Next (predicitive markers).1.1 Prostate cancer1.1.1 The prostate –

Next to lung cancer, prostate cancer (PC) is the second most commonly diagnosed cancer worldwide4. It is the fifth leading cause of death from cancer in men, with an estimated 307,000 deaths wordwide representing 6.6% of the total male cancer mortality. However, in developed countries, PC is the most common malignancy in men, constituting 29 % of all new cancers diagnosed in Norwegian men in 2015, as well as being the second most common cause of cancer death5,6. While most PCs are indolent and non-aggressive, some develop into a metastasized and deadly form of PC. Most PCs are diagnosed at an early stage, and due to insufficient prognostic tools, failure to predict which cases lead to an advanced form has led to a significant overtreatment7-9.  After availability of radical treatments, treatment allocation has been to the concept of “better safe than sorry” as many patients and clinicians usually prefer to err on the safe side not to miss the window of cure for a cancer that could later be lethal. Most men with localized prostate cancer are hence treated and left with permanent post-therapeutic sequelae and side-effects10.There is an urgent need for better prognostic tools to aid decisions in which patients to offer curative treatment. The use of a wide variety of biomarkers are utilized for a variety of different cancers with prostate cancer being a major exception due to lack of prospective validation11. Biomarkers may function as predictors of disease outcome (prognostic markers) and/or to aid selection of patients for different therapies (predicitive markers).1.1 Prostate cancer1.1.1 The prostate – functions and anatomyThe prostate (from Ancient Greek: “protector”, “guardian”, “one who stands before”) is an exocrine gland found only in males12. It secrets the milky white fluid that constitutes about 30 % of semen. Most of the fluid is produced by the seminal vesicles located just behind the prostate, and the rest of the semen consists of spermatozoa. To prolong the lifespan of sperm, the alkalinity of the prostate ejaculate helps neutralize the acidity of the vaginal tract. The prostate is located below the bladder and in front of the rectum, and its posterior regions are palpable in a digital rectal exam. The gland increases in size during puberty, and attains its full size of a walnut during the early twenties and remains stable thereafter. Sometimes after the age of 40 the cells in the prostate gland undergo multiplication and cause the gland to further enlarge. For adult males, the mean weight of a normal prostate range from 7 – 16 grams, and is related to body mass index13. The prostate is dependent of male hormones (androgens) to function properly, where the testosterone metabolite dihydrotestosterone (DHT) predominantly regulates the prostate.The prostate may, like all other organs, be subject to different diseases. Inflammation of the prostate gland, prostatitis, may be caused by bacterial infections or by other non-bacterial inflammations like male chronic pelvic pain syndrome. Benign prostatic hyperplasic (BPH) is common among older men, and many of its symptoms are shared with those of PC, including increased urination hesitancy or frequency of urination due to enlargement of the prostate. A growing prostate can cause obstruction of the prostatic urethra, leading to difficulties in urination and may result in urine retention. Medical treatment of BPH consists mainly of ?1-receptor blockers that relaxes the muscle fibers in the prostate and urethra, and 5?-reductase inhibitors (antiandrogen) that shrinks the prostate and hence reduces pressure on the urethra, allowing for easier passage of urine. The most common surgical treatment for BPH is a transurethral resection of the prostate (TUR-P), where obstructive prostatic tissue is resected to allow better flow of urine. In extreme cases, a surgical removal of the prostate (ex. Millins open prostatectomy in form of enucleation of adenoma) is needed. An estimated 50% of men have histologic evidence of BPH by the age of 50. Although prostate specific antigen (PSA) levels may be elevated in men affected by BPH because of increased organ volume and inflammation due to urinary tract infections, BPH does not lead to cancer or increase the risk of cancer14,15.As BPH and PC share many symptoms, there is a need to differentiate benign from malign disease for men with symptoms of BPH or PC.1.1.2 Risk factors and causesThe chance of having PC rises rapidly after the age of 50, where 6 in 10 cases of PC are found in men older than 6516. Race/ethnicity is also a risk factor, where African-American men are more than twice as likely to die of PC as white men and generally have a more lethal course of disease, while PC occurs less often in Asian and Latino men compared to white men17. While PC is less common in Asia, Africa, Central and South America, it is more common in North America, Northwestern Europe, Australia and on the Caribbean Islands. Family history is a risk factor, where having a father or brother with PC more than doubles the risk for developing PC18,19. The risk is much higher for men with several affected relatives, particularly for relatives with PC in young age. Some studies have found that inflammation in the prostate may contribute to PC. Smoking and obesity, however, has not been shown to increase the risk of PC.Exact etiology of PC are unknown, but on a basic level, PC is caused by DNA changes in normal PC tissue. 