Abstract P1-09-04: Flaxseed & breast cancer: A systematic review
Authors: Wang Rui , Yang Mingxiao , Zhi Iris , Bao Ting 
Published: March 2022

Background: Flaxseed has been extensively studied in in vitro and in vivo models for possible association with reducing the risk of breast cancer. Clinical trials have been limited. There has been confusion regarding whether it is safe and beneficial for breast cancer survivors to take flaxseed. Therefore, we conducted a systematic review to evaluate the existing randomized controlled trial to understand the safety and efficacy of using flaxseed for symptom control and reducing the risk of recurrence among breast cancer survivors. Patients and Methods: We conducted a literature search of English language publications in MEDLINE, EMBASE, and Cochrane from the databases’ inception to May 2021 using the keywords flaxseed, breast cancer, randomized clinical trial, and human studies. Results: We identified three randomized controlled trials (RCT) that include patients with a history of breast cancer. Sample size ranged from 24 to 178 patients and treatment duration ranged from 13 to 42 days. The primary end points were hot flash severity (one study) and tumor biomarkers (two studies). There was no statistically significant reduction in mean hot flash score in the flaxseed group compared to the placebo group. One study showed a statistically significant reduction in Ki-67 (34.2%; P=0.001) and in c-erbB2 expression (71.0%; P=0.003), and an increase in apoptosis (30.7%; P=0.007) in the group that received flaxseed, but not in the placebo group. On the contrary, another study showed no difference in Ki-67, caspase, the Ki-67/caspase ratio, and Estrogen-receptor β. Two studies reported mild adverse events as shown in Table 1. None of the studies assessed the change in estrogen level. Risk of bias assessment showed that the overall risk of bias associated with the included studies is moderate to high. The high risk of bias originates from lack of blinding of participants and personnel. Conclusion: Current clinical research in breast cancer survivors is too limited to recommend flaxseed for cancer prevention. Flaxseed appears to be safe with mild side effects, however, the effect of flaxseed on estrogen concentration has not been established.

Table 1.Characteristics of included studies and risk of bias assessmentIDBreast cancer participantsSample sizeExperimentalControlOutcomesAdverse eventsRisk of biasPruthi 2012(U.S.)With breast cancer: (Yes/No)Flaxseed: 44/88Placebo: 47/90Flaxseed: 88Placebo: 90Flaxseed bar: 7.5g of flaxseed, 200 calories, one bar daily, 6 weeksPlacebo bar: 2g protein, 20% fiber, 200 calories, one bar daily, 6 weeksFrequency and severity of hot flash; hot flash interference; the Profile of Mood States; the Menopause Quality of Life Scale; the Global Impression of BenefitAbdominal distension and pain, diarrhea, flatulence, nausea, pruritus, maculopapular rash, vomitingLowThompson 2005(Canada)Flaxseed: (ER+ & PR+) 17/19; (ER- OR PR-) 2/19Placebo: (ER+ & PR+) 11/13; (ER- OR PR-) 2/13Flaxseed: 19Placebo: 13Flaxseed muffin: 25g flaxseed + 20.7g white wheat flour, one daily, 32 daysPlacebo muffin: 20.7g whole wheat flour+10g canola oil, one daily, 39 daysBreast cancer biomarkers including Ki-67, apoptosis, C-erbB2, ER and PR scoresAbdominal fullness and increased bowel movementsSome concernMcCann 2014(Canada)Clinical stage: Flaxseed: I 4/6; IIA 1/6; IIB 1/6;Anastrozole: I 6/7; IIA 1/7;Flaxseed/Anastrozole: I 5/6; IIA 1/6;Placebo: I 3/5; IIA 2/5Flaxseed: 6;Anastrozole: 7;Flaxseed/Anastrozole: 6;Placebo: I5;Flaxseed: 25 g/d ground flaxseed + 1/d placebo pill, 13-16 daysAnastrozole: 1 mg/d;Flaxseed/Anastrazole: 25 g/d ground flaxseed + 1 mg/d Anastrozole;Placebo: 1/d; 13-16 daysBreast cancer biomarkers including Ki-67, caspase, the Ki-67/caspase ratio, and Estrogen-receptor βNot reportedHigh

Citation Format: Rui Wang, Mingxiao Yang, Iris Zhi, Ting Bao. Flaxseed & breast cancer: A systematic review [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P1-09-04.