Coriolus (Trametes) versicolor mushroom to reduce adverse effects from chemotherapy or radiotherapy in people with colorectal cancer.

Background: Radiotherapy and chemotherapy are used to improve survival in colorectal cancer but adverse effects can be a problem. Severe adverse effects may result in dose reduction or cessation of treatment, which have an impact on survival. Coriolus versicolor (Trametes versicolor or 'Turkey Tail') mushroom and its extracts have been used by cancer patients to help with adverse effects.

Objectives: To assess the effects of adjunctive Coriolus versicolor (Trametes versicolor) and its extracts on adverse effects and on survival during colorectal cancer treatment (chemotherapy and radiotherapy) compared with no adjunctive treatment.

Search Methods: We searched databases including CENTRAL, MEDLINE, Embase, AMED and CINAHL, Chinese and Japanese databases, and trials registers to 12th April 2022 without restriction of language or publication status. We screened reference lists and attempted to contact researchers in the field to identify additional studies.

Selection Criteria: We included randomised controlled trials (RCTs) investigating the efficacy and safety of Coriolus versicolor and its extracts in adult participants with a confirmed diagnosis of colorectal cancer, in addition to conventional treatment. Interventions included any preparation of Coriolus versicolor (raw, decoction, capsule, tablet, tincture, extract, injection), any part of the fungus (cap, stem, mycelium or whole), in any dose or regimen. Outcomes included adverse events rates, survival, disease progression and recurrence, response rates and quality of life.

Data Collection And Analysis: Two review authors independently screened and selected studies, extracted outcome data, and assessed risk of bias. We evaluated the overall certainty of evidence using the GRADE approach.

Main Results: We included seven parallel RCTs (1569 participants). Six studies (1516 participants) were conducted in Japan and one study (53 participants) in China. Studies included both male and female participants with colorectal cancer (five studies), colon cancer (one study) or rectal cancer (one study). Participants were diagnosed with cancer ranging from stage II to stage IV. Coriolus was used in the form of an extract in all seven studies and was generally used after curative resection, although in one study it was used preoperatively. Duration of treatment with the extract varied between four weeks and three years. Chemotherapeutic regimens in six studies consisted of an oral fluoropyrimidine which was preceded by weekly intravenous 5-Fluorouracil (5-FU) in one study, by mitomycin C in two studies, and which was combined with folinic acid (Leucovorin) in two studies and with radiotherapy preoperatively in one study. XELOX (oxaliplatin intravenous infusion and capecitabine) was used in the remaining study. We found very low-certainty evidence of little to no effect of adjunctive treatment with Coriolus (in the form of an extract, polysaccharide-Krestin, PSK) on withdrawal from treatment due to adverse events  (risk ratio (RR) 1.03, 95% confidence interval (CI) 0.45 to 2.34; 703 participants; 3 studies;). We are uncertain whether adjunctive Coriolus versicolor and its extracts compared to usual care alone resulted in a difference in adverse events including neutropenia (RR 0.41, 95% CI 0.24 to 0.71; 133 participants; 3 studies; very low certainty), oral cavity disorders such as oral dryness and mucositis (RR 0.37, 95% CI 0.13 to 1.03; 1022 participants; 5 studies; very low certainty), nausea (RR 0.73, 95% CI 0.44 to 1.22; 969 participants; 4 studies; very low certainty), diarrhoea (RR 0.77, 95% CI 0.32 to 1.86; 1022 participants; 5 studies; very low certainty), and fatigue (RR 0.76; 95% CI 0.33 to 1.78; 133 participants; 3 studies; very low certainty). We found low-certainty evidence of a small effect of adjunctive Coriolus on improved survival at five years compared with no adjunctive care (RR 1.08, 95% CI 1.01 to 1.15; 1094 participants; 3 studies; number needed to benefit (NNTB) = 16 (95% Cl 9 to 70). The effect at earlier time points was unclear.

Authors' Conclusions: Due to the very low certainty of evidence, we were uncertain about the effect of adjunctive Coriolus (in the form of an extract PSK) on adverse events resulting from conventional chemotherapy for colorectal cancer. This includes effects on withdrawal of treatment due to adverse events and on specific adverse outcomes such as neutropenia and nausea. The uncertainty in the evidence also means that it was unclear whether any adverse events were due to the chemotherapy or to the extract itself. While there was low-certainty evidence of a small effect on overall survival at five years, the influence of reduced adverse effects on this could not be determined. In addition, chemotherapy regimens used in assessing this outcome do not reflect current preferred practice.