Effect of carbon monoxide breathing on hypoxia and radiation response in the SCCVII tumor in vivo

Tumor hypoxia and radiotherapy: A major driver of resistance even for novel radiotherapy modalities

Hypoxia in solid tumors is an important predictor of poor clinical outcome to radiotherapy. Both physicochemical and biological processes contribute to a reduced sensitivity of hypoxic tumor cells to ionizing radiation and hypoxia-related treatment resistances. A conventional low-dose fractionated radiotherapy regimen exploits iterative reoxygenation in between the individual fractions, nevertheless tumor hypoxia still remains a major hurdle for successful treatment outcome. The technological advances achieved in image guidance and highly conformal dose delivery make it nowadays possible to prescribe larger doses to the tumor as part of single high-dose or hypofractionated radiotherapy, while keeping an acceptable level of normal tissue complication in the co-irradiated organs at risk. However, we insufficiently understand the impact of tumor hypoxia to single high-doses of RT and hypofractionated RT. So-called FLASH radiotherapy, which delivers ionizing radiation at ultrahigh dose rates (> 40 Gy/sec), has recently emerged as an important breakthrough in the radiotherapy field to reduce normal tissue toxicity compared to irradiation at conventional dose rates (few Gy/min). Not surprisingly, oxygen consumption and tumor hypoxia also seem to play an intriguing role for FLASH radiotherapy. Here we will discuss the role of tumor hypoxia for radiotherapy in general and in the context of novel radiotherapy treatment approaches.

Quitting smoking improves two-year survival after a diagnosis of non-small cell lung cancer

BACKGROUND

Smoking at diagnosis is associated with worse survival in lung cancer but the effects of quitting smoking on survival remain unclear.

METHODS

In a UK multi-centre study (NCT01192256) we followed all 2751 patients with newly diagnosed non-small cell lung cancer (NSCLC) for up to 2 years or until death as part of the observational trial. Patients were offered smoking cessation advice and treatments according to national guidelines and local services. Smoking status was verified by exhaled carbon monoxide levels. Kaplan-Meier survival analysis and Cox Proportional Hazards Modelling examined the effects of quitting smoking on survival at 2 years.

FINDINGS

646 were current smokers at the time of diagnosis. The unadjusted two-year Kaplan-Meier survivor functions for quitters (0.45, 95 %CI 0.37 to 0.53) and continuers (0.32, 0.28 to 0.36) were significantly different (log-rank test p < 0.01). Median survival times were 659 days for quitters and 348 days for continuers. After adjusting for age, sex, stage, performance status, curative intent surgery, radical radiotherapy and comorbidity, the hazard ratio for quitting at diagnosis (0.75, 95 % CI 0.58 to 0.98) indicated a statistically significant reduction in the risk of death across the two-year study period.

INTERPRETATION

Quitting smoking is independently and significantly associated with improved survival regardless of stage in NSCLC. We recommend that smoking cessation advice and treatments should be offered to smokers with lung cancer.

TRIAL REGISTRATION

ClinicalTrials.gov, identifier NCT01192256.

FUNDING

This work was supported by a 2010 Global Research Award for Nicotine Dependence (GRAND), Pfizer.

Impact of smoking on survival in nasopharyngeal carcinoma: A cohort study with 23,325 patients diagnosed from 1990 to 2016

BACKGROUND

We aimed to compare the survival outcomes of patients with nasopharyngeal carcinoma (NPC) who had different smoking behaviors and were treated with two- or three-dimensional radiotherapy (2D/3DRT) or intensity-modulated radiotherapy (IMRT) with a long-term follow up.

METHODS

From 1990 to 2016, 23,325 patients with NPC were included. The primary endpoint of this study was overall survival (OS). The log-rank test and Cox proportional hazards regression model were used to assess the patients' survival outcomes.

