4.1 General information
In this study, the bibliometric analysis of Cancer-CSR was performed. A total of 607 publications in Cancer-CSR were retrieved using the online WoSCC database, covering many fields in cancer, such as gastrointestinal tumors(27), gynecological oncology(28), haematological malignancies(29), palliative and supportive care(30), and so on. Compared with other disciplines, the number of publications of cancer was higher than that in other topics in Cochrane Database Syst Rev(5). This might be due to the Cochrane Review Group in Cochrane Library, which contained a variety of cancer groups, such as colorectal cancer group, breast cancer group, lung cancer group and so on(31). Interestingly, according to the Global Cancer Statistics 2018, lung cancer is the most commonly diagnosed cancer (11.6% of the total cases) and the leading cause of cancer death (18.4% of the total cancer deaths), but the number of Cochrane SRs about lung cancer took only 4.3% of total(24). Breast cancer and colorectal cancer are among the top five in incidence and mortality, so automatically more publications are focused in this field. For women, the cumulative incidence of cervical cancer (6.6%), endometrial cancer (4.4%), and ovary cancer (3.4%) are less than breast cancer, but there are 16.3% of Cochrane SRs concentrate on gynecological cancer. To some extent, the incidence and mortality of cancer may influence the preference of Cochrane SRs. Nonetheless, uneven development among Cochrane review group, completion of protocols, and preference of authors themselves may also contribute to these results (6).
UK, USA, Canada, Australia, and Germany were the countries with high centrality and production, which worked closely with other countries. Unlike other bibliometric studies in cancer field, UK rather than USA ranked first in productivity, with the highest centrality, containing more than half of the top 10 contributive institutes(32, 33). This may be due to the publication country of Cochrane Database Syst Rev is UK. In 1993, British physician and epidemiologist Archie Cochrane and his colleagues developed the Cochrane Collaboration, which represents the watershed movement responsible for the biggest advances in systematic review methodology(34, 35). Although the publications of USA were only one-third of UK, the centrality was almost the same. China and Brazil were the only two developing countries among the top 10 contributive countries. However, as for the centrality, China was the last but one among the top 10 contributive countries, which indicated that the importance of the studies we Chinese researchers involved in was not high. On the other hand, the overall methodological and reporting quality of systematic reviews by authors from China were similar to those from the USA(1). So, the possible reason may be that the topics of the Chinese Cancer-CSR studies are not attractive and innovative enough. Egypt and Austria were the first time to publish the reviews in Cancer-CSR during the latest ten years, which focused more on the chemotherapy and multimodality therapy in cancer field(36, 37).
With respect to the institutes involved, Newcastle University, one of the Ivy League schools and has the top medical school in UK, which was founded in 1834 as the College of medicine and surgery, was the most productive institution. The reviews of Newcastle University focused on surgical treatment(38), chemotherapy(39) and prognosis(40) of gynecological cancer. The most cited review was the evaluation of the efficacy, safety, and cost-effectiveness of primary cytoreductive surgery in patients with advanced epithelial ovarian cancer surgery(41), published in 2011. The top 10 contributive institutions collaborated closely with other institutions, except for the Sichuan University and the University of Nottingham. Checking the incidence rate of the districts of top 10 institutes and 10 countries, we also found that the incidence of all kinds of cancer in these districts was above the world average level (197.9)(42).
