Can yoga improve fatigue in breast cancer patients? A systematic review

To the Editor,

Fatigue is one of the most common symptoms of breast cancer and its treatment [1]. Yoga is among the most commonly used complementary therapies for breast cancer [2]. Yoga encompasses physical postures, breath control and meditation. Recent systematic reviews indicate that yoga is effective as an adjunct treatment for cancer [3]. The aim of this systematic review was to assess the evidence of yoga for fatigue in breast cancer patients.

Medline, EMBASE, the Cochrane Library, PsycINFO, and CAMBASE were searched through September 2011. Medline search strategy was: (yoga[MeSH Terms] OR yog*[Title/Abstract]) AND (fatigue[MeSH Terms] OR fatigue[Title/Abstract]) AND (breast neoplasms[MeSH Terms] OR (breast[Title/Abstract] AND (neoplasm[Title/Abstract] OR cancer [Title/Abstract] OR oncology[Title/Abstract]))). Reference lists of identified original and review papers were also reviewed. Additionally, the table of contents of the International Journal of Yoga Therapy was reviewed.

Randomized controlled trials (RCTs) that assessed the influence of yoga on fatigue in breast cancer patients were included. Risk of bias was assessed using the Cochrane tool. This tool assesses risk of bias on the following domains: random sequence generation, allocation concealment, blinding of participants and personnel, blinding of outcome assessment, incomplete outcome data, selective reporting, and other bias [4]. Publication bias was assessed by visual analysis of funnel plots, generated using Review Manager software (Version 5.1, The Nordic Cochrane Centre, Copenhagen) [4]. Data extraction and quality assessment were conducted by two reviewers independently. Standardized mean differences (SMD) with 95% confidence intervals (CI) were calculated as the difference in means of fatigue scores between groups divided by the pooled standard deviation using Review Manager software. As a measure of heterogeneity between studies, I² statistics was used. Values of more than 50% were taken to indicate notable heterogeneity.

Of 68 records identified (51 after duplicates removed), six RCTs and 362 patients were included in the review (Table I). RCTs were heterogeneous regarding yoga tradition, length and intensity of intervention, control condition, fatigue score and disease characteristics. Yoga compared to control showed significantly greater improvements in fatigue scores (SMD = 0.33, 95% CI 0.01–0.65, p = 0.04, I² = 49%). Due to the small number of eligible studies, visual analysis of funnel plots leaded to inconclusive results regarding risk of publication bias.

Table I Characteristics of included studies.

Author, year	N	Mean age	Stage of cancer	Treatment group: Intervention, length, frequency, duration	Control group: Intervention, length, frequency, duration	Risk of bias	Fatigue score	Group difference SMD [95% CI]
Banasik, 2011 [5]	18	62.87	I–IV	Iyengar Yoga, 8 weeks, 2× 90 min/week	Wait-list, no intervention, 6 weeks	RS:U, AC:U, BP:H, BA:U, IO:L, SR:L, O:L	Unclear	0.57 [−0.51, 1.65]
Chandwani, 2010 [6]	81	Unclear	0–III	Patanjali's yoga tradition, 6 weeks, 2×60 min/week	Wait-list, no intervention, 6 weeks	RS:L, AC:U, BP: H, BA:U, IO:L, SR:L, O:L	BFI	0.00 [−0.50, 0.50]
Danhauer, 2009 [7]	44	55.8	any	Restorative yoga, 10 weeks, 1×75 min/week	Wait-list, no intervention, 10 weeks	RS:U, AC:U, BP: H, BA:U, IO:L, SR:L, O:L	FACIT-F	0.51 [−0.26, 1.28]
Littman, 2011 [8]	63	60.6	0–III	Viniyoga, 6 month, 1–3×75 min/week	Wait-list, no intervention, 6 month	RS:L, AC:U, BP: H, BA:H, IO:L, SR:L, O:L	FACIT-F	0.23 [−0.29, 0.75]
Moadel, 2007 [9]	164	54.81	I–III	Hatha yoga, 12 weeks, 1× 90 min/week	Wait-list, no intervention, 12 weeks	RS:U, AC:U, BP: H, BA:U, IO:L, SR:L, O:L	FACIT-F	0.05 [−0.32, 0.41]
Vadiraja, 2009 [10]	88	47.23	II–III	Integrated yoga program, 6 weeks, 3×60 min/week	Brief therapy, 6 weeks, 15 min every 10 days	RS:L, AC:L, BP: H, BA:U, IO:H, SR:H, O:L	EORTC QLQ-C30	0.90 [0.42, 1.37]

Risk of bias: AC, allocation concealment; BA, blinding of outcome assessment; BP, blinding of participants and personnel; H, High risk; IO, incomplete outcome data; O, other bias; L, Low risk; RS, random sequence generation; SR, selective reporting; U, Unclear. Fatigue scores: BFI, Brief Fatigue Inventory; EORTC QLQ-C30, European Organisation for Research and Treatment of Cancer Quality of Life Questionnaire C30; FACIT-F, Functional Assessment of Chronic Illness Therapy-Fatigue.

While statistical heterogeneity was acceptable, the number of studies included in this systematic review was small and every study had several risks of bias. Risk of publication bias could not be ruled out. In conclusion, there is evidence that yoga has beneficial effects on fatigue in breast cancer patients and survivors. However, this evidence is limited by possible risk of bias. Future studies of yoga for fatigue in breast cancer patients should ensure rigorous trial design and reporting.

Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.