Effects of mindfulness-based interventions on quality of life of women with breast cancer: a systematic review

Types of studies: all clinical trials were included in this review.

Types of participants: participants included adult women with a clinical diagnosis of breast cancer (Stage 0–IV).

Types of interventions: only studies that assessed MBSR or MBCT as the major intervention were eligible for inclusion. However, certain differences in MBSR or MBCT interventions, such as session length, frequency or duration did not hinder inclusion. Studies of mindfulness-based interventions that were different from the original MBSR or MBCT programs, such as acceptance and commitment therapy, mindfulness-based exercise, or art therapy were excluded. Acceptable control interventions were usual care, wait list or any other active treatments.

Types of outcomes: the studies were required to report quality of life as one outcome measure.

In October 2018, the electronic literature was systematically searched via PubMed, Cochrane library, EMBASE, Web of Science and CINAHL, limited to English language articles. The searches were based on the following strategy: ‘mindfulness’ OR ‘insight meditation’ OR ‘MBSR’ OR ‘MBCT’ AND ‘breast cancer’ OR ‘breast neoplasm’ OR ‘breast oncology’ OR ‘breast carcinoma’ OR ‘breast tumor’ OR ‘mammary tumor’ AND ‘quality of life.’ We also identified related systematic reviews and meta-analyses and checked their reference lists.

The study selection process is outlined in Figure 1. Eligibility was assessed by two independent raters in a standardized manner. Study titles and abstracts were independently assessed twice to confirm relevance to the topic of this review. If there was inadequate information to include or exclude an article, the full-text version was sought. Full-text versions of all the relevant studies were obtained and read by two independent reviewers to ensure eligible inclusion criteria.

Two reviewers independently assessed the quality of all selected studies using the Downs and Black Quality Index (QI), which assesses the quality of articles for both nonrandomized and randomized trials [18]. The scale includes reporting, external validity, bias, confounding and power; the maximum possible scores are 11, 3, 7, 6 and 5, respectively and the maximum total score is 32. The quality scores were estimated and ranked on a four-category scale: poor (<18), moderate (18–23), good (24–29) and excellent (>30). Scoring differences were rechecked between the two reviewers and discussed until consensus was reached.

Two reviewers used a standard data extraction checklist to independently extract the following data from each study: study characteristics, sample population characteristics, characteristics of the intervention and control groups, and outcomes. One investigator conducted the data extraction, which was checked by a second investigator. The results from different study designs should be considered systematically to avoid increased heterogeneity of results [19]. Therefore, no meta-analysis was performed due to the heterogeneity of study designs and outcomes.

Figure 1 shows the literature search flow chart of the 1149 records identified. Two additional studies were retrieved via a manual search of the reference lists of the full-text versions collected during the initial search. Of these, 568 records were excluded as they represented duplicate records, and the initial sifting based on the title and abstract through Endnote X9 resulted in the exclusion of a further 491 records. The full-text version of 92 studies were investigated, and 73 studies were excluded because the intervention was not eligible, they were duplicate publications, subjects included other cancers, they were unavailable conference abstracts, or they did not report quality of life as an outcome measurement. Finally, 19 records [20–38] of 15 study samples with 1518 participants were included in our systematic review.

Table 2 shows the quality assessment of the 15 studies in this systematic review. Most of the studies demonstrated good reporting quality; however, most of the studies had a high risk of bias in terms of study design. Five studies were of poor quality, with a mean score of 13; of the remaining ten studies, six were deemed to be of high quality and four were deemed to be of moderate quality.

The characteristics of the included articles are listed in Table 1. In the 15 selected studies, the sample size ranged from 15 [35] to 322 [26] participants. Mean age ranged from 43.25 [33] to 57.6 [26] years. Of these included studies, seven were performed in the United States [20,25,26,29,35–37], two in the United Kingdom [27,30], one in Canada [31], one in Japan [15], one in Iran [33], one in The Netherlands [32], one in Korea [28] and one in Denmark [34]. The patient samples ranged from Stage 0 (nonmetastatic breast cancer) to Stage III breast cancer. Cancer treatment status varied among studies, with nine studies including patients who were post-adjuvant or surgery treatment [25–27,29,31,34–36,38] and only two studies including patients who undergoing adjuvant treatment [20,28], excluding four studies that did not report patients cancer treatment status [30,32,33,37]. The interventions included 13 MBSR program studies [20,25–33,35–37], and two MBCT program studies. Control groups included usual care (six studies) [20,25,26,31,33,37], wait list (four studies) [27,28,34,36], supportive expressive group therapy (one study) [31], metacognition group therapy (one study) [33] and group nutrition education program (NEP) (one study) [20]. Five studies did not have a control group [29,30,32,35,38].

Thirteen studies containing 1377 participants reported the effect of MBSR interventions on the quality of life in patients with breast cancer [20,25–33,35–37]. The interventions included eight studies of the original MBSR program [20,27–29,32,33,36,37], and five studies that assessed modified MBSR interventions [25,26,30,31,35]. Of these five, three studies were mainly modifications of the original MBSR program in terms of duration period [25,26,35], and two studies were mainly modifications of the original MBSR program in terms of session time [30,31]. The duration of the training sessions varied from at least 90 min [31] to 2.5 h [20,32,37] weekly, the duration of the total training period only including 6 weeks [25,26,32,35] and 8 weeks [20,27–31,33,36,37]. Among the included studies, three studies compared intervention type with two control groups [20,31,33]. Quality of life was assessed using three breast cancer-specific measures: four studies used the Functional Assessment of Cancer Therapy-Breast quality-of-life instrument (FACT-B) [20,27,28,31]; three studies used the European Organization for Research and Treatment of Cancer Quality of Life Questionnaire Core-30 (EORTC QLQ C30) [30,32,33]; and two studies used the European Organization of Research and Treatment of Cancer Quality of Life Questionnaire – Breast Cancer Module (EORTC QLQ-BR23) [33,36]. Furthermore, two generic quality of life tools were used: four studies used the Medical Outcomes Study Short Form Health Survey (SF-36) [25,26,29,35]; and one study used Quality of Life Index Cancer Version III [37]. Among the included studies, one study used two quality of life measures [33].

