Hypoxic Proportion Research Articles

A tumor hypoxic niche protects human colon cancer stem cells from chemotherapy

Hypoxia has been found to play an important role in regulating the biological characteristics of cancer stem cells (cCSCs). In this study, we tested whether a tumor hypoxic niche serves to the chemotherapeutic resistance of colon cCSCs. Each of 23 fresh samples of human colon adenocarcinoma was transplanted into nude mice. The tumor-bearing mice randomly and equally received (A) saline, (B) 5-fluorouracil (15 mg/kg), (C) oxaliplatin (10 mg/kg), and (D) oxaliplatin plus 5-fluorouracil when xenografts reached 250 mm(3) (n = 10). After 2-week treatment, tumor cells were quantified by flow cytometry for expression of CD133 and the hypoxic proportion of CD133(+) and CD133(-) cells which were also sorted and detected for ki67 and pimonidazole via immunofluorescence. The hypoxic subpopulation of CD133(+) and CD133(-) cells was 66.5 and 26.4 %, respectively. Although there was no marked change for the hypoxic subpopulation of CD133(+) cells after treatment, the hypoxic fraction of proliferative CD133(+) cells was increased by 14.62, 16.45, and 20.46 % in groups B, C, and D, respectively. Furthermore, proliferative cells in CD133(+) and CD133(-) cells were reduced by 29.93 and 62.5 % in group C, and by 25.26 and 68.22 % in group D; in group B, however, the proliferative CD133(+) cells were increased by 37.09 %; the CD133(-) cells were unchanged. Most CD133(+) cCSCs are located in a hypoxic niche, where cCSCs are better at retaining proliferating property under chemotherapy. Oxaliplatin, rather than 5-FU, inhibits proliferation of cCSCs, which may be the mechanism underlying a better outcome by oxaliplatin in colon cancer patients.

A phase I/II study of cisplatin and radiation in combination with sorafenib in cervical cancer: Evaluation of biomarkers.

5037 Background: This is a single-arm, open-label, phase I/II trial in patients with early stage carcinoma of the cervix investigating the addition of sorafenib (S), a dual kinase inhibitor with anti-VEGF properties which may increase the affect of chemotherapy and radiation on tumor cells. Methods: All patients received conventional treatment with radiation and chemotherapy (RTCT) but a low risk/para-aortic group received S alone in escalating doses for 1 week prior to the start of (RTCT), while high risk patients received S alone in escalating doses for 1 week prior to the start of RTCT, plus concurrently with RTCT. Biomarkers of response to S were measured at baseline, after 7 days of S alone (400 or 800 mg daily) and after 1 week of RTCT. Three Magnetic Resonance (MR) biomarkers of perfusion and vascular permeability were evaluated: 1. Enhancement fraction at 25s (EF25) - indicative of early phase enhancement; 2. Relative signal intensity (RSI) - indicative of late phase enhancement; and 3. iAUC60. In addition, tumor median pO2 (mpO2), hypoxic proportion (HP) and interstitial fluid pressure (IFP) were measured using needle-based techniques. The paired Wilcoxin signed ranks test was used to evaluate differences in the biomarkers relative to baseline. Results: Thirteen patients have been enrolled onto the study and the low risk cohort is complete. Most common toxicities of any grade include diarrhea (82%), lymphopenia (82%), and nausea (82%). Tumor volume increased with 7 days of S alone (86 vs 78 cm3, p<0.01), and EF (73 vs 86%, p=0.02) were decreased and RSI (1.7 vs 1.9, p=0.07) was unchanged. The tumors also became more hypoxic (mpO2 3 vs 14 mm Hg, p=0.01; and HP 67 vs 51%, p=0.06) but there was no change in IFP (21 vs 24 mm Hg). MR biomarkers were also obtained in week 2 (after the start of RTCT) for 12/13 patients, IFP in 10 and mpO2/HP in 7. Tumor volume decreased (57 vs 81 cm3, p=0.01) and there was a significant reduction in IFP (16 vs 24 mm Hg, p=0.04). However, EF, RSI, mpO2 and HP were not significantly different from baseline. Conclusions: Thus study demonstrates that the combination of RTCT and S is tolerable and that biomarkers show increasing hypoxia, and indications of reductions in markers of vasculature with S.

