Cancer rates significantly higher in gay men, but study lacked data on HIV

Cancer rates are almost twice as high in gay men than the male heterosexual population, US researchers report in the online edition of the journal Cancer.

The study also showed that bisexual women had elevated rates of cervical cancer. Bisexual women and lesbians diagnosed with cancer were more likely to report fair or poor health than heterosexual women who had survived cancer.

Conducted in California, the study utilised data obtained from approximately 120,000 adults who participated in three household-based health surveys conducted in 2001, 2003 and 2005.

However, no information was obtained on the participants’ HIV status. The investigators acknowledge that this was a major weakness of the study.

“We did not have data available on HIV infection, which is higher among gay men, and may have contributed to the significant association of cancer prevalence and sexual orientation,” write the authors. “HIV infection has been linked with certain cancers, both AIDS-defining cancers (Kaposi sarcoma and non-Hodgkin lymphoma) and non-AIDS-defining cancers, which are anal, lung, and testicular cancer and Hodgkin lymphoma.”

Nevertheless, the investigators believe that their findings show that gay men require improved cancer screening, and that lesbians and bisexual women cancer survivors would benefit from improved support.

Investigators undertook the study because there is currently little information about sexual orientation and cancer survival and the support needs of survivors. Data collected from the California Health Interview Survey provided them with an opportunity to address these questions.

“We believe this is the first study to provide generalizable results about men and women’s cancer prevalence and cancer survivors’ self-reported health by sexual orientation,” note the researchers.

As part of the survey, participants were asked to self-identify their sexual orientation and to state if they had ever been diagnosed with cancer.

Individuals who stated that they had developed a malignancy were asked to provide more information about the diagnosis, including the type of cancer and their age at diagnosis. The investigators supplied detailed information on the prevalence and risk for six types of common cancer (melanoma, prostate, cervical, breast, uterine and colon). All other cancer diagnoses were reported together – including those associated with HIV.

Of the 71,112 women included in the study, 7252 reported that they had been diagnosed with cancer. The prevalence did not differ significantly according to sexual orientation.

However, when rates of individual cancers were analysed according to sexual orientation, the investigators found that bisexual women were significantly more likely to report cervical cancer (p < 0.001) than other groups, and that lesbian women were more likely to have been diagnosed with uterine cancer (= 0.03).

“Our findings suggest a need to target bisexual women with screening interventions to reduce prevalence of cervical cancer,” comment the authors.

A total of 3690 men (of 51,233) reported a cancer diagnosis. Rates differed according to sexual orientation and were markedly higher in gay men than either bisexual and heterosexual men (8 vs 5 vs 5% < 0.001).

Moreover, gay men were approximately ten years younger at the time of cancer diagnosis than either bisexual or heterosexual men (41 vs 50 vs 51 years, p < 0.001).

Rates of prostate cancer were significantly lower in gay men than other groups (p = 0.0009). However, both gay and bisexual men were significantly more likely than heterosexual men to have been diagnosed with an “other” form of malignancy (p = 0.04).

“The greater prevalence among gay men may be caused by a higher rate of anal cancer,” write the investigators, who also acknowledge a probable role for HIV in their findings.

The investigators then performed a series of statistical analyses. These showed that gay men had almost twice the risk if cancer compared to heterosexual men (adjusted odds ratio [AOR] = 1.932; 95% CI, 1.4-2.5, p < 0.001).

They also found that bisexual women and lesbians diagnosed with cancer were significantly more likely to report being in fair or poor health than heterosexual women (p < 0.001 and p = 0.01).

“These novel findings with respect to sexual orientation can be used to set priorities for lesbian/gay/bisexual populations with respect to cancer, and inform the need for the design of programs and services to assist cancer survival,” conclude the authors.