Post-mastectomy radiotherapy can improve survival in breast cancer patients aged 35 years or younger with four or more positive nodes but not in one to three positive nodes

Figures & data

Table 1 Patient characteristics and treatment protocols

Characteristic	n	PMRT		P-value
		None (%)	Yes (%)
Age (y)
Median (range)	221	32 (23–35)	33 (20–35)	–
Tumor stage
pT1	54	36 (66.7)	18 (33.3)	0.024
pT2	134	81 (60.4)	53 (39.6)
pT3	23	7 (30.4)	16 (69.6)
pT4	10	5 (50.0)	5 (50.0)
Nodal stage
pN1	116	92 (79.3)	24 (20.7)	<0.001
pN2	54	19 (35.2)	35 (64.8)
pN3	51	18 (35.3)	33 (64.7)
TNM stage
II	116	92 (79.3)	24 (20.7)	<0.001
III	105	37 (35.2)	68 (64.8)
ER statusa
Negative	95	48 (50.5)	47 (49.5)	0.060
Positive	119	75 (63.0)	44 (37.0)
Unknown	7	6 (85.7)	1 (14.3)
PR statusa
Negative	71	38 (53.5)	33 (36.5)	0.234
Positive	143	85 (59.4)	58 (40.6)
Unknown	7	6 (85.7)	1 (14.3)
HER-2 statusb
Negative	129	78 (60.4)	51 (39.6)	0.181
Positive	71	36 (50.7)	35 (49.3)
Unknown	21	15 (71.4)	6 (28.6)
Adjuvant chemotherapy regimen
CMF	24	16 (66.7)	8 (33.3)	0.383
Anthracycline and/or taxane	197	113 (57.4)	84 (42.6)

Notes:

a Positive status refers to 10% immuno-stained cells by immunohistochemical results.

b Positive status refers to 3+ or 2+ score by immunohistochemical results that is confirmed to be positive by FISH test.

Abbreviations: CMF, cyclophosphamide, methotrexate, and 5-Fu; ER, estrogen receptor; FISH, fluorescence in situ hybridization; HER-2, human epidermal growth factor receptor-2; PMRT, post-mastectomy radiotherapy; PR, progesterone receptor; TNM, tumor, lymph nodes, metastasis; 5-Fu, 5-fluorouracil.

Table 2 Clinical characteristics of patients with one to three positive nodes and four or more positive nodes

Characteristic	One to three positive nodes				Four or more positive nodes
	n	PMRT		P-value	n	PMRT		P-value
		None (%)	Yes (%)			None (%)	Yes (%)
Tumor stage
pT1	38	30 (78.9)	8 (21.1)	0.564	16	6 (37.5)	10 (62.5)	0.737
pT2	78	62 (79.5)	16 (20.5)		56	19 (33.9)	37 (66.1)
pT3	–	–	–		23	7 (30.4)	16 (69.6)
pT4	–	–	–		10	5 (50.0)	5 (50.0)
Nodal stage
pN1	116	92 (79.3)	24 (20.7)	–	–	–	–	–
pN2	–	–	–		54	19 (35.2)	35 (64.8)	0.991
pN3	–	–	–		51	18 (35.3)	33 (64.7)
ER status
Negative	41	30 (73.1)	11 (26.9)	0.482	54	18 (33.3)	36 (66.7)	0.380
Positive	69	57 (82.6)	12 (17.4)		50	18 (36.0)	32 (64.0)
Unknown	6	5 (83.3)	1 (16.7)		1	1 (100)	0 (0)
PR status
Negative	34	25 (73.5)	9 (26.5)	0.610	37	13 (35.1)	24 (64.9)	0.394
Positive	76	62 (81.6)	14 (18.4)		67	23 (34.3)	44 (65.7)
Unknown	6	5 (83.3)	1 (16.7)		1	1 (100)	0 (0)
HER-2 status
Negative	61	56 (91.8)	5 (9.2)	0.002	68	22 (32.4)	46 (67.4)	0.040
Positive	40	26 (65.0)	14 (35.0)		31	10 (32.3)	21 (67.7)
Unknown	15	10 (66.7)	5 (33.3)		6	5 (83.3)	1 (16.7)
Adjuvant chemotherapy regimen
CMF	15	11 (73.3)	4 (26.7)	0.540	9	5 (55.6)	4 (44.4)	0.166
Anthracycline and/or taxane	101	81 (80.2)	20 (19.8)		96	32 (33.3)	64 (66.7)

Note: P-values for comparison between PMRT group and non-PMRT group with chi-square test.