Prostate cancer hypoxia as a predictor of early biochemical and local failure after radiotherapy.

20 Background: Tumor hypoxia is an important determinant of patient outcome in many human malignancies, and has been associated with radioresistance and the development of metastases. The aim of this study was to determine the predictive effect of hypoxia in prostate cancer patients treated with RT. Methods: A total of 256 patients with clinically localized prostate cancer underwent pre-treatment, transrectal, ultrasound-guided measurement of tumor oxygen using a needle electrode. The median pO2 (mpO2) was 6.7 mm Hg and the median hypoxic proportion &lt;10 mm Hg (HP10) was 0.63. Most patients were treated with IMRT to the prostate alone using doses in the range of 75.6-79.8 Gy. Sixty-one received neoadjuvant and concurrent hormonal therapy. The Phoenix definition of biochemical relapse was used, and the median follow-up was 5.4 years. Results: The 5-year bRFR was 78%. High PSA and Gleason score were independently associated with biochemical relapse, and formed the baseline clinical multivariate model. The effect of hypoxia was found to vary with the duration of patient follow- up. HP10, when added to the clinical multivariate model as a time-dependent variable, was a significant, independent predictor of early bRFR (p=0.015). The predictive effect of hypoxia diminished with increasing follow-up and was lost by 36 to 48 months. The relationship between hypoxia and early biochemical recurrence was more pronounced when the analysis was restricted to 144 patients with bulk tumor at the site of the oxygen measurements (p=0.008). Prostate biopsy was performed in 73 patients a median of 36 months after completing RT. Hypoxia was the only factor predictive of local recurrence in this sub-group, with the effect being greatest early in follow-up (p=0.038). Conclusions: This is the largest clinical study of prostate cancer hypoxia with direct measurement of tumor oxygen levels. It suggests that hypoxia in the index tumor increases the risk of recurrence early after completing RT but not at longer times. The results imply a complex interaction between hypoxia and local vs. distant failure, which may be better elucidated with longer follow-up. No significant financial relationships to disclose.

MO‐D‐204B‐01: Characterizing Uncertainties in Hypoxia Imaging‐Based Dose Painting Prescriptions

Purpose: Inadequate characterization of variability from dose escalation models limits the precise definition of dose painting prescriptions. The purpose of this study was to quantify uncertainties in hypoxia imaging‐based prescriptions using an empirically‐driven and patient‐specific model. Materials and Methods: The model coupled an electrochemical formalism, which related Cu‐ATSM (hypoxia surrogate) uptake and pO2, with a modified oxygen enhancement ratio (OER) equation to yield non‐uniform dose prescriptions. This methodology was applied to eight head and neck cancer patients who underwent Cu‐ATSM PET/CT scans. Integral dose escalation was determined as a function of tumor hypoxic proportion (HP2.5 = percent tumor voxels with pO2 &lt; 2.5 mmHg). Model parameters included intracellular acidity ‐ pH, dose boost as a function of hypoxic proportion ‐ Dboost(HP2.5), max OER ‐ OERmax, and half‐max sensitization oxygen tension ‐ Pmid. Parameters were varied within published ranges for this patient population, and uncertainties were propagated to variations in the maximum dose heterogeneity Results: Model parameters had differing impact on dose prescription uncertainties. Over the range of pH values [7.1–7.3], variation in MDH was 4 percent (maximum 9 percent). Within the 95 percent confidence intervals of the Dboost(HP2.5) functional fit, variability in MDH was 5 percent (maximum 14 percent). Between the limits of OERmax values [1.4–3.0], variation in MDH was 1 percent (maximum 2 percent). From the array of Pmid values [2–5 mmHg], variation in MDH forallparameterswas 1 percent (maximum 2 percent). The total variation in MDH for all parameters was 10 percent (maximum 17 percent). Conclusions: Dose prescription variability was on the order of 10 percent. Variations were due primarily to uncertainties in cellular acidity and dose boost functional fit, which are parameters governing calculated oxygen tension distributions. Ultimately, the derivation of a hypoxia imaging‐based prescription function will require fitting model parameters to outcome data in dose escalation clinical trials.

