Half of all cancer patients show an increase in resting energy expenditure. The causes of hypermetabolism have only recently been investigated in cancerology. One established cause is inflammation, but other causes have yet to be identified.

The interest in hypermetabolism is due to the fact that it appears early, before the onset of clinical deterioration (weight loss, sarcopenia, altered performance status) and that it correlates with patient morbidity and mortality. Like the other parameters that make up cachexia, it is both a predictor of toxicity and reduced efficacy of anti-tumour treatments and a prognostic factor, regardless of the tumour.

A therapeutic goal is to correct hypermetabolism for two reasons:

• avoid progression to clinical cachexia, which is an independent cause of morbidity and mortality
• increase the efficacy of anti-PD1/PDL1 immunotherapies. This new class of therapy has revolutionised the therapeutic management of many cancers but is less effective in cases of inflammation and/or altered performance status and/or hypermetabolism.

Investigator hypothesises that it is possible to develop a patient-specific treatment to correct hypermetabolism, depending on the predominant clinical or biological cause.

Inclusion Criteria:

• Age ≥ 18 years
• Patient with solid malignancy (any possible primary tumor), stage IV (M1), progressive or stable
• Without treatment or with anti-tumour treatment
• WHO performance status ≤ 2
• Person affiliated or benefiting from a social security scheme
• Having signed a consent to participate in the study
• Patient with hypermetabolism at the inclusion visit

Exclusion Criteria:

• Patient agitated, or unable to understand or tolerate wearing a mask for 20 minutes
• No active tumour disease (complete remission or ongoing tumour response)
• Care plan that does not allow for two calorimetry sessions 1 month apart
• Pregnant, breastfeeding or parturient woman
• Person deprived of liberty by judicial or administrative decision
• Person subject to forced psychiatric care
• Person subject to a legal protection measure
• Inclusion in another interventional study