Introduction: Annually 400,000 children are diagnosed with cancer in the world. Approximately 90% live in low/middle-income countries, with survival rates of 10-30%. In Mexico, children and adolescents' hospital admissions for cancer are mainly leukemias (46%), being acute lymphoblastic leukemia (ALL) the most common. Half of ALL patients have an altered nutritional status at the time of diagnosis. Nutritional assessment is performed using conventional anthropometric measures, which are not sensitive to changes in fat-free mass and fat mass (FFM and FFM). Our objective is to evaluate the body composition and nutritional status in pediatric patients with HM. This is a pre-test/post-test clinical trial. Children 2-14 y olds diagnosed with leukemia, myeloma and lymphoma in any stage of oncological treatment will participate. The nutritional status will be evaluated using questionnaires and body composition. Measurements will occur at the enrrollment of the study and 6 months after.

JUSTIFICATION Nutritional assessment of cancer patients is usually performed using conventional anthropometric techniques, which are not sensitive to short-term changes and do not reflect changes in the FFM, FM, and hydration status. Assessing body composition using reference techniques such as deuterium oxide dilution (DOD), and also using field methods (BIA and anthropometry), which are more accessible in clinical practice, can detect short-term changes in children and adolescents with HM.

In cancer patients, protein and muscle stores are frequently affected; an increase in FM and a decrease in FFM were observed within the first 6 months of antineoplastic treatment. The DOD technique identifies three compartments (total body water, FFM, and FM). Similar changes in body composition are seen in patients with breast cancer; the work carried out by Limón-Miró et al; where it was observed that an individualized nutritional intervention preserved FFM while reducing FM, both associated with quality of life and survival in breast cancer patients. This highlights the importance of specialized nutritional and body composition evaluations in the comprehensive treatment of cancer patients; in children and adolescents with HM, monitoring body composition combined with a nutrition intervention, could reduce the deterioration of FFM and provide a window to assess prognosis, clinical outcome, and survival of HM pediatric patients.

HYPOTHESES The body composition (fat and fat-free mass) and nutritional status of pediatric patients with HM in active treatment will be different at the beginning vs. the end of the study (6 months), in addition to showing differences against the healthy reference population.

GENERAL OBJECTIVE To evaluate changes in body composition and nutritional status in pediatric patients with HM under active treatment.

SPECIFIC OBJECTIVES

• To evaluate nutritional status using anthropometric and dietary indicators at the beginning and 6 months after the intervention.
• To assess fat mass and fat-free mass using reference and field techniques, at baseline and 6 months after the intervention.
• To establish a protocol on monitoring nutrition status and body composition that can be applied routinely in clinical practice.

METHODOLOGY Study design This is a pre-test/post-test design. Children from 2 to 14 years old with a diagnosis of HM two areas of Mexico (Hermosillo, Sonora / Guadalajara, Jalisco) will participate.

Sample size: To determine the sample size, we will work on the assumptions of a standard deviation (SD) of Fat-Free Mass (FFM) of 2.19 Kg, with a Variance of 4.8 Kg, a Zα of 1.96 for a p = 0.05, with a mean difference (Ԁ) of 1 Kg. The sample size was calculated considering the Beta error of 20% (B = 0.84), depending on the availability of the number of patients who agreed to participate, as well as those excluded by established criteria. Based on the data mentioned, the estimated sample size calculation is 38 participants, as detailed in the following equation.

N = ((Zα + Zβ) ^ 2 〖(DE)〗 ^ 2) / 〖(d)〗 ^ 2 = 38 participants Clinical record: The principles of the Official Mexican Norm (NOM) NOM-024-SSA3-201 will be followed, which establishes the functional objectives and functionalities that must be followed in the use of electronic clinical records. For this purpose, a confidential file number will be assigned, so that when analyzing the biological samples or data collected in the field, no access will be given to the names, address, telephone number, or related information that may be exposed to the participant.

Screening: Predictive screening will be used for the "Nutrition Screening Tool For Childhood Cancer (SCAN)" which consists of 6 questions. This tool identifies the need for a nutritional intervention according to the symptoms of the patients who classify at risk of malnutrition. Screening should be applied to all study subjects at each consultation or weekly to patients who are hospitalized since they are at high risk of malnutrition at the time of diagnosis and increases in the stages of treatment. The Lansky pediatric scale will also be applied, which allows evaluating the general condition of the patient, representing the degree of autonomy in the activities of daily life. In addition, the PedsQL Cancer Module © will be used, which is derived from the Pediatric Quality of Life Questionnaire (PedsQL), which is a generic instrument designed for children and parents to assess the quality of life as a self-report.