Androgen Withdrawal in Patients Reduces Prostate Cancer Hypoxia: Implications for Disease Progression and Radiation Response

Hypoxia is a feature of many human malignancies, and leads to aggressive clinical behavior and recurrence after treatment. Here, we show for the first time that androgen withdrawal reduces prostate cancer hypoxia in patients. Oxygen measurements were done in 248 patients with clinically localized prostate cancer prior to radiotherapy, and showed hypoxia of potential biological and clinical significance. In 22 of these patients, prostate oxygen levels were measured both before and after 30 to 145 days of the androgen antagonist bicalutamide. There was a significant reduction in tumor hypoxia with androgen withdrawal (P=0.005). The median pO(2) increased from 6.4 to 15 mm Hg, and the hypoxic proportion decreased from 40% to 31%. However, the response was heterogeneous, with improvement in 12 patients, stable oxygen readings in 9 patients and worsening hypoxia in 1 patient. Among the responding patients, the median pO(2) increased from 4.9 to 33 mm Hg, and the hypoxic proportion decreased from 51% to 23%. There was no apparent relationship between the change in oxygenation and baseline prostatic volume, T category, Gleason score, prostate-specific antigen levels, the duration of treatment with bicalutamide, or the change in prostate-specific antigen levels with bicalutamide. These results might, in part, explain the improved patient outcome that has been observed in clinical trials of radiotherapy and hormones, and suggest a role for novel therapeutic agents that block the molecular response to hypoxia in prostate cancer either alone or in combination with other established treatments.

Long-term performance of interstial fluid pressure and hypoxia as prognostic factors in cervix cancer

Objectives Hypoxia and high interstitial fluid pressure (IFP) have been shown to independently predict for nodal and distant metastases, as well as survival, in patients with cervix cancer. Using data from our prospective trial, we updated a cohort of patients treated with definitive radiation alone without chemotherapy, to assess the long-term prognostic impact of these microenvironmental features. Methods Between April 1994 and January 1999, 107 eligible patients with cervix cancer were entered into a prospective study of tumor oxygenation and IFP prior to primary radiation therapy. Oxygenation data are presented as the hypoxic proportion, defined as the percentage of pO 2 readings <5 mm Hg (abbreviated as HP 5). Patients with HP 5 values >50% were considered to have hypoxic tumors. IFP is presented in mm Hg, divided into high and low IFP groups by the median value. Patients ranged in age from 23 to 78 years with a mean of 53 years. The maximum tumor size ranged from 2 to 10 cm, with a median diameter of 5 cm. FIGO stage was IB in 28 patients, IIA in 4, IIB in 42 and IIIB in 33 patients. Twenty-two patients (21%) had evidence of pelvic lymph node involvement on staging CT abdomen/pelvis or MR pelvis. HP 5 ranged from 0% to 99% with a median of 48%. IFP ranged from −3 to 48 mm Hg (median 19 mm Hg). Median follow-up was 6.7 years (range 0.9–10.6). Results Disease-free survival (DFS) at 5 years was 50%. Five year DFS was 42% for patients with hypoxic tumors (HP 5 > 50%), and 58% in patients with oxygenated tumors (HR 1.01 per %, p = 0.05). DFS at 5 years was 42% for patients with interstitial hypertension (IFP >19 mm Hg), and 63% in patients with IFP ⩽19 mm Hg (HR 1.05 per mm Hg, p = 0.001). In a multivariate analysis only tumor size (HR 1.2, p = 0.009) pelvic nodal metastases (HR 3.3, p = 0.0004) and IFP (HR 1.06, p = 0.0005) were predictive of DFS. Because an interaction between nodal status and oxygenation was observed ( p = 0.03), further analysis indicated a borderline significant impact of HP 5 in addition to tumor size in node negative patients (HR 1.01, p = 0.06). These results were similar when local or distant relapse was used as an endpoint. Conclusions These results confirm our initial finding of the strong independent prognostic impact of IFP for relapse and survival in patients with cervix cancer. In contrast, the independent prognostic impact of HP 5 is of borderline significance and is limited to patients without imaging evidence of nodal metastases. However, these findings do not diminish the biologic significance of hypoxia, or the role of hypoxia and IFP as biomarkers of treatment response and as therapeutic targets.

