Despite over a century of clinical use, and thousands of books, articles, and research publications, including a number of meta-analyses, the use of mistletoe lectins for cancer has been characterized as lacking in evidence. In this recent publication by Paller, et al., we see the first evidence generated in the United States to validate this practice.
This was a Phase I trial of intravenous mistletoe extract to evaluate safety and to set doses for a Phase II trial. Patients with solid tumor progression on at least one line of chemotherapy received escalating doses of the mistletoe extract three times a week.
Twenty-one patients were given doses up to 600 mg and were followed for a median of 15.3 weeks. Treatment-related adverse events (AE) occurred in 13 patients (61.9%), with the most common being fatigue (28.6%), nausea (9.5%), and chills (9.5%). Grade 3+ treatment-related AEs were noted in three patients (14.8%).
Five participants achieved stable disease and three had reductions in lesions. The disease control rate (percentage of complete/partial response and stable disease) was 23.8%.
Tumour marker Ca-125 in serum showed a slower rate of increase at higher dose levels.
The median quality of life (QoL by Functional Assessment of Cancer Therapy-General) score increased from 79.7 at week 1 to 93 at week 4.
The authors concluded that Intravenous mistletoe extract demonstrated manageable toxicities with disease control and improved QoL in a heavily pretreated solid tumor population. This supports further studies specifically designed to show therapeutic efficacy.
It should be noted that the most common method of use of mistletoe is by subcutaneous injection over very long-time scales. Physicians around the world have used various brands and types of mistletoe, determined by the specific cancer type, and primarily as an adjunct concurrent with chemotherapy and immunotherapy to manage adverse effects, and to maintain quality of life through into palliative care. It is hoped that studies that reflect these practices will also occur, rather than solely focusing on tumour reduction in advanced cases by a single type of mistletoe extract.
Reference:
1. Paller, C.J., Wang, L., Fu, W., et al., Phase I Trial of Intravenous Mistletoe Extract, Cancer Res. Comm. 2023; 3 (2): 338-346. doi.org/10.1158/2767-9764.CRC-23-0002
