EXTRACELLULAR PH DISTRIBUTION IN HUMAN TUMORS

Extracellular pH (pH(e)) was determined by needle microelectrodes in 6 7 tumour nodules in 58 patients. The objective was to evaluate the rel ationship between pH(e), tumour histology and tumour volume. The mean age of the patients was 62 years, mean depth of the lesions was 2.7 +/ - 0.2 cm, and mean tumour volume was 187 +/- 60 cm(3) Lesions were loc ated in readily accessible areas such as on the limbs, neck or chest w all. Tumour histologies included: 48% adenocarcinoma; 34% squamous cel l carcinoma; 8% soft tissue sarcoma; and 10% malignant melanoma. The m ean tumour pH(e) for the entire group of tumours was 7.06 +/- O.05 (ra nge 5.66-7.78). Variation in pH(e) measurements between tumours was gr eater than the variation in measurements within tumour (F = 7.11, p < 0.01). In adenocarcinomas pH(e) was 6.93 +/- 0.08 (range 5.66-7.78), i n soft tissue sarcomas 7.01 +/- 0.21 (6.25-7.45), in squamous cell car cinomas 7.16 +/- 0.08 (6.2-7.6), and in malignant melanomas 7.36 +/- 0 .1 (6.98-7.77). Tumour pH(e) was significantly different between the f our histological groups (p < 0.001). When adenocarcinoma and soft tiss ue sarcoma lesions were grouped together, pH(e) was 6.94 +/- 0.08 comp ared with 7.20 +/- 0.07 in squamous cell carcinomas and malignant mela nomas lesions (p < 0.01). Tumour pH(e) increased as a function of the logarithm of tumour volume at 0.07 +/-0.02 pH unit/ln cm(3) (p = 0.006 , r = 0.34). In conclusion, tumour histology and tumour volume were th e most important factors determining the range of pH(e)'s. These obser vations correlated with previous findings that adenocarcinoma and soft tissue sarcoma were more responsive to thermoradiotherapy than squamo us cell carcinoma and malignant melanoma.