Standard (STD) or hyperfractionated (HFX) conformal radiation therapy (CRT) in prostate cancer: A prospective trial evaluating toxicities and early biochemical control

In 1993 we activated a prospective, non randomized trial in prostate cancer using CRT and 2 different fractionation regimens. The end points were to compare genito-urinary (GU) and gastro-intestinal (GI) toxicities (tox) as well as biochemical control (bRFS), utilizing a STD (2.0 Gy daily) or a HFX schedule. HFX (1.2 Gy BID) was chosen as a radiobiological method to try to reduce late tox without compromising local control (1). 370 consecutive patients (pts) entered the study in the period January 1993-January 2003. 209 were treated with STD and 161 with HFX CRT. 179 pts (87%) in the STD and 151 (94%) in the HFX were evaluable for late tox and bRFS analysis, while all 370 pts were considered for acute tox evaluation. Pre-treatment clinical variables (STD vs. HFX: median age 71 vs. 69; T1-2 64.8% vs. 60.4%; median iPSA 11.2 vs. 12 ng/ml; GPS ≥ 7 39% vs. 40%) and treatment characteristics (pelvis irradiation 43% vs. 44%; androgen deprivation 79% vs. 71%) were not statistically different in the 2 groups. CRT consisted of a 4-field technique for prostate and/or pelvic nodes and a 5-field boost with rectal shielding. Median doses were 74 Gy and 79.2 Gy (EQD2:73.9 Gy, isoeffective for tumor control assuming α/β = 10) for STD and HFX patients, respectively. Median follow-up was 29.4 months (STD: 25.2 mos; HFX: 37.7 mos; p < 0.01 t-test). GU/GI acute and late tox (RTOG-EORTC scoring) and 5-year bRFS were compared in the 2 fractionation regimens using univariate (Chi-square, log-rank test) and multivariate analyses (Cox regression hazard model). Acute ≥ grade 2 GU tox was higher in the STD group (48.6% vs. 37.3% in the HFX group, p = 0.03) while no significant difference was found for acute GI tox. Late ≥ grade 2 GU and GI tox were lower in the HFX group (5-year actuarial rate: GU: 10.1% vs. 20.3%, p = 0.05; GI: 6.0% vs. 10.6%, p = 0.18). 5-year bRFS were 70% (±13.8%, 95% CI) and 82.6 % (±7.2%) for STD and HFX, respectively (p = 0.44); a trend favouring HFX was found in the subgroup of pts who did not receive hormonal therapy (5-year bRFS: 85.9% ± 12.4% vs. 63.9% ± 23.8%, p = 0.15). Multivariate analysis revealed that only Pisansky risk groups and age were statistically related to bRFS but not fractionation regimens. Using the Nahum-Chapman TLCP model and prostate parameter set, which includes hypoxia, the TLCPs are approximately equal for the 2 regimens, whereas assuming α/β = 1.5 and no hypoxia we obtain 73% for the STD group but only 36% for the HFX group. As expected from radiobiology, HFX reduces GI and GU late tox. Concerning early bRFS, our clinical findings suggest that HFX is, at least, not detrimental with respect to standard fractionation when delivering an isoeffective total dose equivalent to 2 Gy/fr (considering α/β = 10). Whilst accepting that caution is appropriate due to the relatively short follow-up, this result seems to be inconsistent with a low α/β ratio for prostate cancer. The trend of a non-detrimental, possibly improved, clinical outcome with HFX is more consistent with the idea that α/β is relatively high and that some prostate tumours are hypoxic (2–4), with hyperfractionation probably reducing this hypoxic proportion through increased reoxygenation. If the bRFS with HFX is genuinely higher than with STD, then a plausible explanation is that hyperfractionation reduces this hypoxic proportion through increased reoxygenation.

