World J Oncol

World Journal of Oncology, ISSN 1920-4531 print, 1920-454X online, Open Access

Article copyright, the authors; Journal compilation copyright, World J Oncol and Elmer Press Inc

Journal website http://www.wjon.org

Original Article

Volume 11, Number 3, June 2020, pages 88-97

Breast Cancer Incidence and Behavior in Younger Patients: A Study From the Surveillance, Epidemiology and End Results Database

**Table 1.** Demographic and Clinical Characteristics Comparison of Two Groups
Variables	Younger group (0 - 39), n = 28,243 (4.709%)	Older group (40+), n = 571,539 (95.291%)	P-value
NOS: not otherwise specified; SD: standard deviation; IQR: interquartile range.
Age at diagnosis			< 0.001
Mean (SD)	34.889 (3.81)	62.158 (12.51)
Median (IQR)	36 (33 - 38)	61 (52 - 71)
Marital status, n (%)			< 0.001
Single (never married)	8,133 (28.80)	76,542 (13.39)
Married (including common law)	17,730 (62.78)	331,938 (58.08)
Separated	433 (1.53)	5,703 (1.00)
Divorced	1,755 (6.21)	64,914 (11.36)
Widowed	130 (0.46)	91,723 (16.05)
Unmarried/domestic partner	62 (0.22)	719 (0.13)
Race, n (%)			< 0.001
White	20,345 (72.04)	463,663 (81.13)
Black	4,328 (15.32)	58,330 (10.21)
American Indian/Alaska Native	185 (0.66)	2,784 (0.49)
Asian or Pacific Islander	3,385 (11.99)	46,762 (8.18)
Insurance status, n (%)			< 0.001
Uninsured	679 (2.40)	6,057 (1.06)
Any Medicaid	3,375 (11.95)	43,192 (7.56)
Insured	14,467 (51.22)	318,414 (55.71)
Insured/no specifics	1,965 (6.96)	60,277 (10.55)
Insurance status unknown	252 (0.89)	5,137 (0.90)
Undocumented	7,505 (26.57)	138,462 (24.23)
Primary site, n (%)			< 0.001
Nipple	79 (0.28)	2,746 (0.48)
Central portion of breast	1,130 (4.00)	31,136 (5.45)
Upper-inner quadrant of breast	3,104 (10.99)	65,068 (11.38)
Lower-inner quadrant of breast	1,437 (5.09)	33,857 (5.92)
Upper-outer quadrant of breast	9,516 (33.69)	195,041 (34.13)
Lower-outer quadrant of breast	2,254 (7.98)	41,689 (7.29)
Axillary tail of breast	228 (0.81)	2,967 (0.52)
Overlapping lesion of breast	6,206 (21.97)	128,795 (22.54)
Breast, NOS	4,289 (15.19)	70,240 (12.29)
Diagnosis confirmation, n (%)			0.008
Positive histology	28,175 (99.76)	570,584 (99.83)
Positive cytology	63 (0.22)	809 (0.14)
Positive histology and positive immunophenotyping and/or positive genetic studies	0 (0.00)	2 (0.00)
Positive microscopic confirmation, method not specified	5 (0.02)	144 (0.03)

Table 1. Demographic and Clinical Characteristics Comparison of Two Groups

Variables

Younger group (0 - 39), n = 28,243 (4.709%)

Older group (40+), n = 571,539 (95.291%)

P-value

NOS: not otherwise specified; SD: standard deviation; IQR: interquartile range.

