In this descriptive study, we found an upward trend in the rate of malignant brain tumors in the Fars province which is located in south part of Iran between 2001 and 2016. The most common types of such tumors were unspecified glioma, Astrocytoma and Glioblastoma. This finding is compatible with the previous reports in Iran (19, 20). In term of incidence rate trend, Araghi et al have reported a stabilization in the trends after 2008 (9); in our study in the most subgroups based on the histopathological features, it shows such a stabilization. However, an upward trend was found in malignant subgroups such as Glioblastoma and anaplastic astrocytoma. Yet, the difference between our study and Araghi et al. study is the duration of our study. They reported data from 2004 to 2013 while we are reporting data from 2001 to 2016 which may affect the reliability of our data. However, the geographical location for the studies has also been reported as an important factor in recent studies both from Iran and worldwide (21) which could affect the result of each study. Besides, an important result of our study showed a dramatic increase in the TGR of malignant brain tumors in age group less than 20 years (a 100% increase in TGR), in addition to a considerable increase in TGR of Glioblastoma which showed a +306.7 percent increase during these years. Additionally, in those aged between 30 and 59 years of age, the IR of the most important primary malignant brain tumors showed the highest level which is not reported before in Iran. On the other hand, in a recent study published by Salimi et al in 2020, they also have reported an increasing trend of overall CNS tumors (21). However they have reported of all kind of the CNS tumors while we are reporting of just the malignant brain tumors. The stabilization in the incidence trend of malignant tumors are reported in different studies in Europe, although they reported an increase in incidence rate of overall benign tumors but malignant glioma of brain remained in a plateau (13,23). Such important results need to be accurately followed in the future to fully understand whether an outbreak of malignant brain tumors is happening in special group of people in the Iranian society or not.
There are several reports of trends in brain tumors incidence worldwide both in adults and children (10, 11, 13-17, 22, 23). Some of these studies have reported a stable increase rate with no departure from linearity (13). On the other hand, some has reported an increase in annual incidence rate of benign tumors only and has reported the malignant ones stable (23). In our study, we found a quite upward trend in malignant brain tumors incidence rate such as Glioblastoma, Oligodendroglioma, Astrocytoma (2001 to 2010) and a stability in some other tumors such as Ependymoma. On the other hand, the same study (13) has reported an increase in only those older than 80 years of age. While in our study, we found the highest incidence rate in those aged between 30 to 59 years. In term of TGR, on the other hand, almost all the age groups showed an increase during the entire sixteen years of which the least TGR was found in those with 20 to 30 years of age. Additionally, there are reports consistent with our findings regarding an increase in the burden of primary CNS tumors for a period of 60 years but a steady rate of that from early 2010 (14). Although we are reporting the primary malignant brain tumors only, while they have reported the overall CNS tumors and also benign brain tumors such as meningioma.
Regarding the reason why such increase in trends and incidence rates of the tumors have occurred, some research suggest the advances in diagnosis and risk factor augmentation (15, 21). We believe that since at least 20 years ago, Computed Tomography which is quite capable of diagnosing brain tumors has been always available at our center, Shiraz University of Medical Sciences as the referral center for the southwest part of the Iran; so, that could not be the reason underlying the upward trend of such tumors. On the other hand, risk factor which have been suggested as the underlying etiology of these tumors such as environmental factors including radiation, in addition to genetics, would be the main reason which needs more investigation as more studies are reporting the importance of the genetic factors related to the incidence of the brain tumors (4, 24-26).
It is important to be mentioned that, in this study we have reported the malignant brain tumors only and we have investigate the incidence rate and trend of such tumors. Investigating all the brain tumors including benign ones such as meningioma and also all the brain tumors such as metastatic in addition to primary ones may lead to a report different from what we are reporting which of course need of such an investigation is sensible. What we are reporting, is showing an alarm and bringing up a serious question whether an outbreak in malignant brain tumors especially glioblastoma as the most lethal one is happening or not? Additionally there are reports and evidence that non-ionizing radiofrequency radiation could lead to brain tumors such as Schwannomas and malignant gliomas (27, 28). Recently the exposure to this type of radiation has increased considering the more use of mobile phones and expansion of telecommunication towers. Also the radiofrequency radiation used to noise in TV networks should not also be forgotten. So the question is, acting as a radiofrequency non-ionizing radiation, and based on the amount of the radiation applied, could it such these noises applied to International TY networks, be a possible reason for such an increase in the brain tumors in Fars province of Iran? Another important factor is the regional environmental changes that have affected the climate in southern Iran and Iraq such as air prolusion, warming and increased use of toxins in food industry. Answering such questions needs further investigation on malignant brain tumor trends in other provenance of Iran and also in neighboring contraries. Also access to the accurate information regarding the level of these radiofrequency noises can be helpful.