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Gastric Cancer

, Volume 22, Issue 3, pp 456–462 | Cite as

How long should we continue gastric cancer screening? From an epidemiological point of view

  • Yuri MizotaEmail author
  • Seiichiro Yamamoto
Open Access
Original Article

Abstract

Background

In Japan, incidence of gastric cancer is expected to follow the current downward trend as the younger generation has lower incidence of Helicobacter pylori infection. In this study we aimed to estimate how long gastric cancer screening is deemed necessary in the future from epidemiologic perspectives.

Methods

Following the Japanese guidelines for gastric cancer screening 2014, recommendation of providing population-based gastric cancer screening is judged by balancing benefits and harms. Benefits and harms are estimated by number needed to screen (NNS) < 1000 and Number Needed to Recall (NNR) < 100. NNS is the number of people required to participate in a screening to prevent one death and NNR is the number of people required to undergo diagnostic examination to prevent one death. These index are estimated for 2020–2035 using future projections of gastric cancer mortality for the scenarios of relative risk (RR) of 0.5–0.9 for mortality reduction by the screening.

Results

The criteria of both NNS < 1000 and NNR < 100 are fulfilled for the following age groups: when RR is set as 0.6, men ≥ 55 and women ≥ 65; when RR is set as 0.7 and 0.8, men ≥ 65 and women ≥ 75; when RR is set as 0.9, men ≥ 75 only.

Conclusions

In case of RR of 0.5 and 0.6, the gastric cancer screening are recommended for men ≥ 55 and women ≥ 65 until 2035, while it is not recommended for men and women in the 45–54 even in 2010 and 2015.

Keywords

Gastric cancer Cancer screening Guidelines 

Introduction

In Japan, incidence of gastric cancer is expected to follow the current downward trend as the younger generation has lower incidence of Helicobacter pylori infection [1]. In this study, therefore, we aimed to estimate how long gastric cancer screening is deemed necessary in the future from epidemiologic and statistical perspectives. Of note, for clarification purposes, population-based screening was selected as a screening mode to be analyzed in this study.

In Japan, based on the “Japanese guidelines for gastric cancer screening 2014 edition” edited by the National Cancer Center [2], the Ministry of Health, Labor, and Welfare recommends radiographic screening and endoscopy as population-based screening [3]. Especially, endoscopy screening was recommended very recently since 2016. In principle, population-based screening should be introduced and conducted after comparing and weighing the benefits regarding mortality reduction and harms concerning screening [4, 5]. Even though there are many disagreements over whether performing screenings falling short of such standard is justifiable, few may take a critical attitude toward conducting screenings if they meet this standard. The challenge here is how to compare the benefits, i.e., size of mortality reduction, to the potential harms of screening. The most common harms associated with screening include false-negative test results, false-positive test results, overdiagnosis, as well as adverse reactions to screening and diagnostic examination procedures. It is not easy to compare these issues with the size of mortality reduction effect because they have fundamentally different natures. In the Japanese guidelines for cancer screening 2014 edition, for comparison between benefits and harms of screening, Number Needed to Screen (NNS), representing the size of mortality reduction effect, is used as a benefit indicator, while recall rate is employed as a risk indicator, which is the same as the Japanese guidelines for breast cancer screening [6]. NNS is an estimated number of people required to participate in a screening program to prevent one death over a defined time interval, and thus the smaller NNS implies larger benefits. On the other hand, recall rate is the number of people required to undergo diagnostic examination procedures to prevent one death over a defined time interval, referred as number needed to recall (NNR) in this article, and the larger NNR implies larger harms, i.e., causing inconvenience to more people. In the above-mentioned Guidelines, the thresholds of 1000 and 100 are set as tentative criteria for NNS and NNR, respectively. To judge the length to continue gastric cancer screening, these criteria were used in the present study due to the following facts: these numbers have been employed in the Guidelines in widespread use; using them can allow qualitative analyses; and there are no alternative proven criteria available. In short, we calculate NNS and NNR, compare them to their corresponding threshold of 1000 and 100, and use the comparison results as a part of a basis for deciding whether it is justifiable to continue or discontinue the gastric cancer screening programs.

To maximize the effect of population-based screening, higher participation rate is necessary. Nevertheless, participation rate is as low as 40% in Japan [7] and the government set the goal as 50% in the Third term Basic Plan to Promote Cancer Control Programs in Japan [8]. Since the number of life saved (NLS) varies according to the participation rate, NLS of participation rate 50% and 100% compared to that of NLS of present rate (40%) are also used as a benefit indicator in this study.

