Normal transcutaneous oxygen pressure in skin after radiation therapy for cancer

Chronic deleterious changes in human skin after radiation therapy often have been ascribed to progressive ischemia (decreased blood supply and oxygenation). Recent studies suggest, however, that damaged irradiated skin is not ischemic. Transcutaneous oxygen pressure (TCPO2), that accurately reflects skin oxygenation, was studied in 100 patients who had undergone prior extensive radiation therapy for cancer.

In the 100 patients, the mean time since radiation was 7.86 +/- 10.56 years (mean, +/- SD) (range, 1-58 years). Radiation skin effects were graded (0-4+), and TCPO2 was measured in irradiated and control nonirradiated sites, with patients first breathing room air, then 100% O2 6 l/min for 10 minutes. Data were stratified according to skin grades, sex, time since irradiation, site, type, and dose of radiation.

The mean TCPO2 in patients breathing room air was 52.0 17.8 mm Hg (mean +/- SD) for all irradiated skin, compared with 131.8 +/- 51.1 at the same irradiated sites in response to oxygen breathing (P < 0.0001); the mean TCPO2 for normal, nonirradiated skin was 56.5 +/- 12.6 when patients were breathing room air, compared with 151.5 +/- 48.1 when breathing 100% oxygen (P < 0.0001). Higher skin damage grades correlated with increasing time after radiation therapy. However, neither increasing time after irradiation nor grade of skin damage correlated with TCPO2, which was normal in 88% of the patients.

Human skin, even many decades after radiation therapy, retains normal tissue oxygenation and TCPO2 response to inspired oxygen. Postradiation scarring, poor healing, and rare ulceration are not solely due to ischemia and may be caused by other radiation effects, such as permanent changes in fibroblasts.