More than 40 per cent of cancer patients at the Lancashire Teaching Hospitals NHS Foundation Trust say they do not feel they have been kept fully informed about whether their treatment is working.
Patients aged 16 and over, who underwent cancer-related treatment with the trust between April and June 2017, were asked about their care as part of this year's National Cancer Patient Experience Survey.
The survey, which is carried out annually by Quality Health on behalf of NHS England, monitors patients' impressions of their diagnosis, treatment, and aftercare.
It showed experiences of cancer patients across England were "generally very positive", with patients giving an average rating of 8.8 out of ten for their overall care.
For the Lancashire trust , this figure was 8.84, a slight deterioration on the previous year.
However, the results raised concerns about the level of information provided while patients were having treatment.
Some 60 per cent of patients at the Lancashire Teaching Hospitals NHS Foundation Trust answered 'yes, completely' when asked if they had been given enough information in terms they could understand about how their radiotherapy or chemotherapy was going.
The rest answered 'yes, to some extent' or 'no', which were both counted as negative responses.
The results were worse for patients having radiotherapy than for those undergoing chemotherapy - just 57 per cent of the former said they had enough information, compared to 64 per cent of the latter.
On average, 35 per cent of patients in England said they had not had enough information.
Dr Jeanette Dickson, vice president of clinical oncology at The Royal College of Radiologists, said cancer specialists worked in high-pressure environments, and that giving ongoing updates to patients during their treatment could be very complicated.
She continued: "Many cancer treatments are not straightforward and response to therapy is not immediately able to be assessed as patients would wish.
"While patients are being treated with modern chemotherapy and radiotherapy they are in a fast-moving situation where progress might seem to stall and then change quickly, and the impact of treatments is not always clear every step of the way, especially as we try novel drugs that act in new ways.
"Doctors are aware of this, but perhaps need to acknowledge this uncertainty more often in view of this survey.
"Ultimately, the survey results remind us that cancer patients are in a vulnerable situation, and oncologists need to be continually assessing all their patients’ needs every time they have a consultation or a meeting."
The only England-wide figure that saw a drop in this year's survey concerned support provided by GPs.
Four in ten patients said they didn't think staff at their local practice had done everything they could to support them while they were going through treatment, or that they had only done so to some extent.
In the Lancashire trust, 40 per cent of patients said the same.
Across England, some of the lowest scores were seen in patients' experiences of health and social services - such as home visits by nurses and physiotherapy.
Only 62 per cent of the patients surveyed for the Lancashire trust said they had enough support from health and social services during their treatment.
For support provided after treatment had ended, this dropped to 51 per cent.
Cancer Support UK, which provides practical and emotional help for people with cancer, said the survey showed post-treatment support options needed to be "urgently addressed".
Chief executive Gemma Holding said: "Inequalities in health and well-being provision across the UK mean that some patients - based on where they live - have better access to, and receive higher quality health care than others.
"We know that when people’s official treatment ends, rather than feeling better, this is often when people can feel at their worst.
"However, once physical treatment ends, cancer patients are often discharged with no support to manage the ongoing emotional challenges.
"Psychological support for people with cancer is essential to recovery, during and after treatment."