Age at diagnosis

< 0.001

Mean (SD)

34.889 (3.81)

62.158 (12.51)

Median (IQR)

36 (33 - 38)

61 (52 - 71)

Marital status, n (%)

< 0.001

Single (never married)

8,133 (28.80)

76,542 (13.39)

Married (including common law)

17,730 (62.78)

331,938 (58.08)

Separated

433 (1.53)

5,703 (1.00)

Divorced

1,755 (6.21)

64,914 (11.36)

Widowed

130 (0.46)

91,723 (16.05)

Unmarried/domestic partner

62 (0.22)

719 (0.13)

Race, n (%)

< 0.001

White

20,345 (72.04)

463,663 (81.13)

Black

4,328 (15.32)

58,330 (10.21)

American Indian/Alaska Native

185 (0.66)

2,784 (0.49)

Asian or Pacific Islander

3,385 (11.99)

46,762 (8.18)

Insurance status, n (%)

< 0.001

Uninsured

679 (2.40)

6,057 (1.06)

Any Medicaid

3,375 (11.95)

43,192 (7.56)

Insured

14,467 (51.22)

318,414 (55.71)

Insured/no specifics

1,965 (6.96)

60,277 (10.55)

Insurance status unknown

252 (0.89)

5,137 (0.90)

Undocumented

7,505 (26.57)

138,462 (24.23)

Primary site, n (%)

< 0.001

Nipple

79 (0.28)

2,746 (0.48)

Central portion of breast

1,130 (4.00)

31,136 (5.45)

Upper-inner quadrant of breast

3,104 (10.99)

65,068 (11.38)

Lower-inner quadrant of breast

1,437 (5.09)

33,857 (5.92)

Upper-outer quadrant of breast

9,516 (33.69)

195,041 (34.13)

Lower-outer quadrant of breast

2,254 (7.98)

41,689 (7.29)

Axillary tail of breast

228 (0.81)

2,967 (0.52)

Overlapping lesion of breast

6,206 (21.97)

128,795 (22.54)

Breast, NOS

4,289 (15.19)

70,240 (12.29)

Diagnosis confirmation, n (%)

0.008

Positive histology

28,175 (99.76)

570,584 (99.83)

Positive cytology

63 (0.22)

809 (0.14)

Positive histology and positive immunophenotyping and/or positive genetic studies

0 (0.00)

2 (0.00)

Positive microscopic confirmation, method not specified

5 (0.02)

144 (0.03)

