Seventeen-year-old Lily Anderson used to be an avid reader. But after she was treated for Hodgkin's Lymphoma at 14, her enjoyment of books became a rarity.
"I used to read a book a day. It's getting easier now but I couldn't read at all before.
"I kept re-reading the same sentence and my memory and concentration were awful."
Lily, from Suffolk, is now cancer-free, after being treated with chemotherapy, radiotherapy and a stem cell transplant, but the treatment has taken its toll.
When she tried to go back to school after her treatment had finished just after her 16th birthday, her brain felt exhausted.
She found it impossible to focus on anything for more than half an hour and learning new things was very difficult. A year off school followed.
The changes in memory and concentration which Lily experienced following cancer treatment are often referred to as "chemo brain" or "chemo fog".
They were first reported by women who had been treated for breast cancer, but it is still not known why the changes occur or if they are caused by chemotherapy.
Cancer Research UK describes the symptoms of "chemo brain" as forgetting things that you normally remember, difficulty thinking of the right word and following the flow of a conversation, trouble concentrating and feelings of confusion and mental fogginess.
The charity's website says "the changes are often mild and very subtle. But if you have them they can reduce your quality of life".
Preliminary results of new research, to be announced at a conference on teenage and young adult cancer this week, suggests that a significant number of young cancer patients suffer memory-related side effects from chemotherapy.
The University of Manchester study - which is not yet published - compared the results of memory tests on young adults who had gone through chemotherapy with those of young adults who had not had chemotherapy.
From a study of 75 cancer patients, aged 16 to 50, after treatment, it found that more than a half experienced a drop in performance on spatial ability tests and a quarter performed worse in long-term verbal memory tests after treatment.
These effects can last for up to five years after treatment has ended, the initial findings suggest.
Previous research had only looked at memory problems in people who had developed cancer in late adulthood or survived childhood cancers.
Helen Thompson, senior cancer information nurse at Cancer Research UK, said it was important to better understand the impact on teenagers.
"Adding the physical and emotional burden of treatment on top of a changing body and school exams can be difficult.
"This preliminary research should help us learn more about how this affects memory in teenagers so they can be provided with the right support."
Nigel Revell, from Teenage Cancer Trust, said the findings confirmed what they had long suspected.
"As we work with young people with cancer this is of particular interest for us as most of them are still in education and want to continue down this path once their chemotherapy is over."
Mild cognitive impairment, which describes the symptoms of "chemo brain", is a huge challenge when you are entering sixth form, as Lily discovered.
"The memory problems were a bit of a shock. I thought it was just hair loss and sickness I had to worry about."
Oana Lindner, author of the Manchester study, says just when young cancer survivors want their lives to return to normal, they can find themselves dealing with another setback.
However, she says recognising that "chemo brain" can affect them is a good thing because it encourages research on how to prevent and treat it.
"Counselling might help reduce the problems or help them cope, and cognitive training strategies could help increase their memory performance."
Lindner says it is obvious that chemotherapy does something to the brain of some cancer patients, but research is still ongoing to find out how the mechanism works and why.
She says larger studies are needed to find out how long lasting these effects are, the impact of different chemotherapy drugs and different doses on patients.
There are also other factors which have to be taken into account, such as the impact of depression and tiredness on cancer patients' cognitive functions, and their low quality of life during and after treatment, which is common.
Lily is planning to return to school in September and move on with her life. She knows her teachers are very understanding and will give her as much support as she needs during her sixth form.
As for the future, she has her heart set on becoming a nurse because "it would be an amazing way to help others".