Oral and injectable Marsdenia tenacissima extract (MTE) as adjuvant therapy to chemotherapy for gastric cancer: a systematic review

Marsdenia tenacissima extract (MTE) is a phytochemical widely used as complementary therapy in cancer care. This systematic review was conducted to investigate the anticancer and detoxification effects of MTE, as an adjuvant therapy to chemotherapy, for treating gastric cancer. Ten databases were searched to identify randomized controlled trials (RCTs) comparing oral or injectable MTE plus chemotherapy versus chemotherapy alone for treating gastric cancer up to May 1, 2019. In meta-analyses, proportional odds ratios (PORs) with 95% confidence intervals (CIs) were pooled for the ordinal outcomes using the generalized linear model, and risk ratios (RRs) with 95% CIs were pooled for dichotomous outcomes using the Mantel-Haenszel method. Seventeen RCTs with 1329 individuals were included, with a moderate to high risk of selection and performance bias. Compared to chemotherapy alone, MTE adjuvant therapy significantly improved the response to anticancer treatment (POR 2.01, 95% CI 1.60–2.53) and patients’ performance status (POR 3.15, 95% CI 2.22–4.48) and reduce the incidences of chemotherapy-induced leukopenia (RR 0.66, 95% CI 0.56–0.78), thrombocytopenia (RR 0.64, 95% CI 0.48–0.86), anemia (RR 0.89, 95% CI 0.72–1.10), nausea/vomiting (RR 0.79, 95% CI 0.69–0.91), hepatic injury (RR 0.77, 95% CI 0.61–0.96), and peripheral neurotoxicity (RR 0.77, 95% CI 0.59–1.01). However, MTE did not significantly alleviate anemia, diarrhea, constipation, kidney injury, and oral mucosal lesions after chemotherapy. Incidence of nausea/vomiting was lower in patients receiving oral MTE than those receiving injectable MTE (RR 0.47 vs. 0.82, interaction P = 0.04). Heterogeneity was generally low among these outcomes. Three out of five RCTs that reported survival data supported the effects of MTE for prolonging progression-free and/or overall survival. No studies reported safety outcomes of MTE. The current evidence with limitations of risk of selection and performance bias suggests that MTE, as an adjuvant therapy to chemotherapy, is effective for inhibiting cancer growth and reducing incidences of multiple chemotherapy side effects. Oral MTE may be a better choice. Uncertainty remains regarding the effects of MTE on survival endpoints and the subgroup differences between acute and chronic use of MTE and between different chemotherapy regimens.