The effect of nonmalignant systemic disease on tolerance to radiation therapy

Some patients with nonmalignant systemic diseases, like collagen vascular disease (CVD), hypertension, diabetes mellitus, and inflammatory bowel disease (IBD), tolerate radiation therapy poorly. Although the mechanisms of each of these disease processes are different, they share a common microvessel pathology that is potentially exacerbated by radiotherapy. This article reviews and evaluates available data examining the effects of these benign disease processes on radiation tolerance.

We conducted a thorough review of the Anglo-American medical literature from 1960 to 2001 on the effects of radiotherapy on CVD, hypertension, diabetes mellitus, and IBD.

Fifteen studies were identified that examined the effects of radiation therapy for cancer in patients with CVDs. Thirteen of 15 studies documented greater occurrences of acute and late toxicities (range 7%-100%). Higher rates of complications were noted especially for nonrheumatoid arthritis CVDs. Nine studies evaluated the effects of hypertension and diabetes on radiation tolerance. All nine studies documented higher rates of late toxicities than in a "control" group (range 34%-100%). When patients had both diabetes and hypertension, the risk of late toxicities was even higher. Six studies examined radiation tolerance of patients with IBD irradiated to the abdomen and pelvis. Five of these six studies showed greater occurrences of acute and late toxicities for patients with IBD, even with precautionary measures like reduced fraction size and volume and patient immobilization (13%-29%).

The majority of published studies documented lower radiation tolerance for patients who have CVD, diabetes mellitus, hypertension, and IBD. This may reflect a publication bias, as the majority of these studies are retrospective with small numbers of patients and use different scoring scales for complications. These factors may contribute to an overestimation of true radiation-induced morbidity. Although the paucity of data makes precise estimates difficult, a subset of patients, in particular, those with active CVD, IBD, or a combination of uncontrolled hypertension with type I diabetes, is likely to be at higher risk. Future prospective trials need to document these disease entities when reporting treatment-related complications and also must monitor toxicities associated with quiescent versus active IBD and CVD, type I versus type II diabetes, and levels of hypertension (controlled versus uncontrolled) matched for radiation-specific treatment sites, field size, fractionation, and total dose.