1. Background
Head and neck cancers represent the sixth most common cancer globally and is responsible for more than 5% of human malignancies. Head and neck cancer is a general term for epithelial malignancies of the nasal cavity, paranasal sinuses, oral cavity, larynx, and pharynx (1, 2). Several risk factors including tobacco consumption, alcohol use, and human papillomavirus infection have been recognized for head and neck cancers (3, 4). It has been demonstrated that the rate of some cancers is lower in regions with more exposure to UV light. This is believed to be due to increased production of vitamin D in these populations (5, 6). The importance of attention to vitamin D increases when it is known to affect significant medical problems such as cancers, cardiovascular diseases, and diabetes (7). The importance of attention to vitamin D increases whenever it is known to affect significant medical problems such as cancers, cardiovascular diseases, and diabetes (8-10). Vitamin D has been linked to cancer development. The antitumor properties of vitamin D were first proposed by Peller and Stephenson (11) and Apperly (12) in the 1940s when they reported a lower incidence of all other malignancies except skin cancers. This hypothesis was supported by further investigations that showed an increased prevalence of colorectal, prostate, and breast cancer among individuals with vitamin D deficiency (8, 13, 14). The majority of patients with head and neck cancer have a higher incidence of vitamin D deficiency compared to age- and sex-matched healthy controls (15). An association between low serum levels of vitamin D and a higher tumor incidence has been reported (16, 17). Additionally, the anti-tumor function of the immune system also appears to depend on an adequate supply of vitamin D (18, 19). The role of vitamin D deficiency in head and neck cancers, especially laryngeal cancer, is controversial, and few studies have investigated the association between them. It was shown that vitamin D deficiency is an independent predictor of head and neck squamous cell carcinoma mortality (20). However, another observational study found no association between head and neck cancer outcome and vitamin D level (21). Vitamin D deficiency was also not found to be a risk factor for laryngeal cancer according to a retrospective study by Arem et al. (22). Conversely, a large high-quality study revealed that a higher circulating vitamin D level associates with lower incident of larynx and hypopharynx cancer combined (23). Few studies have addressed the association between larynx malignancies and vitamin D levels in Iran. Regarding the high prevalence of vitamin D deficiency in Iran (over half of the population) (24), determining the relationship between vitamin D levels and laryngeal cancer is important since it could be a preventable risk factor for this cancer.
2. Objectives
This study aimed at evaluating the association between larynx malignancies and vitamin D levels.
3. Methods
This 1: 1 matched case-control study was performed from January 2021 to March 2022 in Ghaem and Imam Reza hospitals, Mashhad, Iran. All the participants consented to enter the study. The study protocol was approved by the Mashhad University of Medical Sciences (MUMS) ethical committee (ethical code: IR.MUMS.MEDICAL.REC.1401.186).
3.1. Participants
Participants between the ages of 35 to 85 who consented to participate in the study were included. The case group consisted of patients who had histologically confirmed laryngeal cancer. By convenience sampling, data of relevant patients who referred to the mentioned hospitals between 2021 and 2022 was gathered. The control group were selected from healthy individuals and were matched by the case group in terms of sex, age, and alcohol and cigarette consumption. Patients with immunodeficiency conditions that affect the serum vitamin D levels and those who consumed vitamin D supplements 3 months before study onset were excluded. The relevant checklist (including age, occupation, consumption of tobacco, alcohol use, etc.; history of contact with mustard gas, wood, stone, metal, and cement industry; as well as history of reflux in the individual and cancer in relatives) was completed for all case and control group members. Ten milliliters of peripheral blood were collected from each participant (centrifuged at 3000 rpm at 4°C for 10 min). All samples were stored at -80°C before measurements of circulating 25OHD concentration.
3.2. Sample Size and Statistical Analysis
Sample size was estimated based on the data reported serum level of vitamin D as 32 ± 2.7 in healthy population and 31 ± 2.5 in those with head and neck malignancies (22). Considering α = 0.05 and β = 0.2 the minimum sample size was calculated as 108 individuals in each group. Categorical and continuous variables were presented as frequency (%) and mean ± standard deviation, respectively. Chi-square test was used to compare the categorical variables between study groups. To compare the continuous measures between the two groups, independent samples T-test or Mann-Whitney test were used. Logistic regression analysis was used to determine the predictive factors of laryngeal cancer. P-values below 0.05 was considered statistically significant.
4. Results
A total of 216 participants were enrolled, of which 108 had laryngeal cancer, and 108 were healthy controls. The mean age of patients with laryngeal cancer was 58.87 ± 10.77 years and 58.75 ± 10.89 for the control group (P = 0.93). The gender distribution, social and family history were not significantly different between the study groups. None of the participants had a history of Mustard gas exposure. Occupational exposure was significantly more frequent in patients with laryngeal cancer compared to healthy controls (Table 1).