**Table 2.** Tumor Characteristics Between the Two Groups
Variables	Younger group (0 - 39), n = 28,243 (4.709%)	Older group (40+), n = 571,539 (95.291%)	P-value
NOS: not otherwise specified; ITCs: isolated tumor cells.
Tumor size, n (%)			< 0.001
0.1 - 2.0 cm	12,121 (42.92)	362,102 (63.36)
2.1 - 5.0 cm	12,045 (42.65)	164,218 (28.73)
5.1 - 10.0 cm	3,278 (11.61)	32,596 (5.70)
10.1 cm+	419 (1.48)	4,348 (0.76)
Diagnosis confirmed but size undefined	380 (1.35)	8,275 (1.45)
Grade, n (%)			< 0.001
Grade I: well differentiated; differentiated, NOS	2,249 (7.96)	123,875 (21.67)
Grade II: moderately differentiated; intermediate differentiation	9,560 (33.85)	247,788 (43.36)
Grade III: poorly differentiated; differentiated	15,783 (55.88)	187,737 (32.85)
Grade IV: undifferentiated; anaplastic	651 (2.31)	12,139 (2.12)
Immunohistochemistry (IHC) of regional lymph nodes, n (%)			< 0.001
Nodes clinically negative, not examined pathologically	9,560 (33.85)	275,155 (48.14)
Negative on routine H and E, IHC studies done, negative for tumor	5,233 (18.53)	134,288 (23.50)
Negative on routine H and E, IHC studies done, positive for ITCs	349 (1.24)	6,020 (1.05)
Negative on routine H and E, IHC tumor positive, metastases not stated	56 (0.20)	1,115 (0.20)
Not applicable	13,045 (46.19)	154,961 (27.11)
Molecular (MOL) studies of regional lymph nodes, n (%)			< 0.001
Nodes clinically negative, not examined pathologically	14,212 (50.32)	392,877 (68.74)
Negative on routine H and E, RT-PCR MOL studies done, negative for tumor	954 (3.38)	23,175 (4.06)
Negative on routine H and E, RT-PCR MOL studies done, positive for tumor	32 (0.11)	526 (0.09)
Not applicable	13,045 (46.19)	154,961 (27.11)
Metastasis at diagnosis, n (%)			< 0.001
No distant metastasis	26,949 (95.42)	555,563 (97.21)
Microscopic, < 0.2 mm without symptoms or signs of metastasis	2 (0.01)	27 (0.01)
Stated as M0(i+) with no other information on distant metastasis	1 (0.00)	4 (0.00)
Unilateral or bilateral axillary or cervical nodes	122 (0.43)	1,148 (0.20)
Distant metastasis except distant lymph node(s); Carcinomatosis	415 (1.47)	4,848 (0.85)
Skin over: axilla, contralateral (opposite) breast, sternum, upper abdomen	13 (0.05)	166 (0.03)
Adrenal bone, lung ovary satellite nodule, or opposite breast metastasis	512 (1.81)	6,735 (1.18)
Distant lymph nodes; carcinomatosis	196 (0.69)	2,506 (0.44)
Distant metastasis, NOS	33 (0.12)	542 (0.10)
Behavior, n (%)			< 0.001
Carcinoma in situ; intraepithelial; non-infiltrating; noninvasive	2,413 (8.54)	84,397 (14.77)
Malignant, primary site (invasive)	25,830 (91.46)	487,142 (85.23)
Simplified stage, n (%)			< 0.001
In situ	2,413 (8.54)	84,397 (14.77)
Localized	12,388 (43.86)	322,914 (56.50)
Regional	11,512 (40.76)	142,482 (24.93)
Distant	1,930 (6.83)	21,746 (3.81)
Size of tumor-invasive component, n (%)			< 0.001
Entire tumor reported as invasive	8,153 (28.87)	159,696 (27.94)
Entire tumor reported as in situ	2,407 (8.52)	84,191 (14.73)
Invasive and in situ components present	10,788 (38.20)	217,644 (38.08)
Invasive/in situ components present, in situ described as minimal (< 25%)	2,376 (8.41)	52,107 (9.12)
Invasive/in situ components present, in situ described as extensive (> 25%)	1,026 (3.63)	13,855 (2.42)
Invasive/in situ components present, proportions in situ and invasive unknown	1,866 (6.61)	30,050 (5.26)
Unknown if invasive/in situ components present, unknown if tumor “pure” or “mixed”	1,627 (5.76)	13,996 (2.45)
Estrogen receptor (ER) status, n (%)			< 0.001
Positive	18,676 (66.13)	446,374 (78.10)
Negative	8,476 (30.01)	97,525 (17.06)
Borderline	53 (0.19)	714 (0.13)
Unknown	1,038 (3.68)	26,926 (4.71)
Progesterone receptor (PR) status, n (%)			< 0.001
Positive	16,232 (57.47)	379,407 (66.38)
Negative	10,619 (37.60)	155,506 (27.21)
Borderline	121 (0.43)	2,129 (0.37)
Unknown	1,271 (4.50)	34,497 (6.04)
Human epidermal growth factor receptor 2 (HER2), n (%)			< 0.001
Positive	2,954 (10.46)	32,687 (5.72)
Negative	8,366 (29.62)	193,630 (33.88)
Borderline	229 (0.81)	5,332 (0.93)
Unknown	1,261 (4.47)	44,744 (7.83)
Not 2010+ breast	15,433 (54.64)	295,146 (51.64)
Breast subtype, n (%)			< 0.001
Her2+/HR+	2,136 (7.56)	22,848 (4.00)
Her2+/HR-	814 (2.88)	9,771 (1.71)
Her2-/HR+	6,146 (21.76)	168,694 (29.52)
Triple negative	2,212 (7.83)	24,654 (4.31)
Unknown	1,502 (5.32)	50,426 (8.82)
Not 2010+ breast	15,433 (54.64)	295,146 (51.64)
High grade, n (%)			< 0.001
Higher grade	16,434 (58.19)	199,876 (34.97)
Lower grade	11,809 (41.81)	371,663 (65.03)

Table 2. Tumor Characteristics Between the Two Groups

Variables

Younger group (0 - 39), n = 28,243 (4.709%)

Older group (40+), n = 571,539 (95.291%)

P-value

NOS: not otherwise specified; ITCs: isolated tumor cells.

