Chinese Put Cancer of the Parotid Gland on Center Stage

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Chinese Put Cancer of the Parotid Gland on Center Stage

_http://www.microwavenews.com/Duan.Zhang.html_

(http://www.microwavenews.com/Duan.Zhang.html)

April 18, 2011

Chinese researchers in Beijing are seeing some of the highest rates of

cancer ever reported in any cell phone study. They have found that long-term,

heavy users have rates of malignant parotid gland tumors that are seven to

13 times higher than might otherwise be expected.

The raw data —that is, before being adjusted for other possible risk

factors like sex, age, income, smoking status and the like— point to cancer

risks that are elevated 10-fold, 20-fold, and even 30-fold, depending on the

type of tumor and how heavy cell phone use is defined (see table below). For

instance, those who had used mobile phones for over ten years had more than

ten times the rate of _epithelial parotid gland malignancies_

(http://www.cancer.gov/cancertopics/pdq/treatment/salivarygland/HealthProfession\

al/page2)

, the dominant type of cancer of parotid gland. The risk rose to 20 times

that of controls for mucoepidermoid carcinoma, the primary subtype of

parotid gland cancer. Those who used a cell phone for more than two-and-a-half

hours a day had a more than 15-to-30 fold elevated cancer risk. Previous

studies have rarely pointed to a risk that is more than double or triple the

expected rate.

These elevated risks, though based on a small number of cases —at most 15

in the highest exposure category— are statistically significant.

Importantly, Y. Duan, Haizhong Zhang and R.F. Bu at the _Chinese PLA General

Hospital_ (http://en.wikipedia.org/wiki/301_Military_Hospital) in Beijing see

**general indications** of a dose-response relationship. The _new paper_

(http://dx.doi.org/10.1016/j.ijom.2011.03.007) was posted on the Web site of

the

Journal of Oral and Maxillofacial Surgery on April 6. Zhang is the

corresponding author of the paper.

[GRAPH]

Cell Phone use and epithelial parotid gland malignancies

Table 1. Correlation between risk of epilthelial gland malignancies,

mucoepidermoid carcinoma and use of cellular phone (univariate analysis)#.

Source: _International Journal of Oral & Maxillofacial Surgery,_

(http://dx.doi.org/10.1016/j.ijom.2011.03.007) posted online on April 6, 2011

Parotid gland tumors are rare, with an incidence of 2.5-3 cases per

100,000 per year in Western countries, according to the _National Cancer

Institute_

(http://www.cancer.gov/cancertopics/pdq/treatment/salivarygland/HealthProfession\

al/page1) (the rate in China is not clear). Benign parotid gland are

_much more common_

(http://www.nlm.nih.gov/medlineplus/ency/article/001040.htm) than malignant

tumors. So far, no other group has been able to look

at the risk for malignant parotid gland tumors in such detail. The Chinese

researchers have 136 cases, enough to do a separate analysis for the 64

cases of the mucoepidermoid carcinoma subtype (these make up about 35% of all

malignant tumors of the parotid gland). Fifteen of the cases had used a

cell phone for more than 10 years; 13 of the 15 had mucoepidermoid carcinoma.

There were 747 million users of cell phones in China at the end of 2009,

according to Zhang and colleagues.

In comparison, the Israeli Interphone team, which was the first to report

a _long-term risk of parotid gland tumors_ (http://aje.oxfordjournals.org/

content/167/4/457.long) three years ago, had a total of 58 cases with

malignant tumors and only one of these had used a mobile phone for at least ten

years. The elevated risk seen by _Siegal Sadetzki_

(http://www.gertnerinst.org.il/e/epidemiology_e/cancer_e/Cancer_director_e/)

and her Israeli

coworkers was based on an excess of benign tumors. _Stefan Lönn and the

Swedish

Interphone team_ (http://aje.oxfordjournals.org/content/164/7/637.long) had

60 cases with this malignancy, and here again only one case with a

ten-year use history. _Two earlier studies_

(http://www.ncbi.nlm.nih.gov/pubmed/11964939,15258273) were unable to look at

the risk among long-term users.

Late last year, a group at Hebrew University reported _sharp increase in

the incidence of parotid gland tumors in Israel over the last 30 years_

(http://journals.lww.com/epidem/Fulltext/2011/01000/Risk_of_Parotid_Malignant_Tu\

mo

rs_in_Israel.25.aspx) . This finding lent support to Sadetzki findings (see

_ " Game Changer? " _ (http://www.microwavenews.com/#GameChanger?) ).

The new Chinese paper comes on the eve of the International Agency for

Research on Cancer's (_IARC_ (http://www.iarc.fr/) ) review of the cancer risks

associated with wireless radiation, which begins in Lyon, France, on May

24. The IARC review panel will most likely consider it as it was released

before the _April 24 cut off for new data_

(http://monographs.iarc.fr/ENG/Meetings/vol102-calldata.php) .

A number of aspects of the Chinese paper do not fit current understanding

of cell phone tumor risks. For instance, Zhang and colleagues did not see a

significant association between the location of the tumor and the

preferred side for using a cell phone (known as laterality). They warn that

this is

a reason for them not to reach a **definitive conclusion about the effect

of cellular phone usage.**

A second anomaly is that the team found that rural residents had a lower

risk than those in the city, the opposite of what Sadetzki reported. (Cell

phones tend to operate at higher power levels in the countryside where

towers are spaced further apart. This leads to higher radiation exposures and

possibly higher tumor risks.) Zhang explains that this finding may be because

rural residents in China tend to have lower incomes than urban residents

and cannot afford cell phones. In addition, the Chinese team was unable to

look at the possible different effects of digital and analog phones,

because, they explain, **most regular users did not know their cellular phone

type.**

Zhang and colleagues conclude that their study could not exclude the

possibility of recall or selection bias. They suggest that **additional

large-scale studies, especially those with a prospective design, be performed

to

reduce the sources of bias and to confirm the significance of the present

results.**

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