Saturday, September 12, 2015

The Women's Intervention Nutrition Study (Low Fat Diet for Breast Cancer)

Hooper et al included The Women's Intervention Nutrition Study (WINS) as a reduced fat trial in their 2012 meta-analysis and as a reduced SFA trial in their 2015 meta-analysis

Studies Associated with the Trial

Dietary fat reduction in adjuvant breast cancer therapy: current rationale and feasibility issues (1990) (no URL and no access)
Effects of tamoxifen adjuvant therapy and a low-fat diet on serum binding proteins and estradiol bioavailability in postmenopausal breast cancer patients (1992) [1]
The effects of a low-fat dietary intervention and tamoxifen adjuvant therapy on the serum estrogen and sex hormone-binding globulin concentrations of postmenopausal breast cancer patients (1993) [2]
Adherence to a dietary fat intake reduction program in postmenopausal women receiving therapy for early breast cancer. The Women's Intervention Nutrition Study (1993) [3]
The challenges of assessing fat intake in cancer research investigations (1997) [4]
Dietary fat reduction and breast cancer outcome: interim efficacy results from the women's intervention nutrition study (2006) [5]
Implementing a low-fat eating plan in the Women's Intervention Nutrition Study [6]

Methods

The basis of this trial was that ecological and animal studies suggested a link between fat intake and the development of cancer (but cohort studies didn’t) [4].  “The Women's Intervention Nutrition Study (WINS) was subsequently designed to test the hypothesis that a dietary intervention targeting fat intake reduction would prolong relapse-free survival in women with resected breast cancer.” [5]

Women aged between 48-79 with breast cancer (other criteria listed here [5]) were randomised to a reduced fat group or a control group.  The participants were similar at baseline (table 1 and table 2) [5]

The reduced fat group were given a fat gram goal to reduce fat intake to 15% while maintaining weight, with the researchers expecting this would be maintained at 20% of total calories based on an earlier feasibility study.  Other methods to reduce fat intake included dietary counselling, goal setting, self-monitoring and social support (see [5] [6] for more info).

“Those classified as “strictly adherent” who met their fat gram goal not only decreased their intake of discretionary fat from oils, sweets and fat, but also reduced their intake of sweet breads, pastries, and desserts; cheese; poultry, beef, pork, and lamb; nuts and seeds; and eggs to a greater degree than did those who were not strictly adherent” [6]

Results

The experimental group maintained a fat intake of ~20% at 1 year and despite aiming to maintain weight, the reduced fat group lowered their calorie intake and lost a small amount of weight [5].  This was also fairly well maintained for 6 years as fat intake only crept up to ~23% [6].  After 5 years the reduced fat group lost 4.6 lb while the control group gained 1.7 lb [6].


Experimental Group
Control Group
Baseline
1 Year
Baseline
1 Year
Energy (kcal)
1687
1460
1531
1660
Total fat
57.3 (29.6%)
33.3 (20.3%)
51.3 (29.2%)
56.3 (29.6%)
SFA (g)
18.7
10.4
16.6
18.5
MUFA (g)
21.6
12.3
19.6
21.3
PUFA (g)
12.2
7.3
10.8
11.9
Fibre (g)
18.4
19.5
17.3
18.0
BMI
27.6
26.8
27.5
27.6

The experimental group had a lower incidence of relapse after a median of 5 years (also see table 4).  “Based on the effects on the primary endpoint, 38 women would need to adopt a lifestyle intervention reducing dietary fat intake to prevent one additional breast cancer recurrence” [5]


Hazard Ratio
(95% CI)
P value
Relapse free survival
0.76 (0.60-0.98)
0.077
Recurrence free survival
(excluding contralateral breast cancers)
0.71 (0.53-0.94)
0.050
Disease free survival
0.81 (0.65-0.99)
0.078
Overall survival
0.89 (0.65-1.21)
0.560

Hooper et al was not able to get information on CVD events or mortality so they only total mortality (which comes from “Death (without breast cancer recurrence)” in table 4)


Experimental
Control
Risk Ratio
Total Mortality
15/975
19/1462
1.18

Hooper et al assessed this trial as having a high risk of bias in ‘systematic difference in care’ and a low risk of bias in ‘dietary differences other than fat’

This concludes my series of blog posts on the clinical trials that have been included in meta-analyses related to saturated fat and/or polyunsaturated fat and coronary heart disease

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