Table 1.Baseline Characteristics of Study Participants a
| Variable | Study Groups | ||
|---|---|---|---|
| Laryngeal Cancer Group (n = 108) | Control Group (n = 108) | P Value b | |
| Age (y) | 58.87 ± 10.77 | 58.75 ± 10.89 | 0.93 c |
| Gender (female) | 32 (29.6) | 36 (33.3) | 0.56 |
| Mustard gas inhalation | 0 | 0 | > 0.99 |
| Social and family history | |||
| Hookah | 69 (63.9) | 67 (62.0) | 0.78 |
| Opium | 41 (38.0) | 34 (31.5) | 0.32 |
| Naswar | 8 (7.4) | 4 (3.7) | 0.23 |
| Alcohol | 22 (20.4) | 20 (18.5) | 0.73 |
| Smoking pack/year | 13.25 ± 5.36 | 13.08 ± 5.43 | 0.81 |
| Family history of cancer | 21 (19.4) | 12 (11.1) | 0.09 |
| Underlying diseases | |||
| GERD | 68 (63.0) | 54 (50.0) | 0.06 |
| Occupation | 0.05 | ||
| Self-employee | 30 (27.8) | 42 (23.1) | |
| Unemployed | 31 (28.7) | 40 (38.9) | |
| Housekeeper | 11 (10.2) | 13 (12.0) | |
| Farmer | 20 (18.5) | 6 (5.6) | |
| Worker | 8 (7.4) | 13 (12.0) | |
| Government employee | 9 (8.3) | 8 (7.4) | |
| Occupational exposure | < 0.001 | ||
| Wood | 17 (15.7) | 4 (3.7) | |
| Stone | 2 (1.9) | 1 (0.9) | |
| Metal | 3 (2.8) | 2 (2.8) | |
| Cement | 16 (14.8) | 7 (6.5) | |
| Total | 38 (35.2) | 14 (13.0) | |
a Data are presented as mean ± standard deviation (SD) or frequency (%).
b Chi-square the was used unless otherwise stated.
c Independent sample t-test
The vitamin D level was 16.0 ± 3.6 ng/mL in the laryngeal cancer group and 25.19 ± 3.40 ng/mL in the control group (P < 0.001). Table 2 indicates the frequency of vitamin D deficiency in each study group.
Table 2.Mean Vitamin D Level and Frequency of Vitamin D Deficiency in Study Groups a
a Data are presented as mean ± SD or frequency (%).
b Independent sample t-test
c Chi-square test
Significant variable in univariate analysis were entered to the logistic regression model to find out their role in laryngeal cancer. The logistic regression analysis showed that the vitamin D level has a protective effect against laryngeal cancer (OR = 0.54, 95%CI = 0.46 to 0.63, P < 0.001) (Table 3).
Table 3.Predictors of Laryngeal Cancer Using Logistic Regression (Enter Method)
| Variables | Odds Ratio | 95% CI | P-Value |
|---|---|---|---|
| Serum level of vitamin D | 0.54 | 0.46 - 0.63 | < 0.001 |
| Wood | 1.61 | 0.33 - 7.81 | 0.55 |
| Sement | 0.40 | 0.05 - 2.93 | 0.36 |
| Reflux | 1.84 | 0.66 - 5.11 | 0.24 |
| Family history of cancer | 2.37 | 0.65 - 8.65 | 0.19 |
| Naswar | 4.32 | 0.61 - 30.59 | 0.14 |
5. Discussion
According to evidence, vitamin D is an essential regulator of calcium and bone homeostasis. Studies have shown a potential role for vitamin D in head and neck cancer. Vitamin D, as a prohormone, undergoes two-step metabolism, resulting in the production of biologically active metabolite.
During exposure to sunlight, dehydrocholesterol in the skin absorbs UV radiation and is converted to previtamin D3. The liver converts vitamin D to 25-hydroxyvitamin-D (25(OH)D), or calcifediol.
Another hydroxylation step of active vitamin D formation takes place in the kidney, to become the active form of vitamin D, 1alpha-25-dihydroxyvitamin D (1,25(OH)2D), or calcitriol. The dominant function of vitamin D in its hormonal form calcitriol and functions systemically via the vitamin D receptor, which is present in several tissues and cells. Our study showed that the vitamin D level is lower in laryngeal cancer group. The relation between head and neck cancers and vitamin D levels has been rarely studied, and the results are highly controversial. In 2021, two research groups systematically reviewed the literature on the relation between vitamin D levels and head and neck cancers. Makitie et al. (25) reviewed 13 articles. In their research and found that despite the higher prevalence of vitamin D deficiency among patients with head and neck cancer compared to the normal population, there is no evidence for a causal relationship. On the other hand, Pu et al. (26) reviewed 16 studies with a total of 81908 cases. Their meta-analysis showed that higher circulating vitamin D levels have a protective effect against head and neck cancers (OR (95% CI): 0.68 (0.59 to 0.78)). In a study by Anand et al. (27), vitamin D scores were significantly lower in patients with oral neoplasms compared to healthy controls. Besides, vitamin D supplementation markedly decreased the therapy-related toxicities, therefore decreasing morbidity and improving quality of life in patients with oral neoplasms. One study showed that 25(OH)D supplements improved the immune function of patients with head and neck cancer by temporarily decreasing the number of CD34-positive cells and enhancing the number of IL-12 and IFN-γ-neurotransmitters (28). In one study, giving 1,25(OH)2D treatment before surgery in head and neck squamous cell carcinoma patients rises the plasma levels of both type 1 and type 2 T helper cell system mediators. 1,25(OH)2D also enhanced the levels of the tumorigenic and angiogenic mediators IL-8 and VEGF in plasma, but not in cancerous tissue (18). Several factors may explain the discrepancy in the literature. Firstly, not all the populations have similar baseline vitamin D level. Vitamin D is higher in most developed countries compared to developing countries, which highlights the importance of conducting multicenter studies. Secondly, while some studies have included a mixture of smokers and non-smokers in the final analysis (14), most studies, including our investigation, solely evaluated the smoking subjects (14). This study had some limitations; changes in diet and exposure to sunlight during the study were not investigated. Also, the participant’s history of alcohol consumption and smoking, as well as exposure to carcinogenic substances were not assessed. Moreover, a larger sample size would have been preferable.
5.1. Conclusions
A lower vitamin D level may be associated with laryngeal cancer. However, the potential role of vitamin D deficiency as a risk factor for head and neck cancers and whether addressing this deficiency could prevent the incidence of such cancers requires further investigation in the future.
