Cancer Epidemiology 39 (2015) 838–841

Contents lists available at ScienceDirect

Cancer Epidemiology
The International Journal of Cancer Epidemiology, Detection, and Prevention
journal homepage: www.cancerepidemiology.net

A national proﬁle of the impact of parental cancer on their children inJapan
Izumi Inouea,* , Takahiro Higashia , Momoko Iwamotoa , Sue P. Heineyb ,Tomohiro Tamakic , Kaori Osawad, Miho Inouee , Keiko Shiraishif , Rebekah Kojimag,
Motohiro MatobahaDivision of Health Services Research, Center for Cancer Control and Information Services, National Cancer Center, Japan
College of Nursing, University of South Carolina, United Statesc
Palliative Care Team, Hokkaido University Hospital, JapandTokyo Kyosai Hospital, Japane
Shikoku Cancer Center, JapanfNational Kyushu Cancer Center, Japang
National Cancer Center, Japanh
Department of Palliative Care, Japanese Red Cross Medical Center, Japanb

A R T I C L E I N F O

A B S T R A C T

Article history:
Received 26 March 2015
Received in revised form 24 August 2015
Accepted 2 October 2015
Available online xxx

Objective: Dependent children under the age of 18 are particularly vulnerable to the stress of parental
death from cancer or of having a parent diagnosed and treated for the disease. More and more Japanese
couples are postponing parenthood, which increases their chances of developing cancer while they still
have a dependent child. However, the problem has not received enough attention from healthcare
professionals and policy-makers because the extent and breadth of the problem has never been
examined in the Japanese population. Therefore, we aimed to estimate the nationwide incidence ofcancer patients who have children under the age of 18 years, as well as the incidence of children who havea parent diagnosed with cancer in Japan.
Study design: We calculated the proportion of patients who have children stratiﬁed by age, gender andcancer type using electronic medical records of cancer patients (20–59 years old) admitted to the
National Cancer Center Hospital (NCCH) for the ﬁrst time between January 2009 and December 2013. We
projected these estimates onto the Japanese population using 2010 population-based cancer registrydata, and repeated the projection using 2011 hospital-based cancer registry data so that estimates ofpatients receiving care at Designated Cancer Care (DCC) hospitals could be obtained.
Results: We found that an estimated 56,143 cancer patients who have 87,017 dependent children are
diagnosed with cancer every year in Japan. The proportion of children in Japan who had a parent newly
diagnosed with cancer in 2010 was approximately 0.38%. We estimated that in 2011 there were on
average about 82 cancer patients with minor children and 128 minor children who have at least one
parent diagnosed with cancer in every DCC hospital in Japan.
Conclusion: Parental cancer is common. We have identiﬁed that many adults diagnosed with cancer havethe double burden of coping with the diagnosis and treatment as well as supporting their children
through this experience. Additional data on socioeconomic characteristics and needs assessment of thesepatients are required to understand how best to help children and families cope with cancer.
ã 2015 Elsevier Ltd. All rights reserved.

Keywords:
Parental cancer
ChildrenMinor children
Adolescents
Parents
Incidence
Cancer registry
Japan
Background

1. Background* Corresponding author at: Division of Health Services Research, Center for
Cancer Control and Information Services, National Cancer Center, 5-1-1 Tsukiji,
Chuo-ku, Tokyo 104-0045, Japan. Fax: +81 3 5565 23224.
E-mail address: ikamiya@ncc.go.jp (I. Inoue).
http://dx.doi.org/10.1016/j.canep.2015.10.005
1877-7821/ ã 2015 Elsevier Ltd. All rights reserved.

