Anaemia as a prognostic factor for the therapeutic effect of radiosensitizers

Oxygen tension and vascular density in human cervix carcinoma

Hypoxia-induced radiation resistance has been proposed to be a consequence of low vascular density in tumours. The purpose of the study reported here was to investigate possible relationships between pretreatment oxygen tension (pO2) and vascular density in patients with cervix carcinoma. Tumour pO2 was measured by the use of polarographic needle electrodes. Biopsies were taken from the electrode tracks and vascular density and tissue composition, i.e. volume fraction of carcinoma tissue, stroma and necrosis, were determined by stereological analysis. The vascular density of individual biopsies was related to the median pO2 of the corresponding electrode track. Tumour regions with vascular density below 24 mm mm(-3) always showed low pO2, whereas tumour areas with vascular density above 24 mm mm(-3) could show a high or a low pO2. This indicates the existence of a threshold value of about 24 mm mm(-3) for vascular density in cervix carcinoma; a vascular density above this value is probably needed before high pO2 can occur. Low vascular density might, therefore, be a useful predictor of hypoxia-induced radiation resistance in cervix carcinoma. High vascular density, on the other hand, can probably not be used to exclude radiation resistance. The differences in pO2 among tumour regions with high vascular density were not a consequence of differences in the amount of necrosis or stroma or in the haemoglobin concentration in peripheral blood of the patients. Model calculations indicated that these differences in pO2 could be explained by differences in the oxygen delivery alone and by differences in the oxygen consumption rate alone.

Radiotherapy and anaemia--the clinical experience

Review of the literature shows good evidence of an impaired outlook for anaemic compared with apparently similar, but non-anaemic patients, treated by radiotherapy for tumors at a number of sites. Some of the adverse associations, may be because anaemic patients, compared with the non-anaemic at the same site and with the same clinical stage, may have in actuality a more advanced disease. However, there is good evidence, especially in carcinoma of the cervix, that there occurs an impairment of the response of tumor to radiotherapy in anaemic patients. Where cure is the object of radiotherapy, restoration of the haemoglobin level is necessary before the course is begun. During the past 60 years there has been much interest in the relationship between anaemia and response to radiotherapy. In 25 series of cases where an effect of anaemia has been sought an adverse influence has been found in 23. An examination of these papers, however, reveals a complex pattern demanding some analysis. Anaemia itself requires definition. As can be seen in Fig. 1, there are different normal ranges for men and women and there is some variation in what is accepted as normal. Haemoglobin levels are commonly given in g%, but they are also expressed as mmol/l. There are also reports which refer to the haematocrit. The haemoglobin value at first presentation may be recorded, but the picture may change by the time treatment is instituted, either because of haemorrhage or because of blood transfusion. In examining reports it is sometimes not easy to know which value is related to response.(ABSTRACT TRUNCATED AT 250 WORDS)

Chronic anaemia, hyperbaric oxygen and tumour radiosensitivity

Anaemia is an important factor in the response of some human tumours to radiotherapy. The outcome is also influenced by whether the treatment is given in air or high pressure oxygen (HPO). The present study examined the relationship between anaemia and tumour response to radiation given in air or HPO in C3H mice transplanted with a mammary adenocarcinoma using a growth delay assay to assess the radiation response. Chronic anaemia was induced by the use of a low iron diet and was characterized by a significant reduction in host haematocrit and whole blood viscosity. In addition, anaemia was associated with a right shift in the oxyhaemoglobin dissociation curve and an increase in the volume doubling time of the tumour; but there was no change in the concentration of 2,3-diphosphoglycerate in the red cells. Radiation studies with these anaemic mice demonstrated that the tumour radiosensitivity was decreased when treatment was given in air. HPO was successful in overcoming the increased radioresistance associated with anaemia. This result suggested that tumours grown in anaemic mice have a higher hypoxic fraction than those grown in control mice. Changes in host physiology with chronic anaemia may contribute to the benefit seen with HPO but such alterations per se may be inadequate to maintain tumour oxygenation when treatment is given in air.