RESULTS

The 5-year OS rates in the entire cohort were 76.4%, 68.9%, and 79.8% in the former, current, and never smokers, respectively. In the IMRT cohort, the OS rates showed the same trend. Compared with the never smokers, the 5-year distant metastasis-free survival (DMFS) was lower in the former (P = 0.004) and current smokers (P < 0.001). In the multivariate analysis of the IMRT cohort, the risk of death (P = 0.003) and recurrence (P = 0.027) was higher in the current smokers, while the risk of metastasis was higher in the former and current smokers (P = 0.031 and P = 0.019, respectively) than the never smokers. A total of 53.9% of the effect of smoking status on OS was through sex, age, and Epstein-Barr virus DNA, which were significant mediators.

CONCLUSION

In the IMRT era, being a former smoker or current smoker was an independent risk factor for DMFS. The difference in OS and locoregional relapse-free survival was significant only between the current smokers and never smokers.

Monitoring expiratory carbon monoxide to study the effect of complete smoking cessation on definitive radiation therapy for early stage glottic carcinoma

BACKGROUND

Previous studies reported that cigarette smoking during radiation therapy was associated with unfavorable outcomes in various cancers using medical interviewing or monitoring of cotinine. Here, we evaluated the effect of smoking cessation on definitive radiation therapy for early stage glottic carcinoma by monitoring expiratory carbon monoxide (CO).

MATERIAL AND METHODS

We enrolled 103 patients with early glottic carcinoma (T1N0/T2N0 = 79/24) who underwent conventional radiotherapy between 2005 and 2016. The median age was 70 years. Pathologically, all patients had squamous cell carcinoma. Since 2009, we confirmed smoking cessation before radiation therapy by medical interviews. Since 2014, we measured expiratory CO to strictly monitor smoking cessation. The patients were divided according to diagnosis years: 'no cessation' (2005-2008), 'incomplete cessation' (2009-2013), and 'complete cessation' (2014-2016). We retrospectively analyzed the local recurrence rate and disease-free survival (DFS).

RESULTS

The median follow-up period was 60.1 months (range, 1.9-110.0 months). The 2-year local recurrence rate in the 'complete cessation' group was 5.3% and tended to be lower than that in the 'incomplete cessation' group (13.7%) and 'no cessation' group (21.2%). Multivariate analysis revealed that 'no cessation' was a risk factor for DFS (hazard ratio [HR] = 4.25) and local recurrence rate (HR = 16.5, p < .05) compared to 'complete cessation.'

DISCUSSION

We confirmed that the 'complete cessation' group had better prognosis than the 'no cessation' group by monitoring expiratory CO during radiation therapy for early stage glottic carcinoma. Moreover, monitoring expiratory CO was easier and more suitable than conventional methods for evaluating smoking cessation because it provided real-time measurements.

Impact of Smoking on Survival Outcomes in HPV-Related Oropharyngeal Carcinoma: A Meta-analysis

Objective

Characterize the survival impact of smoking on HPV-related (human papillomavirus) oropharyngeal squamous cell carcinoma.

Data Sources

Articles from 2000 to 2019 in the PubMed, Embase, and Cochrane Library databases were systematically reviewed for content and inclusion/exclusion criteria.

Review Methods

Two reviewers independently analyzed the databases for eligibility and quality of the articles. Demographic data, smoking history, and survival outcomes were recorded. Hazard ratios and 95% CIs were collectively analyzed through a random effects meta-analysis model.

Results

Fifteen articles were included in the meta-analysis for overall survival, disease-specific survival, disease-free survival, progression-free survival, and locoregional recurrence outcomes. The overall survival hazard ratio was 2.4 for ever having smoked (95% CI, 1.4-4.0; P = .0006, I2 = .384) and 3.2 for current smoking (95% CI, 2.2-4.6; P < .0001, I2 = 0). The hazard ratio for disease-specific survival in current smokers was 6.3 (95% CI, 1.3-29.3; P = .0194, I2 = 0). Ever smoking had a larger impact on overall survival and disease-specific survival than the 10–pack year smoking threshold.