Tumor size, n (%)

< 0.001

0.1 - 2.0 cm

12,121 (42.92)

362,102 (63.36)

2.1 - 5.0 cm

12,045 (42.65)

164,218 (28.73)

5.1 - 10.0 cm

3,278 (11.61)

32,596 (5.70)

10.1 cm+

419 (1.48)

4,348 (0.76)

Diagnosis confirmed but size undefined

380 (1.35)

8,275 (1.45)

Grade, n (%)

< 0.001

Grade I: well differentiated; differentiated, NOS

2,249 (7.96)

123,875 (21.67)

Grade II: moderately differentiated; intermediate differentiation

9,560 (33.85)

247,788 (43.36)

Grade III: poorly differentiated; differentiated

15,783 (55.88)

187,737 (32.85)

Grade IV: undifferentiated; anaplastic

651 (2.31)

12,139 (2.12)

Immunohistochemistry (IHC) of regional lymph nodes, n (%)

< 0.001

Nodes clinically negative, not examined pathologically

9,560 (33.85)

275,155 (48.14)

Negative on routine H and E, IHC studies done, negative for tumor

5,233 (18.53)

134,288 (23.50)

Negative on routine H and E, IHC studies done, positive for ITCs

349 (1.24)

6,020 (1.05)

Negative on routine H and E, IHC tumor positive, metastases not stated

56 (0.20)

1,115 (0.20)

Not applicable

13,045 (46.19)

154,961 (27.11)

Molecular (MOL) studies of regional lymph nodes, n (%)

< 0.001

Nodes clinically negative, not examined pathologically

14,212 (50.32)

392,877 (68.74)

Negative on routine H and E, RT-PCR MOL studies done, negative for tumor

954 (3.38)

23,175 (4.06)

Negative on routine H and E, RT-PCR MOL studies done, positive for tumor

32 (0.11)

526 (0.09)

Not applicable

13,045 (46.19)

154,961 (27.11)

Metastasis at diagnosis, n (%)

< 0.001

No distant metastasis

26,949 (95.42)

555,563 (97.21)

Microscopic, < 0.2 mm without symptoms or signs of metastasis

2 (0.01)

27 (0.01)

Stated as M0(i+) with no other information on distant metastasis

1 (0.00)

4 (0.00)

Unilateral or bilateral axillary or cervical nodes

122 (0.43)

1,148 (0.20)

Distant metastasis except distant lymph node(s); Carcinomatosis

415 (1.47)

4,848 (0.85)

Skin over: axilla, contralateral (opposite) breast, sternum, upper abdomen

13 (0.05)

166 (0.03)

Adrenal bone, lung ovary satellite nodule, or opposite breast metastasis

512 (1.81)

6,735 (1.18)

Distant lymph nodes; carcinomatosis

196 (0.69)

2,506 (0.44)

Distant metastasis, NOS

33 (0.12)

542 (0.10)

Behavior, n (%)

< 0.001

Carcinoma in situ; intraepithelial; non-infiltrating; noninvasive

2,413 (8.54)

84,397 (14.77)

Malignant, primary site (invasive)

25,830 (91.46)

487,142 (85.23)

Simplified stage, n (%)

< 0.001

In situ

2,413 (8.54)

84,397 (14.77)

Localized

12,388 (43.86)

322,914 (56.50)

Regional

11,512 (40.76)

142,482 (24.93)

Distant

1,930 (6.83)

21,746 (3.81)

Size of tumor-invasive component, n (%)

< 0.001

Entire tumor reported as invasive

8,153 (28.87)

159,696 (27.94)