A cancer diagnosis often has a signiﬁcant negative impact on
the lives of patients and their families [1]. It inﬂuences thepsychosocial and emotional wellbeing of minor children. [2]However, cancer among parents who have dependent children is
becoming an increasing problem in many developed countries as
more people postpone parenthood [3]. The lifetime risk of cancer

I. Inoue et al. / Cancer Epidemiology 39 (2015) 838–841

in Japan is stunningly high compared to that in other countries –56% for males and 43% for females [4] (US: 43% and 38% [5], UK:
44% and 40% [6], respectively) – which means that a greaternumber of individuals will become parents at an age where cancer
risks are high and their children are still young and dependent.
Even if these patients constitute a small group of cancer patients, it
is nonetheless a growing problem that deserves special attention
because of its severe and long-lasting impact on both the child andthe patient.
In spite of this clear need for more attention, no study has ever
captured the severity of the issue in Japan. In Norway, approximately
4% of children aged 0–25 years have or have had parents diagnosed
with cancer, which corresponds to a population prevalence of 1.4%
[7]. At least 18% of cancer patients in the United States have minor
children. [8] The purpose of this study was to obtain national
estimates for the number and proportion of cancer patients who
have dependent minor children, as well as the national estimates forthe number of children with a cancer parent in Japan.
2. Methods
2.1. Data sources
Using the NCCH’s electronic medical records (EMRs), we
identiﬁed patients between the ages of 20 and 59 who wereadmitted to the National Cancer Center Hospital (NCCH) for the ﬁrst
time between January 2009 and December 2013. We extracted theirage at their ﬁrst hospital admission, gender, and the number, age, andgender of their children, and excluded patients who could not be
identiﬁed within the hospital-based cancer registry (HBCR) databasewhich contained their International Classiﬁcation of Diseases
Oncology, 3rd edition (ICD-O-3) topography and morphology codes.
We used the 2010 population-based cancer registry (PBCR) andthe 2011 HBCR data to make inferences for the burden of cancer
among patients with children for the total Japanese population andalso for patients who received care at a designated cancer care

839

(DCC) hospital in Japan. The PBCR collects cancer surveillance datafrom 35 prefectures (out of a total of 47) that have a case reporting
system for newly diagnosed and treated cancer patients from
hospitals and clinics within their prefecture. Because casereporting is not mandatory, PBCR data do not capture all cancer
incidence in Japan [9]. The HBCR, on the other hand, is acompulsory cancer incidence reporting system for DCC hospitals
in Japan. In 2011, there were 395 hospitals that were designated as
DCC by the Ministry of Health, Labor, and Welfare, to play a majorrole in the prevention, diagnosis, and treatment of cancer for mostcancer patients. Although there are non-designated hospitals that
also care for cancer patients, they are not required to submit theirsurveillance data to the HBCR.
2.2. Analyses
We calculated the number and proportion of cancer patientswith dependent children under the age of 18, stratiﬁed by thepatient’s gender, age group (ages 20–29, 30–39, 40–49 and 50–59)
and cancer types from data obtained from NCCH’s EMRs. We alsocounted the total number of children among all cancer parents
according to the child's age group (ages 0–6, 7–12, 13–15, and 16–18) and gender. Data were analyzed using Stata 13.1 (StataCorporation, College Station, TX, USA).
We made inferences for the number of cancer patients who havedependent children in Japan, as well as the number of children with aparent diagnosed with cancer in a year, by multiplying them by theincidence of cancer for patients in the same strata of gender, agegroup, and cancer type as the PBCR. We also estimated the number ofcancer parents and the number of children who have a parent withcancer who received care at DCC hospitals in Japan.
3. Results
Among 12,399 men and 10,786 women who were admitted to
the NCCH for the ﬁrst time between January 2009 and December

Table 1The distribution of cancer patients who are parents between the ages of 20 and 59 at the time of ﬁrst admission to the National Cancer Center Hospital between 2009 and
2013.
Male

FemaleTotal

Age ofpatients

N of patients (% of patientswith minors)

Average N ofchildren

N of patients (% of patientswith minors)

Average N ofchildren

N of patients (% of patientswith minors)

