Introduction
Globally, liver cancer is the seventh most common cancer and the fourth most common cause of death [
1]. In hepatocellular carcinoma (HCC), which accounts for 70% to 85% of all liver cancers [
2], chronic viral hepatitis plays a major role; approximately 77% of liver cancer cases were estimated to be attributable to either hepatitis B virus (HBV) or hepatitis C virus (HCV) infection in 2008 [
3].
While HCC is a typical example of virus-related cancer, it is also strongly related to lifestyle. Chronic alcoholism is a classical risk factor [
4]. Growing evidence suggests that obesity and diabetes increase various cancer risks [
5‐
9], and the liver is one of the organs upon which obesity and obesity-associated conditions have the largest impact [
5,
8,
10,
11]. Obesity and diabetes represent the largest risk factors for liver cancer development in the United States [
12], and the increase in the incidence of HCC was the highest among all types of cancers between 2003 and 2012 [
13].
Due to changes in dietary habits in the last four decades, the proportion of overweight males has continued to increase for all ages and in elderly females in Japan. The increase in the overweight and obese population has resulted in an increased number of patients with diabetes mellitus and fatty liver [
14,
15]. The Japan Diabetes Society (JDS) conducted a nationwide survey investigating causes of death in 45,708 diseased Japanese patients with diabetes from 2001–2010 [
16]. According to the report, the most frequent cause of death was malignant neoplasia (38.3%), followed by infections (17.0%), and then vascular diseases (14.9%). The liver was the second commonest site of cancer-related death after the lung in Japanese diabetic patients, whereas it ranked fifth in the general Japanese population [
17]. We also reported that the incidence of HCC with a non-viral etiology increased rapidly between 1991 and 2015 in Japan from a nationwide survey including more than 7000 patients with non-viral etiology [
18]. In that report, we concluded that the increase in the rate of obesity among Japanese males over the last three decades has contributed to the increase based on the larger proportion of obese and diabetic patients in the cohort.
International guidelines for HCC recommend surveillance for HCC in cirrhotic patients [
19‐
21]. However, the precise definition of at-risk population is still controversial. Generally, the definition should be based on the incidence of HCC and potential therapeutic options to be applied. Some reports suggested that an annual incidence of 1.5–2.0% would warrant the cost-effectiveness of HCC surveillance. According to a large-scale case–control study using the Surveillance Epidemiology and End-Results Program (SEER) database, diabetes carries a threefold increase in the risk of HCC, which is much lower than the 24-fold increased risk of HBV and HCV [
20,
22]. The estimated annual incidence of HCC development in diabetic patients is less than 0.1% [
23], far below the threshold of efficient surveillance. To elucidate the risk factors for HCC in Japanese diabetic patients and provide the best criteria for surveillance candidates, we conducted a nation-wide survey.
Discussion
Diabetes is recognized as a well-established risk factor for HCC, however, other risk factors in diabetes patients without viral hepatitis have rarely been investigated so far because of the low incidence rate in the population [
32]. In this study, we elucidated various potential risk factors for HCC, including male sex, old age, higher BMI, and higher FIB-4. The FIB-4 index, in particular, showed outstanding ability for extracting a high-risk group for surveillance.
Among various mechanisms that have been suggested as involved in the link between diabetes and hepatocarcinogenesis, insulin resistance and subsequent hyperinsulinemia, a key driver in metabolic syndrome, play a major role [
33]. Nonalcoholic fatty liver disease (NAFLD), known as a hepatic manifestation of metabolic syndrome, and its progressive form, nonalcoholic steatohepatitis (NASH), are evident background conditions of HCC development [
32]. However, the HCC incidence rate in NAFLD or NASH patients is as low as less than 0.1 per year unless the patients progress to cirrhosis [
34‐
36]. Therefore, to identify patients with advanced fibrosis is mandatory for the surveillance of non-viral HCC. Besides, hepatic steatosis decreases according to disease progression, and in the final stage of the disease, known as burned-out NASH, fatty liver cannot be detected by regular ultrasonography [
37]. The proportion of patients with fatty liver decreased during the follow-up period of this study. Therefore, the presence of fatty liver is not necessary for the enrollment of surveillance.