Methods

NNS, NNR, and NLS are estimated by sex and age group. Estimations of NNS, NNR, and NLS require data on gastric cancer mortality, screening effect on mortality reduction, and recall rate. The projections of future gastric cancer deaths by sex and age group in Japan are available from the National Cancer Center [9]. While people are divided into the 7 age groups as follows: 0–14, 15–44, 45–54, 55–64, 65–74, older than or equal to 75 years of age, and all ages, we selected age groups at the time of screening as follows: 45–54, 55–64, 65–74, and older than or equal to 75 years of age in our study. In addition to the number of deaths, estimations of mortality rates require estimates of future population, which should be calculated using the same method and numbers used for calculation of the number of deaths, and thus, we used the method described in the reference [10]. However, since there is no publicly disclosed prediction for the future Japanese population in the period of 2015 and beyond, a ratio of Japanese population to the total population in Japan by sex and 5-year age groups were calculated, which in turn was multiplied by the total population estimates (estimated median numbers of births and deaths) for the year of 2020, 2025, 2030, and 2035, to obtain estimates of future Japanese population by sex and 5-year age groups. These data on the Japanese total population are published by The National Institute of Population and Social Security Research [11]. The projections of the gastric cancer mortality rates are estimated for 2020, 2025, 2030, and 2035 using future number of deaths estimates of 2020–2024, 2025–2029, 2030–2034, and 2035–2039, respectively. Mortality trends are shown using observed value until 2015 [12] and estimates for 2020–2035.

To estimate NNS, the above-mentioned Guidelines used relative risks (RR) of gastric cancer mortality reduction for effectiveness of radiography test and endoscopy test from several studies [13, 14, 15]. In this study, several relative risk values associated with screening are used for estimation of future NNSs and NNRs in different scenarios. For reference, Table 1 lists the relative risk values used in the Guidelines. These relative risk values ranged from 0.1 to 1.07, which included those either too large or too small to exert any effects, and thus 5 values (0.5, 0.6, 0.7, 0.8, and 0.9) were selected to be used in the scenarios in this study. Recently Korean study reported that the effectiveness of endoscopy screening is RR of 0.53 (95% CI 0.51–0.56), which is not contradict from our scenarios [16].

Table 1

Relative risk used to estimate number needed to screen in the Japanese guidelines for gastric cancer

Screening

Study

Sex

Age-specific relative risk

40

45

50

55

60

65

70

75

Radiography

Abe et al. [13]

Male

0.105

0.105

0.25

0.25

0.271

0.271

0.429

0.429

Female

0.778

0.778

0.2

0.2

0.385

0.385

0.882

0.882

Fukao et al. [14]

Male

  

0.46

0.46

0.34

0.34

0.25

0.25

Female

  

1.07

1.07

0.45

0.45

0.63

0.63

Hamashima et al. [15]

Male

0.865

0.865

0.865

0.865

0.865

0.865

0.865

0.865

Female

0.865

0.865

0.865

0.865

0.865

0.865

0.865

0.865

Endoscopy

Hamashima et al. [15]

Male

0.695

0.695

0.695

0.695

0.695

0.695

0.695

0.695

Female

0.695

0.695

0.695

0.695

0.695

0.695

0.695

0.695

Japanese Guidelines for Gastric Cancer 2014 edition. http://canscreen.ncc.go.jp/

Recall rates cited in the above-mentioned Guidelines are radiography test data derived from the annual report 2011 of The Japanese Society of Gastrointestinal Cancer Screening [17], and endoscopy data collected in Niigata City reported in 2012 [18] (Table 2). The ranges of recall rates for radiography test and endoscopy were reported as 4.1–12.2% and 2.9–11.6%, respectively. In this study, we used relative risks of 5% and 10% as scenarios.

Table 2

Recall rate used to estimate number needed to recall in the Japanese guidelines for gastric cancer

Screening

Study

Sex

Age-specific recall rate (%)

40

45

50

55

60

65

70

75

Radiography

JSGCS [17]

Male

4.8

6.0

7.9

9.8

11.3

11.9

12.2

12.2

Female

4.1

4.72

5.7

6.5

7.3

7.9

8.5

8.5

Endoscopy

Niigata City [18]