Estimating hypoxic status in human tumors: A simulation using Eppendorf oxygen probe data in cervical cancer patients

Purpose To define the minimal number of pO 2 measurements, with 90% sensitivity and 90% specificity, needed to categorize cervical tumors as either hypoxic or oxic. Methods and materials Using Eppendorf oxygen probe data from our ongoing prospective trial, we simulated the measurement of tumor oxygenation with a smaller number of data points in 135 patients with cervical cancer. The hypoxic proportion, defined as the percentage of pO 2 values <5 mm Hg (HP5), was calculated for each tumor. Hypoxic tumors were defined as those with a median HP5 >50%, and tumors with normal oxygen levels as those with a median HP5 ≤50%. A small number of pO 2 measurements were randomly selected from the Eppendorf measurements in each tumor, or per Eppendorf track, and used to define the tumor as hypoxic or oxic. The sensitivity and specificity were calculated, considering the classification as given by the complete set of Eppendorf measurements as the reference standard. Results The probability of falsely classifying the tumor decreased as the selected number of pO 2 measurements per tumor increased, and at 16 measurements was approximately 10%. Adding additional measurements per tumor beyond 24 improved the ability to classify the tumor accurately only slightly. The probability of falsely classifying the tumor decreased as the pO 2 measurements per track increased. At five measurements per track, the probability of falsely classifying the tumor was approximately 9%. Conclusion Approximately 20 measurements per tumor, or five measurements per track, using the Eppendorf pO 2 histograph, are sufficient to categorize cervical tumors as hypoxic or oxic. The results of this study will serve as a guide for research clinicians in the use of this and other systems in the assessment of tumor oxygenation in humans.

The effect of smoking on tumour oxygenation and treatment outcome in cervical cancer.

Tumour hypoxia is associated with an increased risk of cervical tumour recurrence and death. Because smoking is a modifiable behaviour, it is important to establish the importance of smoking as a prognostic factor. We hypothesized that there is an association between smoking and tumour hypoxia, and that smoking adversely affects radiation response and survival. A smoking history was obtained from 100 of 115 patients with cervical cancer entered into a prospective study of tumour oxygenation. Eighty-seven of these had clinically evident disease and radiation therapy alone was the planned treatment. Patients who smoked within 2 weeks of commencing radiation therapy were considered smokers, and the amount that they smoked was recorded in packs per day. Patients who had never smoked or quit at least 2 weeks prior to radiation therapy were considered non-smokers. Tumour oxygenation was determined using the Eppendorf polarographic oxygen electrode and tumour oxygenation is represented by the hypoxic proportion HP5 (% of pO2 measurements <5 mmHg). There was no significant association between smoking and tumour hypoxia (P=0.3), haemoglobin (P=0.6) nor tumour size (P=0.1). Progression-free survival at 3 years was 56% for non-smokers and 44% for smokers (P=0.23). In both univariate and multivariate analysis, neither smoking status nor amount smoked were significant predictors of progression-free survival or local control. There was no significant association between smoking and tumour hypoxia, treatment response or survival in this study of patients with cervix cancer.