Dietary evaluation: The ENSANUT frequency questionnaire will be applied for the respective age groups: preschoolers, schoolchildren, and adolescents.

Anthropometry Weight and height: Body weight will be measured (electronic scale with 0.150 + 0.05 kg scales) or child scale (0-20 kg). Height will be measured by SECA stadiometers or infantometers, as required to the nearest 0.1 cm.

Mid-upper arm circumference (MUAC): This measure allows the identification of malnutrition in children under 5 years of age without taking weight, height, and age, by measuring the arm circumference at its midpoint.

Tricipital skinfold (TSF): With the participant standing, with the feet together, the shoulders relaxed and the arms hanging relaxed at the sides. The examiner will stand on the right side of the patient and place the top point on the back surface of the arm in the same area as the midpoint marked for the arm circumference. The skin fold of the skin and subcutaneous adipose tissue will be gently grasped with the thumb and index finger, approximately 1.0 cm above the point where the skin was scored, with the skin fold parallel to the longitudinal axis of the upper arm. The jaws of the calipers will be placed at the level that the skin was marked, these should be positioned perpendicular to the length of the fold. The skinfold will be held gently and the skinfold thickness will be measured to the nearest 1mm.

Waist circumference (WC): The waist circumference will be measured with a retractable tape at the level of the umbilical scar in a standing position and after exhaling.

All measurements will be processed by the Anthro software of the World Health Organization, for the calculation of nutritional indices such as Z score of weight/age, height/age, and weight/height in children <60 months, BMI-age- sex, and height/age in children> 60 months. A physical examination will be performed to observe signs of malnutrition (loss of subcutaneous fat, muscle wasting, edema, etc.).

Body composition Deuterium oxide dilution: Total body water will be measured by dilution of deuterium oxide (DOD) using Fourier transform infrared spectroscopy (FTIR) with a saliva sample. The doses of deuterium will be those recommended for field studies by the International Atomic Energy Agency (an amount that does not represent a risk for minors).

The measurement will be taken once the patient has gone to the bathroom, sterile material will be used taking care of the cleanliness and safety of the personnel in charge of the measurement. A pre-dose saliva sample will be taken, once the dose is calculated by the patient's weight, the DOD will be administered, this should be taken with syringe to avoid spilling the dose. After 3 hours, a post-dose saliva sample will be taken, at the time of calculation, it will be taken into account if the patient ingested extra fluids.

Electrical bioimpedance (BIA): BIA is considered a simple, fast, and non-invasive technique that allows the estimation of total body water (TBW), fat-free mass (FFM), and, by difference, fat mass (FM). The patient must be in the supine position at the time of measurement for at least 5 minutes before starting. 4 electrodes will be placed on its left ends, two on the hand and two on the foot, 5 cm away from each other, a current of 50 mHz is administered, then a resistance and reactance reading is taken to obtain the result of the test. impedance, following the standardized methodology.

For the study population, it is proposed to use the equation validated in the child population proposed by Ramírez E., et al. In this way, when knowing the FFM, the FM will be estimated by difference with the total body weight.

FFM(kg) = 0.661 x Ht2 / R + 0.200 x Wt - 0.320 Where Ht is height in cm squared, R is resistance, and Wt is weight in kg. Individualized nutritional intervention

Statistic analysis Descriptive statistics will be used using NCSS v11. To evaluate the effectiveness of the intervention, the t-student test or non-parametric tests will be performed depending on the distribution of the data. For BIA an algorithm will be used to predict total body water for the calculation of FFM and FM compared to the results of dilution with deuterium. Intention-to-treat analysis will also be performed, which should be seen more as a global strategy for the design, execution, and analysis of clinical trials, rather than solely as an alternative analysis.

Inclusion Criteria:

• Patients in remission stage (4 - 6 weeks)
• Life expectancy> 6 months and sufficient general conditions according to scales (Lansky ≥ 50 points for children <16 years)
• Histopathological/molecular clinical confirmation of the HM diagnosis
• Signature of the consent by the relative or legal guardian of the patient and as well as the consent informed by the patient.

Exclusion Criteria:

• Pathological conditions that can alter body composition (diabetes, hypothyroidism, among others)
• Patients with sepsis that causes hemodynamic compromise and cannot be evaluated
• Severely ill patients unable to participate in baseline measurements
• Relapsed patients
• Patients with developmental problems of a genetic order as well as innate errors of metabolism

Masking during data analysis. Technicians and investigators will not be aware of the participants personal data and particularities.