Microstyle study aims to evaluate the effect of a 6-month intervention in a group of prostate cancer patients undergoing radiotherapy. Intervention is designed to control side effects and to improve adherence to a healthy lifestyle (diet and increase level of physical activity and decreased sedentary time) measured by the change in adherence to a healthy lifestyle score. The impact of the intervention on toxicity and gastrointestinal symptomatology will be measured by a mediation framework analysis. This approach allows investigating how microbiome may mediate effect of treatment. It will be also assessed the change in microbiome in relation to the change in cytokines/ adipokines in association with early and late toxicity.

MicroStyle study is a randomized two-arm crossover clinical trial. Study participants will be recruited among men undergoing radiotherapy (RT) in two centers (Milan and Naples). The study will be conducted over a three-year period, during which patients will receive a 6-month intervention and will be followed for other 6 months. The crossover design is used to reduce drop-out and to offer all patients the same opportunities, and also to evaluate the effect of the intervention after 6-month from RT when patients should have recreated a healthier microbiome and have less treatment side effects.

Three hundred patients will be enrolled over the study period and randomized in two arms: Intervention Group (IG) and Control Group (CG). Participants allocated to the IG will meet a dietitian and a physiotherapist before RT to receive personalized diet and exercise recommendations, according to their health status, to improve overall lifestyle and reduce side effects (bowel and/or urinary problems). The dietitian will give indication to limit the gastrointestinal side effects reducing consumption of foods rich in fiber, lactose and simple sugars, and the physiotherapist will set individualized goals based on capabilities, lifestyle pattern and preferences to increase physical activity and to reduce sedentary time. Moreover, the physiotherapist will provide specific indication to improve genitourinary health to reduce urinary incontinence that follows prostate treatments, erectile dysfunction and pelvic pain due to muscle spasm. All participants will be given a pedometer device (steps counter) in order to monitor and interfere (in the intervention group) with participants' physical activity and sedentary time. Participants included in the CG will receive at baseline general advice and materials available for patients undergoing RT. According to the crossover design, the CG will cross to the intervention as proposed for the IG, after the initial 6 months period.

Microstyle study foresee a 6-month intervention followed by 6-months of follow-up, over a period of 12 months for the intervention group (IG) while the control group (CG) will start the intervention 6 months after RT and they will follow-up for other 6 months over a period of 18 months.

Inclusion Criteria:

• men aged 18 or older
• candidates for a prostate curative treatment with RT (which includes exclusive RT +/-hormone therapy, surgery followed by RT +/- hormone therapy) AND
• good performance status (ECOG < 2) AND
• written informed consent obtained AND
• willing to be randomized to either group, AND
• willing to wear the wrist-based activity monitor during the 6-month study period.

Exclusion Criteria:

• BMI <18.5 AND
• extra pelvic lymph node involvement or metastasis and severe medical condition(s) that would prevent optimal participation in the physical activities prescribed AND
• Malnutrition Universal Screening Tool (MUST) ≥ 2. It considers body mass index, weight change and acute disease effect equally and determines a malnutrition risk score. A score ≥2 identify a patient at high risk of malnutrition AND
• investigator does not approve participation in the study in case of severe clinical condition that would prevent optimal participation in the physical activities prescribed; any other severe medical condition or advanced age impeding the patient to adhere at the planned study follow-up period.