Entire tumor reported as in situ

2,407 (8.52)

84,191 (14.73)

Invasive and in situ components present

10,788 (38.20)

217,644 (38.08)

Invasive/in situ components present, in situ described as minimal (< 25%)

2,376 (8.41)

52,107 (9.12)

Invasive/in situ components present, in situ described as extensive (> 25%)

1,026 (3.63)

13,855 (2.42)

Invasive/in situ components present, proportions in situ and invasive unknown

1,866 (6.61)

30,050 (5.26)

Unknown if invasive/in situ components present, unknown if tumor “pure” or “mixed”

1,627 (5.76)

13,996 (2.45)

Estrogen receptor (ER) status, n (%)

< 0.001

Positive

18,676 (66.13)

446,374 (78.10)

Negative

8,476 (30.01)

97,525 (17.06)

Borderline

53 (0.19)

714 (0.13)

Unknown

1,038 (3.68)

26,926 (4.71)

Progesterone receptor (PR) status, n (%)

< 0.001

Positive

16,232 (57.47)

379,407 (66.38)

Negative

10,619 (37.60)

155,506 (27.21)

Borderline

121 (0.43)

2,129 (0.37)

Unknown

1,271 (4.50)

34,497 (6.04)

Human epidermal growth factor receptor 2 (HER2), n (%)

< 0.001

Positive

2,954 (10.46)

32,687 (5.72)

Negative

8,366 (29.62)

193,630 (33.88)

Borderline

229 (0.81)

5,332 (0.93)

Unknown

1,261 (4.47)

44,744 (7.83)

Not 2010+ breast

15,433 (54.64)

295,146 (51.64)

Breast subtype, n (%)

< 0.001

Her2+/HR+

2,136 (7.56)

22,848 (4.00)

Her2+/HR-

814 (2.88)

9,771 (1.71)

Her2-/HR+

6,146 (21.76)

168,694 (29.52)

Triple negative

2,212 (7.83)

24,654 (4.31)

Unknown

1,502 (5.32)

50,426 (8.82)

Not 2010+ breast

15,433 (54.64)

295,146 (51.64)

High grade, n (%)

< 0.001

Higher grade

16,434 (58.19)

199,876 (34.97)

Lower grade

11,809 (41.81)

371,663 (65.03)

**Table 3.** Adjusted Stage Based on TNM Classification (Seventh Edition)
Stage, n (%)	Younger group (0 - 39), n = 28,243 (4.709%)	Older group (40+), n = 571,539 (95.291%)
NOS: not otherwise specified.
0	1,201 (4.25)	44,979 (7.87)
IA	3,102 (10.98)	119,099 (20.84)
IB	285 (1.01)	5,456 (0.95)
IIA	3,152 (11.16)	51,100 (8.94)
IIB	2,300 (8.14)	25,060 (4.38)
III NOS	4 (0.01)	14 (0.00)
IIIA	1,419 (5.02)	13,959 (2.44)
IIIB	316 (1.12)	4,322 (0.76)
IIIC	498 (1.76)	5,741 (1.00)
IV	683 (2.42)	8,464 (1.48)
Not applicable	25 (0.09)	171 (0.03)
Stage unknown	31 (0.11)	387 (0.07)
Undocumented/missing	15,227 (53.91)	292,787 (51.23)

Table 3. Adjusted Stage Based on TNM Classification (Seventh Edition)

Stage, n (%)

Younger group (0 - 39), n = 28,243 (4.709%)

Older group (40+), n = 571,539 (95.291%)

P < 0.001

NOS: not otherwise specified.