Conclusion

Smoking negatively affects survival in patients with HPV-related oropharyngeal carcinoma across all outcomes. Current smoking during treatment is associated with the greatest reduction in survival, possibly secondary to diminished radiation therapy efficacy.

Prognostic impact of cigarette smoking on the survival of patients with established esophageal squamous cell carcinoma receiving radiotherapy: A retrospective study from southern China

Cigarette smoking is associated with the development of esophageal squamous cell carcinoma (ESCC); however, the influence of smoking on survival of patients with ESCC receiving radiotherapy, with or without chemotherapy, has remained elusive. The present study retrospectively analyzed 479 patients with ESCC from southern China who were categorized based on their smoking history (never, previous or current). To consider the cumulative effect of smoking, the number of pack years (PYs) was used as a representative variable. Associations between cigarette smoking and survival were evaluated using the Kaplan-Meier analysis and Cox proportional hazards model. Among the 497 patients, 308 (64.3%) had reported a history of cigarette smoking. The 5-year overall survival for patients void of a smoking history, former smokers and current smokers was 50.9, 27.0 and 34.3%, respectively. The adjusted hazard ratios (HRs) for previous and current smoking vs. no smoking history were 1.57 [95% confidence interval (CI), 1.06–2.32] and 3.01 (95% CI, 1.15–7.86), respectively. Heavy smokers with a high number of PYs had a HR for death of 1.75 (95% CI, 1.28–2.41) compared with light smokers. In the cohort of 407 patients treated with intensity-modulated radiotherapy/three-dimensional conformal radiotherapy, similarly significant results were obtained. In conclusion, cigarette smoking is an independent and poor prognostic factor for patients with ESCC treated with radiotherapy and/or chemotherapy. It is associated with an increased risk of death, and the risk increases with the increase in PYs. This result may help to manage tobacco use among patients with ESCC. The smoking status should be taken into consideration in prospective studies on ESCC. More frequent follow-ups are recommended for those patients with ESCC with a history of smoking.

Longitudinal study to assess impact of smoking at diagnosis and quitting on 1-year survival for people with non-small cell lung cancer

OBJECTIVES

To update the prevalence of smoking in people as they were diagnosed with non-small cell lung cancer (NSCLC) and to see whether smoking status at baseline and quitting are independently associated with 1-year survival.

DESIGN

A real-world cohort study following patients from diagnosis for up to 1 year or until death.

SETTING

UK multi-centre study (28 sites) based in secondary and primary care.

PARTICIPANTS

1124 patients with newly diagnosed NSCLC between 2010-2016.

MAIN OUTCOME MEASURES

Smoking status was validated at diagnosis and at every routine and emergency hospital visit. Cancer treatments were offered according to local multi-disciplinary team decisions following UK guidelines and smoking cessation treatments offered according to local practice /availability. Survival analysis and Cox Proportional Hazards Modelling examined the associations of a) smoking at baseline and b) quitting smoking, on survival at 1 year.

RESULTS

77% of never smokers, 60% of ex-smokers and 57% of current smokers, were alive at 1 year (p = 0.01). After adjusting for age, stage, EGOG, surgery and gender, ex smokers (adjusted HR 1.96, 95% CI 1.16-2.31) and current smokers (aHR 2.04, 1.19-3.48) were both more likely to die within one year. 23% of smokers with NSCLC quit within 3 months of diagnosis. At 1 year, 69% of those who quit were alive versus 53% of those who continued to smoke (p < 0.01). After adjusting the risk of dying was lower (aHR 0.75), in those who quit smoking, although this was not statistically significant (p = 0.23).

CONCLUSIONS

This is the largest prospective study that validates smoking in NSCLC; it shows a third of people are smoking at the time of diagnosis. Smokers have lower 12-month survival than never and ex -smokers. Quitting smoking was associated with 25% reduction in mortality which may be clinically important although not statistically significant, after adjusting for other factors.