Hypoxia and reoxygenation in human melanoma xenografts

Tumor hypoxia and reoxygenation pattern following single dose (10.0 Gy) and fractionated (7 fractions of 2.0 Gy, 1 fraction per day) irradiation were studied in five human melanoma xenograft lines using the paired survival curve method. The hypoxic fractions differed significantly among the melanoma lines; they were found to be 6 +/- 3% (E.E.), 22 +/- 8% (E.F.), 31 +/- 11% (G.E.), 45 +/- 17% (M.F.), and 15 +/- 5% (V.N.). There were no clear correlations between hypoxic fraction and tumor volume-doubling time or vascular density, suggesting that intrinsic cellular characteristics, for example, rate of oxygen consumption and ability to retain clonogenicity under hypoxic stress, also may play an important role for the magnitude of the hypoxic fractions in the melanomas. Reoxygenation was rapid and extensive in all melanoma lines; 12-24 hr after the single dose irradiation or the last fraction of the fractionated irradiation, the hypoxic fractions were similar to those in untreated tumors and stayed at that level up to at least 10 days after irradiation. The hypoxic fractions 1-10 days after irradiation tended to be higher after fractionated than after single dose irradiation, but the differences were not statistically significant. There was a positive correlation between the hypoxic fractions in untreated tumors and the hypoxic fractions after irradiation and reoxygenation, suggesting that it may be possible to predict radiation resistance caused by hypoxia from the hypoxic fractions in tumors before start of radiation therapy. However, hypoxia is probably not a major cause of failure in the radiation therapy of malignant melanoma.

Misonidazole combined with radiotherapy in the treatment of carcinoma of the uterine cervix

Between April 1979 and January 1982, 331 patients were included in a study to establish whether misonidazole (MISO) had any effect as an adjuvant to radiotherapy in the treatment of squamous cell carcinoma of the uterine cervix (FIGO Stage IIb, III, and IVa). Patients were randomized to receive either MISO (12 g/m2 applied within 6 weeks) or placebo. This was given in conjunction with each institution's normal radiotherapy schedule and thus varied with regard to external and intracavitary irradiation. The analysis was performed based on patients' status at January 1986, with all patients observed for at least 4 years. One hundred and sixty-four patients received MISO and 167 placebo. Compliance to radiotherapy was good and MISO was well tolerated. The overall rates for MISO vs. placebo were as follows: local tumour control, 50 vs. 54%; disease-free survival, 47 vs. 46%, and crude survival, 39 vs. 45%. A similar lack of MISO effect was found in the individual stages. However, patients in all stages with hemoglobin concentrations below 7 mmol/l had a significantly lower local control probability (overall 24 vs. 47%), whereas the incidence of distant metastases was unaffected. We conclude that the addition of MISO did not influence the radiation response in advanced uterine carcinoma. The reasons for this ineffectiveness are yet to be clarified.

Intracapillary HbO2 saturations in murine tumours and human tumour xenografts measured by cryospectrophotometry: relationship to tumour volume, tumour pH and fraction of radiobiologically hypoxic cells

Frequency distributions for intracapillary HbO2 saturation were determined for two murine tumour lines (KHT, RIF-1) and two human ovarian carcinoma xenograft lines (MLS, OWI) using a cryospectrophotometric method. The aim was to search for possible relationships between HbO2 saturation status and tumour volume, tumour pH and fraction of radiobiologically hypoxic cells. Tumour pH was measured by 31P NMR spectroscopy. Hypoxic fractions were determined from cell survival curves for tumours irradiated in vivo and assayed in vitro. Tumours in the volume range 100-4000 mm3 were studied and the majority of the vessels were found to have HbO2 saturations below 10%. The volume-dependence of the HbO2 frequency distributions differed significantly among the four tumour lines; HbO2 saturation status decreased with increasing tumour volume for the KHT, RIF-1 and MLS lines and was independent of tumour volume for the OWI line. The data indicated that the rate of decrease in HbO2 saturation status during tumour growth was related to the rate of development of necrosis. The volume-dependence of tumour pH was very similar to that of the HbO2 saturation status for all tumour lines. Significant correlations were therefore found between HbO2 saturation status and tumour pH, both within tumour lines and across the four tumour lines, reflecting that the volume-dependence of both parameters probably was a compulsory consequence of reduced oxygen supply conditions during tumour growth. Hypoxic fraction increased during tumour growth for the KHT, RIF-1 and MLS lines and was volume-independent for the OWI line, suggesting a relationship between HbO2 saturation status and hypoxic fraction within tumour lines. However, there was no correlation between these two parameters across the four tumour lines, indicating that the hypoxic fraction of a tumour is not determined only by the oxygen supply conditions; other parameters may also be important, e.g. oxygen diffusivity, rate of oxygen consumption and cell survival time under hypoxic stress.