Male

2.9

8.9

11.6

9.7

11.5

11.0

11.2

11.2

Female

5.8

5.4

6.4

6.7

7.5

7.3

7.3

7.3

Japanese Guidelines for Gastric Cancer 2014 edition. http://canscreen.ncc.go.jp/

For estimating NLS, hypothetical number of gastric cancer deaths without screening, D0s, is estimated as follows:
$${\hat {D}_0}=\frac{{{D_{{\text{obs}}}}}}{{1 - {P_{{\text{obs}}}}\left( {1 - {\text{RR}}} \right)}},$$
where Dobs is observed number of deaths and Pobs is observed participation rate of screening. NLSt is estimated as a function of target participation rate Pt:
$$N\hat {L}{S_t}={D_0}\left( {1 - {P_t}\left( {1 - {\text{RR}}} \right)} \right).$$

The observed participation rate is set as 40% and target participation rates are set as 50% and 100%. For the future predication, Pobs is assumed as the same as the present participation rate, i.e., 40%.

Results

Figures 1 and 2 show past transition and future projections of gastric cancer mortalities by age groups. Downward trends are obvious for both men and women in every age group equal to and older than 45 years old.

Fig. 1

Observed and projected trends of age-specific gastric cancer mortality in Japan for male

Fig. 2

Observed and projected trends of age-specific gastric cancer mortality in Japan for female

Tables 3 and 4 show estimates of NNS and NNR. It might be obvious, but higher relative risks (small effect) and/or lower mortality rates make NNS higher. The results indicated that the benefits of the screening exceeded harms more prominently in men than women, older than younger age groups, and now than future. The criteria of both NNS and NNR would be fulfilled, that is, the both benefits and harms are considered within acceptable limits to justify the screening, for the following age groups (year-old): when relative risk (RR) of screening is set as 0.5, men ≥ 55 and women ≥ 65; when RR is set as 0.6, men ≥ 55 and women ≥ 65; when RR is set as 0.7, men ≥ 65 and women ≥ 75; and when RR is set as 0.8, men ≥ 65 and women ≥ 75; when RR is set as 0.9, men ≥ 75 only.

Table 3

Number needed to screen, number needed to recall, and number of life saved by gastric cancer screening based on future prediction of gastric cancer mortality

Mortality reductiona

Year

Age 45–54

Age 55–64

Age 65–74

Age 75-

Mortality rate for 10 yearsb (%)

NNSc

NNRd

NLS5

Mortality rate for 10 years (%)

NNS

NNR

NLS

Mortality rate for 10 years (%)

NNS

NNR

NLS

Mortality rate for 10 years (%)

NNS

NNR

NLS

Recall rate

Participation rate

Recall rate

Participation rate

Recall rate

Participation rate

Recall rate

Participation rate

5%

10%

50%

100%

5%

10%

50%

100%

5%

10%

50%

100%

5%

10%

50%

100%

RRd = 0.5

2010

0.13

1560

78

156

63

376

0.54

372

19

37

310

1861

1.32

151

8

15

593

3559

3.21

62

3

6

1071

6428

 

2015

0.09

2140

107

214

49

293

0.40

497

25

50

199

1197

1.09

184

9

18

565

3393

2.79

72

4

7

1095

6572

 

2020

0.07

2709

135

271

43

255

0.31

643

32

64

147

881

0.93

214

11

21

486

2914

2.54

79

4

8

1165

6990

 

2025

0.10

2725

136

273

41

248

0.33

706

35

71

143

855

0.89

252

13

25

354

2126

2.55

89

4

9

1229

7376

 

2030

0.08

2503

125

250

39

233

0.28

725

36

73

153

919

0.72

278

14

28

308

1849

2.13

94

5

9

1224

7346

 

2035

0.09

2210

110

221

39

233

0.27

732

37

73

148

889

0.69

290

14

29

317

1901

2.04

98

5

10

1148

6885

RR = 0.6

2010

0.13

1950

97

195

48

287

0.54

465

23

47

236

1418

1.32

189

9

19

452

2711

3.21

78

4

8

816

4897

 

2015

0.09

2675

134

268

37

223

0.40

621

31

62

152

912

1.09

230

11

23

431

2585

2.79

90

4

9

835

5007

 

2020

0.07

3386

169

339

32

194

0.31

804

40

80

112

671

0.93

268

13

27

370

2220

2.54

98

5

10

888

5326

 

2025

0.10

3407

170

341

31

189

0.33

882

44

88

109

651

0.89

315

16

32

270

1620

2.55

111

6

11

937

5620

 

2030

0.08

3129

156

313

30

177

0.28

906

45

91

117

700

0.72

348

17

35

235

1409

2.13

117

6

12

933

5597

 

