The value of prophylactic cranial irradiation in limited-stage small cell lung cancer: should it always be recommended?

Efficacy of Prophylactic Cranial Irradiation According to the Risk of Extracranial Recurrence in Limited-Stage Small Cell Lung Cancer

PURPOSE

We aimed to evaluate the effectiveness of prophylactic cranial irradiation (PCI) for "early brain metastasis", which occurs before extracranial recurrence (ECR), and "late brain metastasis", which occurs after ECR, in limited-stage small cell lung cancer (LS-SCLC).

Materials and Methods

We retrospectively analyzed 271 LS-SCLC patients who underwent definitive chemoradiation. All patients were initially staged with brain magnetic resonance imaging and positron emission tomography. Intracranial recurrence (ICR), ECR, progression-free rate (PFR), and overall survival (OS) were analyzed as clinical endpoints. The competing risk of the first recurrence with ICR (ICRfirst) was evaluated. Significantly associated variables in multivariate analysis of ECR were considered as ECR risk factors. Patients were stratified according to the number of ECR risk factors.

RESULTS

The application of PCI was associated with higher PFR (p=0.008) and OS (p=0.045). However, PCI was not associated with any of the clinical endpoints in multivariate analysis. The competing risk of ICRfirst was significantly decreased with the application of PCI (hazard ratio, 0.476; 95% confidence interval, 0.243 to 0.931; p=0.030). Stage III disease, sequential, and stable disease after thoracic radiation were selected as ECR risk factors. For patients without these risk factors, the application of PCI was significantly associated with increased OS (p=0.048) and a decreased risk of ICRfirst (p=0.026).

CONCLUSION

PCI may play a role in preventing early brain metastasis rather than late brain metastasis after ECR, suggesting that only patients with a low risk of ECR may currently benefit from PCI.

Prophylactic cranial irradiation-related lymphopenia affects survival in patients with limited-stage small cell lung cancer

Background

The study aimed to identify the relations of the absolute lymphocyte count (ALC) nadir during prophylactic cranial irradiation (PCI) and patient outcomes in limited-stage small cell lung cancer (LS-SCLC).

Methods

We analyzed 268 L S-SCLC patients who underwent PCI from 2012 to 2019. ALC values were collected prior, during, and 3 months post PCI. Kaplan-Meier and Cox regression analyses were performed to assess the relation of ALC to patient prognosis. Two nomograms were developed on the basis of clinical variables for survival prediction.

Results

Compared with the ALC before PCI (1.13 × 10⁹ cells/L), the ALC nadir during PCI was significantly reduced by 0.68 × 10⁹ cells/L (P < 0.001) and raised to 1.02 × 10⁹ cells/L 3 months post PCI. Patients with a low ALC nadir during PCI (<0.68 × 10⁹ cells/L) had inferior progression free survival (PFS) (median PFS: 17.2 m vs. 43.7 m, P = 0.019) and overall survival (OS) (median OS: 29.0 m vs 39.1 m, P = 0.012). Multivariate Cox analysis revealed that age, smoking history, clinical stage, and ALC nadir were independent OS (P = 0.006, P = 0.005, P < 0.001 and P = 0.027, respectively), as well as independent PFS predictors (P = 0.032, P = 0.012, P = 0.012 and P = 0.018, respectively). After internal cross-validation, the corrected concordance indices of the predictive nomograms for PFS and OS were 0.637 and 0.663, respectively.

Conclusion

LS-SCLC patients with a low ALC nadir during PCI likely have worse survival outcomes. Dynamic evaluation of the ALC during PCI is recommended for LS-SCLC patients.

A systematic literature review of real-world treatment outcomes of small cell lung cancer

BACKGROUND

Robust evidence from real-world studies is needed to aid decision-makers and other stakeholders in choosing the best treatment options for patients. The objective of this work was to assess real-world outcomes of treatment strategies for limited- and extensive-stage small cell lung cancer (SCLC) prior to the global introduction of immunotherapies for this disease.

METHODS

Searches were conducted in MEDLINE and Embase to identify articles published in English from October 1, 2015, through May 20, 2020. Searches were designed using a combination of Medical Subject Heading (Medline), Emtree (Embase subject headings), and free-text terms such as SCLC. Observational studies reporting data on outcomes of initial treatment strategies in patients with limited- and extensive-stage SCLC were included. Studies with limited sample sizes (<100 patients), enrolled all patients prior to 2010, or did not report outcomes for limited- and extensive-stage SCLC separately were excluded. Data were extracted into a predesigned template by a single researcher. All extractions were validated by a second researcher, with disagreements resolved via consensus.

