Following baseline-assessment patients will be allocated to one of two experimental arms I) InterWalk or II) waiting-list control. To account for potential bias, patients will be stratified by prior treatment (adjuvant chemotherapy/no adjuvant chemotherapy), which may have significant impact on study outcomes. A random allocation sequence of treatment assignments for each stratification group will be created by the trial biostatistician and concealed from the study personal. The study coordinator will inform the patient of the treatment assignment and the patient will remain in this group for the full study period.