If you have ever cared for a loved one toward the end of their fight against cancer, you may find it hard to understand why someone would choose to die from the disease if they had any other option. Yet in the UK, more than half of medical staff who care for those with cancer have known patients who reject treatment altogether because they lack support at home from family and friends.

Having cancer is a life-changing experience, and how people choose to deal with the disease is a deeply personal decision. Some may stand to gain only a few extra weeks from treatment and so decide not to go down that route. For others, it could offer the chance of a much longer life or even a cure. We should all be troubled to hear that some patients are accepting a potentially avoidable death from cancer simply because they have no-one in their personal lives to help them through treatment.

Cancer patients by no means have a monopoly on feeling isolated and alone. Far too many people in our society, many of them elderly, lack the practical and emotional support of family and friends that the rest of us often take for granted. In fact the government is currently trying to measure loneliness amid concerns it is having severe consequences on people's health. Cancer and its treatment, however, can inflict a particularly debilitating toll on the body and mind - one made worse by isolation.

Imagine only having your colon cancer diagnosed after you collapse in the street because no-one has nagged you to see the doctor about your recent weight loss and tiredness. You'd noticed some blood in your stools, but didn't feel close enough to anyone to confide your worries.

Now imagine you've been told that you've a decent chance of surviving the cancer but you'll need to have a major operation that will leave you with a colostomy bag, and several rounds of chemotherapy that will make you feel sick and exhausted. There are no family or friends at home or nearby to help you wash, cook, clean or shop, give you a lift home from your chemotherapy appointments, or raise your spirits when you're feeling down.

Sadly, and understandably it is possible to understand why some isolated cancer patients choose not to go through with it all. But does that mean we should simply shrug our shoulders and leave them to what is effectively a slow suicide? What if they would have chosen differently with just a bit more support at home?

Rejecting treatment is, of course, an extreme example of the effects of isolation on cancer patients. The wider picture, although less dramatic, is equally distressing. One in four people newly diagnosed with cancer in the UK will lack support from family or friends during their treatment and recovery - that's more than an estimated 70,000 people every year not getting help at a time when they need it more than ever. Of those, around a third - an estimated 20,000 people each year - will receive no support whatsoever, facing cancer completely alone.

More than half of those who are isolated have skipped meals or not eaten properly because of a lack of support at home. More than one in six have not been able to collect a prescription for their medication, and more than one in 10 have missed a hospital or GP appointment. The numbers, revealed by Macmillan's new Facing the Fight Alone report, show that isolation affects a significant proportion of cancer patients and has a real and negative impact on their lives.

Most people who lack support say it's because their family and friends are too busy to help or live too far away. More than two-thirds say they would have benefited from more support from their loved ones, which means that right now there could be as many as 50,000 people recently diagnosed with cancer across the UK who could do with help from someone close to them. Does someone you know have cancer? You might want to have a word, or offer a hand.

At Macmillan, we believe no-one should face cancer alone. Both healthcare professionals and society as a whole must recognise how serious isolation can be for cancer patients. We must make every effort possible to mitigate the effects. The government's plan to measure isolation nationally will keep momentum going on this issue, but we need them to do more than just measure for those with cancer. All patients must be given a care plan to capture their problems and highlight any extra support they may need during and after treatment.

The lives of those who are isolated are just as valuable as those with close family and friends, and we must give them just as much of a fighting chance. People may or may not choose to accept treatment for cancer for many reasons, but if someone who chooses not to would they have changed their mind if they simply had a bit more support, is that really a choice at all?