Final Report of a Phase I Trial of Olaparib with Cetuximab and Radiation for Heavy Smoker Patients with Locally Advanced Head and Neck Cancer

Purpose: Our goal was to evaluate the safety and toxicity of combining a PARP inhibitor, olaparib, with cetuximab and fractionated intensity-modulated radiotherapy for patients with locally advanced head and neck cancer and heavy smoking histories.Patients and Methods: Patients with ≥10 packs/year history of smoking were treated with olaparib at doses ranging from 25-200 mg orally twice daily beginning approximately 10 days prior to initiation of and with concurrent radiation (69.3 Gy in 33 fractions) using a time-to-event continual reassessment method model. Cetuximab was administered starting approximately 5 days prior to radiation per standard of care.Results: A total of 16 patients were entered onto the study, with 15 evaluable for acute toxicity. The most common treatment-related grade 3-4 side effects were radiation dermatitis and mucositis (38% and 69%, respectively). The MTD was determined to be 50 mg orally twice daily, but the recommended phase II dose was deemed to be 25 mg orally twice daily. At a median follow-up of 26 months, the actuarial median overall survival was 37 months, but was not reached for other endpoints. Two-year overall survival, progression-free survival, local control, and distant control rates were 72%, 63%, 72%, and 79%, respectively. Patients who continued to smoke during therapy experienced higher recurrence rates. MYC and KMT2A were identified as potential correlatives of response on gene amplification and mutational analysis.Conclusions: Olaparib at 25 mg orally twice daily with concurrent cetuximab and radiation was well tolerated with reduced dermatitis within the radiation field. Response rates were promising for this high-risk population. Clin Cancer Res; 24(20); 4949-59. ©2018 AACR.

Cigarette smoking complements the prognostic value of baseline plasma Epstein-Barr virus deoxyribonucleic acid in patients with nasopharyngeal carcinoma undergoing intensity-modulated radiation therapy: a large-scale retrospective cohort study

We evaluated the combined prognostic value of cigarette smoking and baseline plasma Epstein-Barr virus deoxyribonucleic acid (EBV DNA) in patients with nasopharyngeal carcinoma (NPC) treated with intensity-modulated radiation therapy (IMRT). Of consecutive patients, 1501 with complete data were eligible for retrospective analysis. Smoking index (SI; cigarette packs per day times smoking duration [years]), was used to evaluate the cumulative effect of smoking. Primary endpoint was overall survival (OS); progression-free survival (PFS), distant metastasisfree survival (DMFS) and locoregional relapse-free survival (LRFS) were secondary end-points. Both cigarette smoking and baseline plasma EBV DNA load were associated with poorer survival (P<0.001). Patients were divided into four groups: low EBV DNA and light smoker (LL), low EBV DNA and heavy smoker (LH), high EBV DNA and light smoker (HL), and high EBV DNA and heavy smoker (HH). The respective 5-year survival rates were: OS (93.1%, 87.2%, 82.9%, and 76.3%, P<0.001), PFS (87.0%, 84.0%, 73.9%, and 64.6%, P<0.001), DMFS (94.1%, 92.1%, 82.4%, and72.5%, P<0.001), and LRFS (92.8%, 92.4%, 88.7%, and 84.0%, P=0.012).OS and PFS were significantly different between the LH and HL groups and HL and HH groups, but not LL and LH groups (pairwise comparisons). The combined risk stratification remained an independent prognostic factor for all endpoints (all P_trend<0.001; multivariate analysis). Both cigarette smoking and baseline plasma EBV DNA were independent prognostic factors for survival outcomes. Combined interpretation of EBV DNA with smoking led to the refinement of the risks stratification for patient subsets, especially with improved risk discrimination in patients with high baseline plasma EBV DNA.

