One in four (23%) of the 325,000 newly diagnosed cancer patients in the UK - an estimated 70,000 patients each year - lack support from family and friends during their treatment and recovery, according to Macmillan Cancer Support.
A third of those (7%) - an estimated 20,000 people each year - will receive no help whatsoever, facing cancer completely alone.
While four in five (80%) say the financial impact of cancer means they can't afford to see their family or friends as much, over one in six (18%) have lost touch with family or friends because of their diagnosis.
Macmillan's Facing the Fight Alone report found 53% of health professionals have had patients opt not to have treatment at all due to a lack of support at home from family and friends.
Ciarán Devane, Chief Executive of Macmillan Cancer Support, commented: '"This research shows that isolation can have a truly shattering impact on people living with cancer.
Patients are going hungry, missing medical appointments and even deciding to reject treatment altogether which could be putting their lives at risk - all because of a lack of support.
"As the number of people living with cancer is set to double from two to four million by 2030, isolation will become an increasing problem and we need to address this now.
"That's why we are launching a new campaign to help tackle this crisis and to ensure that in future, no-one faces cancer alone."
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