Bullous pemphigoid (BP) is the most common autoimmunemediated subepidermal blistering skin disease and occurs mostly in elderly persons. The association of malignant neoplasms with BP has been controversial. 1 This study compared the incidence of cancer in patients with BP with that of the ageand sex-matched general population. with BP were matched with persons in the Singapore Cancer Registry and Death Registry to identify those who had cancer and/or had died. Person-years were accrued from BP diagnosis until death, cancer diagnosis, or December 31, 2011, whichever was earliest. The expected number of cancer cases was calculated as the exposure multiplied by the incidence within each age-and sex-specific category and then summed across all categories for the period 2004-2008 in Singapore. The standardized incidence ratio was calculated as the ratio of observed to expected cancers, and 95% CIs were calculated for the standard incidence ratio based on Poisson distribution. The study was approved by the ethics committee of the National Healthcare Group, Singapore. Patient consent was waived.Results | A total of 359 patients with BP (mean age, 75.7 years; range, 27.8-100.8 years) were included ( Table 1). Of these, 48 (13.4%) had a malignant neoplasm, of which 16 preceded BP diagnosis by more than 5 years (mean, 17.1 years; range, 6.8-26.9 years). Of the 32 recent cancers, 14 occurred within 5 years preceding BP diagnosis. The remaining 18 occurred either in the same year as a BP diagnosis (n = 4) or after BP diagnosis (n = 14). These included 6 lung cancers, 5 skin cancers (nonmelanoma), 3 colorectal cancers, 2 breast cancers, 1 pancreatic cancer, and 1 prostate cancer. The mean follow-up period from BP diagnosis was 2.5 years (range, 0.2-7.4 years); the mean time from BP diagnosis to cancer diagnosis was 0.9 years (range, -1.0 to -4.2 years). The mean time from cancer diagnosis to death was 1.3 years (range, 0-7.4 years), and 7 of the 15 deaths (46.7%) that occurred during follow-up were cancer related.The expected number of incident cancer diagnoses after BP diagnosis was 14.48, with 14 cancers observed (within 4.2 years) after BP diagnosis, yielding an age-and sex-matched standard incidence ratio of 0.97 (95% CI, 0.53-1.62) ( Table 2). There was no association with malignant neoplasms, even when cancers in the concurrent year but preceding BP diagnosis or up to 5 years preceding BP diagnosis were included. No association was observed with any particular type of malignant neoplasm. While studies initially reported an association between BP and cancer, 1 subsequent studies 4,5 have refuted this association, including a recent British study.
6Although there is a possibility of increased risk of malignant neoplasm in younger patients with BP, 7 we did not find this association.Discussion | Our study found no significant increase in the incidence of cancer among patients with BP compared with those in the age-and sex-matched general population. Strengths of this study included a relatively large, welldefined cohort, ...