Pretreatment anemia and survival in nasopharyngeal carcinoma

Due to the low incidence of pretreatment anemia in nasopharyngeal carcinoma (NPC), the true prognostic impact of pretreatment anemia may be underestimated before. We retrospectively analyzed the association of pretreatment anemia with disease-specific survival (DSS), distant-metastasis-free survival (DMFS), and locoregional-relapse-free survival (LRFS) by Cox regression in a cohort of 5830 patients, stratifying by midtreatment anemia, smoking, body mass index (BMI), etc. Pretreatment anemia was significantly associated with adverse DSS (hazard ratio (HR) = 2.15, 95 % confidence interval (CI) 1.62-2.85, P < 0.001) and DMFS (HR = 1.53, 95 % CI 1.08-2.17, P = 0.018), comparing to patients with normal hemoglobin, after adjusting for covariates. Moreover, the association with DSS remained unchanged regardless of smoking status and clinical stage, whereas it was limited in the subgroups of above 45 years, male sex, and BMI <25 kg/m(2). With restriction to midtreatment anemic patients, pretreatment anemia was still strongly correlated with inferior DSS and DMFS. This study, in the largest reported cohort, is the first to show the adverse prognostic impact of pretreatment anemia on DSS and DMFS in NPC.

Prognostic impact of cigarette smoking on the survival of patients with established nasopharyngeal carcinoma

BACKGROUND

Cigarette smoking is associated with the etiology of nasopharyngeal carcinoma; however, the influence of smoking on survival in patients with established nasopharyngeal carcinoma remains unknown.

METHODS

We retrospectively analyzed 1,849 patients with nasopharyngeal carcinoma who were categorized as never, former, and current smokers. Cumulative effect of smoking was defined in terms of pack-years. Associations between cigarette exposure and survival were estimated by Cox proportional hazards model.

RESULTS

The risks of death, progression, locoregional relapse, and distant metastasis were significantly higher for former and current smokers (all P ≤ 0.002) than never smokers. Heavy smokers with high pack-years had HRs for death of 3.31 [95% confidence interval (CI), 2.58-4.26; P < 0.001], for progression of 2.53 (95% CI, 2.03-3.16; P < 0.001), and for distant metastasis of 2.65 (95% CI, 1.89-3.70; P < 0.001). Specifically, in the cohort of 495 patients treated with intensity-modulated radiotherapy/three-dimensional conformal radiotherapy, we obtained similarly significant results. All of the survival outcomes remained significant in multivariate analyses.

CONCLUSIONS

Pretreatment cigarette smoking is an independent, poor prognostic factor for patients with nasopharyngeal carcinoma, which is associated with increased risk of death, progression, locoregional relapse, and distant metastasis, with the risk increasing with pack-years.

IMPACT

It is clear that cigarette smoking not only promotes carcinogenesis in the normal nasopharyngeal epithelium, but also affects the survival of patients with nasopharyngeal carcinoma.

Tobacco smoking and increased risk of death and progression for patients with p16-positive and p16-negative oropharyngeal cancer

PURPOSE

Tobacco smoking is associated with oropharynx cancer survival, but to what extent cancer progression or death increases with increasing tobacco exposure is unknown.

PATIENTS AND METHODS

Patients with oropharynx cancer enrolled onto a phase III trial of radiotherapy from 1991 to 1997 (Radiation Therapy Oncology Group [RTOG] 9003) or of chemoradiotherapy from 2002 to 2005 (RTOG 0129) were evaluated for tumor human papillomavirus status by a surrogate, p16 immunohistochemistry, and for tobacco exposure by a standardized questionnaire. Associations between tobacco exposure and overall survival (OS) and progression-free survival (PFS) were estimated by Cox proportional hazards models.

