Forest adjuvant anti-cancer therapy to enhance natural cytotoxicity in urban women with breast cancer: A preliminary prospective interventional study

Introduction: Studies have shown both significantly diminished natural cytotoxicity and immunosuppression in breast cancer patients after standard anti-cancer treatments. Therefore, an integrative approach employing adjuvant therapy in addition to current treatments is required to enhance immunoactivation. This preliminary prospective interventional study aimed to assess the feasibility of forest therapy as an adjuvant to enhance natural cytotoxicity. Methods: This was a feasibility study of 11 volunteer women aged 25-60 years with stage III breast cancer. All subjects were exposed to daily forest therapy for 14 days whilst living in accommodation in a forest. Interventions included a relaxing daily 2-h morning walk (3 miles), free time tailored to subjects interest, group interaction and prepared meals based on nutritional standards. Outcome measures included natural killer (NK) cell populations and levels of perforin and granzyme B. Results: Data from all participants were analysed. The mean volume of NK cells increased from 319.4 mL in the city to 444.6 mL in the forest after forest therapy (p < 0.01). The mean level of perforin increased from 216.9 pg/mL in the city to 344.9 pg/mL in the forest and then further increased to 463.2 pg/mL after subjects returned to the city (p < 0.02). The mean level of granzyme B increased from 4.4 pg/mL in the city to 11.2 pg/mL in the forest and then further increased to 20.2 pg/mL after subjects returned to the city (p < 0.02). Conclusions: This study demonstrates the potential of forest therapy as an adjuvant anti-cancer therapy after standard treatments. A definitive trial with a control group should now be performed with larger sample sizes and long-term follow-up periods to confirm the feasibility and potential therapeutic effectiveness of this approach. (C) 2015 Published by Elsevier GmbH.