How Many Are Online?
How many of these millions of Internet users are persons with cancer? One crude way to estimate this number is to multiply the number of persons with cancer worldwide, which is, according to the World Cancer Report, approximately 22 million,3 by the global proportion of persons using the Internet (which is, as noted previously, approximately 10%), which would lead to an estimate of about 2.2 million persons with cancer online. However, we know that persons living with cancer are older than the general population, and in this age group Internet use is less common than in a younger population, so this might lead to an overestimate. On the other hand, cancer is more prevalent in the developed world, where people generally have better Internet access, so that taking the global proportion of Internet users of 10% might lead to an underestimate.
A more accurate way may be to focus our discussion on the industrialized world. We can estimate the proportion of persons with cancer who are using the Internet in the industrialized world based on published surveys among persons with cancer, and multiply this by the number of persons with cancer in the developed world. I conducted a systematic review of all studies containing data on the proportion of persons with cancer who are using the Internet (see the appendix for the search strategy).
The Table 1 is a compilation of the 24 identified surveys that contain data on the proportion of persons with cancer who are Internet users.4–27 Taken together, these studies surveyed 8,697 persons with cancer. The average proportion of Internet users is 39%. Interestingly, this figure corresponds well with what oncologists estimate when asked what proportion of their patients use the Internet: 30%.11 If we assume that the developed world contains approximately 6 million persons living with cancer, and if we further believe that about 39% of them are online, this would translate into approximately 2.3 million persons with cancer online, an estimate that is not far from our first figure.
Table TABLE 1. Published Survey Data About the Proportions of Internet Users Among Persons With Cancer
|Chen and Siu,4 2001||Canada||2000||50||Ambulatory cancer patients using the Internet||Major cancer hospital||191||NR|
| || || ||(7)||Ambulatory cancer patients citing the Internet as primary information source|| || || |
|Jadad, et al.5 2001||Canada||1998||47||Cancer patients reporting regular use of Internet||Regional Cancer Centre||1001||74|
| || ||1999||51|| || ||496||71|
| || ||2000||51|| || ||501||71|
|Fogel, et al.6 2002||USA||2000||42||Breast cancer patients using the Internet||University hospital||188||74.9|
|Pereira, et al.7 2000||Canada||1999||43||Breast cancer patients having looked for cancer-related information||Cancer care center||107||15|
|Ranson, et al.8 2003||USA||2001/2002||44||Cancer patients (mainly breast cancer) using the Internet||Nearly 100 Community Clinical Oncology Program Facilities||925||91|
|Norum, et al.9 2001||Norway||2001||36||Cancer patients using the Internet||University Hospital (outpatients)||31||NR|
|Norum, et al.10 2003||Norway||2001/2002||33||Cancer patients having searched for medial information to the Internet||University Hospital (outpatients)||127||NR|
|Helft, et al.11 2003||USA||2001||(30)||Median of oncologists estimates on “what percentage of your patients obtain information about cancer from the Internet”||Members of ASCO||266||46.2|
|Mills and Davidson,12 2002||Ireland||NR||10||Colorectal, lung, breast, prostate, gynecological, or gastric cancer patients having used the Internet||NR||430||NR|
|Carlsson,13 2000||Sweden||NR||35||Cancer patients having access to the Internet||University Hospital||142||74|
| || || ||(6)||Cancer patients having used the Internet as information source|| || || |
|Satterlund, et al.14 2003||USA||1999–2002||49||Breast cancer patients 3 months after diagnosis, using the Internet to gather any information about their disease.||Regional Cancer Centre, in context of clinical trial||224||77|
| || || ||40||Breast cancer patients 16 months after diagnosis, using the Internet to gather any information about their disease.|| ||217|| |
|Diefenbach, et al.15 2002||USA||NR||45||Early-stage prostate cancer patients having used the Internet as information source||Cancer Center||654||72|
| || || ||(7)||Prostate cancer patients reporting Internet as most important reason for making specific treatment decision|| || || |
|Smith, et al.16* 2003||USA||NR||(32)||Prostate cancer patients using the Internet||Radiation Oncology Centres—Total||295||99|
| || || ||48|| || Academic centre||171|| |
| || || ||8|| || VA Hospital||104|| |
| || || ||20|| ||Community hospital||20|| |
|Brotherton, et al.17 2002||Australia||1999||33||Oncology patients having accessed Internet for information related to their illness personally or through proxy||Teaching hospitals||142||59|
| || ||2001|| || || ||153||NR|
| || ||2001||46||to their illness, personally or through proxy|| ||153||NR|
|Raupach and Hiller,18 2002||Australia||1999||4||Breast cancer patients who received information within the previous 6 months via the Internet||Major tertiary hospital||217||82|
|Peterson and Fretz,19 2003||USA||NR||16||Thoracic oncology patients seeking information on the Internet||Cancer Centre, thoracic oncology clinic||139||76|
|Metz, et al.20 2003*||USA||NR||(29)||Cancer patients (mainly prostate, lung, and breast cancer) using the Internet to find cancer-related information—total||Radiation Oncology Centres—total||921||99|
| || || ||42|| || Academic centre||436|| |
| || || ||5|| || VA Hospital||201|| |
| || || ||25|| ||Community hospital||284|| |
|Yakren, et al.21 2001||USA||NR||44||Cancer patients using the Internet to obtain cancer-related information||Cancer Center||223||71|
|Vordermark, et al.22 2000||Germany||2000||12||Radiation oncology patients using the Internet directly||University Hospital||139||95|
| || || ||(15)||Radiation oncology patients using the Internet indirectly|| || || |
|Hellawell, et al.23 2000||UK||NR||24||Prostate cancer patients using the Internet||Prostate Cancer Clinic||143||73|
|Pautler, et al.24 2001||Canada||1999||35||Prostate cancer patients having used the Internet||Mailed questionnaire||335||68|
| || || ||(29)||Prostate cancer patients having used the Internet to obtain information about p.c.|| || || |
|Fleisher, et al.25 2002||USA||2000–2002||44||Cancer patients being “direct” users of the Internet||Cancer Information Service callers||357||87|