2035

0.09

2762

138

276

30

177

0.27

915

46

92

113

677

0.69

362

18

36

241

1449

2.04

123

6

12

874

5246

RR = 0.7

2010

0.13

2600

130

260

34

205

0.54

620

31

62

169

1015

1.32

252

13

25

324

1941

3.21

104

5

10

584

3506

 

2015

0.09

3567

178

357

27

160

0.40

829

41

83

109

653

1.09

306

15

31

308

1851

2.79

120

6

12

597

3585

 

2020

0.07

4515

226

452

23

139

0.31

1072

54

107

80

481

0.93

357

18

36

265

1589

2.54

131

7

13

635

3813

 

2025

0.10

4542

227

454

23

135

0.33

1176

59

118

78

466

0.89

420

21

42

193

1160

2.55

148

7

15

671

4023

 

2030

0.08

4171

209

417

21

127

0.28

1208

60

121

84

501

0.72

463

23

46

168

1008

2.13

156

8

16

668

4007

 

2035

0.09

3683

184

368

21

127

0.27

1220

61

122

81

485

0.69

483

24

48

173

1037

2.04

163

8

16

626

3755

RR = 0.8

2010

0.13

3900

195

390

22

131

0.54

930

47

93

108

647

1.32

378

19

38

206

1238

3.21

156

8

16

373

2236

 

2015

0.09

5351

268

535

17

102

0.40

1243

62

124

69

416

1.09

459

23

46

197

1180

2.79

179

9

18

381

2286

 

2020

0.07

6773

339

677

15

89

0.31

1608

80

161

51

307

0.93

535

27

54

169

1013

2.54

197

10

20

405

2431

 

2025

0.10

6814

341

681

14

86

0.33

1765

88

176

50

297

0.89

630

32

63

123

740

2.55

222

11

22

428

2566

 

2030

0.08

6257

313

626

13

81

0.28

1813

91

181

53

320

0.72

695

35

70

107

643

2.13

234

12

23

426

2555

 

2035

0.09

5525

276

552

13

81

0.27

1830

92

183

52

309

0.69

724

36

72

110

661

2.04

245

12

25

399

2395

RR = 0.9

2010

0.13

7799

390

780

10

63

0.54

1860

93

186

52

310

1.32

755

38

76

99

593

3.21

312

16

31

179

1071

 

2015

0.09

10702

535

1070

8

49

0.40

2486

124

249

33

199

1.09

918

46

92

94

565

2.79

359

18

36

183

1095

 

2020

0.07

13546

677

1355

7

43

0.31

3215

161

322

24

147

0.93

1071

54

107

81

486

2.54

394

20

39

194

1165

 

2025

0.10

13627

681

1363

7

41

0.33

3529

176

353

24

143

0.89

1261

63

126

59

354

2.55

444

22

44

205

1229

 

2030

0.08

12514

626

1251

6

39

0.28

3625

181

363

26

153

0.72

1390

70

139

51

308

2.13

469

23

47

204

1224

 

2035

0.09

11050

552

1105

6

39

0.27

3661

183

366

25

148

0.69

1448

72

145

53

317

2.04

490

25

49

191

1148

aRelative risk for mortality reduction by screening

bGastric cancer mortality rate fro 10 years

cNumber needed to screen

dNumber needed to recall

eNumber of life saved

Table 4

Number needed to screen, number needed to recall, and number of life saved by gastric cancer screening based on future prediction of gastric cancer mortality

Mortality reductiona

Year

Age 45–54

Age 55–64

Age 65–74

Age 75-

Mortality rate for 10 yearsb (%)

NNSc

NNRd

NLSe

Mortality rate for 10 years (%)

NNS

NNR

NLS

Mortality rate for 10 years (%)

NNS

NNR

NLS

Mortality rate for 10 years (%)

NNS

NNR

NLS

Recall rate

Participation rate

Recall rate

Participation rate

Recall rate

Participation rate

Recall rate

Participation rate

5%

10%

50%

100%

5%

10%

50%

100%

5%

10%

50%

100%

5%

10%

50%

100%

RR = 0.5

2010

0.08

2497

125

250

39

233

0.20

1019

51

102

116

698

0.38

525

26

53

192

1149

1.28

156

8

16

706

4236

 

2015

0.06

3339

167

334

31

184

0.15

1304

65

130

77

465

0.32

617

31

62

186

1113

1.09

183

9

18

680

4081

 

2020

0.04

4893

245

489

23

139

0.12

1722

86

172

56

334

0.30

675

34

68

168

1009

0.98

204

10

20

694

4166

 

