Peter A. McCullough, a former cardiologist who promoted unproven treatments like ivermectin and hydroxychloroquine at the height of the pandemic, posted a video to Instagram claiming that Biden’s cancer was “turbo cancer.”

Cancer patients rarely face a diagnosis alone. Sometimes, experts say, family caregivers step into a caregiving role before they even realize it.

Dr. Ezekiel Emanuel, who served on the former president's COVID-19 advisory board, said Joe Biden has likely had cancer years before announcing his diagnosis.