Unproven alternative treatments are clearly risky. Some carry the risk of direct harms, such as improperly diluted homeopathic tablets, blinding stem cell injections, contaminated supplements, or tainted placenta pills. And others, such as magic healing crystals and useless detoxes, may risk indirect harm by taking the place of evidence-based treatments.

However obvious the risks, measuring them has been tricky. For one thing, patients aren’t always eager to provide data, let alone admit to their doctors that they’ve ditched conventional therapies. But, by digging into the National Cancer database, researchers at Yale have finally quantified one type of risk for cancer patients—the risk of death. And the results are grim.

Those who skipped or delayed conventional treatment to use alternative ones had as much as a 5.7-fold increased risk of dying within five years than those who stuck with conventional medicine, the researchers reported in the Journal of the National Cancer Institute. Though the study was small and had several gaps—including not knowing the types of alternative treatments patients had tried—the researchers hope that it spurs discussion and “greater scrutiny of the use of [alternative medicine] for the initial treatment of cancer.”

For the analysis, the researchers, led by Skyler Johnson, focused on the four most prevalent types of cancer in the US between 2004 and 2013: breast, lung, colorectal, and prostate. Mining the database, they sought cases of patients who received no conventional treatment and whose medical records contained codes for alternative treatments. Those treatments were simply defined as: “other-unproven: cancer treatments administered by non-medical personnel.” The researchers excluded patients with incomplete records and those with an initial diagnosis of metastatic or late-stage cancers.

The researchers ended up with only 280 records of patients who chose alternative medicine over conventional therapies. Those patients tended to be female, young, have high education and income, and have few complicating health conditions.

For comparison, the researchers matched each of those patients with two other patients who were diagnosed in the same year, had matching age, race, disease, disease stage, and insurance type—but had opted for conventional treatments. Those treatments were defined as “chemotherapy, radiotherapy, surgery, and/or hormone therapy.” Together, the researchers analyzed medical records of 840 patients who were tracked for a median of 66 months.

Alternative survival

Overall, those in the alternative treatment group were 2.5 times more likely to die within five years of treatment than the conventional group. But, that figure is dragged down by cases of prostate cancer, which tend to progress slowly. The researchers found no statistically significant difference in mortality risks among prostate cancer patients regardless of what types of treatments they chose.

But, among patients with breast cancer, alternative medicine users were 5.7 times more likely to die within five years than their conventional counterparts. Those with colorectal cancer were 4.6 times more likely to die if they used alternative medicine. And those with lung cancer who opted for alternative medicine were 2.2 times more likely to die.

The study has limitations, the researchers caution. Most notably, it’s an observational study, so it cannot determine if alternative therapies—or lack of evidence-based conventional ones—are the actual cause of the drops in survival rates. That said, the researchers also don’t know if some of the patients who initially opted for alternative medicine later turned to conventional treatments. Thus, it’s possible that the survival rates may be even worse for those who rely solely on alternative treatments. Last, because of the vague coding the researchers don’t know exactly what kinds of treatments patients were trying and if some are more dangerous than others.

Still, the researchers hope that the study raises flags with caregivers when their patients want to swap conventional treatments for alternative ones.

Journal of the National Cancer Institute, 2017. DOI: 10.1093/jnci/djx145 (About DOIs).