[Prophylactic cranial irradiation for limited-stage small cell lung cancer: controversies and advances]

Association of Twice-Daily Radiotherapy With Subsequent Brain Metastases in Adults With Small Cell Lung Cancer

IMPORTANCE

Although thoracic twice-daily radiotherapy (TDRT) is one of the standards of care for small cell lung cancer, its association with brain metastases remains unknown.

OBJECTIVE

To investigate the association of TDRT vs once-daily radiotherapy (ODRT) with brain metastases after prophylactic cranial irradiation in patients with small cell lung cancer.

DESIGN, SETTING, AND PARTICIPANTS

In this multicenter cohort study, data on 778 consecutive patients with small cell lung cancer who had undergone thoracic radiotherapy (609 received ODRT and 169 received TDRT), chemotherapy, and prophylactic cranial irradiation were retrieved from the databases of 8 hospitals in China between July 1, 2003, and June 30, 2016. A 1:1 propensity score matching approach was used to control for confounding between the ODRT and TDRT groups. Confounding covariates included 8 demographic variables and 8 treatment-related covariates. Data analysis was conducted from November 1, 2017, to May 31, 2018, and reanalyzed for revision.

EXPOSURES

The ODRT group received 50 to 66 Gy given in 25 to 33 fractions. The TDRT group received 45 Gy given in 30 fractions.

MAIN OUTCOMES AND MEASURES

The primary end point was brain metastases. Secondary end points included progression-free survival and overall survival.

RESULTS

Of the 778 patients (median age, 55 years [interquartile range, 48-61 years]), 204 were women and 574 were men. At a median follow-up of 23.6 months (interquartile range, 14.2-38.2 months), 131 patients (16.8%) experienced brain metastases. The rate of brain metastasis at 3 years in the TDRT group was significantly higher than in the ODRT group (26.0% vs 16.9%; hazard ratio, 1.55; 95% CI, 1.06-2.26; P = .03). Of the 338 matched patients (169 in the ODRT group vs 169 in the TDRT group), 60 (17.8%) experienced brain metastases, with a rate at 3 years of 14.9% in the ODRT group vs 26.0% in the TDRT group (hazard ratio, 1.71; 95% CI, 1.02-2.88; P = .04). Progression-free survival was similar in both the whole cohort and the matched cohort. Median overall survival in the ODRT group tended to be significantly longer than in the TDRT group after matching (47.2 vs 32.8 months; hazard ratio, 1.41; 95% CI, 0.99-2.01; P = .06).

CONCLUSIONS AND RELEVANCE

In this study, patients with small cell lung cancer who received thoracic TDRT appeared to have a higher risk of brain metastases than those who received ODRT, which supports the need for further prospective randomized clinical trials, especially in China and other parts of Asia.

Risk factors for brain metastases after prophylactic cranial irradiation in small cell lung cancer

Despite administration of prophylactic cranial irradiation (PCI), some small cell lung cancer (SCLC) patients still suffer from brain metastases (BM) with unknown risk factors. We conducted this study to identify patients with higher BM risk after PCI and improve their outcome. The characteristics and survival of all the SCLC patients underwent PCI in our institute from 2003 to 2014 were analyzed. Kaplan-Meier method was applied to estimate BM free survival (BMFS) and overall survival (OS). Cox regression analyses were performed to explore risk factors for BM. A total of 175 patients with the median age of 55 years (range, 29–76) were eligible, among whom 36 (20.6%) developed BM with median follow-up of 42 months. Both univariate and multivariate analyses showed HART and TNM classification (p < 0.05) were associated with BM. Two-stage system was not related with BMFS or OS (p > 0.05). Stage IIIB-IV and HART were independent risk factors for BM after PCI in SCLC. TNM classification was more valuable on prognosis than two-stage system. Further large-scale studies are needed to confirm our findings.