2025

0.04

5198

260

520

21

128

0.10

1980

99

198

51

308

0.25

792

40

79

123

735

0.91

221

11

22

736

4418

 

2030

0.04

5090

255

509

19

113

0.09

2124

106

212

53

315

0.23

887

44

89

104

623

0.90

222

11

22

768

4609

 

2035

0.04

4791

240

479

18

105

0.09

2234

112

223

49

293

0.21

959

48

96

102

611

0.92

218

11

22

775

4650

RR = 0.6

2010

0.08

3121

156

312

30

177

0.20

1273

64

127

89

532

0.38

656

33

66

146

876

1.28

195

10

19

538

3227

 

2015

0.06

4174

209

417

23

140

0.15

1630

82

163

59

354

0.32

771

39

77

141

848

1.09

229

11

23

518

3109

 

2020

0.04

6117

306

612

18

106

0.12

2153

108

215

42

254

0.30

844

42

84

128

769

0.98

255

13

25

529

3174

 

2025

0.04

6497

325

650

16

97

0.10

2475

124

247

39

234

0.25

990

50

99

93

560

0.91

276

14

28

561

3366

 

2030

0.04

6363

318

636

14

86

0.09

2655

133

266

40

240

0.23

1109

55

111

79

474

0.90

277

14

28

585

3511

 

2035

0.04

5989

299

599

13

80

0.09

2792

140

279

37

223

0.21

1199

60

120

78

466

0.92

273

14

27

590

3543

RR = 0.7

2010

0.08

4161

208

416

21

127

0.20

1698

85

170

63

381

0.38

875

44

88

104

627

1.28

260

13

26

385

2311

 

2015

0.06

5565

278

557

17

100

0.15

2173

109

217

42

253

0.32

1028

51

103

101

607

1.09

306

15

31

371

2226

 

2020

0.04

8156

408

816

13

76

0.12

2870

144

287

30

182

0.30

1125

56

113

92

550

0.98

339

17

34

379

2273

 

2025

0.04

8663

433

866

12

70

0.10

3300

165

330

28

168

0.25

1320

59

132

67

401

0.91

368

18

37

402

2410

 

2030

0.04

8484

424

848

10

61

0.09

3541

177

354

29

172

0.23

1478

74

148

57

340

0.90

370

18

37

419

2514

 

2035

0.04

7985

399

799

10

57

0.09

3723

186

372

27

160

0.21

1599

80

160

56

333

0.92

363

18

36

423

2536

RR = 0.8

2010

0.08

6241

312

624

14

81

0.20

2546

127

255

40

243

0.38

1313

66

131

67

400

1.28

390

19

39

246

1473

 

2015

0.06

8348

417

835

11

64

0.15

3260

163

326

27

162

0.32

1542

77

154

65

387

1.09

459

23

46

237

1420

 

2020

0.04

12234

612

1223

8

48

0.12

4306

215

431

19

116

0.30

1688

84

169

58

351

0.98

509

25

51

242

1449

 

2025

0.04

12994

650

1299

7

44

0.10

4949

247

495

18

107

0.25

1980

99

198

43

256

0.91

551

28

55

256

1537

 

2030

0.04

12726

636

1273

7

39

0.09

5311

266

531

18

110

0.23

2218

111

222

36

217

0.90

554

28

55

267

1603

 

2035

0.04

11978

599

1198

6

37

0.09

5584

279

558

17

102

0.21

2398

120

240

35

213

0.92

545

27

55

270

1617

RR = 0.9

2010

0.08

12483

624

1248

6

39

0.20

5093

255

509

19

116

0.38

2626

131

263

32

192

1.28

779

39

78

118

706

 

2015

0.06

16695

835

1670

5

31

0.15

6520

326

652

13

77

0.32

3083

154

308

31

186

1.09

917

46

92

113

680

 

2020

0.04

24467

1223

2447

4

23

0.12

8611

431

861

9

56

0.30

3376

169

338

28

168

0.98

1018

51

102

116

694

 

2025

0.04

25988

1299

2599

4

21

0.10

9899

495

990

9

51

0.25

3960

198

396

20

123

0.91

1103

55

110

123

736

 

2030

0.04

25452

1273

2545

3

19

0.09

10622

531

1062

9

53

0.23

4435

222

444

17

104

0.90

1109

55

111

128

768

 

2035

0.04

23955

1198

2396

3

18

0.09

11169

558

1117

8

49

0.21

4796

240

480

17

102

0.92

1090

55

109

129

775

aRelative risk for mortality reduction by screening

bGastric cancer mortality rate fro 10 years

cNumber needed to screen

dNumber needed to recall

eNumber of life saved

NLS, which is a function of RR, mortality, and participation rate, is substantial for age 65 or older when participation rate is 50% as a national goal while it is not so large for either two combination of female, RR ≥ 0.8, and age 54 or younger.

