4.1 Health profile across five health dimensions
Pain/discomfort and anxiety/depression were the dimensions of HRQoL where BC patients/survivors were more likely to report problems (75.4% and 57.3%, respectively) - these problems were 2–2.5 times more prevalent than any problems on other dimensions. In fact, these were also the two dimensions where severe or extreme problems were most likely to be reported by BC patients and survivors. The dimension where problems were least likely to be reported by those with BC was self-care (17.5%). These results are similar to findings from other research such as studies in China (n = 2626 BC patients), Korea (n = 827 BC patients), and Malaysia (n = 150 BC survivors) [20, 26, 19].
Pain/discomfort presents even years after the diagnosis and treatment as BC patients and survivors reported no difference in the level of problems in this dimension (79.2% and 73.5% respectively). It also indicates that self-reported pain may not decrease for BC survivors after finishing treatment or may recur at given time points. In all other dimensions (mobility, self-care, usual activities, and anxiety/depression), the survivors had significantly better health status though the extent of the difference varied. The dimension with least difference between patients and survivors was usual activities (8%). The biggest difference between patients and survivors with respect to having problems lay on the dimensions of self-care and anxiety/depression (18%).
Compared to age-matched peers in the general population, BC patients and survivors were significantly more likely to have problems in every dimension, especially in relation to pain/discomfort and anxiety/depression. The difference between patients and general population in these two dimensions were approximately 40–48 percentage points, respectively. The difference between survivors and general population in these two dimensions were 35 and 29 percentage points, respectively. In these other three dimensions, the differences were around 30 percentage points between patients and general population and 13–25 percentage point between survivors and general population. Although the differences are larger than a similar study in Malaysia (compared survivors and general population), the trend is the same . These results indicate the potentially profound psychological impact of BC on those who experienced the disease and imply the importance of not only care for physical health but also mental health of BC patients/survivors.
4.2 EQ-VAS scores and utility scores
The mean (SD) EQ-VAS and utility scores of BC patients were 64.9 (20.1) and 0.74 (0.22) which were significantly lower than that of BC survivors at 76.2 (15.7) and 0.84 (0.15), respectively. Both EQ-VAS and utility scores indicate the level of health (with 1 or 100 is full health) but their measurements are not the same. EQ-VAS is the score that respondents gave themselves based on their own perspective/evaluation while utility scores were calculated using respondents’ self-reported status of five health dimensions and the general population’s perspective on the value of those health dimensions (the country value set). While patients report a lower VAS score than utility score, interestingly the difference between patients and women from the general population is greater when measured with a utility score than with the VAS. In other words, the utility score suggests that the general population (whose views determine the weight in the utility index) assess the impact on QoL as more dramatic than those who experience it. This may indicate a degree of adaption among BC patients to their predicament though further research is required to assess this more fully.
EQ-VAS and utility scores of both BC patients and survivors were also lower than that of age-matched women from the general population at 77.9 (15.0) and 0.91 (0.1), respectively, which speaks to the face validity of the findings. The pattern is clear and consistent as patients have the lowest HRQoL and even when they survived and recovered from cancer, their HRQoL is still lower than general women drawn from the general population. Both cross-sectional studies with matched women from general population [26, 27] and longitudinal study (using other measurement)  reported the same pattern of HRQoL. Compared with similar studies that used EQ-5D-5L, mean utility scores of BC patients in our study is quite similar with China and Malaysia but much lower than Korea (0.75 vs 0.78, 0.71, and 0.92, respectively) [20, 19, 26].
Apart from status of treatment (patients vs survivors), those who are younger, have higher education and household monthly income are more likely to report higher HRQoL. These results are similar to findings from previous studies, including studies that used different instruments for measurement [29, 28, 30–32] and are again suggestive of face validity. Other sociodemographic characteristics such as marital status and living residence area (urban/rural) are not significantly related to either EQ-VAS or utility scores. We also did not find difference in HRQoL amongst patients diagnosed at different stages of BC, unlike the results from study of Wang et al (2018) . This may be due to our small sample size of BC patients (100 vs 2626 in Wang’s study).
Among BC patients, the observed trend in HRQoL amongst different stage of treatment was clear and consistent for both EQ-VAS and utility scores. Lowest HRQoL were reported by patients who have just gone through mastectomy (EQ-VAS = 54, utility score = 0.68). Patients who were being treated with chemotherapy, radiotherapy, or targeted therapy reported the next three lowest HRQoL (respectively, EQ-VAS = 61.8, 70.1, and 69.6; utility score = 0.71, 0.77, and 0.80). Patients who had just completed lumpectomy or breast reconstruction surgery reported better HRQoL than the survivors and on par or even higher than general population (in order of lumpectomy, breast reconstruction surgery, survivors, general population: 90.5, 80.0, 76.2, 77.9 for EQ-VAS; 0.88, 0.92, 0.84, 0.91 for utility score). The results were similar with a recent qualitative study in which Vietnamese BC patients claimed that mastectomy and chemotherapy were the two biggest challenges during their treatment (reference: manuscript under submission). Participants in this study also expressed the hope to regain their body image with breast reconstruction surgery. One said “I only know how bad it is after having a mastectomy… I feel so terrible. To be honest, whenever my husband holds me, I feel the emptiness... I hope that I can have reconstructive surgery because I cannot bear the defective body like that. I want my body to be normal again… Even if I die, I still want to die with a normal body… It is worse than losing my arm. Breast is a special symbol of women's beauty and every woman wants to be beautiful”. Although the results were not statistically significant due to small sample size, it is consistent with previous findings of original studies and systematic reviews with meta-analysis [30, 33, 31, 34–36].
4.3 Strengths and limitations
This is the first study to report EQ-5D-5L data for BC patients and survivors in Vietnam. The use of the standardised EQ-5D-5L instrument also enabled the first comparative study of HRQoL of BC patients, survivors, and age-matched women from the country’s general population. Although the sample size is not large in absolute terms, it is more than twice the minimum requirements for running analysis models [14, 15] and on par with similar studies in Vietnam and elsewhere . Thus, it is sufficient to provide novel and valuable insights into the HRQoL of BC patients and survivors in Vietnam, including its determinants as well as comparison with the general population. The results should continue to be treated with some caution however as they may not generalize to the whole country as the study could not conduct a hospital-based survey in the South region (due to limited resources) which led to the under-representation of this region in the sample. In addition, it is important to note that our sample was dominated by respondents who lived in urban areas, were more educated, and had higher household monthly income even though we applied two data collection methods in order to extend reach to respondents.