The objective of the study is to evaluate the effect of a personalized dietary intervention (cohort A), compared with a standard nutritional intervention based on general recommendations for following a Mediterranean diet (cohort B), in women with advanced solid tumors of gynecologic or breast origin who are receiving treatment with antibody-drug conjugates (ADCs). This intervention is exclusively nutritional and does not involve the use of any investigational drug.

Phase II, proof-of-concept, prospective, interventional, randomized, open-label study designed to evaluate the effect of a personalized dietary intervention on global quality of life in women with advanced gynecologic or breast tumors undergoing treatment with ADCs.

Inclusion Criteria:

1. Written informed consent to participate in the study, obtained prior to performing any specific procedure.
2. Women aged ≥ 18 years.
3. Confirmed diagnosis of advanced, incurable (stage IV or unresectable stage III) breast cancer or gynecologic cancer. This includes cancers of the breast, ovary, cervix, uterus, endometrium, fallopian tubes, vagina, or vulva.
4. Participants must have received a first cycle of ADC treatment in any line of treatment.
5. ECOG performance status 0-2.
6. Availability of their main clinical data with the possibility of follow-up.

Exclusion Criteria:

1. Male patient.
2. BMI <18 or > 40 kg/m2.
3. Patients with a life expectancy of less than 3 months.
4. Type 1 diabetes mellitus, metabolic diseases, and severe gastrointestinal disorders that interfere with the digestion or absorption of nutrients, as well as patients with severe renal or hepatic impairment.
5. Planned participation in treatment within a double-blind clinical trial.
6. History of previous or concomitant malignant disease of any other type that could affect compliance with the protocol or interpretation of results. Patients with curatively treated basal cell carcinoma of the skin or in situ cervical cancer are eligible for the study.
7. Presence of concurrent diseases or clinical conditions that, in the investigator's judgment, may significantly interfere with participation in the study, particularly those that limit the ability to adequately use the required digital tools (APP and wearable device). Patients will not be excluded due to common comorbidities if they retain adequate cognitive functioning and digital familiarity to comply with study procedures.
8. Carriers of therapeutic electronic devices: pacemakers, defibrillators, and cardiac resynchronization devices (due to potential interference caused by the wearable).
9. Patients who, in the investigator's judgment, do not possess sufficient digital capability to comply with the study procedures.

Confirmed diagnosis of advanced, incurable (stage IV or unresectable stage III) breast cancer or gynecologic cancer. This includes cancers of the breast, ovary, cervix, uterus, endometrium, fallopian tubes, vagina, or vulva.