Abbreviations: CMF, cyclophosphamide, methotrexate, and 5-Fu; ER, estrogen receptor; HER-2, human epidermal growth factor receptor-2; PMRT, post-mastectomy radiotherapy; PR, progesterone receptor; 5-Fu, 5-fluorouracil.

Table 3 Distribution of the first event by specific distant metastases sites

Distant metastases site	n	%
Isolated lung	10	12.8
Isolated bone	19	24.4
Isolated liver	14	17.9
Isolated soft tissue	10	12.8
Isolated brain	6	7.7
Multiple sites	19	24.4

Table 4 Univariate analysis of locoregional recurrence-free survival

Characteristic	5-year LRFS (%)	P-value
Tumor stage
pT1–2	84.4	0.555
pT3–4	82.2
Nodal stage
pN1	86.0	0.041
pN2	93.2
pN3	70.1
ER status
Negative	87.9	0.484
Positive	80.1
PR status
Negative	88.6	0.406
Positive	81.1
HER-2 status
Negative	81.0	0.641
Positive	86.3
Adjuvant chemotherapy regimen
CMF	86.8	0.823
Anthracycline and/or taxane	83.7
PMRT
None	76.3	0.003
Yes	94.4

Note: P-value was calculated using the Log-rank test.

Abbreviations: CMF, cyclophosphamide, methotrexate, and 5-Fu; ER, estrogen receptor; HER-2, human epidermal growth factor receptor-2; LRFS, locoregional recurrence-free survival; PMRT, post-mastectomy radiotherapy; PR, progesterone receptor; 5-Fu, 5-fluorouracil.

Table 5 Multivariate analyses of locoregional recurrence-free survival

Characteristic	HR	95% CI	P-value
Nodal stage
pN1	1
pN2	1.511	0.543–4.205	0.430
pN3	4.631	2.093–10.247	<0.001
PMRT
None vs yes	5.553	2.263–13.627	<0.001

Abbreviations: CI, confidence interval; HR, hazard ratio; PMRT, post-mastectomy radiotherapy.

Figure 1 Comparison of Kaplan–Meier curves for patients with and without post-mastectomy radiotherapy in patients with four or more positive nodes.

Notes: (A) Locoregional recurrence-free survival; (B) distant metastasis-free survival; (C) disease-free survival; (D) overall survival.
Abbreviations: Cum, cumulative; PMRT, post-mastectomy radiotherapy.

Table 6 Impact of post-mastectomy radiotherapy on survival in different subgroups

Survival endpoint (%)	Entire			One to three positive nodes			Four or more positive nodes
	Non-PMRT	PMRT	P-value	Non-PMRT	PMRT	P-value	Non-PMRT	PMRT	P-value
5-year LRFS	76.3	94.4	0.003	80.9	90.9	0.068	63.2	92.4	0.001
5-year DMFS	61.2	70.3	0.429	66.8	91.5	0.132	47.8	62.7	0.085
5-year DFS	55.3	69.3	0.146	61.8	91.5	0.064	39.7	61.3	0.017
5-year OS	75.6	79.3	0.750	84.1	95.7	0.240	54.6	73.2	0.042

Note: P-value was calculated using the Log-rank test.

Abbreviations: DFS, disease-free survival; DMFS, distant metastasis-free survival; LRFS, locoregional recurrence-free survival; OS, overall survival; PMRT, post-mastectomy radiotherapy.