Participants’ characteristics
The baseline demographic and clinical characteristics of patients included in this analysis are provided in Table 1. The mean age at diagnosis was 52 years. Sixty-two percent had no comorbidity. Nearly half of the patients (47%) were post-menopausal at diagnosis. Obesity was observed in 28% of patients. Thirty-seven percent belonged to AJCC stage 0-I, 46% stage II and 17% stage III. ER, PR and HER2 positivity were presented in 75%, 59% and 17% of the patients. All patients in this analysis have completed breast cancer surgery. Majority of patients had received adjuvant chemotherapy, radiotherapy and endocrine therapy, with the corresponding figure being 76.0%, 70.8% and 76.3%, respectively. At baseline, only a small group of patients were current smokers or drinkers, at 1.1% and 1.5%, respectively.
Table 1
Baseline socio-demographic and clinical characteristics of patients included in this study (n = 1019)
Characteristics | No. of patients | Frequency, % |
Age, mean ± SD, year | 52.1 ± 8.8 | |
Education level High school or below Collage or above | 868 151 | 85.2 14.8 |
Marital status Married or cohabitating Unmarried or divorced or widowed | 728 291 | 71.4 28.6 |
Household income (HKD/month) <15,000 15,000–30,000 30,000–50,000 ≥50,000 | 463 326 151 79 | 45.4 32.0 14.8 7.8 |
Employment status Full time Part time Not working | 378 129 512 | 37.1 12.7 50.2 |
Menopausal status Pre-menopausal Post-menopausal | 539 480 | 52.9 47.1 |
BMI at diagnosis, kg/m2 Underweight (< 18.5) Normal (18.5–22.9) Overweight (23-24.9) Obese (≥ 25) | 37 488 209 285 | 3.6 47.9 20.5 28.0 |
No. of comorbid condition None 1 2 ≥3 | 629 259 101 30 | 61.7 25.4 9.9 2.9 |
AJCC stage at diagnosis 0-I II III Missing | 375 471 169 4 | 36.9 46.2 16.6 0.4 |
Histology IDC ILC DCIS Others | 858 31 56 74 | 84.2 3.0 5.5 7.3 |
ER status Positive Negative Missing | 763 233 23 | 74.9 22.9 2.3 |
PR status Positive Negative Missing | 598 395 26 | 58.7 38.8 2.6 |
HER 2 status Positive Negative Missing | 274 686 59 | 26.9 67.3 5.8 |
Surgery Mastectomy Conservation | 628 391 | 61.6 38.4 |
Chemotherapy Yes No | 774 245 | 76.0 24.0 |
Radiotherapy Yes No | 721 298 | 70.8 29.2 |
Endocrine therapy Yes No | 777 242 | 76.3 23.7 |
Smoking status Yes No | 11 1008 | 1.1 98.9 |
Drinking status Yes No | 15 1004 | 1.5 98.5 |
Comparison Of Physical Activity Between Pre- And Post-diagnosis
The median levels of physical activity at T0 (pre-diagnosis), T1, T2 and T3 were 0.6, 5.3, 4.4 and 3.9 MET-hours/week, respectively. The overall level of physical activity at post-diagnosis was significantly higher than that at pre-diagnosis, with median values of 5.8 vs 0.6 MET-hours/week respectively, P < 0.001 (Table 2). When comparing between T1 and T2, T1 and T3 as well as T2 and T3, there was no significant difference between any two follow-ups at post-diagnosis (P > 0.05, each). The proportions of participants who never did exercise at pre- and post-diagnosis were 46.4% and 10.9%, respectively. However, for those did exercise, the proportions of participants who met the exercise recommendation of WCRF/AICR were relatively low; the figures increased from 20.7% at pre-diagnosis to 35.1% post-diagnosis (P < 0.001).
