Concentration distributions of isoprene (determined by PTR-MS) in exhaled breath of lung carcinoma patients treated with radiotherapy ( CA-patients-radiotherapy-female (n = 22) : magenta; CA-patients-radiotherapy-male (n = 36) : green), carcinoma patients not treated with radiotherapy ( CA-patients-no radiotherapy-female (n = 50) : cyan; CA-patients-no radiotherapy-male (n = 88) : black) and healthy volunteers ( control < 50 years, female (n = 121) : dark red; control < 50 years, male (n = 70) : dark blue; control > 50 years, female (n = 142) : red; control > 50 years, male (n = 94) : blue). 19 CA-patients (7 female, 12 male) were excluded from consideration, because they did not clearly fit into one of the two groups (with/without radiotherapy). The concentration is shown in logarithmic scaling. For females, the median concentration for isoprene in breath is: for CA-patients-radiotherapy 85.1 ppb; for CA-patients-no radiotherapy 68.1 ppb; for control < 50 years 103.9 ppb and for controls > 50 years 98.1 ppb. For males, the median concentration for isoprene in breath is: for CA-patients-radiotherapy 89.9 ppb; for CA-patients-no radiotherapy 85.4 ppb; for control < 50 years 133.7 ppb and for controls > 50 years 100.0 ppb. A discussion of age- and gender effects in healthy volunteers is given in reference .