Anti-EGFR (Epidermal Growth Factor Receptor) therapies, namely cetuximab and panitumumab, have become standards in the management of metastatic colorectal and head and neck cancers. These therapies are used in daily practice, that requiring to manage their skin and digestive toxicities. However, anti-EGFR are also frequently responsible for hypomagnesemia often neglected and under-treated.

Hypomagnesemia may manifest as asthenia, cramps, muscle weakness, mood disorders. She is often underestimated because they are difficult to identify and accountable by clinicians in the context of cancer under chemotherapy.

There is currently no national or international recommendation on the management of hypomagnesaemia in oncology and medicine in general. There are, however, on the market many nutritional supplements rich in magnesium in the form of tablets or oral solution, in multiple dosages.

These food supplements rich in magnesium are sold without proof of effectiveness. Moreover, the prescription of oral magnesium supplementation adds to the oncology patient an over-medicalization, which can be poorly tolerated at the digestive level, and responsible for diarrhea and a lack of compliance.

The European Food Safety Authority (EFSA) recommends in its opinion on "Dietary reference values for water" to consume 2 liters for women and 2.5 liters for men every day, all sources combined (food and beverages). The drink represent 80% of the water intake, that is about 1.5 Liter per day excluding food. However, there are multiple water marketed or distributed freely, with different compositions. Thus the quantity and quality of the mineral water consumed can influence the metabolism. Rozana® mineral water, has the double advantage of being the French water the most concentrated in magnesium (160 mg / L) and of being lowly concentrated in sulphate, responsible of the laxative power of certain waters.

Instead of adding magnesium supplements with a poor digestive tolerance, to patients with metastatic cancer and often with a heavy treatment , the aim of this study is to evaluate whether a change in oral hydration in quantitative and qualitative terms can decrease the rate of hypomagnesemia in patients treated with anti-EGFR.

Anti-EGFR (Epidermal Growth Factor Receptor) therapies, namely cetuximab and panitumumab, have become standards in the management of metastatic colorectal and head and neck cancers. These therapies are used in daily practice, that requiring to manage their skin and digestive toxicities. However, anti-EGFR are also frequently responsible for hypomagnesemia often neglected and under-treated.

Magnesium remains the fourth cation and the second most important intracellular cation in the body. It is an indispensable cofactor in multiple enzymatic reactions. Hypomagnesemia may manifest as asthenia, cramps, muscle weakness, mood disorders. She is often underestimated because they are difficult to identify and accountable by clinicians in the context of cancer under chemotherapy.

There is currently no national or international recommendation on the management of hypomagnesaemia in oncology and medicine in general. Hypomagnesemia is, in daily practice, mostly undiagnosed or untreated. There are, however, on the market many nutritional supplements rich in magnesium in the form of tablets or oral solution, in multiple dosages.

To date, these food supplements rich in magnesium are sold without proof of effectiveness. The clinical data are very insufficient, and no oral supplementation is reimbursed. Moreover, the prescription of oral magnesium supplementation, often several intakes a day, adds to the oncology patient an over-medicalization, which can be poorly tolerated at the digestive level, and responsible for diarrhea and a lack of compliance. Oral hydration is one of the most prescribed medical advice and remains essential to combat the risk of dehydration in extreme ages. The European Food Safety Authority (EFSA) recommends in its opinion on "Dietary reference values for water" to consume 2 liters for women and 2.5 liters for men every day, all sources combined (food and beverages). The drink represent 80% of the water intake, that is about 1.5 Liter per day excluding food. However, there are multiple water marketed or distributed freely, with different compositions. Thus the quantity and quality of the mineral water consumed can influence the metabolism.

The digestive absorption of magnesium provided by mineral water in a healthy individual was evaluated at around 40 to 50%. Rozana® mineral water, has the double advantage of being the French water the most concentrated in magnesium (160 mg / L) and of being lowly concentrated in sulphate, responsible of the laxative power of certain waters.

Instead of adding magnesium supplements with a poor digestive tolerance, to patients with metastatic cancer and often with a heavy treatment , the aim of this study is to evaluate whether a change in oral hydration in quantitative and qualitative terms can decrease the rate of hypomagnesemia in patients treated with anti-EGFR.

Inclusion Criteria:

1. Patient having either:

   • a metastatic head and neck cancer or in locoregional relapse, proved histologically, authorizing an oral feeding or by gastrostomy or nasogastric tube,
   • a metastatic colorectal cancer, histologically proved, wild-type RAS

2. Patient who must be treated by anti-EGFR for this cancer

3. Age ≥ 18 years

4. Performance Status = 0, 1 or 2

5. Patient affiliated to a social security scheme

6. Patient who have given written consent prior to any specific study-related procedure

Exclusion Criteria:

1. Cerebral metastasis
2. Previous anti-EGFR treatment
3. Patient requiring exclusive parenteral nutrition and hydration
4. Concomitant treatment by radiotherapy
5. Presence of another invasive cancer, other than head and neck or digestive, except basal cell carcinoma or intracervical neoplasia treated
6. Presence of hypomagnesemia at randomization
7. Ongoing oral or intravenous magnesium supplementation within 2 weeks before randomization
8. Patient with grade III or IV diarrhea within 2 weeks before randomization
9. Patient who have had a jejunostomy or ileostomy
10. Patient with constitutional tubulopathy
11. Patient with chronic renal insufficiency (MDRD Clarity <60 mL / min)
12. Pregnancy or breast-feeding
13. Persons deprived of their liberty or under guardianship
14. Dementia, mental impairment or psychiatric pathology that may compromise the patient's informed consent and / or adherence to the protocol and follow-up of the trial
15. Patient who can not follow protocol for psychological, social, family or geographical reasons