Survival probability and prognostic factors for breast cancer patients in Vietnam

Figures & data

Table 1. Characteristics of breast cancer patients for groups with and without loss of follow-up

Characteristics	Group without loss of follow-up (N=948),%	Group with loss of follow-up (N=636),%	p ^*
Ethnic group
Majority (Kinh)	94.41	95.75	0.231
Minority	5.59	4.25
Age group
<40	14.24	13.99
40–49	43.25	36.62
50–59	26.05	29.72	0.436
60–69	13.71	13.21
≥70	2.74	3.46
Stage at diagnosis
Stage 0	0.42	0.94
Stage I	10.76	11.01	0.094
Stage II	61.18	57.08
Stage III	19.41	24.21
Stage IV	8.23	6.76
The primary treatment
Surgery	78.69	72.96
Radiation	0.42	0.94	0.039
Chemotherapy	10.55	11.32
Hormone therapy	0.11	0.31
No treatment	10.23	14.47

*Pearson chi-square.

Table 2. Goodness-of-fit test assessing proportional hazards assumption

Predictors	rho*	Chi-square test	df**	p
Ethnic group	−0.06846	1.28	1	0.2571
Age group	0.03237	0.29	1	0.5871
Marital status	−0.02643	0.19	1	0.6619
Education level	−0.16793	7.48	1	0.0062
Stage at diagnosis	−0.33341	27.11	1	0.0000
Primary treatment	0.09538	2.76	1	0.0967
Hormone therapy	0.11012	3.12	1	0.5871
Global test		38.11	7	0.0000

*The correlation coefficient between the residuals and time.

**Degree of freedom.

Table 3. Characteristics of patients with breast cancer

Characteristics	Number of patients	Percent
Ethnic group
Majority group	894	94.3
Minority group	54	5.7
Age at diagnosis
Mean (SD)	50 (9.2)
Age group
<40	103	10.9
40–49	408	43.0
50–59	270	28.5
60–69	131	13.8
≥70	36	3.8
Marital status
Married	788	83.1
Unmarried	160	16.9
Education level
Illiterate	40	4.2
Primary school	285	30.1
Secondary school	264	27.8
High school	250	26.4
Higher	109	11.5
Stage at diagnosis
Stage 0 and I	106	11.2
Stage II	580	61.2
Stage III	184	19.4
Stage IV	78	8.2
The first treatment
Surgery	746	78.7
Radiotherapy	4	0.4
Chemotherapy	100	10.6
Hormone therapy	1	0.1
No treatment	97	10.2
Hormone therapy
Yes	707	74.6
No	241	25.4
Total	948	100

Fig. 1.  Overall survival rate at 1, 3, and 5 years following diagnosis for breast cancer.

Fig. 2.  The extended Cox model assessing the effect of characteristics of patients on mortality from breast cancer.

Table 4. Extended Cox model, including patient characteristics and interaction terms

	Hazard ratio	p	95% CI
Ethnic group	1.01	0.961	0.61–1.67
Marital status	2.41	0.093	0.86–6.74
Primary treatment	0.89	0.542	0.61–1.30
Hormone therapy	0.22	0.000	0.12–0.40
Age group	1.11	0.100	0.98–1.25
Education level*	0.86†	0.034	0.76–0.99
Stage at diagnosis*	1.25‡	0.019	1.04–1.51
Primary treatment×stage**	1.02	0.235	0.99–1.06
Marital status×stage**	0.95	0.367	0.85–1.06
Education level×stage**	1.03	0.325	0.98–1.08
Hormone therapy×stage**	1.08	0.023	1.01–1.16

95% CI: 95% confidence interval for hazard ratio.

*Variables continuously vary with respect to time.

**Interaction terms defined as theproduct of hormone therapy and stage at diagnosis

†Estimate of regression coefficient for variable education level is −0.14.

‡Estimate of regression coefficient for variable stage at diagnosis is 0.22.

Table 5. Subgroup analysis of potential prognostic factors

Prognostic factors	Hazard ratio	p	95% CI
Marital status
Unmarried	1 (baseline)
Married	1.53	0.030	1.04–2.24
Hormone therapy
No	1 (baseline)
Yes	0.24	0.000	0.13–0.44
Education level*
Illiterate	1 (baseline)
Primary school	1.00	0.974	0.83–1.20
Secondary school	0.95	0.571	0.78–1.14
High school	0.79	0.020	0.64–0.96
Higher	0.79	0.046	0.62–0.99
Stage at diagnosis*
Stage I	1 (baseline)
Stage II	1.24	0.060	0.99–1.56
Stage III	1.64	0.000	1.29–2.09
Stage IV	2.27	0.000	1.71–2.99
Hormone therapy×stage**	1.07	0.053	0.99–1.14

95% CI: 95% confidence interval for hazard ratio.

*Variables continuously vary with respect to time.

**Interaction terms defined as the product of hormone therapy and stage at diagnosis.