As many as 1 in 5 cancer patients enrolled in phase 3 clinical trials may use complementary medicine, according to a study published in The Oncologist

The study also showed superior outcomes among patients taking complementary medicines, though these results may have been influenced by baseline characteristics or other factors, according to researchers. 

For this study, the researchers looked at medication lists from 6 phase 3 trials to identify patients using complementary medicine. Enrolled patients had metastatic breast, colorectal, or lung cancer. 

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Of 3707 patients examined, 20.3% used at least 1 complementary medicine. A total of 651 medications were identified as complementary. Complementary medicine use was more common in patients with breast cancer (35.6%) than in patients with colorectal (15.6%) or lung (18.5%) cancer. 

The most common complementary medicines were herbal/natural products (46.6%), dietary supplements (22.1%), fish oils (18.0%), glucosamine (11.0%), and homeopathy (2.3%). 

The patients who used complementary medicine were more likely to have favorable baseline prognostic factors, such as younger age, better performance statues, non-smoking status, and fewer sites of metastasis. 

Complementary medicine use was associated with longer overall survival (adjusted hazard ratio [aHR], 0.84; 95% CI, 0.75-0.93; P =.001) and a lower risk of disease progression (aHR, 0.90; 95% CI, 0.82-0.987; P =.024) overall.

However, when the researchers looked at each cancer type individually, complementary medicine use was only associated with a survival or progression benefit for patients with lung cancer. There was no significant association between complementary medicine and survival or progression for colorectal or breast cancer. 

Complementary medicine was not associated with any improvements in quality of life. However, the incidence of grade 3 or higher adverse events was lower in patients using complementary medicine (50.0% vs 61.6%; P =.002).  

“Complementary medicines were not associated with worse cancer specific-outcomes; however, this may be influenced by having more favorable baseline characteristics and other uncaptured variables,” the researchers wrote. 

“Given the absence of conclusive clinical trial data demonstrating the efficacy of complementary medicines, the use of these agents remains controversial. Our findings do not replace the need for an open patient-physician relationship to encourage disclosure of complementary medicine use and for careful pharmacological review of complementary medicines to identify potential drug interactions.”

Disclosures: Some study authors declared affiliations with biotech, pharmaceutical, and/or device companies. Please see the original reference for a full list of disclosures.


Wells JC, Sidhu A, Ding K, et al. Complementary medicine use amongst patients with metastatic cancer enrolled in phase III clinical trials. Oncologist. Published online February 19, 2022. doi:10.1093/oncolo/oyac020