The Yale group’s two 2018 papers (Johnson et al., JNCI January 2018 and JAMA Oncology July 2018) form the spine of evidence on what happens when patients with curable cancer reject conventional treatment in favor of alternative medicine. In the JNCI study, 280 patients with non-metastatic breast, prostate, lung, or colorectal cancer who chose alternative medicine without any conventional cancer treatment had a 5-year overall survival of 54.7% — compared with 78.3% for propensity-matched patients receiving standard oncological care. The mortality hazard ratio was 2.50, and the disparity was largest for breast cancer (HR 5.68) and colorectal cancer (HR 4.57). The follow-up JAMA Oncology paper unpacked the mechanism: complementary medicine users refused conventional treatments at dramatically higher rates (53% refused radiotherapy, 34% refused chemotherapy, 7% refused surgery), and once refusal was controlled for, the mortality association disappeared. The death risk was not from the alternative therapies themselves — it was from the refusal of effective treatment they enabled.
Direct regret data for patients who choose alt-only is structurally limited by survivorship bias. Stub et al. 2023 (The Oncologist) interviewed seven CAM-only cancer patients at least one year post-decision and found that none expressed regret — but that sample, by construction, excludes the patients who died of progressive disease and cannot be asked. No published source reports a regret percentage for this population, so this entry does not claim one. What is measurable is the mortality cost: the action-side figure is a floor proxy anchored to the Johnson et al. survival gap — 23.6 percentage points of excess 5-year mortality (54.7% vs. 78.3%), roughly a quarter of alt-only patients who died within five years and would likely have survived under conventional care. That is a mortality rate, not a surveyed regret rate, and it almost certainly understates lived regret among the deceased and their families, who cannot self-report. The inaction-side estimate is grounded in the much larger survivor literature: in the Fernandes-Taylor & Bloom cohort, 42.5% of the 449 survivors regretted some aspect of treatment, and of those who regretted anything, 21.5% named the chemotherapy/radiation component — which works out to about 9% of all survivors regretting that component specifically. The regret structure there is dominated by side-effect intensity, modality choice (mastectomy vs. lumpectomy), and sequencing, not by regret about having pursued conventional care at all. Only a small minority regret having accepted conventional treatment in the first place; in that cohort the majority of survivor regret (59.2%) was over inactions — things they wished they had done — rather than the treatment they underwent.
The action-dominates pattern is unusually clean in this entry because the survival delta is large, well-documented, and mechanistically explained. It does not extend to every interaction between complementary and conventional medicine. Patients who use complementary therapies alongside conventional treatment (acupuncture for chemotherapy-induced nausea, mindfulness for cancer-related fatigue, physical therapy and nutrition support during recovery) are a distinct population — Johnson et al. 2018 JAMA Oncology showed that the mortality risk is mediated entirely by refusal, not by complementary modalities themselves. The entry addresses the specific decision to reject conventional cancer treatment entirely in favor of alternative medicine alone. For metastatic disease where curative treatment is no longer the goal, the relevant decision is intensity of end-of-life care and early palliative integration — covered in Aggressive chemo vs. early palliative. For non-metastatic curable cancer, the evidence base for accepting conventional treatment is among the strongest in modern oncology, and the regret asymmetry reflects that.