Among 13 studies, three studies reported no significant impact of MBSR interventions on quality of life in patients with breast cancer. Lee et al. investigated Korean patients with metastatic breast cancer undergoing adjuvant treatment [28]. A randomized trial by Lengacher et al. studied the large sample; their patients underwent a 6-week modified MBSR intervention for breast cancer survivors [26].

Ten studies reported a significant effect of MBSR interventions on the quality of life in patients with breast cancer compared with those in the control group.

Henderson et al. conducted a randomized controlled trial comparing the original MBSR program with NEP for early-stage breast cancer. MBSR intervention was associated with significant improvement on measures of emotional well-being and spirituality subscales of FACT-B versus women in NEP and usual care, and social-family well-being after control for confounding variables [20]. Hoffman et al. examined the relationship between original MBSR intervention and breast cancer-specific quality of life after hospital treatment in women with Stage 0 to III breast cancer. Participants were asked to record the time and amount of home activities on record sheets. They found that there were significant improvements in mood, well-being and breast- and endocrine-related quality of life in the experimental group in women with breast cancer compared with standard care and these results persisted at 3 months [27]. Rahmani et al. found metacognition treatment and the MBSR treatment were effective in improving global and specific quality of life compared with the control group. The MBSR treatment was superior in improving fatigue, pain, future perspective and treatment side effects symptoms at the end of the treatment in comparison to the metacognition treatment, which persisted until the two-month follow-up. The important finding in this study was that the MBSR program had a broader effect range in specific life quality and in reducing pain intensity associated with cancer [33]. Witek-Janusek et al. evaluated women with early-stage breast cancer enrolled in an original 8-week MBSR program and found significantly reduced cortisol levels compared with the non-MBSR group. They suggested that the early provision of original MBSR intervention during the peritreatment period may be conducive to restore immune function, probably mediated by neuroendocrine activation resulting in the production or reduction of proinflammatory cytokines. They also found significant improvements compared with that of usual care on two of four domains of used Quality of Life Index Cancer Version III, in other words, ‘psychological–spiritual’ and ‘family.’ This suggests that MBSR allows individuals facing a potentially life-threatening situation to find more satisfaction in family and psychological–spiritual domains when evaluated using the Quality of Life Index Cancer Version III [37].

Lengacher et al. conducted a randomized controlled trial of a modified 6-week MBSR program with 84 female breast cancer survivors and found that compared with usual care, subjects in the MBSR group had significantly lower mean levels of depression, and anxiety, along with mean quality of life scores including physical functioning, and role limitations related to physical health. They also found that subjects who were more compliant with the MBSR intervention and practiced more tended to have larger reductions in perceived stress and pain of adjusted quality of life scores using SF-36 [25]. Carlson et al. measured the effects of modified MBCR intervention and supportive expressive group therapy (SET) in 252 distressed Stage I–III breast cancer survivors. They reported that patients in the MBCR intervention group reported increased emotional and functional quality of life relative to those in the SET group and control group, with benefits lasting more than 1 year. Improvements in fatigue and depression were noted but not significant [31]. Lengacher et al. tested the impact on delivering a mobile 6-week MBSR program using an iPad for breast cancer survivors on symptom improvement. Using video file modules on an iPad, the MBCR intervention group participants and to record practice time on the iPad. The authors reported significant improvements in energy, emotional well-being, general health and physical health scores of the SF-36, and sleep quality and fatigue from baseline to 6 weeks post MBSR [35].

Therefore, these results indicate a beneficial effect of MBSR interventions on quality of life among patients with breast cancer.

The interventions were both modified MBCT programs. Among the included studies, quality of life was assessed using FACT-B [38] and the WHO Well-Being Index (WHO-5) [34] separately.

Johannsen et al. assessed the efficacy of a modified 8-week MBCT for late post-treatment pain in 129 women treated for primary breast cancer. They found that the intervention group reported significantly reduced neuropathic pain, and the present pain intensity and increased quality of life after correction for multiple comparisons, and these effects persisted to the 6-month follow-up [34]. Park et al. examined effect of a modified MBCT intervention on quality of life in patients with breast cancer. They observed that MBCT had a favorable effect on anxiety, trauma-related psychological symptoms, and emotional and functional well-being scores of the FACT-B [38].

These results indicate a beneficial effect of MBCT interventions on quality of life in patients with breast cancer.

No study formally reported adverse events. In one trial, one patient was lost to follow-up from the MBSR group, and her drop-out was related to recurrence of disease [25]. Another trial reported two patients discontinued MBSR classes in the MBSR group because of breast cancer recurrence when the intervention began [27]. Lee et al. reported one patient experienced a lumbar sprain and cancelled the MBSR session [28]. However, all other trials reported neither absence nor adverse events, with the exception of four studies that did not report detailed reasons for dropping out [20,31,36,37].