Discussion

In this study, target population and length appropriate to continue gastric cancer screening were investigated based on the future projection of gastric cancer mortality, from the standpoint of balancing the benefits and harms of the screening. As a result, until 2035, screening programs with higher mortality reduction effects (relative risk 0.5 and 0.6) are shown to be beneficial for men ≥ age 55 and women ≥ age 65. It is expected that, under conditions and scenarios selected in this study, both men and women in the 45–54 age group did not meet the criteria for benefits and harms even in 2010 and 2015.

This study can provide evidence for the decision based on benefits and harms by numerical criteria using NNS, NNR, and NSL. In this way, balancing estimates of benefits and harms is a standard method to evaluate whether to introduce and continue population-based screening [5, 19, 20]. While more comprehensive balance sheets have been proposed [21, 22], typical indicators are those for concerning mortality reduction for benefit and false-positive, overdiagnosis, and adverse reactions to screening and diagnostic examination procedures for harm [19, 20, 23]. The NNS and NNR used in this study are transformed indictors of mortality reduction and false-positive for intuitive interpretation. Overdiagnosis indicators cannot be examined due to lack of reports about overdiagnosis for gastric cancer screening [2]. Because of the difficulty of comparing severity of adverse reactions with screening benefit in numerical way, NNS and NNR were used to balance benefits and harms in this study. As for the threshold, no consensus was obtained due to the uncertainty and variability in the evidence used to make these estimates [20] or a matter of individual judgement [19]. In this study, we used threshold of 1000 for NNS and 100 for NNR based on the Japanese guidelines for cancer screening 2014 edition [2]. These threshold has some sense in Japan because the recommendation of the guideline and following government decision was made based on this value. Even in case of not using such threshold, combination of NNS and NNR for various scenarios in Tables 3 and 4 will help to evaluate whether to continue gastric cancer screening.

There are several limitations in this study. NNSs, NNRs, and NLS addressed in this study are limited to those estimated using the data obtained for both male and female in the age groups of 45–54, 55–64, 65–74, and equal to and older than 75 years, projected for 2020, 2025, 2030, and 2035, due to limited availability of the relevant data. The accurate data of the effect size of screening on mortality, recall rate, and participation rate are not available in Japan, while the detailed and accurate data on mortality rates and their projections were available. Unfortunately, however, although stomach cancer screening has been recommended for age 40 or older until 2015 and is recommended for age 50 or older since 2016, the projections are only available for age groups of 45–54, 55–64, 65–74, and equal to and older than 75 years old. Although NNSs, NNRs, and NLSs outside of these scenarios cannot be estimated due to data availability, they can be speculated by intrapolation of the values of mortality rate, relative risk, and recall rate within the scenarios. Owing to the simple relationships among these values, the results can be speculated that gastric cancer screening is not recommended for men and women with age 50 based on the threshold of NNS < 1000 and NNR > 100 for all the scenarios (Tables 3, 4). As a matter of course, in real situations, other benefits and harms of the screening should be considered such as less invasive treatment due to early detection as benefits and adverse reactions of the screening and diagnostic examinations as harms.

Considering the criteria of benefits and harms as NNS < 1000 and NNR > 100, respectively, these estimates may imply that, compared to sex, age and screening effect, the trend toward mortality reduction may have less impact on NNS and NNR, at least until 2035. Recall rates are closely related to prevalence, sensitivity, specificity, and screening effect, and therefore, it is important to manage the accuracy level of screening to maintain the recall rates in reasonable range. Furthermore, NLS heavily depends on participation rate of screening, it is most important to increase participation rate as high as possible.

Notes

Funding

This study was supported by the National Cancer Center Research and Developmental Fund (29-A-20).

Compliance with ethical standards

Conflict of interest

The authors declare that they have no conflict of interest.

Ethical consideration

This article does not contain any studies with human or animal subjects performed by any of the authors.

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© The Author(s) 2018

Open AccessThis article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.

Authors and Affiliations

  1. 1.Division of Health Sociology, Center for Public Health SciencesNational Cancer CenterTokyoJapan

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