Average N ofchildren

20–29

142
3.5%

1.2

136
11.8%

1.6

278
7.6%

1.5

30–39

389
31.1%

1.7

555
34.2%

1.7

944
32.9%

1.7

40–49

726
46.4%

1.7

1310
41.3%

1.6

2036
43.1%

1.7

50–59

1705
16.8%

1.4

1727
8.9%

1.3

3432
12.8%

1.3

Total

2962
25.3%

1.6

3728
24.1%

1.6

6690
24.7%

1.6

Commoncancer types

Gastric
Lung
Colorectal
Sarcoma
Lymphoma

FemaleMale
N of patients with minors

Total N of patientswith minors

Patients’ age
20–29
30–39

40–49

50–59

0
0
0
0
1

48
41
44
31
27

54
45
37
13
16

15
13
7
23
18

117 (15.6%)
99 (13.2%)
88 (11.7%)
67 (8.9%)
62 (8.3%)

Commoncancer types

BreastUterusGastric
Sarcoma
Colorectal

N of patients with minors

Total N of patientswith minors

Patients’ age
20–29
30–39

40–49

50–59

2
0
2
6
2

241
61
44
31
31

57
15
9
5
14

61
18
12
23
11

361 (40.1%)
94 (10.4%)
67 (7.4%)
65 (7.2%)
58 (6.4%)

840

I. Inoue et al. / Cancer Epidemiology 39 (2015) 838–841

2013, we identiﬁed 8412 patients between the ages of 20 and 59.
We excluded 1295 patients whose data could not be linked to
HBCR data, and further excluded 427 patients with in-situ
carcinoma because these patients were not registered within the
PBCR. This left 2962 males (44.3%) and 3731 females (55.7%) in
the analyses.
We identiﬁed 2593 minor children among 1650 cancer patientsin our study. Roughly a quarter of both male (25.3%) and female(24.1%) patients had at least one minor child (Table 1). The averageage of fathers who had cancer was 3 years older than mothers withcancer (mean: 46.6 versus 43.7 years, SD: 7.0 versus 6.1 years,
P < 0.05). The average number of minor children for a cancer
patient in our study was highest among patients in their 30s and40s. The most common cancer types for fathers with children were
gastric (15.6%), lung (13.2%), and colorectal (11.7%) cancers, and forthe mothers breast (40.1%), uterus (10.4%), gastric (7.4%) cancers(Table 1). The average age of the children was 11.2 years (SD: 5.2).
The proportion of children whose parent had cancer tended toincrease as the child’s age increased (Fig. 1).
Using incidence rates of cancer patients from the PBCR and
HBCR within the same strata of age, gender, and cancer type, weestimated that 56,143 patients with 87,017 children were diagnosed with cancer in Japan in 2010, and among these 32,679 cancer
patients with 50,752 minor children received care at DCC hospitals(Table 2).
4. Discussion
Our study showed that an estimated 56,143 cancer patients
who had 87,017 dependent children were diagnosed with cancer inJapan in a year. Given that the total population of minors in Japanwas 22,780,000 in 2010 [10], the proportion of children with aparent diagnosed with cancer was approximately 0.38%. The mostcommon age group for cancer patients with children was 40–
49 years old, and the most common cancer type was breast cancer.
The number of children with parental cancer increased as thechild’s age increased.

Table 2National estimates of the incidence of cancer patients with children and children
with cancer parents projected from population-based and hospital-based cancer
registry (PBCR and HBCR) data (per 1 year).
Female

Male

Total

Age of patients

PBCR

HBCR

PBCR

HBCR

PBCR

HBCR

20–29
30–39
40–49
50–59

66
1922
9460
13478

78
1417
5210
5910

310
5702
18885
6320

291
5196
11121
3456

377
7623
28345
19797

369
6613
16331
9366

Total

24926

12615

31217

20064

56143

32679

Age of children

PBCR

HBCR

PBCR

HBCR

PBCR

HBCR

0–6
7–12
13–15
16–18

13591
14598
8625
7886

7927
8515
5030
4600

13625
12685
8759
7249

7947
7399
5108
4228

27216
27283
17383
15135

15874
15913
10139
8827

Total

44700

26071

42317

24681

87017

50752

Girls

Boys

Total

PBCR, population-based cancer registry; HBCR, hospital-based cancer registry.