The FIB-4 index was originally developed for the prediction of significant fibrosis in patients with HIV/HCV coinfection [
27]. Now, it is widely used for prediction of various liver diseases, including NAFLD [
31]. Since the FIB-4 index includes age, there can be an argument that it overestimates liver fibrosis in elderly patients [
38]. However, this disadvantage of the FIB-4 index in fibrosis estimation is rather an advantage in the risk estimation for HCC because old age is a strong risk factor in hepatocarcinogenesis. The APRI, another commonly used index for liver fibrosis, showed similar but slightly smaller predictive power than the FIB-4 index since the former does not include age as a component.
Although the specific protocol of surveillance for HCC in diabetes patients is open to debate, it would be a good idea to use the FIB-4 index as an entry test. Once-a-year examination of AST, ALT, and platelet count is inexpensive and acceptable. The cut-off value of 3.61 may identify patients at a 1% annual risk of HCC development. However, since the cut-off value misses approximately two-thirds of HCC patients, a two-step screening strategy combining FIB-4 and other non-invasive tests would be better. For that purpose, the cut-off value of 2.67 is a promising candidate. If the cut-off value of 2.67 was applied, approximately 10% of patients in the T2DM cohort would have undergone further examination.
In this study, higher BMI indicated an increased risk of HCC even after adjustment for other risk factors. Obesity, a key component of metabolic syndrome, causes adipose tissue remodeling and induces increased secretion of pro-inflammatory adipokines, including TNF-α and IL-6, and decreased anti-inflammatory adipokines like adiponectin, which potentially accelerates hepatocarcinogenesis [
39,
40]. Obesity is reported to be a risk factor for HCC in both hepatitis B and C [
41,
42].
Among key components of metabolic syndrome, whilst hypertension was an independent risk factor for HCC in this study, dyslipidemia was inversely related to HCC development, probably because of reduced cholesterol synthesis in advanced liver diseases. It should be noted that the absence of dyslipidemia along with decreased hepatic steatosis may not indicate a lower risk of HCC. Similarly, HbA1c superficially improved during the observation period of 5 years. This was mainly because the hemoglobin level also decreased due to the shortened half-life of erythrocytes according to cirrhosis progression. Thus, improved HbA1c values may also not indicate a decreased risk of HCC.
Excessive alcohol intake is an established risk for HCC [
43]. In the present study, 16.3% of HCC patients and 27.8% of patients in the T2DM cohort who develop HCC were categorized as heavy drinkers (≥ 60 g/day), whereas the proportion was 4.4% in non-HCC patients. It is controversial whether heavy alcohol drinkers with T2DM should be treated within the same surveillance strategy for non-drinkers and moderate drinkers or outside the framework as a definite category of alcoholic liver disease. There is a concern that the FIB-4 index may not be useful for alcoholic liver disease in which AST elevation is more prominent than NAFLD. However, our previous reports of a nation-wide survey of non-viral HCC showed that the FIB-4 index was stable compared to AST and GGT during moderation in drinking [
18].
The present study has several limitations. First, since the number of HCC cases in the cohort study was only 18, the annual incidence of HCC may not be statistically accurate. The cut-off points of the FIB-4 index, which was based on the incidence, should be validated in a prospective study. Second, this study could not elucidate the effect of anti-diabetic treatment on hepatocarcinogenesis. Metformin reportedly reduces the risk of HCC in diabetic patients [
44]. We collected data regarding anti-diabetic treatment in this study. However, as metformin was regarded as contraindicated for cirrhosis and treatment choice for anti-diabetic drugs varies according to years, the statistical power was not enough to obtain a robust result. Third, as the HCC patients can be regarded as cancer-free for 5 years ahead of HCC diagnosis according to the enrollment criteria, the magnitude of risk factors for HCC development may be underestimated. Nevertheless, the risk factors that remained after multivariate analysis would be invariant.
Forth, the prospective cohort consisted only of patients who were followed at the tertiary care hospitals. Since those who were referred to other affiliated hospitals and thus excluded from the prospective study might have a better condition, the cumulative HCC incidence could be overestimated.
In conclusion, we found various common risk factors for HCC development in diabetic patients. A simple calculation of the FIB-4 index in diabetes clinics can be the first step for the surveillance of HCC with non-viral etiology. We would start a prospective study to validate the efficacy of FIB-4-based surveillance strategy in the near future.