Table 2
Comparison of level of physical activity across four study time-points
level of recreational physical activity | T0 | T1 | T2 | T3 | Average of T1,2,3 | P T0 vs mean of T1,2,3 |
MET-hours/week, median (IQR; range) | 0.6 (7.4; 0-95.8) | 5.3 (13.2; 0-111.3) | 4.4 (13.5; 0-118.3) | 3.9 (12.5; 0-118.1) | 5.8 (11.8; 0-98.3) | < 0.001 |
Physical activity group, n (%) No exercise Low-exercise-level group High-exercise-level group | 473 (46.4) 335 (32.9) 211 (20.7) | 209 (20.5) 465 (45.6) 345 (33.9) | 298 (29.2) 397 (39.0) 324 (31.8) | 340 (33.4) 376 (36.9) 303 (29.7) | 111 (10.9) 550 (54.0) 358 (35.1) |
Change in level of physical activity between pre- and post-diagnosis in individual patient
The changes of physical activity between pre- and post-diagnosis in individual patient are shown in supplementary Table 1. Compared to pre-diagnosis, most of the patients improved or had no change in level of physical activity at post-diagnosis, with the respective proportions being 48.2% and 43.8%, respectively. Only 8.0% of the patients had their level of physical activity declined at post-diagnosis.
In total, 20.7% of patients changed from no or low to high level of physical activity after diagnosis. The proportions patients with such positive change by socio-demographic, clinical and lifestyle factors are presented in Table 3. Univariate analysis showed that patients with the following characteristics are more likely to make such positive changes: patients who were aged ≥ 40 years (compared to those who were aged < 40 years), non-obese (compared to obese), stage II-III (compared to stage 0-I), and having received adjuvant chemotherapy (compared to no chemotherapy).
Table 3
Changes from no or low to high level of exercise group for individual patient by baseline socio-demographic and clinical factors
Characteristics | N | % | Changes from no or low to high exercise group, n (%) | P value |
Total | 1019 | 100.0 | 211 (20.7) | |
Age at diagnosis, year <40 40–49 50–59 ≥60 | 92 329 394 204 | 9.0 32.3 38.7 20.0 | 13 (14.1) 78 (23.7) 87 (22.1) 33 (16.3) | 0.068 |
Education High school or below Collage or above | 868 151 | 85.2 14.8 | 161 (20.7) 50 (20.5) | 0.954 |
Marital status Married or cohabitating Unmarried or divorced or widowed | 728 291 | 71.4 28.6 | 2.7 (22.1) 1.3 (17.2) | 0.079 |
Household income, HKD/month <15,000 15,000–30,000 30,000–50,000 ≥50,000 | 463 326 151 79 | 45.4 32.0 14.8 7.8 | 92 (29.9) 64 (19.6) 31 (20.5) 24 (30.4) | 0.177 |
Employment status Full time Part time Not working | 378 129 512 | 37.1 12.7 50.2 | 77 (20.4) 22 (17.1) 112 (21.9) | 0.472 |
Menopausal status Premenopausal Postmenopausal | 539 480 | 52.9 47.1 | 124 (23.0) 87 (18.1) | 0.055 |
BMI at diagnosis, kg/m2 Underweight (< 18.5) Normal (18.5–22.9) Overweight (23-24.9) Obese (≥ 25) | 37 488 209 285 | 3.6 47.9 20.5 28.0 | 9 (24.3) 108 (22.1) 54 (25.8) 40 (14.0) | 0.007 |
