With the number of cancer patients in Wales set to double from 120,000 to 240,000 by 2030, cancer charities say the issue of isolation must be tackled 'immediately'.
It comes as a report by Macmillan reveals almost one in five people diagnosed with cancer here each year lack support from their family and friends.
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. But these figures are just the tip of the iceberg.
Some cancer patients in Wales are going hungry, missing medical appointments or even deciding to reject live-saving treatment because they feel isolated by their loved ones - according to a report published today.
Macmillan Cancer Support says one in five people diagnosed with cancer here each year lack vital support from family and friends.
Their report 'Facing the Fight Alone' report reveals 19% of the 18,000 newly-diagnosed cancer patients in Wales - an estimated 3,420 people every year - feel isolation during their treatment and recovery.
The report found some people's isolation appeared to be a direct result of their illness, with 18% saying they'd lost touch with loved ones because of their diagnosis.