Evolution of the Management of Brain Metastases: A Bibliometric Analysis

Abstract

A systematic review of the published literature was conducted to analyze the management evolution of brain metastases from different cancers. Using the keywords "brain metastasis", "brain metastases", "CNS metastasis", "CNS metastases", "phase III" AND/OR "Randomized Controlled Trial" (RCT), relevant articles were searched for on the SCOPUS database. A total of 1986 articles were retrieved, published over a 45-year period (1977-2022). Relevant articles were defined as clinical studies describing the treatment or prevention of brain metastases from any cancer. Articles on imaging, quality of life, cognitive impairment after treatment, or primary brain tumors were excluded. After a secondary analysis, reviewing the abstracts and/or full texts, 724 articles were found to be relevant. Publications significantly increased in the last 10 years. A total of 252 articles (34.8%) were published in 12 core journals, receiving 50% of the citations. The number of publications in Frontiers in Oncology, BMC Cancer, and Radiotherapy and Oncology have increased considerably over the last few years. There were 111 randomized controlled trials, 128 review articles, and 63 meta-analyses. Most randomized trials reported on brain metastases management from unselected tumors (49), lung cancer (47), or breast cancer (11). In the last 5 years (2017 to 2022), management of brain metastasis has moved on from WBRT, the use of chemotherapy, and radio-sensitization to three directions. First, Radiosurgery or Radiotherapy (SRS/SRT), or hippocampal-sparing WBRT is employed to reduce radiation toxicity. Second, it has moved to the use of novel agents, such as tyrosine kinase inhibitors (TKI) and immune checkpoint inhibitors (ICI) and third, to the use of molecularly directed therapy such as TKIs, in asymptomatic low volume metastasis, obviating the need for WBRT.

Keywords: CNS metastasis; Oman; SRS; Simultaneous Integrated Boost (SIB); Whole Brain Radiotherapy (WBRT); brain metastasis; hippocampal sparing radiotherapy; integrative review; randomized controlled trial.

Figure 1

Article selection flow chart (PRISMA) [24,25,26,27].

Figure 2

Publication trends over the course of time.

Figure 3

(A) Bradford’s law, Core journals publish almost 1/3rd of all articles, and the journals in zone 2 and zone 3 also publish 1/3rd of all articles each. However, articles published in the 12 core journals receive almost 50% of all citations. (B) Publication trend over the course of time in 12 core journals.

Figure 3

(A) Bradford’s law, Core journals publish almost 1/3rd of all articles, and the journals in zone 2 and zone 3 also publish 1/3rd of all articles each. However, articles published in the 12 core journals receive almost 50% of all citations. (B) Publication trend over the course of time in 12 core journals.

Figure 4

(A) Author production over time. Red line indicates the author′s timeline, the bubble size indicates the number of documents published that year, and the color intensity indicates the total number of citations per year. (B) Author productivity using Lotka’s law. Solid black line indicates the distribution of published articles according to Lotkaw’s law. The dotted line indicates the publication on subject matter. The solid and the dotted lines almost overlap, suggesting the publication trend in management of metastases from breast cancer follows the law.

Figure 5

Author’s keyword clusters.

Figure 6

(A) Nature of publications. (B) Investigational arm of the randomized control trials.

Figure 7

Temporal pattern of the modalities of treatment introduced for the management of brain metastases.