No. of comorbidities None 1 2 ≥3 | 629 259 101 30 | 61.7 25.4 9.9 2.9 | 144 (22.9) 46 (17.8) 17 (16.8) 4 (13.3) | 0.163 |
AJCC stage at diagnosis 0-I II III Missing | 375 471 169 4 | 36.9 46.2 16.6 0.4 | 61 (16.2) 109 (23.1) 41 (24.3) 0 (0) | 0.024 a |
Histology IDC ILC DCIS Others | 858 31 56 74 | 84.2 3.0 5.5 7.3 | 176 (20.5) 8 (25.8) 11 (19.6) 16 (21.6) | 0.899 |
ER status Positive Negative Missing | 763 233 23 | 74.9 22.9 2.3 | 47 (20.2) 159 (20.8) 5 (21.7) | 0.969 a |
PR status Positive Negative Missing | 598 395 26 | 58.7 38.8 2.6 | 81 (20.5) 124 (20.7) 6 (23.1) | 0.952 a |
HER 2 status Positive Negative Missing | 274 686 59 | 26.9 67.3 5.8 | 146 (20.1) 55 (21.3) 10 (16.9) | 0.832 a |
Surgery Mastectomy Conservation | 628 391 | 61.6 38.4 | 126 (20.1) 85 (21.7) | 0.521 |
Chemotherapy Yes No | 774 245 | 76.0 24.0 | 172 (22.2) 39 (15.9) | 0.034 |
Radiotherapy Yes No | 721 298 | 70.8 29.2 | 154 (21.4) 57 (19.1) | 0.424 |
Endocrine therapy Yes No | 777 242 | 76.3 23.7 | 157 (20.2) 54 (22.3) | 0.480 |
Smoking status Yes No | 11 1008 | 98.9 1.1 | 0 (0) 211 (20.9) | 0.133 |
Drinking status Yes No | 15 1004 | 1.5 98.5 | 3 (20.7) 208 (20.7) | 1.00 |
a. Missing group did not include in P value test. |
Multivariate logistic regression model was used to investigate potential characteristics which could predict higher likelihood of such positive changes. The variables entered into the model were those with P < 0.1 in the univariate analysis, which included age at diagnosis, marital status, menopausal status, BMI at diagnosis, AJCC stage and chemotherapy. The results of multivariate analysis are presented in supplementary Table 2. Compared to patients who were aged < 40 years, those who were aged from 40 to 59 years were more likely to make such positive change [age group 40–49 years and 50–59 years: odds ratio (OR) = 2.7, 95%CI: 1.3 ~ 5.8, P = 0.008; OR = 3.2, 95%CI: 1.5 ~ 7.2, P = 0.004, respectively. Patients who were obese at diagnosis were unlikely to make such change after diagnosis compared to those who were underweight (OR = 0.4, 95%CI: 0.2 ~ 1.0, P = 0.042).
Absolute changes of physical activity between pre- and post-diagnosis by socio-demographic, clinical and lifestyle factors
The absolute changes in level of physical activity between pre- and post-diagnosis by socio-demographic, clinical and lifestyle factors were presented in Table 4. Compared to pre-diagnosis, the level of physical activity increased by 2.2 MET-hours/week at post-diagnosis. Univariate analysis showed that higher increase in physical activity was observed among breast cancer patients aged between 40–59 years (compared to those who were aged ≥ 60 years), had a partner (married or cohabitating), not working (compared to full time or part-time) and had no comorbidity (compared to patients who had 1 or more comorbidities).
