An Analysis Of Colorectal Cancer (Crc) Following A Diagnosis Of Prostate Cancer (Cap): Is It Due To Earlier Diagnosis Or Increased Incidence?

1560 Background: Treatment for CaP is reported to be associated with a subsequent diagnosis of CRC, based on studies of large series of CaP patients (pts), often with short follow-up and limited detail of the CRC diagnosis. Radiation and hormonal therapy for CaP are suggested factors. Methods: Examining a comprehensive prospective CRC database, where previous cancer history is routinely recorded, we performed a detailed analysis of CRC pts with a prior diagnosis of CaP. Contemporary treatment strategies for CaP were derived from a CaP database and practice surveys. Victorian cancer registry data was also examined for expected CaP incidence. Results: Of 3935 cases of CRC diagnosed at 4 hospitals between 1998 and 2010, 2256 were male, median age 68 years (yrs) (range 16 – 96), with 69 (3.1%, median age 73) having a history of CaP, consistent with the expected rate based on registry data. Median age at diagnosis of CRC varied with CaP treatment modality, 71 yrs for pts managed with observation (n = 10), 72 yrs for hormonal therapy (n = 26), 63yrs (n = 10) for prostatectomy and 67 yrs (n = 24) for radiotherapy. This age distribution was consistent with contemporary treatment strategies for CaP. Time from diagnosis of CaP to CRC diagnosis ranged from 0.2 – 20.7 yrs, median ranged from 4.1 yrs (observation) to 6.1 yrs (surgery). There was a trend for a lower rate of metastatic CRC at presentation (8.7% vs 16.8%, p = NS) in pts with a CaP history than for all males with CRC, and a trend for an increased rate of screen detected CRC (6.2% vs 3.3%, p = NS). There was no excess of rectal cancer in pts treated with radiotherapy for their CaP (2/24 = 8.3%) compared to other modalities (18/69 = 26.1%). Stage specific survival was as expected. Conclusions: We found no evidence for an overall increased risk of CRC following a diagnosis of CaP, and no impact of individual CaP treatment modality on CRC diagnosis or outcome. Previous findings of an increased rate of CRC may be due to earlier diagnosis, rather than an increased risk of CRC, possibly due to increased participation in screening, or early investigation of symptoms or incidental findings in pts with regular medical contact. Risk of CRC should not influence treatment selection for CaP.