Sample Characteristics
As shown in Table 1, the female breast cancer patients were evenly distributed (~ 30%) among Native Hawaiians/Pacific Islanders (NHPI), Asians, and Whites, which is roughly consistent with the racial/ethnic diversity of Hawaii. Mean age at surgery of the overall cohort was 71.1 years with a range of 54–94 years. NHPI and White patients were younger, whereas Asian patients were older. Mean body mass index (BMI) at surgery was 28.3 kg/m2 for the entire cohort; NHPI patients had the highest mean BMI and Asian patients the lowest (31.7 and 26.2 kg/m2, respectively).
Table 1
Patient Characteristics at Breast Cancer Surgery
Patient Characteristics at Surgery, n (%) | All | NHPI | Asian | White | Other/Unknown |
N | 389 | 118 | 132 | 129 | 10 |
Age, years, mean (SD) | 71.1 (7.8) | 69.9 (7.9) | 73.2 (7.7) | 70.1 (8.8) | 71.7 (8.8) |
<65 | 86 (22.1) | 31 (26.3) | 22 (16.7) | 31 (24.0) | 2 (20.0) |
65–74 | 177 (45.5) | 55 (46.6) | 53 (40.2) | 66 (51.2) | 3 (30.0) |
75+ | 126 (32.4) | 32 (27.1) | 57 (43.1) | 32 (24.8) | 5 (50.0) |
Height, inches, mean (SD) | 62.6 (2.8) | 63.6 (2.6) | 60.6 (2.3) | 63.8 (2.3) | 63.1 (4.2) |
Weight, lbs, mean (SD) | 158.4 (41.9) | 182.5 (45.3) | 136.7 (30.1) | 157.8 (35.1) | 167.0 (35.1) |
BMI, kg/m2, mean (SD) | 28.3 (6.7) | 31.7 (7.1) | 26.2 (5.3) | 27.3 (6.1) | 29.6 (10.5) |
<25 | 129 (33.2) | 18 (15.3) | 61 (46.2) | 47 (36.4) | 3 (30.0) |
25-29.9 | 126 (32.3) | 35 (29.7) | 45 (34.1) | 43 (33.3) | 3 (30.0) |
30-34.9 | 75 (19.3) | 28 (23.6) | 18 (13.6) | 26 (20.2) | 3 (30.0) |
35+ | 59 (15.2) | 37 (31.4) | 8 (6.1) | 13 (10.1) | 1 (10.0) |
Table 2 presents characteristics of the patients’ breast cancer tumors. All 389 patients had early stage breast cancer, defined as invasive breast cancer in KPHI EMR. The average tumor size was 18.7mm, with moderately differentiated grade and lymph node negative disease. The majority of patients had estrogen receptor (ER) and progesterone receptor (PR) positive disease (84.1% and 74.0%, respectively) with 40.4% of cases having unknown HER2 status. NHPI patients were more likely to have regional stage, when compared to Asian and White patients (28% vs 20% and 19%, respectively), and to have lymph node positive disease (26% vs 17% and 16%, respectively).
Table 2
Tumor Characteristics, N (%) | All | NHPI | Asian | White | Other/Unknown |
Stage | | | | | |
In situ | 61 (15.7) | 15 (12.7) | 25 (18.9) | 18 (14) | 3 (30) |
Localized | 241 (62) | 70 (59.3) | 80 (60.6) | 87 (67.4) | 4 (40) |
Regional | 87 (22.4) | 33 (28) | 27 (20.5) | 24 (18.6) | 3 (30) |
Tumor size, mm, mean (SD) | 18.7 (14.5) | 19.1 (16.8) | 18.9 (15.4) | 17.7 (11.3) | 24.7 (11.9) |
Grade | | | | | |
Well differentiated | 78 (20.1) | 25 (21.2) | 25 (18.9) | 28 (21.7) | 0 |
Moderately differentiated | 183 (47) | 58 (49.2) | 67 (50.8) | 55 (42.6) | 3 (30) |
Poorly differentiated | 90 (23.1) | 25 (21.2) | 28 (21.2) | 34 (26.4) | 3 (30) |
Undifferentiated | 12 (3.1) | 5 (4.2) | 3 (2.3) | 4 (3.1) | 0 |
Unknown | 26 (6.7) | 5 (4.2) | 9 (6.8) | 8 (6.2) | 4 (40) |
Lymph node | | | | | |
Positive | 77 (19.8) | 31 (26.3) | 22 (16.7) | 21 (16.3) | 3 (30) |
Negative | 309 (79.4) | 87 (73.7) | 107 (81.1) | 108 (83.7) | 7 (70) |
Unknown | 3 (0.8) | 0 | 3 (2.3) | 0 | 0 |
Estrogen receptor status | | | | | |
Positive | 327 (84) | 102 (86.4) | 108 (81.8) | 109 (84.5) | 8 (80) |
Negative | 52 (13.4) | 13 (11) | 19 (14.4) | 18 (14) | 2 (20) |
Borderline | 1 (0.3) | 1 (0.9) | 0 (0) | 0 (0) | 0 (0) |
Unknown | 9 (2.3) | 2 (1.7) | 5 (3.8) | 2 (1.6) | 0 (0) |
Progesterone receptor status | | | | | |
Positive | 288 (74) | 93 (78.8) | 94 (71.1) | 94 (72.9) | 7 (70) |
Negative | 89 (22.9) | 23 (19.5) | 31 (23.5) | 32 (24.8) | 3 (30) |
Borderline | 2 (0.5) | 0 (0) | 1 (0.8) | 1 (0.8) | 0 (0) |
Unknown | 10 (2.6) | 2 (1.7) | 6 (4.6) | 2 (1.6) | 0 (0) |
Her2 status | | | | | |
Positive | 20 (5.1) | 3 (2.5) | 10 (7.6) | 6 (4.7) | 1 (10) |
Negative | 210 (54) | 66 (55.9) | 62 (47) | 77 (59.7) | 5 (50) |
Borderline | 2 (0.5) | 0 | 0 | 2 (1.6) | 0 (0) |
Unknown | 157 (40.4) | 49 (41.5) | 60 (45.5) | 44 (34.1) | 4 (40) |
Table 3 shows the patients’ treatment regimen following surgery. The majority of patients had either surgery followed by radiation or surgery followed by endocrine therapy, 35% and 31%, respectively. The primary treatment differed by race/ethnic group, with the most common being surgery-endocrine for NHPIs (36%) and surgery-radiation for Asians (37.9%) and Whites (38.0%). Surgery only and surgery followed by chemotherapy were less common primary treatments for the whole cohort, at 18% and 15% respectively.