RESULTS

Prevalence of p16-positive cancer was 39.5% among patients in RTOG 9003 and 68.0% in RTOG 0129. Median pack-years of tobacco smoking were lower among p16-positive than p16-negative patients in both trials (RTOG 9003: 29 v 45.9 pack-years; P = .02; RTOG 0129: 10 v 40 pack-years; P < .001). After adjustment for p16 and other factors, risk of progression (PFS) or death (OS) increased by 1% per pack-year (for both, hazard ratio [HR], 1.01; 95% CI, 1.00 to 1.01; P = .002) or 2% per year of smoking (for both, HR, 1.02; 95% CI, 1.01 to 1.03; P < .001) in both trials. In RTOG 9003, risk of death doubled (HR, 2.19; 95% CI, 1.46 to 3.28) among those who smoked during radiotherapy after accounting for pack-years and other factors, and risk of second primary tumors increased by 1.5% per pack-year (HR, 1.015; 95% CI, 1.005 to 1.026).

CONCLUSION

Risk of oropharyngeal cancer progression and death increases directly as a function of tobacco exposure at diagnosis and during therapy and is independent of tumor p16 status and treatment.

Importance of hemoglobin concentration and its modification for the outcome of head and neck cancer patients treated with radiotherapy

INTRODUCTION

Hypoxia induced radioresistance has been acknowledged for decades. One of the indirect evidences of the influence of hypoxia on radiation response comes from the observations of a correlation between tumor control and hemoglobin level. This review examines the clinical data on the prognostic and predictive role of hemoglobin level and hemoglobin manipulation in radiotherapy of squamous cell carcinomas of the head and neck, a tumor type where hypoxic radioresistance have been previously documented.

THE INFLUENCE OF HEMOGLOBIN CONCENTRATION ON TUMOR OXYGENATION AND OUTCOME

The aim is to evaluate the existing literature for information of the influence of hemoglobin concentration and hemoglobin modifications on tumor oxygenation and outcome in head and neck squamous cell cancer patients. The data from several randomized trials show that while most studies have confirmed the prognostic value of hemoglobin, increasing the hemoglobin level through transfusion or erythropoietin stimulation did not result in improved outcome for patients with low initial hemoglobin levels. Clinical studies showed that smoking reduced the oxygen carrying capacity of the blood through formation of carboxyhemoglobin, and lead to poorer response to radiotherapy in smokers compared to non-smokers. Smoking also increased the risk of the development of secondary cancers.

CONCLUSION AND FUTURE PERSPECTIVES

In conclusion, low hemoglobin is a significant negative prognostic factor for radiotherapy of head and neck cancer. Correction of pre-treatment low hemoglobin by blood transfusion and/or erythropoietin stimulating agents does, however, not improve the outcome. Smoking leads to a decrease in effective hemoglobin and poorer treatment outcome. Smoking should be avoided in order to improve the therapeutic efficacy of radiotherapy and development of other smoking-related diseases and/or secondary cancers.

Effect of smoking on oxygen delivery and outcome in patients treated with radiotherapy for head and neck squamous cell carcinoma--a prospective study

BACKGROUND

Head and neck cancer patients with high hemoglobin respond better to irradiation compared to patients with low hemoglobin possibly due to hypoxia induced radioresistance. The hemoglobin level is, however, a crude indicator of the amount of oxygen available to the tissue and may be influenced by a number of factors, smoking being of potential importance. The aim of the present study was to examine the effect of smoking on available oxygen to tumors and the effect on outcome in head and neck cancer patients treated with radiotherapy in a prospective study.

MATERIALS AND METHODS

A total of 232 consecutive patients with squamous cell carcinoma of the larynx, pharynx and oral cavity completed questionnaires on smoking habits prior to treatment. Venous blood samples were collected before and/or during treatment to determine the hemoglobin and carboxyhemoglobin level. Patients were treated with primary curative radiotherapy 62-68 Gy, 2 Gy/fx, 5 fx/week.

