BMI is a simple and widely recorded variable that may capture obesity or cachexia in cancer patients. How BMI is associated to health-related quality of life (HR-QoL) in such patients is poorly investigated.

High BMI may be associated to obesity, an increased burden of comorbidity, reduced physical activity and, in some settings, to more aggressive oncological disease. On the other hand, low BMI may reflect enhanced weight loss, cachectic syndrome, higher tumor burden and adverse prognostic features which all deteriorate quality of life. The aim of the present study is to evaluate the association of BMI and HR-QoL as measured by the EORTC-QLQ-C30 questionnaire in several cancer settings (such as localized vs metastatic or distinct primary tumors).

Health-related quality of life (HRQoL) might have varied association to body weight in patients with solid cancer[1].

On one hand low body weight may reflect cancer-related anorexia and weight loss and cachectic syndrome which are associated to impaired performance status, deteriorated general conditions and advanced cancer[2]. In such patients the probability of recording a low Body Mass Index (BMI) and concomitantly an inferior Health related quality of life (HRQoL, as patient reported outcome, PRO) is high.

On the other hand, some of the hormonal mediators found at increased concentration in obese patients, such as insulin-like growth factor (IGF), have been demonstrated to be involved in biological pathways that favor an improved HRQoL[3].

Adding further apparent contradiction is the fact that obesity and high BMI may represent in some cancer settings an adverse feature. In particular, obesity is associated with an increased risk of developing certain tumor types and, in some cancer patients with radically resected primary, of cancer relapse[4]. Moreover high BMI carries often an increased burden of comorbidity (e.g. cardiovascular and metabolic diseases)[5] and reduced physical activity. All these factors may reduce HRQoL.

Studies investigating specific associations between BMI and HRQoL in specific cancer settings are therefore warranted.

The present prospective observational cohort study has the aim of investigating the relationship between BMI and PRO-HRQoL as measured by the EORTC-QLQ-C30 questionnaire [6] in different primary tumors (breast, lung, colorectal and others) and in different cancer stages (localized vs metastatic). Patients will be also stratified according to the presence of cardiovascular and metabolic comorbidities, to the Karnofsky Performance status and according to the oncological treatment received (chemotherapy vs radically resected patients on follow-up). If available, retrospective data will be used to train possible predictive models.

STUDY PROCEDURES Study participation will be offered to all consecutive patients with a histologically confirmed diagnosis of solid tumor referred to the Medical Oncology Units of the S.I.C.O.G. cooperative group (http://www.sicog.it/). Upon acceptance, patients will sign an informed consent and be asked to fill out the EORTC QLQ C30 questionnaire.

All common antropometric, demographic, clinical and biochemical variables will be recorded around the moment of first referral (within three months).

Re-assessable variables, including EORTC QLQ-C30 questionnaire re-administration, will be recorded every 4-6 months thereafter. All data will be stored in a prospectively maintained database.

Among recorded data will be: age, sex, weight, height, occupation, civil status, primary tumor site, tumor stage, possible metastatic sites, past and actual type of oncological treatment, pain score, Karnofsky Performance Status, vital signs, routine blood tests Patients will be oncologically managed according to standard practice Association between BMI and EORTC QLQ-C30 will be assesses using regression analyses across the different clinical settings identified.

STATISTICAL CONSIDERATIONS The design of the study hypothesizes that in metastatic patients an improved HR-QoL is associated with high BMI (non-cachectic patients) An 'exact single-stage design' will be followed [7]. According to historical data (endometrial cancer), 50% of patients with BMI < 30 has a high global health status score (GHS) of the EORTC QLQ C30 (i.e. a GHS score ≥ 80%) [8].

The hypothesis to be tested will be H0, P < P0 vs H1, P > P1, where P is the percentage of patients with GHS ≥ 80%. One-tail alpha error of 0.05 and false-negative (beta) rate of 0.2 will be considered. P0 will be set at 50% and P1 at 65%, looking for a 15% increase in the percentage of high GHS score among patients with BMI >30. The H0 hypothesis will be rejected and H1 accepted with a statistical power of 80% if at least 42 patients out of 69 with BMI > 30 will report a GHS score ≥ 80.

Since BMI > 30 is observed in about 10% of all metastatic patients, a total of 690 metastatic patients will be required. Since metastatic patients are about half of all cancer patients referred to Medical Oncology Units, a final sample size of 1380 cancer patients (all stages) will be set as the target number.

Inclusion Criteria:

1. Histologically confirmed diagnosis of solid tumor
2. Age >18 years
3. Signed informed consent
4. Life expectancy > 12 weeks

Exclusion Criteria:

1. Inability to fill out the EORTC QLQ-C30 questionnaire.
2. Absence of a certain diagnosis of solid tumor (e.g. subjects on screening programs)
3. Diagnosis of second malignancies that might bias results interpretation

All consecutive patients with a histologically confirmed diagnosis of solid tumor referred to any of the Medical Oncology Units of the S.I.C.O.G. cooperative group (http://www.sicog.it/).