In-bedroom renewed air as anti-inflammatory adjuvant therapy in cancer survivors: protocol for the randomised, placebo-controlled BREATHS N-of-1 trial series.

Inflammation is causally related to cancer progression and cardiovascular toxicities of anticancer treatments. Fine particulate matter (PM2.5) air filtration lowers interleukin-6 and C reactive protein (CRP) levels in high-risk cardiopulmonary groups, though potential synergistic or confounding effects with routine medications-statins, cyclo-oxygenase-2 inhibitors, beta-blockers-remain poorly understood. Whether overnight in-bedroom PM2.5 air filtration effectively reduces inflammation and prothrombotic biomarkers in survivors of adult-onset cancer at high cardiovascular toxicity risk is unknown. BREATHS is a series of randomised, adaptive, blinded, placebo-controlled N-of-1 trials conducted in densely populated urban areas of Valencia, Spain, during winter when PM2.5 concentrations historically exceed WHO guidelines.

Eligible participants are aged ≥18 years with a history of breast, colorectal, prostate, lung or haematological cancer, prior cardiotoxic cancer therapy and CRP ≥3 mg/L. Each participant will undergo up to three cycles, each comprising two 14-day periods of advanced submicron air filtration (clean air delivery rate: 275 m3/hour nightly) or placebo (sham filtration), in random order. Sequence duration ranges from 4 weeks to 12 weeks, depending on whether a clinically meaningful CRP reduction (