Prior study has shown that patients with invasive cancer who
have dependent children tend to be more anxious, more likely toprefer aggressive treatment over palliative care, and more likely tohave worse quality of life in their last weeks of life compared topatients without dependent children [11]. Adolescent teens who
have a parent with cancer experience higher levels of emotional
stress compared to their younger school-aged counterparts [12,13].
Gender, birth order and number of siblings, and single parenthood
also may predict the risk of emotional problems in the child or
adolescent [14]. Future research should investigate the backgroundand speciﬁc needs of cancer patients and their children, so that
healthcare providers and policy-makers can develop necessary
support services for future patients and their children. Other
countries have developed various programs and interventions to
support children who have a parent with cancer. Support ranges
from family sessions to parallel group sessions for children and

Fig. 1. The distribution of the ages of dependent children with a parent diagnosed with cancer in the National Cancer Center Hospital between 2009 and 2013.

I. Inoue et al. / Cancer Epidemiology 39 (2015) 838–841

parents [15]. These programs suggest the need to explore the typesof psychosocial support that might be provided in Japan.
There are several limitations to this study. First, we used ﬁguresobtained at the NCCH to make national inferences using PBCR
cancer incidence data from patients in the same strata of age,gender, and cancer type. Therefore, if the number of the children
within the same stratum in our study is different from that of theentire cancer patient population in Japan, our estimates may bebiased. Another limitation arises from the use of PBCR data, which
does not have a mandatory reporting system and does not capture
all incidences of cancer in Japan. This may have resulted in anunderestimation of our ﬁndings. Lastly, we did not include datafrom cancer patients who were very young or very old. However,
we obtained similar results to those of a study in Norway that usedcancer registry and national birth cohort data of cancer patients
between 17 and 70 years of age. They report that annual incidenceof parental cancer for children under 18 years of age was 0.3%.
Future studies should include data from various hospitals so that amore representative estimate is obtained.
5. Conclusion
To our knowledge, this is the ﬁrst study to estimate thenationwide incidence of cancer among patients who have minor
children in Japan. Our ﬁnding showed that a substantial number ofchildren are likely to be experiencing the hardships of having theirparents diagnosed with cancer. Greater attention should be paid tothese children by both service-providers and policy-makers. The
cancer parent also faces the added burden of child-rearing while
undergoing cancer treatment. More research on the demographic
and socioeconomic characteristics of these patients will be helpful
in understanding the needs of the patients and in planningeffective support programs for both cancer patients and theirchildren.
Authors’ contribution
I declare that all authors participated sufﬁciently in thisresearch. All authors participated in drafting the article or revising
it critically for important content, and gave ﬁnal approval of theversion to be submitted and any revised version.
Speciﬁc contributions were made by:Conception and design: I. Inoue, Higashi, Iwamoto, Heiney,
Tamaki, Osawa, M. Inoue, Shiraishi, Kojima, Matoba.
Analysis and interpretation: I. Inoue, Iwamoto, Heiney,
Higashi.
Data collection: I. Inoue, Higashi, Iwamoto, Heiney, Tamaki,
Osawa, M. Inoue, Shiraishi, Kojima, Matoba.
Writing the article: I. Inoue, Higashi, Iwamoto, Heiney.

841

Critical revision of the article: I. Inoue, Higashi, Iwamoto,Heiney, Tamaki, Osawa, M. Inoue, Shiraishi, Kojima, Matoba.
Final approval of the article: I. Inoue, Higashi, Iwamoto,Heiney, Tamaki, Osawa, M. Inoue, Shiraishi, Kojima, Matoba.
Statistical analysis: I. Inoue, Higashi, Iwamoto.
Obtained funding: Tamaki, Osawa, M. Inoue, Shiraishi, Kojima,
Matoba.
Overall responsibility: I. Inoue, Higashi, Iwamoto, Heiney,
Tamaki, Osawa, M. Inoue, Shiraishi, Kojima, Matoba.
Acknowledgement
This research was supported by a grant from the Ministry of
Education, Culture, Sports, Science and Technology of Japan (JSPS
25282227).
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