Table 4
Absolute changes in level of physical activity between pre- and post-diagnosis by baseline socio-demographic and clinical factors
Characteristics | N | % | Changes in MET-hours/week, Median (IQR) | P value |
Total | 1019 | 100.0 | 2.2 (7.7) | |
Age at diagnosis, year <40 40–49 50–59 ≥60 | 92 329 394 204 | 9.0 32.3 38.7 20.0 | 1.7 (5.3) 2.9 (8.8) 2.1 (8.1) 1.3 (8.3) | 0.011 |
Education High school or below Collage or above | 868 151 | 85.2 14.8 | 2.1 (7.8) 2.6 (7.9) | 0.918 |
Marital status Married or cohabitating Unmarried or divorced or widowed | 728 291 | 71.4 28.6 | 2.7 (8.9) 1.3 (7.2) | 0.006 |
Household income, HKD/month <15,000 15,000–30,000 30,000–50,000 ≥50,000 | 463 326 151 79 | 45.4 32.0 14.8 7.8 | 1.5 (7.4) 2.4 (7.3) 2.9 (7.9) 5.0 (12.1) | 0.059 |
Employment status Full time Part time Not working | 378 129 512 | 37.1 12.7 50.2 | 2.0 (9.6) 1.0 (7.9) 2.9 (7.6) | < 0.001 |
Menopausal status Premenopausal Postmenopausal | 539 480 | 52.9 47.1 | 2.9 (8.8) 1.7 (7.7) | 0.299 |
BMI at diagnosis, kg/m2 Underweight (< 18.5) Normal (18.5–22.9) Overweight (23-24.9) Obese (≥ 25) | 37 488 209 285 | 3.6 47.9 20.5 28.0 | 3.4 (8.6) 2.7 (8.1) 2.5 (9.3) 1.5 (6.8) | 0.086 |
No. of comorbidities None 1 2 ≥3 | 629 259 101 30 | 61.7 25.4 9.9 2.9 | 2.7 (8.9) 2.0 (6.4) 1.3 (7.7) 0.5 (5.6) | 0.002 |
AJCC stage at diagnosis 0-I II III Missing | 375 471 169 4 | 36.9 46.2 16.6 0.4 | 1.4 (7.0) 2.8 (8.7) 2.1 (8.6) -0.7 (16.9) | 0.352 a |
Histology IDC ILC DCIS Others | 858 31 56 74 | 84.2 3.0 5.5 7.3 | 2.2 (7.6) 5.5 (11.0) 1.2 (4.9) 2.3 (9.5) | 0.437 |
ER status Positive Negative Missing | 763 233 23 | 74.9 22.9 2.3 | 2.4 (7.8) 2.1 (7.1) 0 (5.6) | 0.394 a |
PR status Positive Negative Missing | 598 395 26 | 58.7 38.8 2.6 | 2.6 (7.8) 2.1 (7.4) 0 (10.2) | 0.214 a |
HER 2 status Positive Negative Missing | 274 686 59 | 26.9 67.3 5.8 | 2.1 (7.3) 2.6 (8.0) 0.5 (4.3) | 0.124 a |
Surgery Mastectomy Conservation | 628 391 | 61.6 38.4 | 2.2 (7.3) 2.2 (9.0) | 0.648 |
Chemotherapy Yes No | 774 245 | 76.0 24.0 | 2.6 (8.1) 1.3 (6.9) | 0.127 |
Radiotherapy Yes No | 721 298 | 70.8 29.2 | 2.5 (8.0) 2.0 (6.6) | 0.944 |
Endocrine therapy Yes No | 777 242 | 76.3 23.7 | 2.2 (7.7) 2.4 (7.7) | 0.789 |
Smoking status Yes No | 11 1008 | 1.1 98.9 | 0.6 (3.4) 2.3 (7.7) | 0.455 |
Drinking status Yes No | 15 1004 | 1.5 98.5 | 2.1 (7.6) 5.8 (7.4) | 0.866 |
b. Missing group did not include in P value test. |
Multivariate linear regression model was used to investigate the association between absolute changes in level of physical activity and socio-demographic, clinical and lifestyle factors. The variables entered into the model were those with P < 0.1 in the univariate analysis, which included age at diagnosis, marital status, household income, employment status, BMI at diagnosis and number of comorbidities. The results are presented in supplementary Table 3. Compared to patients who had a partner (married or cohabitating), those who were single (unmarried, divorced or widowed) had lower increase in level of physical activity between pre and post-diagnosis (β = -2.0, 95%CI: -3.7~-0.3, P = 0.021). Patients who were not working at baseline showed more increase in level of physical activity after diagnosis compared to those in full-time job (β = 2.7, 95%CI: 0.9 ~ 4.5, P = 0.002). Patients with one comorbidity at baseline showed lower increase in level of physical activity after diagnosis compared with those who had no comorbidity (β = -2.8, 95%CI: 4.7 ~ 1.0, P = 0.002).