RESULTS

Forty articles were included in this review. Most enrolled patients from the United States (n = 18 articles) or China (n = 12 articles). Most examined limited-stage (n = 27 articles) SCLC. All studies examined overall survival as the primary outcome. Articles investigating limited-stage SCLC reported outcomes for surgery, chemotherapy and/or radiotherapy, and adjuvant prophylactic cranial irradiation. In studies examining multiple treatment strategies, chemoradiotherapy was the most commonly utilized therapy (56%-82%), with chemotherapy used in 18% to 44% of patients. Across studies, median overall survival was generally higher for chemoradiotherapy (15-45 months) compared with chemotherapy alone (6.0-15.6 months). Studies of extensive-stage SCLC primarily reported on chemotherapy alone, consolidative thoracic radiotherapy, and radiotherapy for patients presenting with brain metastases. Overall survival was generally lower for patients receiving chemotherapy alone (median: 6.4-16.5 months; 3 years, 5%-14.9%) compared with chemotherapy in combination with consolidative thoracic radiotherapy (median: 12.1-18.0 months; 3 years, 15.0%-18.1%). Studies examining whole-brain radiotherapy for brain metastases reported lower median overall survival (5.6-8.7 months) compared with stereotactic radiosurgery (10.0-14.5 months).

CONCLUSIONS

Under current standard of care, which has remained relatively unchanged over the past few decades, prognosis remains poor for patients with SCLC.

Survival impact of prophylactic cranial irradiation in small-cell lung cancer in the modern era of magnetic resonance imaging staging

Background

In the modern era of magnetic resonance imaging (MRI) staging, the benefit of prophylactic cranial irradiation (PCI) in patients with small-cell lung cancer (SCLC) has been controversial. This study evaluated the prognostic impact of PCI in patients with limited- or extensive-stage SCLC who had no brain metastases at diagnosis according to MRI.

Methods

Data from newly diagnosed patients in 2014 from the Korean Association for Lung Cancer Registry database were used. Patients with limited- or extensive-stage SCLC who had no brain metastases according to MRI were identified. Univariate and multivariate survival analyses were conducted to assess the prognostic association of PCI.

Results

Of 107 and 122 patients with limited- and extensive-stage SCLC, 24% and 14% received PCI, respectively. In the limited-stage SCLC group, the 2-year overall survival (OS) rates of patients who received PCI and those who did not were 50% and 29% (P = 0.018), respectively. However, there was no significant difference in OS for patients with extensive-stage SCLC (P = 0.336). After adjusting for other covariates, PCI was found to be associated with improved OS in the limited-stage SCLC group (P = 0.005). Based on the time-course hazard rate function plots in the limited-stage SCLC group, the OS benefit of PCI was maximized within the first year of follow-up.

Conclusions

In the modern era of MRI staging, PCI might be beneficial for patients with limited-stage SCLC but not for those with extensive-stage SCLC. Further studies with a large sample size are needed to verify the prognostic association of PCI.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13014-022-01994-8.

Limited-Stage Small-Cell Lung Cancer: Current Progress and the Next Frontier

Limited-stage (LS) small-cell lung cancer (SCLC) is defined as disease confined to a tolerable radiation portal without extrathoracic metastases. Despite clinical research over two decades, the prognosis of LS-SCLC patients remains poor. The current standard of care for LS-SCLC patients is concurrent platinum-based chemotherapy with thoracic radiotherapy (RT). Widespread heterogeneity on the optimal radiation dose and fractionation regimen among physicians highlights the logistical challenges of administering BID regimens. Prophylactic cranial irradiation (PCI) is recommended to patients following a good initial response to chemoradiation due to improved overall survival from historical trials and the propensity for LS-SCLC to recur with brain metastases. However, PCI utilization is being debated due to the greater availability of magnetic resonance imaging (MRI) and data in extensive-stage SCLC regarding close MRI surveillance in lieu of PCI while spurring novel RT techniques, such as hippocampal-avoidance PCI. Additionally, novel treatment combinations incorporating targeted small molecule therapies and immunotherapies with or following radiation for LS-SCLC have seen recent interest and some concepts are being investigated in clinical trials. Here, we review the landscape of progress, limitations, and challenges for LS-SCLC including current standard of care, novel radiation techniques, and the integration of novel therapeutic strategies for LS-SCLC.

Re-evaluation of prophylactic cranial irradiation in limited-stage small cell lung cancer: a propensity score matched analysis

We attempted to re-evaluate the efficacy of prophylactic cranial irradiation (PCI) in limited-stage small cell lung cancer (LS-SCLC) with more recent data. A total of 179 patients with LS-SCLC received radical thoracic radiotherapy and chemotherapy at our institution between 1998 and 2018. One hundred twenty-eight patients who achieved complete response (CR), good partial response (PR), and PR without progression for at least for one year after initial therapy were enrolled in this study. These patients were divided into a PCI group (group A, n = 43), and a non-PCI group (group B, n = 85). Survival outcomes were retrospectively evaluated. Because several background factors differed significantly between groups A and B, propensity score (PS) matching was performed as 1:1 match of the two groups. Finally, we analyzed 64 patients (group A/B = 32/32). Median follow-up periods were 53 and 31 months in groups A and B, respectively. There were no significant differences between the groups' backgrounds. Two-year overall survival (OS) rates were 77% in group A and 62% in group B (p = 0.224). Two-year brain metastasis free survival (BMFS) rates were 85% in group A and 57% in group B (p = 0.008). The number of patients who underwent a brain imaging test for confirmation of no brain metastasis (BM) after radical thoracic radiotherapy and chemotherapy (before PCI) was 84 (group A/B = 32/52). A PS matched analysis for cases of pre-PCI brain imaging group, two-year OS rates for group A/B were 73/59% (p = 0.446). Two-year BMFS rates for group A/B were 91/52% (p = 0.021). Retrospectively, PS matched analysis revealed that adding PCI to LS-SCLC patients who achieved good thoracic control significantly improved BMFS, but OS did not improve.