RESULTS

All but 12 patients had a history of smoking, 35 were long term quitters, 23 recent quitters, 54 moderate smokers and 108 heavy smokers (>1 pack/day). There was no relationship between total hemoglobin and carboxyhemoglobin, but effective hemoglobin and carboxyhemoglobin were linearly correlated. The amount of carboxyhemoglobin increased with increasing smoking status. Actuarial 5-year univariate analysis showed that heavy smokers had a significantly reduced probability of loco-regional control (44% vs. 65%, p = 0.001), disease-specific (56% vs. 77%, p = 0.003) and overall survival (39% vs. 66%, p = 0.0004) compared to non-smoking patients. Multivariate analyses showed that patients characterized as non-smokers, with low T and N classifications and high hemoglobin level had the best outcome measurements. A rise in carboxyhemoglobin significantly decreased the probability of loco-regional control and each additional pack year increased the risk of death. Smokers and former smokers develop secondary cancers.

CONCLUSION

The study showed a significant negative impact of smoking during radiotherapy for head and neck cancer and the risk of death was increased with each additional pack year of smoking. The effect on loco-regional control could be explained by a rise in carboxyhemoglobin level in smokers, e.g. a reduced oxygen supply to tumors. The data strongly advocate that smoking should be avoided in order to improve the therapeutic efficacy of radiotherapy and development of other smoking-related diseases and/or secondary cancers.

The effect of smoking on outcome following external radiation for localized prostate cancer

PURPOSE

We investigated whether a smoking habit affects biochemical and survival outcome after curative external beam radiation therapy (EBRT) for localized prostate cancer.

MATERIALS AND METHODS

The study population comprised 601 men treated with curative EBRT between 1994 and 1997 who had a smoking history available. Pretreatment prognostic factors were examined and high risk was defined as any of prostate specific antigen greater than 20, Gleason greater than 7 or stages T3-4. Biochemical outcome (bNED) was assessed by American Society for Therapeutic Radiology and Oncology, and Houston criteria. Biochemical, clinical, prostate cancer and nonprostate cancer death rates were examined by univariate and multivariate statistics.

RESULTS

Of the men 15% were current smokers, 55% were former smokers and 31% were nonsmokers. Current smokers were younger than former smokers or nonsmokers by a mean of 2.5 years (p <0.001). Current smokers had higher risk cancers than former smokers or nonsmokers (high risk 60%, 40% and 43%, respectively, p = 0.017). Five-year bNED rates for smokers were significantly worse than for former smokers or nonsmokers (55%, 69% and 73%, p = 0.01 and 0.0019, respectively). Median followup was 59 months. Multivariate analysis confirmed smoking as an independent adverse factor for bNED (p = 0.013) even when controlling for prostate specific antigen (p <0.0001), Gleason score (p <0.0001), stage (not significant), radiation dose (not significant) and neoadjuvant hormone use (p = 0.0014). Local and metastatic failure did not differ among the groups. Prostate cancer specific mortality was nonsignificantly worse in smokers but overall mortality was much greater.

CONCLUSIONS

Smokers present with higher risk prostate cancers. Outcomes following EBRT are poorer, even when accounting for differences in known pretreatment factors.

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

AIM

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.

METHODS

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).

RESULTS

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.

CONCLUSIONS

There was no significant association between smoking and tumour hypoxia, treatment response or survival in this study of patients with cervix cancer.

Response of hepatoma 9618a and normal liver to host carbogen and carbon monoxide breathing

The effects of hyperoxia (induced by host carbogen [95% oxygen/5% carbon dioxide breathing] and hypoxia (induced by host carbon monoxide [CO at 660 ppm] breathing) were compared by using noninvasive magnetic resonance (MR) methods to gain simultaneous information on blood flow/oxygenation and the bioenergetic status of rat Morris H9618a hepatomas. Both carbogen and CO breathing induced a 1.5- to 2-fold increase in signal intensity in blood oxygenation level dependent (BOLD) MR images. This was due to a decrease in deoxyhemoglobin (deoxyHb), which acts as an endogenous contrast agent, caused either by formation of oxyhemoglobin in the case of carbogen breathing, or carboxyhemoglobin with CO breathing. The results were confirmed by observation of similar changes in deoxyHb in arterial blood samples examined ex vivo after carbogen or CO breathing. There was no change in nucleoside triphosphates (NTP)/P(i) in either tumor or liver after CO breathing, whereas NTP/P(i) increased twofold in the hepatoma (but not in the liver) after carbogen breathing. No changes in tumor intracellular pH were seen after either treatment, whereas extracellular pH became more alkaline after CO breathing and more acid after carbogen breathing, respectively. This tumor type and the liver are unaffected by CO breathing at 660 ppm, which implies an adequate oxygen supply.

