Effect of home-based smartphone-supported high-intensity interval training on cardiorespiratory fitness in breast cancer survivors: A randomized controlled trial of the habit-B program

Abstract Background: A strategy for maintaining and/or improving cardiorespiratory fitness (CRF) in the growing population of cancer survivors is of major clinical importance in the COVID-19 era. With the aim of increasing CRF, recent studies have focused on the use of high-intensity interval training (HIIT) in supervised experimental settings, which appeared to be more beneficial than usual care in cancer survivors at all stages of treatment and aftercare. However, the effect of unsupervised HIIT on increasing CRF in breast cancer survivors is not known. Purpose: To determine whether the newly developed habit-B program, which involves home-based smartphone-supported HIIT using body-weight exercises, improves CRF in early-stage breast cancer survivors. We hypothesized that the habit-B program would improve VO2peak compared with a control group. Methods: This single-center, 12-week, parallel-group, single-blind, randomized controlled trial involved 50 women with stage I-IIa breast cancer, aged 20 to 59 years, who had completed initial treatment except for hormone therapy. Participants wore a smartwatch and were randomized to either the exercise or control group from May 27, 2019 through November 30, 2020. The planned sample size was 60 patients to detect the increase of 2.0 ml/kg/min change in VO2peak with a standard deviation of 2.6 ml/kg/min, one-sided significance level of 2.5% and 80% power. The exercise group underwent home-based HIIT using a smartphone and a Fitbit Versa thrice weekly for 12 weeks (three times per week). The primary outcome was the 12-week change in peak oxygen uptake (VO2peak; mL/kg/min) between the groups. Other outcomes included muscle strength, 6-min walk test, resting heart rate, physical activity, fatigue, safety, and quality of life. Results: Of the 50 participants, 44 (exercise group, n=23; control group, n=21) completed the CRF assessment and 6 did not because of issues related to the COVID-19 pandemic. The change in VO2peak increased significantly in the exercise group (0.9 [95%CI, 0.1 to 1.7]) compared with the control group (-0.8 [95%CI, -1.5 to -0.1]) (mean difference, 1.7 [95% CI, 0.7 to 2.7], p < .01). Leg strength also increased significantly in the exercise group compared with the control group (mean difference, 13.5 [95% CI, 2.9 to 24.1], p < .01). Changes in other outcomes were not significantly different between the groups. Conclusion: A home-based HIIT intervention can lead to improved cardiorespiratory fitness and muscle strength in early-stage breast cancer survivors; however, a multicenter pragmatic clinical trial is required to confirm the benefits of the habit-B program. Table 1.Demographic and medical characteristicsCharacteristicshabit-B (n = 25)Control (n = 25)Age, mean (SD), y48 (6)49 (5)Body mass index, mean (SD), kg/m221.0 (2.2)20.9 (2.0)Diastolic blood pressure, mean (SD), mmHg78 (8)81 (10)Systolic blood pressure, mean (SD), mmHg119 (13)129 (11)Alcohol consumption, n (%)≤weekly8 (32)5 (20)1–6 drinks per week15 (60)19 (76)Daily2 (8)1 (4)Highest Education, n (%)Junior high school0 (0)1 (4)High school3 (12)0 (0)College or more22 (88)24 (96)Employment status, n (%)Full- or part-time worker21 (84)21 (84)On leave1 (4)0 (0)Housewife3 (12)4 (16)Time the patient can use for herself, n (%)<14 hours/week10 (40)5 (20)14–25 hours/week8 (32)11 (44)>25 hours/week7 (28)9 (36)Past history of medical illness, n (%)6 (24)6 (24)Breast cancer stageI18 (72)18 (72)IIA7 (28)7 (28)TumorEstrogen receptor positive24 (96)25 (100)Progesterone receptor positive24 (96)24 (96)HER2 positive1 (4)0 (0)Receiving hormone therapy, n (%)24 (96)23 (92)Tamoxifen, n (%)18 (72)18 (72)Anastrozole, n (%)1 (4)4 (16)Other, n (%)5 (20)1 (4)Receiving radiotherapy, n (%)11 (44)12 (48)Time since surgery, mean (SD) months5 (4)6 (4) Table 2.Changes in cardiorespiratory fitness and muscle strength from baseline to week 12habit-B (n = 21)Control (n = 23)Between-group differenceMean (SD)Mean (SD)Mean (95% CI)ESpPrimary endpointVO2peak (ml/kg/min)Baseline25.0 (3.0)24.9 (4.6)Week 1225.9 (2.8)24.1 (4.0)Within-group difference0.9 (1.7)-0.8 (1.6)1.7 (0.7 to 2.7)1.06<0.01Secondary endpointCardiorespiratory fitness6-min walk test (m)Baseline586 (43)603 (59)Week 12615 (42)631 (68)Within-group difference30 (30)29 (40)1 (-21 to 23)0.260.93VO2peak (L/min)Baseline1.33 (0.18)1.32 (0.29)Week 121.39 (0.23)1.29 (0.26)Within-group difference0.06 (0.11)-0.03 (0.09)0.10 (0.03 to 0.16)0.95<0.01Muscle strengthGrip strength (kgw)Baseline22.4 (3.8)23.3 (4.2)Week 1223.2 (4.2)23.7 (3.4)Within-group difference0.8 (2.0)0.4 (2.1)0.4 (-0.9 to 1.6)0.260.53Leg press one-repetition maximum (kg)Baseline93.6 (24.3)98.7 (40.6)Week 12106.6 (26.7)98.2 (30.9)Within-group difference13.0 (15.9)-0.5 (18.1)13.5 (2.9 to 24.1)0.790.01Chair stand test (s)Baseline14.4 (3.2)13.7 (2.5)Week 1213.5 (2.9)13.3 (2.5)Within-group difference-0.9 (2.7)-0.4 (1.8)-0.5 (-1.9 to 0.9)-0.210.50 Citation Format: Eisuke Ochi, Katsunori Tsuji, Tomomi Narisawa, Yoichi Shimizu, Aya Kuchiba, Akihiko Suto, Kenjiro Jimbo, Shin Takayama, Taro Ueno, Naomi Sakurai, Yutaka J Matsuoka. Effect of home-based smartphone-supported high-intensity interval training on cardiorespiratory fitness in breast cancer survivors: A randomized controlled trial of the habit-B program [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 P4-11-11.