Tumor Hypoxia Has Independent Predictor Impact Only in Patients With Node-Negative Cervix Cancer

PURPOSE: This prospective clinical study was begun in 1994 to validate the independent prognostic impact of tumor hypoxia in patients with cervix cancer treated with definitive radiation therapy. PATIENTS AND METHODS: Between May 1994 and January 1999, 106 eligible patients with epithelial cervix cancer had tumor oxygen pressure (PO2) measured using the Eppendorf probe. Oxygenation data are presented as the hypoxic proportion, defined as the percentage of PO2 readings less than 5 mm/Hg (abbreviated as HP5) and the median PO2. RESULTS: The median HP5 in individual patients was 48%, and the median PO2 was HP5. Progression-free survival (PFS) for patients with hypoxic tumors (HP5 > 50%) was 37% at 3 years versus 67% in those patients with better oxygenated tumors (P = .004). In multivariate analysis, only tumor size (risk ratio [RR], 1.33; P = .0003) and evidence of pelvic nodal metastases on imaging studies (RR, 2.52; P = .0065) were predictive of PFS. However, an interaction between nodal status and oxygenation was observed (P = .006), and further analysis indicated that HP5 was an independent predictor of outcome in patients with negative nodes on imaging (P = .007). There was a significant increase in the 3-year cumulative incidence of distant metastases in the hypoxic group (41% v 15% in those with HP5 < 50%; P = .0023), but not in pelvic relapse (37% v 27%; P = .12). CONCLUSION: Tumor hypoxia is an independent predictor of poor PFS only in patients with node-negative cervix cancer, in addition to tumor size. Its impact appears to be related to an increased risk of distant metastases rather than to an effect on pelvic control.

Tumor hypoxia has independent predictor impact only in patients with node-negative cervix cancer.

This prospective clinical study was begun in 1994 to validate the independent prognostic impact of tumor hypoxia in patients with cervix cancer treated with definitive radiation therapy. Between May 1994 and January 1999, 106 eligible patients with epithelial cervix cancer had tumor oxygen pressure (PO(2)) measured using the Eppendorf probe. Oxygenation data are presented as the hypoxic proportion, defined as the percentage of PO(2) readings less than 5 mm/Hg (abbreviated as HP(5)) and the median PO(2). The median HP(5) in individual patients was 48%, and the median PO(2) was HP(5). Progression-free survival (PFS) for patients with hypoxic tumors (HP(5) > 50%) was 37% at 3 years versus 67% in those patients with better oxygenated tumors (P =.004). In multivariate analysis, only tumor size (risk ratio [RR], 1.33; P =.0003) and evidence of pelvic nodal metastases on imaging studies (RR, 2.52; P =.0065) were predictive of PFS. However, an interaction between nodal status and oxygenation was observed (P =.006), and further analysis indicated that HP(5) was an independent predictor of outcome in patients with negative nodes on imaging (P =.007). There was a significant increase in the 3-year cumulative incidence of distant metastases in the hypoxic group (41% v 15% in those with HP(5) < 50%; P =.0023), but not in pelvic relapse (37% v 27%; P =.12). Tumor hypoxia is an independent predictor of poor PFS only in patients with node-negative cervix cancer, in addition to tumor size. Its impact appears to be related to an increased risk of distant metastases rather than to an effect on pelvic control.

A polarographic electrode study of tumor oxygenation in localized prostate cancer

A polarographic electrode study of tumor oxygenation in localized prostate cancer

Estimating hypoxic status in human tumours: a simulation using eppendorf oxygen probe data in cervix cancer patients