Comparison between the comet assay and the oxygen microelectrode for measurement of tumor hypoxia

BACKGROUND AND PURPOSE

Hypoxic cells are present in some solid tumours and are known to limit radiocurability. To compare two measures of tumour hypoxia, 25 patients with locally advanced disease and accessible tumours or metastatic nodes were examined using an oxygen microelectrode and the alkaline comet assay.

MEASUREMENTS AND METHODS

For the comet assay, fine needle aspirate biopsies were taken immediately following a dose of 5-10 Gy. Single cells were examined for radiation-induced DNA strand breaks, and the percentage of radio-resistant hypoxic cells within the population was calculated from DNA damage histograms. For oxygen tension (pO2) measurements, multiple tracks were made using an Eppendorf oxygen microelectrode. The possibility that application of the first method might influence hypoxic fraction measurement by the second method was examined in a more controlled system by creating four tracks in murine SCC-VII tumours using an oxygen electrode, and measuring hypoxic fraction at subsequent times.

RESULTS

For 28 tumours from 25 patients, hypoxic fraction measured by comet assay correlated with the percentage of PO2 values < 5 mmHg (r2 = 0.46, P < 0.001). The mean comet hypoxic fraction was 0.36 for five tumours with a median PO2 < 10 mmHg. For the remaining 23 tumours with a median PO2 > 10 mmHg, the mean hypoxic fraction was 0.09. Advancement of an oxygen electrode through SCCVII tumours had no significant effect on hypoxic fraction measured 5 min to 24 h later using the alkaline comet assay.

CONCLUSIONS

Tumours defined as hypoxic based on a median pO2 < 10 mmHg appear to contain more than 20% radio-biologically hypoxic cells as estimated by the comet assay. In an animal tumour model, puncture of the tumour with an oxygen electrode did not influence hypoxic fraction measured using the comet assay, in agreement with the clinical data that the order in which the two methods were performed was not important.

Detection of hypoxic cells in a C3H mouse mammary carcinoma using the comet assay

The comet assay was used to estimate radiobiological hypoxic fraction across a full range of tumour oxygenations in C3H mammary tumours implanted into the feet of female CDF1 mice. Tumours were either clamped before irradiation or mice were allowed to breath air, 100% oxygen, carbogen or carbon monoxide for 5-35 min before and during exposure to 15 Gy. For the alkaline comet assay, tumours were excised after irradiation and individual tumour cells were analysed for DNA single-strand breaks. Hypoxic cells were defined as those cells with approximately three times fewer single-strand breaks than aerobic cells. Radiobiological hypoxic fraction was calculated by fitting DNA damage histograms to two normal distributions, representing the response of the aerobic and hypoxic populations. The percentage of hypoxic cells estimated using the comet assay was then compared with hypoxic fraction measured using a clamped tumour control assay. Carbogen and oxygen breathing reduced the normal hypoxic fraction from 14% to 2-3% in this tumour, whereas 75-660 p.p.m. carbon monoxide progressively increased the hypoxic fraction from 18% to 82%. The slope of the line comparing the two methods was 1.23 with 95% confidence limits of 1.12-1.33 (r2 = 0.994). In the SCCVII squamous cell carcinoma growing subcutaneously in C3H mice, a similar correlation was observed between hypoxic fraction measured using the comet assay and hypoxic fraction measured in the same tumour cells using the paired survival curve assay (slope = 1.20 with 95% confidence limits of 1.03-1.37). These results confirm the ability of the comet assay to provide an accurate estimate of radiobiological hypoxic fraction over a wide range of tumour oxygenations and between two tumour types.