Table 1.

Inclusion and exclusion criteria

PICO	Inclusion criteria	Exclusion criteria
Patient	Patients with malignancies (all entities and stages)	Patients with only precancerous conditions or carcinoma in situ
	Adult patients (age > 18)	Preclinical studies
		Study population with more than 20% children or precancerous conditions
Intervention	Every intervention with vitamin C (oral or intravenous)
Comparison	All possible control groups (placebo, standard care, observation)
Outcome	All patient-relevant endpoints (symptoms, safety, survival, quality of life)	No patient-centred data, for example, laboratory parameters
Others	Meta-analyses, systematic reviews, RCTs Controlled, one-arm and cohort studies	Grey literature (conference articles, abstracts, letters, ongoing studies, unpublished literature, etc.
	Language: German and English
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