One in five cancer patients in the East of England fear delays to treatment during the pandemic will impact their chances of survival.
This figure compares to one in nine (11%) who reported feeling the same worries in June last year.
Macmillan Cancer Support says people being treated for cancer are living through the "worst possible Groundhog Day".
The new figures reveal the growing toll of the ongoing pandemic on people with cancer, with many facing rising anxiety, disruption to care, and the disconcerting experience of going through diagnosis and treatment alone.
It comes as the charity reveals nurses took more calls over the Christmas period than they did in 2019.
The charity is urging people who are worried to call their free Support Line, to speak with specially trained cancer nurses and counsellors about financial and emotional support.
"There's been a real change in the feel of the calls to the Support Line recently", Mr Payne added.
"We're hearing from people everyday who are feeling incredibly isolated, who are too scared to go outside because of their vulnerability to coronavirus and who have found receiving a diagnosis and going through treatment without loved ones by their side really distressing.
"We want them to know that they aren't alone."
Anyone in need of cancer support can call the Macmillan Support Line on 0808 808 00 00, which is open 7 days a week, 8am-8pm or visit Macmillan's Online Community.