In their article in this issue of ONCOLOGY, Drs. Aizer and D’Amico provide an excellent overview of current prostate-specific antigen (PSA) screening controversies, highlighting the strengths and weaknesses of recent prospective randomized trials of population-based screening. They emphasize that two of the trials have shown an improvement in prostate cancer–specific survival but failed to mention the lack of an improvement in overall survival (OS) with PSA screening. This is an important omission, as patients who are being offered a screening test should be informed that the test may not impact their survival. Then, using colorectal cancer outcomes data from the Surveillance, Epidemiology and End Results (SEER) database, they propose that patients might benefit from prostate cancer screening following treatment of colorectal cancer.
An understanding of colorectal cancer prognosis is critical for evaluation of the potential PSA screening benefit. Recent advances for adjuvant colon cancer therapy have improved outcomes, with 6-year OS of 87% and 73% for patients with stage II and III disease, respectively, reported in the landmark Multicenter International Study of Oxaliplatin/5-Fluorouracil/Leucovorin in the Adjuvant Treatment of Colon Cancer (MOSAIC trial), which established adjuvant oxaliplatin/5-fluorouracil/leucovorin (FOLFOX) as the standard of care for patients with stage III disease. The importance of selection criteria, including age, in this heterogeneous population is reflected in a subsequent subset analysis of elderly patients, which demonstrated a 5-year OS rate of 76% in patients with stage II disease. Notably, as Drs. Aizer and D’Amico discuss, the median age of patients in the Göteborg study (56 years) is significantly younger than the median ages of patients included with the survival data from that study (60–75 years). While we agree that survivors of rectal cancer should not be subject to discrimination with respect to health maintenance interventions, the age recommendations for prostate screening should not exceed those of the population recommended by the American Urological Association (AUA) or other cancer societies.
Multiple considerations required for a discussion of PSA screening in the context of colorectal cancer mandate individualized discussion accounting for the patient’s age, comorbidities, prostate cancer risk, and colorectal cancer prognosis. PSA screening for an otherwise healthy 50-year-old man with long life expectancy and an elevated prostate cancer risk may be appropriate even in the setting of stage III colon cancer, provided that a sufficient disease-free interval has occurred. In a more elderly patient, screening is less likely to be appropriate, even in the context of stage I or II disease.
The SEER data presented provide a useful starting point to illustrate the importance of stage in patient selection, although significant variability in patient characteristics and the wide 15-year age range create challenges for a patient-specific interpretation. Individualized prognostic tools, such as Adjuvant! Online (www.adjuvantonline.com), that are also based on the SEER database may provide additional guidance for discussion of PSA screening in the context of colorectal cancer prognosis.
In their review, Drs. Aizer and D’Amico failed to discuss the unique challenges associated with prostate cancer screening in men with a history of colorectal cancer. First, there may be lower PSA levels in these patients if they have received prior pelvic radiation therapy during the management of a rectal cancer. The appropriate threshold for recommending a biopsy may not be the same for them as it is for men without a prior history of pelvic radiation. Furthermore, abdominoperineal resections to surgically manage a rectal cancer make both digital rectal examination (DRE) and transrectal ultrasound (TRUS)-guided biopsies impossible in the absence of a rectum. The costs and risks associated with alternative prostate biopsy methods need to be considered. Finally, surgical and radiation therapy management of early prostate cancer will be limited by a previous history of either pelvic surgery or radiation. The Dutch experience with prostate cancer radiation therapy has demonstrated that a history of prior abdominal surgeries increases the risk of rectal toxicity. Patients need to be made aware of the unique challenges associated with the diagnosis and management of prostate cancer in the context of prior colorectal cancer therapy.
In conclusion, we agree that it may be appropriate to offer prostate cancer screening to carefully selected men with a previous history of colorectal cancer. However, the risks and benefits of establishing the diagnosis in this setting, and the unique challenges of treatment, need to be considered and discussed with them.
The authors have no significant financial interest or other relationship with the manufacturers of any products or providers of any service mentioned in this article.
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