The purpose of the study is to determine the impact of a specific nutrition formula with a high content of eicosapentaenoic acid (EPA) and fat in oncology patients receiving radio-/chemotherapy on body weight, body composition, nutritional status and physical function compared to a standard nutrition formula. Using an adaptive design approximately 80 patients will be randomized in the first part of the study. Following an interim analysis further 160 patients may be added, for a total of 240 patients.

Inclusion Criteria:

• patients with head & neck cancer or oesophagus cancer,
• enteral nutrition with PEG at least for 14 weeks,
• cancer patients who receive a combined radio-/chemotherapy,
• start of nutritional therapy latest at beginning of the radio-/chemotherapy, body mass index >=16 and <=30 kg/m2,0
• Kondrup Score>=3 or SGA = B/C,
• life expectancy > 6 months,
• written informed consent.

Exclusion Criteria:

• second active carcinoma,
• severe diarrhea unresponsive to codeine/loperamide,
• positive anti-HIV-test (safety reasons),
• pregnant or lactating women,
• insulin-dependent diabetes mellitus type I and II,
• patients with cardiac pacemaker,
• allergy to contents of the investigational product, to milk protein or to fish oil,
• patient has no PEG,
• participation in concurrent clinical studies with any other investigational nutritional therapy within one months prior to start of the study,
• intake of muscle growth supportan substances (e.g. anabolics),
• additional fish oil or EPA substitution within the last 4 weeks, SGA status A (well nourished).