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Abstract Objectives To investigate if the risk of prostate cancer (PC) differs based on the order of primary PC diagnosed in first‐degree relatives (FDRs) given possibly different risk factors for PC as first primary cancer (PCa‐1) and second primary cancer (PCa‐2). Subjects and Methods In this Swedish nationwide cohort, PC diagnosis was followed for among 149,985 men with one FDR affected by PCa‐1, 10,972 with one FDR affected by PCa‐2 and 2,896,561 without any FDRs affected by cancer in a maximum of 57 years. PC patients were further followed for death due to PC since diagnosis. Relative risk (RR) of PC was estimated with Poisson regression and hazard ratio (HR) with Cox proportional hazard model. Results Compared to men without any FDRs affected by cancer, the RRs of PC in men with one FDR affected by PCa‐1 and PCa‐2 were 2.12 (95% confidence interval [CI]: 2.07–2.17) and 1.69 (1.54–1.85), respectively. The risk in men with one FDR affected by PCa‐2 was significantly lower than those with one FDR affected by PCa‐1 after additionally adjusting for family relationship (father‐son and brothers) and age at diagnosis of PC in FDR (RR PCa‐2 vs PCa‐1, 0.85, 95% CI, 0.78–0.94). PC patients with a family history of PCa‐2 were more likely to be detected at late‐stage and less likely to be diagnosed by screening, compared to those with a family history of PCa‐1. Patients whose PC was diagnosed after the diagnosis of PCa‐1 in FDRs had a better survival than those without a family history of cancer (HR, 0.88, 95% CI, 0.80–0.97), but no such association was observed among patients with a family history of PCa‐2. Conclusion Our study indicates a discrepancy between PC risks associated with a family history of PCa‐1 and PC‐2 and the reason behind it may be multifactorial.

Abstract Background Many cancers are increased in immunosuppressed patients and evidence is accumulating that immune dysfunction may be a contributing risk factor for second primary cancers (SPCs). The aim of this study was to explore the potential influence of immune mechanisms in SPC. Methods We used the Swedish Cancer Registry (1990‐2015) to select 13 male and 14 female first primary cancers (FPCs) that are known to be related to immune suppression. We assessed relative risks (RRs) for any of these as concordant (same first and second cancer) and discordant FPC‐SPC pairs. Hierarchical clustering of significant RRs was performed for cancers as FPC and SPC. Results Concordant risks for SPCs were excessive in men and women for nasal (RRs 59.3 for men and 150.6 for women), tongue/mouth (51.7 and 100.8), and lip (32.4 and 61.2) cancers. Heatmaps showed that some cancers, such as skin cancer, tongue/mouth cancers, and non‐Hodgkin lymphoma had multiple bidirectional associations as FPC and SPC. Nasal cancer and chronic lymphocytic leukemia had associations mainly as FPC while liver and kidney cancers showed most associations as SPC. Conclusions Immune dysfunction may be a plausible contributing factor for most of the associations, which calls for experimental verification.

Abstract Background Previous population‐based studies on second primary cancers (SPCs) in urothelial cancers have focused on known risk factors in bladder cancer patients without data on other urothelial sites of the renal pelvis or ureter. Aims To estimate sex‐specific risks for any SPCs after urothelial cancers, and in reverse order, for urothelial cancers as SPCs after any cancer. Such two‐way analysis may help interpret the results. Methods We employed standardized incidence ratios (SIRs) to estimate bidirectional relative risks of subsequent cancer associated with urothelial cancers. Patient data were obtained from the Swedish Cancer Registry from years 1990 through 2015. Results We identified 46 234 urinary bladder cancers (75% male), 940 ureteral cancers (60% male), and 2410 renal pelvic cancers (57% male). After male bladder cancer, SIRs significantly increased for 9 SPCs, most for ureteral (SIR 41.9) and renal pelvic (17.2) cancers. In the reversed order (bladder cancer as SPC), 10 individual FPCs were associated with an increased risk; highest associations were noted after renal pelvic (21.0) and ureteral (20.9) cancers. After female bladder cancer, SIRs of four SPCs were significantly increased, most for ureteral (87.8) and pelvic (35.7) cancers. Female bladder, ureteral, and pelvic cancers associated are with endometrial cancer. Conclusions The risks of recurrent urothelial cancers were very high, and, at most sites, female risks were twice over the male risks. Risks persisted often to follow‐up periods of >5 years, motivating an extended patient follow‐up. Lynch syndrome‐related cancers were associated with particularly female urothelial cancers, calling for clinical vigilance.

Abstract To assess etiological and clinical consequences of second primary cancers (SPCs) in prostate cancer (PC) patients, we followed newly diagnosed patients to identify men who were diagnosed with a SPC and recorded their causes of death. We used the Swedish Family‐Cancer Database to assess relative risks (RRs) and causes of death in SPCs until the year 2015 in patients with a PC diagnosis between 2001 and 2010. Among a total of 4.26 million men, 76 614 were diagnosed with PC at the median age of 71 years. Among them, 8659 (11.3%) received a subsequent diagnosis of SPC after a median follow‐up of 4 years. The most common SPCs were colorectal, skin, bladder, and lung cancers, melanoma, and non‐Hodgkin lymphoma. The ranking was almost identical with first cancers among elderly men in Sweden. The RR for SPCs in prostate‐specific antigen—detected PC was approximately equal to RR in other PC. Mortality patterns of PC patients were distinct depending on the presence or absence of SPC. Among patients with SPC, 47.8% died as a result of the corresponding SPC, followed by other causes (22.2%) and PC (18.1%). For patients without SPC, PC and non‐neoplastic causes almost matched each other as the main causes of death (48.5% and 47.8%). The results suggest that SPCs appear autonomous from primary PC and reflect incidence and mortality of first cancers in general. SPC was the most common cause of death in patients with SPC; close to half of the patients died due to SPC. For improved survival in PC patients, prevention and early detection of SPCs would be important, and the present results suggest that risk factors for SPC in PC are the same as those for first cancer in general.