4.2 Citation information
Among the top 10 co-citied journals/books, different journals usually favored publication on different scientific subjects. For example, J Clin Oncol, Cancer, Ann Oncol and Eur J Cancer preferred every respect of cancer, from epidemiology, carcinogenesis and biology through to innovations in cancer treatment and patient care; Lancet preferred surgical oncology; Cochrane Database Syst Rev, BMJ, and N Engl J Med were comprehensive journals; Stat Med focused on statistical the methods to a particular medical problem, and C Hdb Sys was the most significant book to all the researchers who intended to conduct systematic reviews, which is the official guide that describes in detail the process of preparing and maintaining Cochrane systematic reviews on the effects of healthcare interventions
The co-cited references were usually considered as the basics of the subject. Being-in Top 10 co-cited references, three versions of C Hdb Sys (Higgins JPT, 2011; 2009; 2008) were included, owing to the Cochrane collaboration has driven the greatest advancement in system review methods, which has brought together more than 13,000 members and over 50,000 supporters come from more than 130 countries dedicated to systematic review(6). The second most co-cited reference was about Review Manager (RevMan)(18), the most frequently used tool in meta-analysis, which facilitated preparation of protocols and full reviews, including characteristics of studies, comparison tables, study data and so on, and was also appropriate to the reviews of diagnostic test accuracy studies, reviews of studies of methodology and overviews of reviews. The rest top 10 co-cited references including methodology studies(20, 25), epidemiological data of cancer(24), and the reporting guideline of systematic reviews(26). The latest co-cited references were focused on the diagnosis and treatment of skin cancer in adults(43-45). All these co-cited references constituted the knowledge base of this field.
4.3 Research hotspots
The cluster of keywords could be used for detecting research hotspots, and monitoring the study frontiers transitions in a certain field(46) Here, we listed three hotspots of Cancer-CSR as follows:
#0 Cytoreductive surgery: Cytoreductive surgery (CRS) is a surgery which removes all visible lesions as much as possible and used to reduce tumor burden of patients and prolong survival, which has been applied in many kinds of cancer (47-49). Because of the unsatisfactory effects of traditional treatment, better treatment regimens were needed(50). The included studies about CRS covered ovarian cancer(51-53), colorectal cancer(54), neuroblastoma(55), breast cancer(56) and lung cancer(57), which mostly focused on the different adjuvant therapy, different chemotherapeutic drugs and different dose of chemotherapy. However, the evidence found was insufficient in these aspects, so new clinical trials are needed to solve these problems.
#7 visual inspection: Nonmelanoma of skin cancer (NMSC) accounted for 5.8% of all new cancer cases in 2018 as well as melanoma of skin accounted for 1.6%. There were an estimated 1,000,000 new cases and 65,000 deaths worldwide, and the male incidence was about twice that of women. One burgeoning approach that has impacted skin cancer detection was reflectance confocal microscopy (RCM), which noninvasively shows nuclear and cellular-level morphology in human skin in vivo(58, 59). Compared with the dermoscopy, RCM had similar sensitivity but the specificity was two times superior, and it could reduce the number of biopsies of benign lesions as a second-level examination following dermoscopy(60-62). Nevertheless, there were some pitfalls. For example, the differentiation of melanocytes from langerhans cells in melanocytic lesions lacks specificity, the misdiagnosis due to specific lesion or missed detection because of sampling error, as well as the clinical experience of the doctors(63). There were four records in Cancer-CSR concentrated on the applying of RCM for diagnosing skin cancer in adults with any suspicious lesion which was all published in 2018(64-67).
#10 Non-steroidal anti-inflammatory drug: Increased survival rates for cancer patients, coupled with the increasing complexity of cancer and the introduction of new therapies, made pain treatments more challenging(68, 69). Non-steroidal anti-inflammatory drugs (NSAIDs) were widely used to treat postoperative fever and surgical pain. What’s more, there was increasing evidence that non-steroidal anti-inflammatory drugs have anticancer activity which could reduce the risk of cancer(70, 71). However, there was no sufficient evidence of the included records about reducing cancer-related pain in children and adolescents(72), and no high-quality evidence to support the use of NSAIDs alone or in combination with opioids for the three step WHO cancer pain ladder(73).
4.4 Strengths and limitations
To the best of our knowledge, this study is the first bibliometric analysis of the Cancer-CSR. The research trends and hot spots of Cancer-CSR reflected that in systematic reviews in the cancer field to some extent, but it was not comprehensive enough, for the Cochrane collaboration had greater scrutiny for systematic reviews, so there were not a lot of publications.