Dr Camilla Hoff
Podcast: ESMO 2011 Interview with Dr Camilla Hoff on the influence of smoking in patients with squamous cell carcinoma of the head and neck
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transcript of interview with Dr Camilla Hoff
Podcast ESMO 2011: Interview with Dr Camilla Hoff on a study evaluating the influence of smoking on effective hemoglobin and outcome in patients with squamous cell carcinoma of the head and neck
EJCMO.tv: Hello and welcome to EJCMO.tv. I have with me Dr. Camilla Hoff of the Department of Experimental and Clinical Oncology at Aarhus University Hospital. Dr. Hoff, thank you for taking the time to speak to us today.
Dr. Camilla Hoff: No problem.
EJCMO.tv: Dr. Hoff, firstly do tell our listeners briefly about your background and your research interests.
Dr. Camilla Hoff: I am currently a PhD at the Department of Experimental and Clinical Oncology and I have been working with the importance of hemoglobin level for the outcome of head and neck cancer patients treated with radiotherapy.
EJCMO.tv: Thank you. You recently gave an important presentation at ESMO this year that discussed the result of a study conducted by your group. The study evaluated the influence of smoking on effective hemoglobin and outcome in patients with squamous cell carcinoma of the head and neck. Can you tell us a little bit more about this particular study.
Dr. Camilla Hoff: Yes, I would love to. We know that head and neck cancer patients with high hemoglobin respond better to irradiation compared to patients with low hemoglobin levels, possibly due to hypoxia-induced radio resistance. 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, and smoking could be one of these factors. So, the aim of the study was to examine the effect of smoking on available oxygen to tumors and the effect of outcome in head and neck cancers treated with radiotherapy in the prospective study.
EJCMO.tv: How was the study designed?
Dr. Camilla Hoff: The study was designed as a prospective study and a total of 232 patients with squamous cell carcinoma of the larynx, pharynx, and oral cavity completed questionnaires on smoking habits prior to treatment. We then collected venous blood samples before and during radiotherapy treatment to determine hemoglobin levels and carboxyhemoglobin levels, and then patients were treated with primary curative radiotherapy.
EJCMO.tv: What were the results of the study?
Dr. Camilla Hoff: We started by looking at the 232 patients we included; we saw that only 12 patients were never smokers, 15% quit smoking for more than a year and were grouped as long-term quitters. Then we had 10% who were recent quitters, and together these patients form the non-current smokers in the study. We then had moderate smokers who were smoking less than 20 cigarettes being equivalent to 1 pack per day and at least we had almost half of the patients who were heavy smokers and again were defined as smoking more than 1 pack a day.
EJCMO.tv: What impact did the hemoglobin level have on response to radiation in this patient group?
Dr. Camilla Hoff: We grouped the patients in a high- and a low-hemoglobin group with females who had less than 13 g/dl and males with more than 14.5 g/dl, and then we showed that hemoglobin was an advantage for all outcome measurements for local–regional control and disease-specific and overall survival.
EJCMO.tv: Did your research help advance any theories as to the case of the poor response to radiation when hemoglobin levels are low?
Dr. Camilla Hoff: Smoking causes an increase in carboxyhemoglobin level. So, the effect of smoking was measured at this level. We did not see a correlation between the level of carboxyhemoglobin in the total hemoglobin but we did see a decrease in the amount of effecting hemoglobin with increasing carboxyhemoglobin levels, and in the multi-variate analysis we saw that carboxyhemoglobin level was significant for local–regional control probably due to the fact that this causes low oxygen content in the tumor. If we look at the patient and the carboxyhemoglobin levels, we saw a clear difference between the former and current smokers and their levels, and we saw that smokers had a significantly poor outcome compared to nonsmokers in the local–regional control, i.e., a ratio of 1.84, and overall survival, i.e., a ratio of 2.01. We also looked at the smokers in a moderate- and a heavy-smoking group where we saw a difference between these two groups in both local–regional control and overall survival at 5 years as well. This difference disappeared when we examined 10-year outcome measurement difference between the moderate- and the heavy-smoking groups.
EJCMO.tv: In this study, what impact did smoking have on hemoglobin level?
Dr. Camilla Hoff: As we just talked about, smoking causes an increase in carboxyhemoglobin and this correlates with low effective hemoglobin. So, we expect that smoking causes less oxygen to the tumor.
EJCMO.tv: So, it would be correct to say that hemoglobin level impacted on the clinical outcome?
Dr. Camilla Hoff: Yes, a high hemoglobin level was an advantage for all outcome measurements both local–regional control and disease-specific and overall survival.
EJCMO.tv: Did your study strengthen the case of initial hemoglobin levels as a prognostic marker for outcome in advanced head and neck cancer?
Dr. Camilla Hoff: We showed that hemoglobin level was a prognostic marker, that apart from advising the patients to quit smoking, we do not show in this study how to deal with a low hemoglobin level.
EJCMO.tv: Dr. Hoff, how do you see your research results potentially guiding clinical practice?
Dr. Camilla Hoff: We saw that smoking increases the amount of carboxyhemoglobin in the blood and reduces the amount of effective hemoglobin. We saw that smokers had a significantly poor outcome than nonsmokers, and we saw that the increased carboxyhemoglobin level reduces local tumor control. We also saw that each additional pack year actually increases the risk of death and that smokers and former smokers develop secondary cancers, and many of these are tobacco-induced cancers. So, we would advise patients with head and neck cancers and then probably all of the smokers to strongly quit smoking permanently.
EJCMO.tv: A very sound advice there. Dr. Hoff, thank you so much for talking to us today.
Dr. Camilla Hoff: You are welcome.