| || || ||(21)||Cancer patients being “indirect” users (via proxy) of the Internet|| || || |
|Monnier, et al.26 2002||USA||NR||58||Cancer patients having used the Internet||Cancer centre clinics||319||NR|
| || || ||(80)||Cancer patients reporting that family members had used the Internet|| || || |
|Duffy, et al.27 2000||Australia||1998||32||Oncology patients seeking information from the Internet about the diagnosis and management||Radiotherapy Clinic||169||97|
The Table 1 also shows that the proportions across studies vary considerably, ranging from 4% to 58%. This partly reflects that these surveys were conducted in different countries over different periods in time. Another reason for the variability is that no standard operational definition of an “Internet user” exists, and different studies may have measured different things. Some surveys frame their question as “Do you have access to the Internet,” others ask “Do you use the Internet,” “Do you use the Internet regularly,” “Do you use the Internet for cancer information,” or “Which of the following information sources are your primary source of information.” How different questions may lead to different answers can be seen in one study, in which 35% of patients said they had access to the Internet, but only 6% said that they had sought cancer information on the Internet.13
A further reason for the heterogeneity of results across surveys is that “cancer is not cancer,” and significant differences in Internet use according to diagnosis exist. In one study, in which different groups of persons with cancer were surveyed using the same instrument, highly significant differences in utilization of the Internet by diagnosis were observed: 16% of lung patients, 18% of head-and-neck patients, 27% of prostate patients, 34% of breast patients, and 45% of gynecologic patients reported using the Internet to obtain cancer-related information.20 This partly reflects demographic differences between the cancer types: We know from many studies that women are more active health seekers than men,28,29 and that younger age7,9,10,12,14,16,20,21,24 is also associated with greater Internet use. Therefore, age and sex are confounders when comparing Internet use, and it is unclear whether differences between diagnostic groups are mainly a result of demographic differences or whether they remain significant when adjusted for patient age and sex.
In addition, well-known socioeconomic predictors for Internet use or nonuse, that is, factors contributing to the “digital divide,”30,31 also cut across the population of persons with cancer: those using the Internet are mostly better educated6,7,14,19,21,24 and have a higher income6,14,19 than nonusers, and they are more likely white.6,16 Metz, et al.20 and Smith, et al.16 found very large differences in Internet use between a cancer patient population from an academic center (48%) and a VA hospital (8%), which again might be due to differences in socioeconomic status between the hospital populations.
What Is the Role of the Internet as an Information Source for Patients Compared With Other Media?
Although in some studies the Internet is cited as the second most important source for cancer information after health professionals,14,19 it may play a somewhat less important role when it comes to making important treatment decisions in cancer: When asked for the most important factor influencing their treatment decision, men with prostate cancer indicated that physician recommendation (51%), advice from friends and family (19%), and information obtained from books and journals (18%) were more often the most important source, with the Internet cited by only 7%.15
Still, for those who use the Internet, information found there certainly influences their decisions, and patients are highly satisfied with the Internet as an information source compared with other media. Raupach and Hiller18 report that persons with breast cancer were mostly satisfied with information from the Internet (89%), with lower proportions of patients satisfied with that from television (46%), newspapers (52%), magazines (58%), and radio (60%).
It is also interesting to note that, according to one longitudinal study of persons with breast cancer, the Internet remains an important source of information years after diagnosis, whereas other sources of information such as health professionals or books quickly become less important after the initial phase of diagnosis.14 It is likely that the ongoing social support provided by Internet communities and the ability to keep up-to-date with recent medical news accounts for this.
What About Internet Access of Family Members?
In addition to the estimated 2.3 million persons with cancer online, an unknown number of friends and relatives of these patients use the Web. Yakren, et al.21 report that 60% of patient companions used the Internet. An often-neglected phenomenon is that many persons with cancer may not actually use the Internet themselves (“direct users”), but rather use their companions (eg, husband or wife, children, or friends) to search and retrieve information or to communicate through e-mail (“indirect users”). It can be estimated that 15%22 to 20%25 of persons living with cancer are indirect users. With time, indirect users often become direct users.25
What Do These Statistics Not Tell Us?
Approximately 39% of persons with cancer use the Internet directly, and an additional 15% to 20% use it indirectly. However, we realize that this statement may be insufficient to describe the reality, as Internet access or use is not a dichotomous variable, but in fact a quantitative and qualitative continuum.32 For direct users, conditions of access (physical accessibility at home or in a library, costs, convenience, and filters), computer literacy and search skills, as well as health literacy are factors that influence Internet use quantitatively and qualitatively. If the Internet access is indirect through proxy persons such as family and friends, the degree to which the proxy persons become active and supply information to the patient varies widely, as does the degree to which the information is preselected and filtered through the proxy. Surveys asking dichotomous questions do not capture and reflect these qualitative differences sufficiently. As Internet use becomes more and more common, new measures will have to be found to describe Internet use on meaningful ordinal or continuous scales.