If the toxicity of cannabis associated with the risk of lung cancer has long been underestimated, recent works question this “false safety”. A population of young patients with significant consumption with aggressive cancers has recently been identified.
The Dre Pauline Pradèrepulmonologist at Marie Lannelongue Hospital (92), which led several studies on the subject, took stock of this question during the ALBATROS addictology congress[1].
Consumption in inhaled form
“France has the sad record to be a champion of cannabis consumption in Europe,” said the speaker right away. In 2019, it was estimated that at 17 years old out of 5 had already consumed at least once in the month of cannabis – consumption, which in our country is mainly in the form of the form of cannabis resin seal, often mixed with tobacco. Faced with such high consumption which tends to increase, knowing precisely the impact of cannabis on human health is very important.
But if, most studies relate to neuropsychic effects -which are in the foreground -the pulmonologist stressed that it is a question here of a substance which is consumed in inhaled form with combustion ”.
This therefore implies the existence of pulmonary effects – which are debated. Why this blindness concerning the harmful impact on the lung? “Because they are, in my opinion, undeled or poorly studied” considered the speaker, before developing his argument-supporting studies.
Cannabis and bronchial cancer: debated effects
And quote a renowned publication in pulmonology, Chest, Who, In 2018, explained, on the basis of a meta-analysis “that smoking cannabis does not induce emphysema or alteration of the inspiratory function”. If the authors admit to find pre-cancerous lesions when making bronchial biopsies in cannabis smoking patients, however the link with the lung is not or little mentioned.
“Another meta analysis published the same year is often used to” innocent “cannabis consumption, but the conclusions of this analysis, in reality, are that it is not possible to conclude because there is not enough studies in this student meta-analysis specifically the consumption of cannabis, is annoyed by Dre Pradère. If we observe an increase in the risk of testicular tumors, it is impossible to conclude on the lung ”.
And also, a recent review published in the New England Journal of Medicine Who also looks at the chronic effects of cannabis, is interested in neuropsychic effects but makes no mention of the lung, adds the pulmonologist. Without forgetting, those which focus on the useful properties of cannabis in cancer, such as management of cancer symptoms, pain related to treatment, or even any antitumoral properties of cannabis with this article with a readily provocative title “Can cannabis cure cancer?” ».
A link between cannabis and bronchial cancer: the arguments
And yet, there are several arguments that argue for a harmful role in chronic inhalation of cannabis. The first is simply the toxicological argument. “In a grass joint-even by removing the question of resin and the question of tobacco co-association-there are carcinogens in significant quantities” explains the speaker. The second argument – that asthmatics will have noticed – is that THC has a bronchodilator effect. It therefore probably leads to a deeper inhalation of carcinogenic compounds compared to the tobacco cigarette.
The pulmonologist also evokes histological arguments. “In a study, where bronchial biopsies were carried out in chronic cannabis smoking patients, pre -tumor lesions were observed which were similar to those observed in smokers of tobacco.”
And finally, there is the epidemiological argument, “even if, once again, there are few studies, because there are few researchers who have thought of carrying out a specific interrogation on cannabis”. For example, a Canadian study has shown that cannabis consumption, declared at 20, has an impact on the subsequent occurrence of lung cancer. A consumption of more than 50 adolescence joints induced a risk more than doubled with bronchial cancer.
We realized that 4 out of 10 patients among our young patients with lung cancer were chronic cannabis consumers
Why such a discrepancy?
To explain that meta-analyzes are so reassuring, the pulmonologist evokes the difficulty that there is in studying the link between chronic cannabis consumption and lung cancer. It cites several reasons: the fact that the majority of patients who consume cannabis smoke tobacco at the same time and, in France, “a context of illegality which makes that often products added in cannabis resin, which complicates the carrying out of really serious studies”. But there is also difficulty studying the real consumption of patients, with a significant sub-declaration if the question is not asked precisely.
It was this underestimation that led the speaker to conduct research on this theme. Exeroning in a center which is very focused on lung cancer surgery and having observed, in its current practice, a very important prevalence of cannabis consumption, the Dre Pradère decided, in a first work, to resume on 3 years, in three large hospitals of Île-de-France, all the patients under 50 who had been operated for lung cancer and to remember them Their cannabis consumption.
Retrospective study of 75 patients of 50 years
“By recalling on the phone these 75 patients included over three years-without any refusal of participation on their part-we realized that 4 patients out of 10 (43%) among our young patients with lung cancer were chronic cannabis consumers,” she said.
In terms of median, they smoked 150 seals per month and, among these cannabis smokers, for six out of 10 patients (61%), no one had ever asked them of their consumption. “They had seen as a general practitioner, an anesthesiologist, a surgeon, a pulmonologist, but no one had ever asked them the question,” she said.
Cannabis smokers presented more emphysema and carcinoma of poor prognosis as carcinomas that are not very different with large cells
By comparing the three groups of patients, cannabis and tobacco smokers, tobacco smokers alone, and non-smokers, the results showed that the group of patients smoking cannabis-very important in proportion-, had more men, had smoked as much tobacco as smokers alone on declarative data, but presented more emphysema and carcinoma like carcinomas that are not very different with large cells.
“Tumors were located more often in the upper lobes, where the majority of what to inhale are concentrated. And then at the same time their surgery, their operating time, the length of hospitalization was longer, probably because the underlying lung was more damaged, “said the speaker.
Results confirmed by one study on 150 patients
From this work resulted in a multicenter and validated prospective study, supported by the Inca. This included 150 patients with primitive pulmonary cancer and an age with diagnosis under 60 years of age. “We have set up a collaboration with the toxicology department of Pr Jean-Claude Alvarez At the Garches Hospital (95) so as to obtain a precise characterization of patients, with toxicological analyzes on the hair but also a self-questionnaire which was given to the patients and which they informed anonymous outside the medical office, “explains the Pradère. The objective was to study both in the prevalence of cannabis consumption but also to understand if the lung cancer of the cannabis smoker was different from the lung cancer of the tobacco smoker.
Although the manuscript is in review, the speaker presented first results. Which confirm “the enormous prevalence of cannabis consumption in this population of young patients who suffer from this highly lethal cancer that is lung cancer, with 38 % of cannabis smokers in the study. These patients smoked 4 seals per day over a median duration of 26 years ”.
Observation of the lung state has shown that cannabis smokers more often have emphysema, and bullous emphysema which also causes an over-risk of pneumothorax. Likewise, the respiratory function showed a greater alteration in the dissemination of gases in the lung compared to smokers of tobacco even though, even though the levels of exposure to tobacco were identical. Researchers also confirmed that cannabis smoking patients were suffering from poor prognosis cancer, such as little differentiated carcinomas and sarcomatoid type carcinomas.
DRE Pradère notes that its work is part of a movement which, recently, looks more closely at the question of the potentially harmful effects of cannabis – evidenced by the last edition of the study KBP . She considers, however, that pulmonologists have not taken sufficient enough of this issue, and are not yet able to offer clear answers to patients and accompany them in cannabinic withdrawal, which is very complicated, often more complicated in practice than that of tobacco. “I think this is a subject on which we must progress in the community,” she concluded.