Purpose: To define the minimum number of pO2 measurements needed to categorize human cervix tumours as either hypoxic or oxic, and to estimate the error resulting from using this minimum number of measurements. Materials and Methods: Using Eppendorf oxygen probe data from our ongoing prospective trial, we simulated the measurement of tumour oxygenation with a small number of data points. The Eppendorf pO2 histograph was used to measure tumour pO2 in 135 patients with locally advanced cancer of the cervix. The majority of subjects had 5 tracks sampled, and the median number of measurements per track was 32. The hypoxic proportion, defined as the percentage of pO2 values <5mm Hg (HP5), was calculated for each tumour. Hypoxic tumours were defined as those with a median HP5 >50%, and oxic tumours as those with median HP5 ≤50%. In assessing the individual track measurements, 1-7 pO2 measurements were randomly selected from each of 4 tracks from each tumour.PO2 measurements were randomly selected from the Eppendorf measurements in each tumour, and the tumour was defined as either hypoxic or oxic, based on the above definitions. Sensitivity and specificity were calculated, considering the classification as given by the Eppendorf measurements as the “gold standard”. The number of measurements chosen randomly was varied, and the process repeated two thousand times. Results: The probability of falsely classifying the tumour decreased as the pO2 measurements per tumour increased from 4 to 28, and at 16 measurements reached a value of approximately 10%. At 24 measurements per tumour, the probability of misclassification of the tumour was approximately 8%. Further measurements per tumour beyond 24 did not improve the ability to accurately classify the tumour. The probability of falsely classifying the tumour decreased as pO2 measurements per track increased. This appeared to plateau at 5 measurements per track, giving a probability of false classification of the tumour of approximately 9%. Conclusion: Approximately 16-24 measurements per tumour, or 5 measurements per track, using the Eppendorf pO2 histograph, are sufficient to categorize cervix tumours as either hypoxic or oxic. The results of this study will serve as a guide for research clinicians in the use of this and other systems in the assessment of tumour oxygenation in humans.

Oxygenation predicts radiation response and survival in patients with cervix cancer

Background and purpose: Hypoxia appears to be an important factor in predicting tumor relapse following radiation therapy. This study measured oxygenation prior to treatment in patients with cervix cancer using a polarographic oxygen electrode to determine if oxygenation was an important prognostic factor with regard to tumor control and survival. Materials and methods: Between May 1994 and June 1997, 74 eligible patients with cervix cancer were entered into an ongoing prospective study of tumor oxygenation prior to primary radiation therapy. All patients were evaluated with an Eppendorf oxygen electrode during examination under anesthesia. Oxygenation data are presented as the hypoxic proportion, defined as the percentage of pO 2 readings of <5 mm Hg (abbreviated as HP 5). Results: The HP 5 ranged from 2 to 99% with a median of 52%. With a median follow-up of 1.2 years, the disease-free survival (DFS) rate was 69% for patients with HP 5 of ≤50% compared with 34% for those with HP 5 of >50% (log-rank P=0.02). Tumor size above and below the median of 5 cm was also significantly related to DFS ( P=0.0003) and patients with bulky hypoxic tumors had a significantly lower DFS (12% at 2 years) than either bulky oxygenated or non-bulky oxygenated or hypoxic tumors (65%, P=0.0001). Conclusions: Hypoxia and tumor size are significant adverse prognostic factors in a univariate analysis of disease-free survival in patients with cervix cancer. A high risk group of patients with bulky hypoxic tumors have a significantly higher probability of relapse and death.

Heterogeneity of polarographic oxygen tension measurements in cervix cancer: An evaluation of within and between tumor variability, probe position, and track depth

To evaluate the heterogeneity of cervix cancer oxygenation as measured using the Eppendorf polarographic electrode and define the optimal number of measurements required to adequately sample a cervix cancer. Two to 6 tracks with 20-30 measurements per track were obtained in each of the 44 patients evaluated. One hundred sixty-eight tracks and 4719 measurements formed the basis of this analysis. Median pO2 and hypoxic proportion (HP5), defined as the percentage of pO2 values <5 mmHg, were calculated for each track and for each tumor. Within-tumor (W) and between-tumor (B) variability in oxygenation was evaluated using a variance component analysis. The standard error of the measured HP5 with each additional track in each patient was analysed as a function of the total number of tracks. The ratio W/W + B was 0.67 and 0.76 for median pO2 and HP5, respectively, indicating that multiple measurements are needed to adequately sample a tumor. The median value of the standard error of the HP5 decreased from 7.0 to 4.0% from the first to the fifth track, respectively. It was estimated that adding the sixth track would only result in a small change (<0.3%) in the standard error. There was no significant difference in oxygen tension measurements as a function of the location of the measurements around the circumference of the cervix or the depth along the measurement tracks. There is significant within tumor variability in oxygen tension in cervix cancer. Five tracks with 20-30 measurements per track is optimal to sample the oxygenation status of a cervix cancer. The present data does not suggest that there is a significant difference related to the position in the tumor at which the pO2 measurements were taken.

