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Radiotherapy to the abdomen or pelvis raises the risk of cancer in the bowel that sat in the field, and the risk is confined to the irradiated segment. For adults no country runs an organised colonoscopy programme afterwards, so bleeding or a change in bowel habit years later should be investigated rather than put down to the old treatment.
What is offered. The ordinary national bowel screening programme, which in England invites people from age 50, and investigation of symptoms. Colonoscopy surveillance on the basis of previous abdominal or pelvic radiotherapy is recommended in the long-term follow-up guidelines for people treated as children, and is covered on this front by the record on paediatric survivorship; for adults treated as adults, there is no equivalent organised programme in the United Kingdom, the United States or Europe. That is a gap rather than a decision against it, and it is worth naming as one.
The strongest evidence that the field is what matters. A SEER cohort compared 30,552 men treated with radiotherapy for prostate cancer with 55,263 treated by surgery alone, between 1973 and 1994, all of whom survived at least five years. Colorectal cancers developed in 1,437 men. The analysis split the bowel into three: definitely irradiated sites (the rectum), potentially irradiated sites (rectosigmoid, sigmoid and caecum) and non-irradiated sites (the rest of the colon), with 267, 686 and 484 cancers respectively. The adjusted hazard ratio for rectal cancer in the radiotherapy group against the surgery-only group was 1.7 (95% CI 1.4 to 2.2). Radiation had no effect on the rest of the colon. The authors' own conclusion is that the effect "is specific to directly irradiated tissue".
The pooled picture. A meta-analysis of 21 observational studies of prostate radiotherapy found raised risks of colorectal cancer (adjusted hazard ratio 1.79, 1.34 to 2.38) and rectal cancer (1.79, 1.34 to 2.38) against men not irradiated. Absolute rates reported across the included studies ranged from 0.3 to 4.2 per cent for colorectal and 0.3 to 1.2 per cent for rectal cancer, a spread the authors attribute to differences in follow-up and study quality. External beam radiotherapy was consistently associated with raised odds; brachytherapy was not, which is a difference with a plausible dosimetric explanation and a practical one for a man choosing between them.
Beyond prostate cancer. In the cohort of 40,576 one-year survivors of testicular cancer from fourteen registries covering 1943 to 2001, among whom 2,285 second solid cancers were recorded, the relative risk of colon cancer was 2.0 (1.7 to 2.5) and of stomach cancer 4.0 (3.2 to 4.8); cancers of the lung, colon, bladder, pancreas and stomach together accounted for almost 60 per cent of the total excess. Those men were treated with infradiaphragmatic radiotherapy fields that are rarely used now, and surveillance or carboplatin has replaced adjuvant radiotherapy for most stage I seminoma.
What a reader should take from this. Not a demand for a colonoscopy, which no guideline currently supports for an adult on this basis alone. But a change in bowel habit, blood in the stool or new abdominal pain in someone who had pelvic radiotherapy a decade or more ago is not something to attribute to radiation proctitis without looking. Late bowel effects of radiotherapy are real and are covered on their own record on this front; they are also the commonest reason a second cancer in the same tissue is explained away.
Showing the technology this term belongs to: Brachytherapy.
Shares No randomised trial shows that any survivorship screening programme reduces death, Second cancers after radiotherapy, Second cancers after treatment: what the risk is, and what is done about it, Radiotherapy and second cancers: field, dose and age at exposure and the tags rejuvenation, survivorship, second-cancers, radiotherapy, screening.
Shares No randomised trial shows that any survivorship screening programme reduces death, Second cancers after radiotherapy, Second cancers after treatment: what the risk is, and what is done about it, Radiotherapy and second cancers: field, dose and age at exposure and the tags rejuvenation, survivorship, second-cancers, radiotherapy, screening.
Shares Second cancers after radiotherapy, Second cancers after treatment: what the risk is, and what is done about it, Radiotherapy and second cancers: field, dose and age at exposure, Screening survivors: where the UK, American and European answers differ and the tags rejuvenation, survivorship, second-cancers, radiotherapy.
Shares Second cancers after radiotherapy, Second cancers after treatment: what the risk is, and what is done about it, Radiotherapy and second cancers: field, dose and age at exposure, Screening survivors: where the UK, American and European answers differ and the tags rejuvenation, survivorship, second-cancers, radiotherapy, screening.
Shares No randomised trial shows that any survivorship screening programme reduces death, Second cancers after radiotherapy, Second cancers after treatment: what the risk is, and what is done about it, Screening survivors: where the UK, American and European answers differ and the tags rejuvenation, survivorship, second-cancers, screening.
Shares No randomised trial shows that any survivorship screening programme reduces death, Second cancers after radiotherapy, Second cancers after treatment: what the risk is, and what is done about it, Radiotherapy and second cancers: field, dose and age at exposure and the tags rejuvenation, survivorship, second-cancers, radiotherapy.
Shares Second cancers after radiotherapy, Seminoma, Second cancers after treatment: what the risk is, and what is done about it, Screening survivors: where the UK, American and European answers differ and the tags rejuvenation, survivorship, second-cancers.
Shares No randomised trial shows that any survivorship screening programme reduces death, Second cancers after treatment: what the risk is, and what is done about it, Choices made at the time of treatment that change the second cancer risk, Secondary malignancy (therapy-related cancer) and the tags rejuvenation, survivorship, second-cancers.