Effect of carbogen on tumour oxygenation and 32P-colloid interstitial irradiation response

Objectives To study the effects of long-term carbogen breathing on tumour oxygenation and ³²P-colloid interstitial irradiation response in murine tumours.

Methods ^99mTc-HL91(^99mTc 4,9-diaza-3,3,10,10-tetramethyldodecan-2,1-dione dioxime) hypoxic imaging was performed in 10 mice bearing sarcoma 180 (S180) before and after 2 h carbogen breathing. Radioactivity ratios of tumour to contralateral limbs (T/L) of the two imaging were calculated and compared. Mice bearing S180 were subjected to long-term carbogen breathing (2 h/day for 24 days), and were treated with or without ³²P-colloid. Tumour growth rate was observed in the S180-bearing mice.

Results T/L of ^99mTc-HL91 uptake before and after carbogen breathing was 1.872±0.391 and 1.354±0.189, respectively (t=4.476, P<0.01). In mice in the ³²P-treated air breathing group and ³²P-treated carbogen breathing group, tumour growth rate did not differ on day 12 after ³²P-colloid treatment, and on day 24, the tumour volume was 2.728±0.469 and 2.237±0.603 cm³ (t=2.128, P<0.05) respectively, with tumour mass being 2.437±0.447 and 1.965±0.538 g (t=2.134, P<0.05), respectively.

Conclusions Long-term carbogen breathing can increase tumour oxygenation and enhance the therapeutic effect of ³²P-colloid interstitial irradiation.