Table 3
Treatment order, N (%) | All | NHPI | Asian | White | Other/Unknown |
Surgery Only (S) | 71 (18.3) | 19 (16.1) | 21 (15.9) | 27 (20.9) | 4 (40) |
Surgery-Chemotherapy (SC) | 59 (15.2) | 19 (16.1) | 18 (13.6) | 20 (15.5) | 2 (20) |
Surgery-Radiation (SR) | 137 (35.2) | 38 (32.2) | 50 (37.9) | 49 (38) | 0 |
Surgery-Endocrine therapy (SE) | 122 (31.4) | 42 (35.6) | 43 (32.6) | 22 (25.6) | 4 (40) |
Weight changes among all 389 patients across six time points, after adjustment for race/ethnicity, age and BMI at surgery are displayed in Fig. 2. The mean predicted probability for patients maintaining their weight < 3 months from surgery was over 90%; however, this percent steadily decreased to 44% at 36–47 months, with weight loss and weight gain at 40% and 16%, respectively.
Additionally, weight changes across time by age at surgery (groups divided at the median age 71 years), race/ethnicity, and BMI groups are shown In Figs. 2A, 2B, 2C, respectively.
Age at surgery (≤ 71 vs > 71 years, see Fig. 2A): The mean predicted probability of patients who maintained their weight steadily decreased across time for both age groups, though lower percentages were observed in patients age ≤ 71 years at surgery compared to patients age > 71 years. A higher percentage of patients who were age ≤ 71 years at surgery gained weight across time.
Race/Ethnicity (NHPI, Asians, Whites, Others, see Fig. 2B): The percentage of patients who had stable weight decreased across time across all race/ethnic groups. NHPIs and Whites, and to a lesser extent Asians, showed similar profiles, however NHPI had a higher percentage of patients who gained weight across time compared to Whites and Asians.
BMI at surgery (< 25, 25-29.9, 30-34.9, 35 + kg/m2, see Fig. 2C): Across all BMI groups, the percentage of patients who maintained their weight decreased across time. More patients with BMI 30 + kg/m2 (at surgery) loss weight across time compared to patients with BMI < 30 kg/m2.
(S) Surgery alone (see Fig. 3A): The percentage of patients who maintained a stable weight from surgery generally decreased over time (89% at < 3 months to 52% at 36–47 months); patients with stable weight comprise the majority at each time point. Weight loss continued throughout the evaluated time frame and peaked 24–35 months after surgery at 41%. The percentage of patients with weight gain was generally consistent throughout this timeframe.
(SC) Surgery-Chemotherapy (see Fig. 3B): From 3 months on, the percentage of patients who maintained weight after surgery was generally constant at roughly 50%. Within 3 months after surgery, a time when patients routinely receive chemotherapy, 16% of patients had significant weight loss, and over 30% of patients had weight loss at each subsequent time point. Weight gain continued to steadily increase during this timeframe and peaked 12–23 months after surgery at 14%. Weight gain was less commonly seen than weight loss throughout the post-surgery period.
(SR) Surgery-Radiation (see Fig. 3C): The percentage of patients who maintained a stable weight from surgery consistently decreased over time (94% at < 3 months to 38% at 36–47 months), and the percentage of patients who loss or gained weight steadily increased after initial surgery. Weight loss was about 2-fold more common than weight gain at each time point.
(SE) Surgery-Endocrine (see Fig. 3D): The pattern of weight change in this patient group was very similar to the pattern in the surgery-radiation patient group, where the percentage of patients with stable weight decreased over time.
Weight changes from surgery were similar between the treatment groups of S, SR and SE across time (p = 0.89 based on a F test with 20 degrees of freedom). A similar model that included all 389 patients and a modified treatment term, collapsing S, SR, SE into one group (vs SC), resulted in a significant interaction term between time and treatment (p = 0.0008 based on a F test with 10 degrees of freedom). Patients who underwent SC treatment experienced different weight changes compared to S, SR, and SE groups; they had the highest percent weight loss, particularly within the first 3 months after surgery, while they received chemotherapy. This percentage with weight loss plateaued at 3–5 months and continued for the remainder of the timeframe, up to 4 years after surgery.