Background: Yoga has been tested in multiple small-randomized studies for its impact on quality of life (QOL) on breast cancer (BC). We propose to study the effect of yoga on disease free survival as the primary endpoint in women with operable breast cancer. (Study methodology details refer to NCT02161900). Methods: Women with non-metastatic BC were randomized to yoga and conventional exercise (YCE) versus conventional exercise only (CE) in addition to standard therapy. Over and above documentation of recurrence and death, QOL was assessed in these women using the EORTC QLQC30, BR23, Brief fatigue inventory (BFI), Visual pain scores (VPS) and a spirituality questionnaire (SQ). EORTC QLQ was assessed at baseline (BL), 6-9 months (mo), 18-21 mo. BFI and VPS at BL, 6-8 mo and 12-15 mo and SQ at BL and 12-15 mo. We report the first interim analysis of QOL in 605 patients randomized to the study with atleast 1 year of follow up. The groups were balanced in both arms with respect to clinico-pathological factors. Results: At 6-9 mo (completion of adjuvant therapy), there was no significant difference in global QOL scores (p = 0.08), however 52% women on YCE showed an improvement from baseline compared to 42% in CE. At 18-21 mo emotional function scores were better in YCE (p = 0.002); with lesser systemic side effects in YCE arm (44% vs 56% p = NS). The median score of fatigue after adjuvant therapy measured by QLQ C30 was lower in YCE (17.37vs22.22, p = 0.003) which was similar to that observed by BFI at 12-15 mo (1.6vs 2, p = 0.04). Also in YCE there was lower reporting of detriment in general activity (41%vs 59%) and mood (34%vs66%) (p = NS). In VPS at 12-15mo, the median scores for pain intensity (p = 0.042), pain on movement (p = 0.038), pain on mobilization (p = 0.008) were lower in YCE. Lastly SQ assessed spirituality and showed no difference, but less deterioration compared to baseline scores in YCE. Conclusions: Yoga did not show a significant difference in global QOL but had a major benefit reaching statistical significance in fatigue, emotional score and pain. Yoga is a low-risk, low-cost complementary therapy that may improve compliance to therapy by improving parameters that can affect day-to-day activity in women with breast cancer. Clinical trial information: NCT02161900