Acknowledgements
The following investigators enrolled patients in the LUCID study: Yoshiyasu Karino, Shuhei Hige, Masatomo Sekiguchi (Hokkaido P.W.F.A.C. Sapporo-Kosei General Hospital), Koji Ogawa, Hideaki Miyoshi, KyuYong Cho (Hokkaido University Hospital), Masaru Baba, Atsushi Inoue (Japan Community Health Care Organization Hokkaido Hospital), Kazuobu Aso, Mitsuyoshi Okada (Asahikawa Medical University), Yasuhiro Takikawa, Kei Endo, Yasushi Ishigaki, Hirobumi Togashi (Iwate Medical University), Michiaki Unno, Takanori Morikawa, Hideki Katagiri, Shojiro Sawada (Tohoku University Hospital), Hiromasa Ohira, Atsushi Takahashi, Michio Shimabukuro, Akihiro Kudo (Fukushima Medical University Hospital), Naomi Tanaka, Junko Mitsuhashi, Toshifumi Tokai (Koyama Memorial Hospital), Yasushi Matsuzaki, Tadashi Ikegami (Tokyo Medical University Ibaraki Medical Center), Masato Imai (Utsunomiya Memorial Hospital), Kou Nishikawa, Sadao Takahashi (Ageo Central General Hospital), Sumiko Nagoshi, Kosuke Maezawa, Masafumi Matsuda (Saitama Medical Center), Tetsuhiro Chiba, Masayuki Yokoyama, Koutaro Yokote, Yoko Hidetaka (Chiba University Hospital), Mitsuhiko Moriyama, Hitomi Nakamura, Midori Fujishiro (Nihon University Hospital), Tadakazu Hisamatsu, Kaori Nishikawa (Kyorin University Hospital), Toshihiko Nouchi, Yuki Sakurai, Harumi Daikoku (Showa General Hospital), Michinori Murayama (Self-Defence Forces Central Hospital), Yoshinori Saigusa, Takashi Matsui (Toho Umiversity Medical Center Ohashi Hospital), Kazuhiko Koike, Ryosuke Tateishi, Naoto Kubota, Takayoshi Sasako (The University of Tokyo Hospital), Hidenari Nagai, Takanori Mukozu, Takahisa Hirose, Masahiko Miyagi (Toho Umiversity Medical Center Omori Hospital), Sumio Watanabe, Kazuyoshi Kon, Hirotaka Watada, Hiroaki Sato (Juntendo University Hospital), Akira Mizuki, Masanori Miura (Keiyu Hospital), Yuzuru Sato, Rena Kaneko, Kumiko Hamano, Hiroko Kato (Japan Organization of Occupational Health and Safety Kanto Rosai Hospital), Kentaro Kikuchi, Yusuke Kajiyama (Teikyo University Hospital, Mizonokuchi), Makoto Chuma, Hiroko Ito (Yokohama City University Medical Center), Hiroshi Yasuda, Nobuyuki Matsumoto, Yasushi Tanaka, Yoshio Nagai (St. Marianna University School of Medicine Hospital), Kento Imajo, Yasuo Terauchi, Yuzuru Ito (Yokohama City University Hospital), Shuji Terai, Hirohito Sone, Satoshi Matsunaga (Niigata University Medical & Dental Hospital), Kiyoshi Furuta (Matsumoto Medical Center), Eiji Tanaka, Takeji Umemura, Mitsuhisa Komatsu, Yoshihiko Sato (Shinshu University Hospital), Yoshinobu Hinoue, Akiko Shimizu (Toyama City Hospital ), Terumi Takahara, Kengo Kawai, Kazuyuki Tobe, Isao Usui (Toyama University Hospital), Hajime Ohta, Takuya Komura, Seiichiro Kurita (National Hospital Organization Kanazawa Medical Center), Nobuyuki Toshikuni, Daisuke Koya, Ai Watanabe (Kanazawa Medical University Hospital), Yasunari Nakamoto, Tomoyuki Nemoto, Tadashi Konoshita (University of Fukui Hospital), Yoshimasa Kobayashi, Shin Shimoyama (Hamamatsu University Hospital), Daisaku Nishimura (Toyota Kosei Hospital ), Masami Imoto, Sayori Nakashima, Tatsuo