1,201 (4.25)

44,979 (7.87)

3,102 (10.98)

119,099 (20.84)

285 (1.01)

5,456 (0.95)

IIA

3,152 (11.16)

51,100 (8.94)

IIB

2,300 (8.14)

25,060 (4.38)

III NOS

4 (0.01)

14 (0.00)

IIIA

1,419 (5.02)

13,959 (2.44)

IIIB

316 (1.12)

4,322 (0.76)

IIIC

498 (1.76)

5,741 (1.00)

683 (2.42)

8,464 (1.48)

Not applicable

25 (0.09)

171 (0.03)

Stage unknown

31 (0.11)

387 (0.07)

Undocumented/missing

15,227 (53.91)

292,787 (51.23)

**Table 4.** Multivariate Analysis of High-Grade Tumor Using Age Group
Covariate	Odds ratio	P-value	95% confidence interval
White race and single marital status were used as a reference in the analysis.
Race
Black	1.660	< 0.001	1.63 - 1.69
American Indian/Alaska Native	1.138	0.001	1.06 - 1.23
Asian or Pacific Islander	1.074	< 0.001	1.05 - 1.10
Marital status
Married (including common law)	0.973	0.001	0.96 - 0.99
Separated	1.057	0.040	1.00 - 1.12
Divorced	1.008	0.483	0.99 - 1.03
Widowed	1.109	< 0.001	1.09 - 1.13
Unmarried/domestic partner	0.853	0.036	0.73 - 0.99
Age at diagnosis	0.978	< 0.001	0.98 - 0.98
Constant	2.025	< 0.001	1.97 - 2.09

Table 4. Multivariate Analysis of High-Grade Tumor Using Age Group

Covariate

Odds ratio

P-value

95% confidence interval

White race and single marital status were used as a reference in the analysis.

Race

Black

1.660

< 0.001

1.63 - 1.69

American Indian/Alaska Native

1.138

0.001

1.06 - 1.23

Asian or Pacific Islander

1.074

< 0.001

1.05 - 1.10

Marital status

Married (including common law)

0.973

0.001

0.96 - 0.99

Separated

1.057

0.040

1.00 - 1.12

Divorced

1.008

0.483

0.99 - 1.03

Widowed

1.109

< 0.001

1.09 - 1.13

Unmarried/domestic partner

0.853

0.036

0.73 - 0.99

Age at diagnosis

0.978

< 0.001

0.98 - 0.98

Constant

2.025

< 0.001

1.97 - 2.09

**Table 5.** Multivariate Analysis of Age Group With High-Grade Tumor
Covariate	Odds ratio	P-value	95% confidence interval
High grade: grades III and IV. Low grade (grades I and II), white race and single marital status were used as references in the analysis.
Younger vs older age	2.437	< 0.001	2.38 - 2.50
Marital status
Married (including common law)	0.535	< 0.001	0.52 - 0.55
Separated	0.696	< 0.001	0.63 - 0.77
Divorced	0.267	< 0.001	0.25 - 0.28
Widowed	0.015	< 0.001	0.01 - 0.02
Unmarried or domestic partner	0.898	0.422	0.69 - 1.17
Race
Black	1.318	< 0.001	1.27 - 1.37
American Indian/Alaska Native	1.347	< 0.001	1.16 - 1.57
Asian or Pacific Islander	1.491	< 0.001	1.44 - 1.55
Constant	0.062	< 0.001	0.06 - 0.06

Table 5. Multivariate Analysis of Age Group With High-Grade Tumor

Covariate

Odds ratio

P-value

95% confidence interval

High grade: grades III and IV. Low grade (grades I and II), white race and single marital status were used as references in the analysis.

Younger vs older age

2.437

< 0.001

2.38 - 2.50

Marital status

Married (including common law)

0.535

< 0.001

0.52 - 0.55

Separated

0.696

< 0.001

0.63 - 0.77

Divorced

0.267

< 0.001

0.25 - 0.28

Widowed

0.015

< 0.001

0.01 - 0.02

Unmarried or domestic partner

0.898

0.422

0.69 - 1.17

Race

Black

1.318

< 0.001

1.27 - 1.37

American Indian/Alaska Native

1.347

< 0.001

1.16 - 1.57

Asian or Pacific Islander

1.491

< 0.001

1.44 - 1.55

Constant

0.062

< 0.001

0.06 - 0.06