Carbogen gas and radiotherapy outcomes in prostate cancer

Abstract

Prostate cancer hypoxia is associated with inferior prognosis and resistance to treatment. The use of androgen deprivation therapy, both prior to and during radiotherapy, may exacerbate underlying hypoxia. Whilst larger radiation doses per fraction may achieve therapeutic gain, this is balanced by the reduced opportunity for re-oxygenation to take place during the course of treatment. Improving the underlying hypoxic tumour environment may therefore improve the treatment outcomes. Strategies to combat tumour hypoxia, with particular focus on the use of carbogen gas breathing concurrently with radiotherapy, is the subject of this review.

Keywords: PARP inhibitor; androgen; cancer; carbogen; hypoxia; prostate; radiotherapy.

Figure 1.

Effect of androgen deprivation of the oxygen status of the prostate as assessed on a magnetic resonance imaging scan. (a) T2W MRI image of the prostate of a patient before receiving neoadjuvant hormone treatment; (b) R₂* maps of prostate in the same patient. The baseline R₂* map is dark throughout the prostate, indicating no evidence of hypoxia; (c) after 1 month of androgen deprivation therapy; (d) after 3 months of androgen deprivation therapy, there was an increase in R₂* across the prostate gland. (Reproduced with permission from Alonzi et al. [2011].)

Figure 2.

Graph showing the change in the R₂* values on the blood oxygen level dependent magnetic resonance imaging scan after the administration of carbogen. Changes in the median R₂* values of the prostate among 14 patients before and after carbogen breathing. The mean reduction in R₂* values was 21.6%. (Reproduced with permission from Alonzi et al. [2009].)