Mizuno (Kariya Toyota General Hospital), Kentaro Yoshioka, Naoto Kawabe, Suzuki Atsushi, Ayako Kakita (Fujita Health University Hospital), Yuji Kojima, Kazuya Murata (Japanese Red Cross Ise Hospital), Yoshiyuki Takei, Motoo Iwasa, Yutaka Yano (Mie University Hospital), Masahiko Kondo, Motozumi Okamoto (Japanese Red Cross Otsu Hospital), Hiroyuki Kimura (Japanese Red Cross Kyoto Daiichi Hospital), Hiroyuki Marusawa, Yuji Eso, Yoshihito Fujita (Kyoto University Hospital), Hideki Fujii, Masaaki Inaba, Masanori Emoto (Osaka City University Hospital), Takeshi Kurose (Kansai Electric Power Hospital), Takeshi Okanoue, Toshihide Shima, Shinichi Mogami (Saiseikai Suita Hospital), Rinako Tsuda, Emiko Nomura (Kansai Medical University Medical Center), Masayoshi Ohnishi (Osaka General Hospital of West Japan Railway Company), Masatoshi Kudo, Naoshi Nishida, Hiroshi Ikegami, Hiroyuki Ito (Kindai University Hospital), Hirokazu Oyamada, Yasutaka Nagao, Hiroshi Okada (Matsushita Memorial Hospital), Masahide Oshita, Tetsuyuki Yasuda (Osaka Police Hospital), Toshifumi Ito, Nobuyuki Tatsumi (Japan Community Health care Organization Osaka Hospital), Teruhisa Morikawa (Akashi City Hospital), Noriko Takahara (Ako City Hospital), Takumi Fukumoto, Motofumi Tanaka, Wataru Ogawa, Yushi Hirota (Kobe University Hospital), Seitetsu Yung, Keiji Iida (Hyogo Prefectural Kakogawa Medical Center), Hitoshi Yoshiji, Naotaka Shimozato (Nara Medical University Hospital), Gen Inoue, Tomonao Hirobata (Japanese Red Cross Wakayama Medical Center), Junichi Okano, Tsuyoshi Okura (Tottori University Hospital ), Yasushi Uchida, Toshiaki Sato (Matsue Red Cross Hospital), Miwa Kawanaka, Takatoshi Anno (Kawasaki Medical School General Medical Center), Keisuke Hino, Yasuyuki Tomiyama, Hideaki Kaneto (Kawasaki Medical School Hospital), Shinichi Fujioka, Eri Sasaki, Tatsuaki Nakato (Okayama Saiseikai General Hospital), Keiji Tsuji, Yohji Honda, Nozomu Kamei, Mitsue Miyahara (Hiroshima Red Cross Hospital & Atomic-bomb Survivors Hospital), Tsutomu Masaki, Kyoko Oura (Kagawa University Hospital), Yoshiyasu Kisaka, Shozo Miyauchi, Isao Makino (Uwajima City Hospital), Yoichi Hiasa, Yohei Koizumi, Osawa Haruhiko, Toshimi Hadate (Ehime University Hospital), Takeaki Sato, Isao Ichino (National Hospital Organization Kokura Medical Center), Hideyuki Nomura, Nobuyuki Yamashita (Shin-Kokura Hospital), Hiroshi Maeno, Sunao Matubayashi, (Fukuoka Tokushukai Hospital), Kenta Motomura, Yukie Ishibashi, Makoto Ide, Yoko Moribe (Aso Iizuka Hospital ), Masaru Harada, Michihiko Shibata, Yosuke Okada, Keiichi Torimoto (Hospital of University of Occupational and Environmental Health, Japan), Takuji Torimura, Takumi Kawaguchi, Yuji Tajiri (Kurume University Hospital), Nobuhiko Higashi, Sakae Nohara (Steel Memorial Yawata Hospital), Yasunori Kawaguchi, Toru Yoshimura (Saga-ken Medical Centre Koseikan), Keizo Anzai, Shinji Iwane, (Saga University Hospital), Kazuhiko Nakao, Naota Taura, Norio Abiru, Yoshitaka Mori (Nagasaki University Hospital), Masataka Seike, Mizuki Endo (Oita University Hospital), Tadanobu Kuribayashi (Koga General Hospital).