6 april 2005: Bron: Medscape en Gastroenterology. 2005;128:819-824, 1114-1117

Bestraling van prostaatkankerpatiënten geeft groter risico op krijgen van rectumkanker na enkele jaren, blijkt uit 20 jarige en grote gerandomiseerde retrospectieve studie onder 85.815 mannen, in de leeftijd van 18 tot 80 jaar, allemaal behandeld voor prostaatkanker. Van de 85.815 mannen, kregen er 30.552 radiotherapie en 55.263 alleeen een operatie. Bij 1.437 patiënten ontwikkelde zich rectaal kanker, 267 patiënten ontwikkelden kanker in het bestraalde gebied, 686 op waarschijnljik meebestraalde plaatsen, en 484 op niet bestraalde plaatsen. Radiotherapie werd onafhankelijk geassocieerd met ontwikkeling van kanker in bestraalde gebieden, maar niet in de rest van de darmen Vergeleken met de groep die alleen geopereerd werd was de hazards ratio voor ontwikkeling van rectumkanker 1,7 voor de bestraalde groep (95% confidence interval, 1.4 - 2.2). De onderzoekers pleiten voor regelmatige controle en onderzoek van bestraalde prostaatkankerpatiënten op ontwikkelen van o.a rectumkanker maar ook andere vomen van kanker in de buikstreek. Hier een artikel uit Medscape over deze studie.

April 4, 2005 — Radiation therapy for prostate cancer increases the risk of rectal cancer in the irradiated field, according to the results of a retrospective, population-based study published in the April issue of Gastroenterology. The authors suggest that physicians should discuss this risk and that treated patients should be screened accordingly.

"Men who have had prostate radiation should be aggressively monitored for rectal cancer starting five years after treatment," lead author Nancy Baxter, MD, PhD, from the University of Minnesota Cancer Center in Minneapolis, says in a news release. "This is the first time rectal cancer risk associated with prostate radiation has been quantified, and these findings may also have implications for patients treated with radiation for other pelvic cancers."

Using Surveillance, Epidemiology, and End Results (SEER) registry data from 1973 through 1994, the investigators focused on men with prostate cancer, but with no prior colorectal cancer, treated with either surgery or radiation, who survived at least five years. A proportional hazards model helped to determine the effect of radiation over time on development of cancer at definitely irradiated sites (rectum), potentially irradiated sites (rectosigmoid, sigmoid, and cecum), and nonirradiated sites (the rest of the colon).

Of 85,815 men, aged 18 to 80 years, with prostate cancer, 30,552 received radiation, and 55,263 underwent surgery only. In 1,437 patients who developed colorectal cancers, 267 developed cancer in irradiated sites, 686 in potentially irradiated sites, and 484 in nonirradiated sites. Radiation was independently associated with development of cancer over time in irradiated sites, but not in the rest of the colon. Compared with the surgery-only group, the adjusted hazards ratio for development of rectal cancer was 1.7 for the radiation group (95% confidence interval, 1.4 - 2.2).

"While the findings of our study do not suggest that prostate cancer treatment should change, we recommend that the potential for developing rectal cancer be included in conversations between doctors and patients when considering the individualized course of treatment and surveillance for patients with prostate cancer," Dr. Baxter says.

Study limitations include lack of data on the type and method of radiation delivery; observational rather than randomized design creating the potential for patient selection bias; and lack of information about colorectal cancer risk factors, other than age. Because the study results are based on men who were treated for prostate cancer before 1995, the risk of developing cancer may be reduced to some extent, but not eliminated, by more modern radiation delivery techniques.

In an accompanying editorial, William M. Grady, MD, and Ken Russell, MD, from the University of Washington Medical School in Seattle note the strengths of this study compared with earlier studies, and they agree with the investigators' conclusions.

"Thus, it appears to be prudent to consider any individual who has undergone pelvic irradiation with treatment fields that have included the rectum to be at increased risk of rectal cancer," Drs. Grady and Russell write. "The study by Baxter et al highlights the fact that as more individuals become long-term survivors of their primary malignancies, clinicians will need to focus on the prevention or early detection of secondary treatment-related cancers."

Gastroenterology. 2005;128:819-824, 1114-1117

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