Comparing Techniques of Measuring Tumor Hypoxia in Different Murine Tumors: Eppendorf pO 2 Histograph, [ 3 H]Misonidazole Binding and Paired Survival Assay

Using five transplantable murine tumors (SCC-VII, B16F1, KHT-C, KHT-LP1, RIF-1), measurements of tumor hypoxia have been made with two techniques which have the potential to be used for assessing oxygenation in human tumors (the Eppendorf pO2 Histograph and binding of [3H]misonidazole) and have been compared with an established radiobiological technique, the paired survival assay. There were significant differences in the pO2 measurements made in individual tumors both within and between the five different tumor types. Significant differences between the tumor types were also found for the [3H]misonidazole binding. A correlation was observed between the mean values of the hypoxic proportion as measured by the paired survival assay and the mean binding of [3H]misonidazole as measured by both tumor activity in dpm/100 mg tissue (r = 0.94, P = 0.02) and the tumor-to-muscle activity ratio (r = 0.87, P = 0.06). No biologically significant correlation was seen between the mean values of the hypoxic proportion from anesthetized mice as measured by the paired survival assay (range 20-58%) and the pooled Eppendorf pO2 Histograph measurements made on groups of tumors. These results with the Eppendorf pO2 Histograph are similar to those reported by others. When both Eppendorf pO2 Histograph measurements and paired survival measurements were made on the same individual KHT-C tumors, it was again found that there was no correlation between the two measurements of hypoxia.

An estimation of changes in the proportions and absolute numbers of hypoxic cells after irradiation of transplanted C3H mousemammary tumours.

Abstract Mice bearing transplanted mammary tumours have been irradiated with 250 kVp X rays using a single dose or two fractions. In the latter case the first dose was 1,500 rads given in air and the second dose, whose magnitude was varied, was given either under anoxic conditions or while the animal was breathing air or three atmospheres of oxygen. Analysis was made in terms of the dose required for 50 per cent cure. The results have been interpretated using a model in which the cells surviving the first dose are assumed to be either aerobic or anoxic, and the proportion in each compartment varies with time. On this basis, at one hour after irradiation the hypoxic proportion was increased from 12 per cent to approximately 100 per cent. By six hours, however, the estimated hypoxic proportion had fallen and continued to do so reaching a minimum value at approximately four days after irradiation, this being significantly lower than the pre-irradiation value. Estimates of changes in the total numbers of hypo...

The influence of intracellular recovery and hypoxic cells on the radiation response of mammary tumours and skin in C3H mice.

Spontaneous and transplanted tumours in the C3H mouse have been irradiated in oxygen at one atmosphere absolute using either single doses or doses split into two equal fractions with the time interval between them being varied from one hour to three days. The response of the tumours was compared with that of the skin over and around the tumour as representing normal tissue. Intracellular recovery for both tumour types, shown by a positive (D2–D1) 6 hours was seen at all doses studied, and evidence was given for recovery in the hypoxic proportion of the tumour. The skin showed a gradual decrease in (D2–D1) 6 hours as the dose increased, until after an initial dose of 2,750 rads no intracellular recovery was seen with a negative (D2–D1) at all intervals up to three days. This and the sensitisation in the tumours seen at longer time intervals (i.e. negative (D2–D1)) are interpreted as reoxygenation phenomena, or change in proportion of hypoxic cells. The rate and amount of reoxygenation were observed to be greater in spontaneous than in transplanted tumours. The therapeutic advantages of short time intervals are discussed.