relevant published abstracts.

CLINICALTRIALS

gov was also queried for relevant trials.

RESULTS

Thoracic radiotherapy improves overall survival in limited stage SCLC, but the timing and dose remain controversial. The role of thoracic radiotherapy in extensive stage SCLC with immunotherapy is the subject of several ongoing trials. Current evidence supports the use of prophylactic cranial irradiation (PCI) for limited stage SCLC but the evidence is equivocal in extensive stage SCLC. Whole brain radiotherapy is well established for the treatment of brain metastases but evidence is rapidly accumulating for the use of stereotactic radiosurgery. Further studies will define the role of PCI, whole brain radiotherapy and hippocampal avoidant PCI in the immunotherapy era.

CONCLUSION

Radiotherapy is an essential component in the multimodality management of SCLC. Technological advances have allowed safer delivery of radiotherapy with reduced toxicities. Discussion at multidisciplinary team meetings is important to ensure radiotherapy is considered and offered in appropriate patients.