Limited-stage small cell lung cancer: Outcomes associated with prophylactic cranial irradiation over a 20-year period at the Princess Margaret Cancer Centre

•

Prophylactic cranial irradiation (PCI) was more commonly used in younger patients.

•

PCI utilization rates did not change throughout our 20-year institutional experience.

•

PCI was associated with improved OS and lower brain metastasis risk, independent of MRI follow-up or era of treatment.

•

For LS-SCLC patients with good thoracic response, PCI remains the standard-of-care.

Background & purpose

Prophylactic cranial irradiation (PCI) is recommended for limited-stage small-cell lung cancer (LS-SCLC) patients with good response to concurrent chemoradiation. We report our institution’s 20-year experience with this patient population and associated clinical outcomes.

Materials & methods

A retrospective cohort of consecutive LS-SCLC patients treated with curative intent chemoradiation at our institution (1997–2018) was reviewed. Overall survival (OS) was calculated using the Kaplan-Meier method, and significant covariates determined by the Cox proportional hazards model. Covariates predictive of PCI were determined using Fisher's exact test and the Mann-Whitney test. Brain failure risk (BFR) was calculated using the cumulative incidence method treating death as a competing event. Treatment cohorts (historic vs. contemporary) were stratified by the median year of diagnosis (2005).

Results

A total of 369 patients with LS-SCLC were identified, of which 278 patients were notionally PCI eligible. PCI was given to 196 patients (71%). Younger age was associated with PCI utilization (p < 0.001). PCI utilization rates did not change between the historic and contemporary treatment era (p = 0.11), whereas magnetic resonance imaging (MRI) use at baseline and follow-up became more prevalent in the contemporary era (p = <0.001). On multivariable analysis, PCI utilization was associated with improved OS (HR 1.88, 95% CI 1.32–2.69) and decreased BFR (HR 4.66, 95% CI 2.58–8.40). Patients who had MRI follow-up had a higher incidence of BFR (HR 0.35, 95% CI 0.18–0.66) in multivariable analyses.

Conclusions

For LS-SCLC patients at our institution, PCI is more frequently utilized in younger patients, and the utilization rate did not change significantly over the past 20 years. PCI was independently associated with improved OS and lower BFR. Omission of PCI in LS-SCLC patients should not be routinely practiced in the absence of further prospective data.

pN1 but not pN0/N2 predicts survival benefits of prophylactic cranial irradiation in small-cell lung cancer patients after surgery

Background

Prophylactic cranial irradiation has been shown to reduce brain metastases and provide survival benefits in small-cell lung cancer (SCLC). However, its role in limited-stage SCLC patients after surgery remains unclear. Further, it is unknown whether the effect of prophylactic cranial irradiation is generalizable in these patients with different pathological nodal (N0-N2) stages, a state indicating the presence of tumor metastases.

Methods

We combined data from a single medical center and Surveillance, Epidemiology, and End Results database. Propensity score matching analyses were performed (1:2) to evaluate the role of prophylactic cranial irradiation in SCLC patients after surgery. Cox proportional hazards regression model was used to identify predictors of survival.

Results

124 (18.7%) out of 664 surgically-treated SCLC patients received prophylactic cranial irradiation treatment. Within the entire cohort, multivariate Cox regression analysis identified dataset source, age, pathological T and N stages, adjuvant chemotherapy, resection type, and histology as independent prognostic factors for overall survival. Prophylactic cranial irradiation appeared to be associated with a better overall survival, but the difference is marginally significant (P=0.063). Further, we stratified patients based on the pathological N0-N2 stages using propensity score matching analyses, which showed that prophylactic cranial irradiation treatment was superior to non-prophylactic cranial irradiation treatment for surgically-treated SCLC patients with N1 stage only (univariate analysis: P=0.026; multivariate Cox: P=0.004), but not N0/N2 stage (univariate analysis: P=0.65 and P=0.28, respectively; multivariate Cox: P=0.99 and P=0.35, respectively).

Conclusions

Prophylactic cranial irradiation provides survival benefits for SCLC patients with pN1 after surgery but not with pathological N0/N2 stage. Our findings may provide helpful stratifications for clinical decision-making of prophylactic cranial irradiation intervention in SCLC patients.