5 to 10 % of PCs are hereditary cancers, where some inherited mutated genes linked to hereditary PC includes mutations of MSH2 and MLH1 (Lynch syndrome / hereditary non-polyposis colorectal cancer) or mutations of BRCA2 (more commonly known for breast cancer in women) amongst others. However, most gene mutations related to PC seem to be acquired mutations (somatic) developed during a man’s life rather than being inherited (germline), and does not pass on to offspring20,21.Regarding prevention of PC, risk factors such as age, race and family history cannot be prevented22. Although the effects of body weight, physical activity and diet on PC risk are not clear, a healthy diet, being physically active and staying at a healthy weight might lower the risk23,24. Some drugs might help reduce the risk of PC, including the 5?-reductase inhibitors finasteride and dutasteride, more commonly used for treatment of BPH. 5?-reductase inhibitors might have the potential for preventing or delaying the development of PC (for Gleason 6 cancers only), but has the potential small increased risk of high-grade PC25-27. Some research suggests that aspirin daily might lower the risk of PC28. However, it is not clear whether the benefits of these drugs outweighs the risks for most men, and more studies are needed. According to the Norwegian national guidelines for diagnosis, treatment and follow-up of PC, there is currently no basis for general recommendations on chemoprophylaxis to prevent PC, whereas the EAU guidelines state that no definitive recommendation can be provided for specific preventive or dietary measures to reduce the risk of developing PC29.1.1.3 Epidemiology5118 new cases of PC were diagnosed in Norway in 2016, which accounted for almost one third of all cancer cases in men6. Based on today’s cancer incidence in Norway, approximately every eighth man (13.6 % in 2011-2014) will be diagnosed with PC before the age of 75 in Norway (lifetime risk in the absence of competing causes of death). However, considerable fewer men die of PC every year. 1045 men died of PC in 2015 in Norway, accounting for about 19 % of all cancer deaths in men.  The lifetime risk before death of PC before the age of 75 is approx. 1.4% (about one in 70 men). A decrease in mortality of PC in Norway (Error! Reference source not found.Figure 2) and in many other countries from the beginning of the 1990s and beyond has been observed, although the cause of decline is uncertain30-32. New cases of PC increase in all age groups, but PC is primarily the old men’s disease. Almost half of all cases occur among men over 74 years, and the proportion of the population of this age group is increasing. As a result of higher overall life expectancy, the incidence of PC has more than quadrupled in 2015 compared to the 1950s. As a result of a marked increase in the use of PSA as a diagnostic tool and that many more are diagnosed with PC each year than the number of people who die from the disease, the number of men living with and who needs some sort of follow-up for their disease has doubled from approximately 22 000 to 44 000 in a ten year span from 2005 to 20156.1.1.4 HistopathologyThe prostate is divided into four histological regions: The peripheral zone, central zone, transition zone and anterior fibromuscular stroma, where the peripheral zone comprises approx. 70 % of the gland33. BPH usually develops in the transition zone, whereas 75% of PC develops in the peripheral zone34. The prostate gland is surrounded by the prostatic “capsule” where the neurovascular bundles outside of the capsule are responsible for erectile function. Given its proximity to the distal rectum, the posterior aspect of the prostate is most prominent on DRE.PC are classified according to the Worth Health Organization classification of tumors. More than 95 % of the PC are adenocarcinomas, arising from the prostate epithelial cells. Less than 5% of prostate carcinomas are variants of adenocarcinoma which often have very poor prognosis (ductal carcinoma, mucosal carcinoma, signet cell carcinoma and small cell carcinoma).1.1.5 Clinical presentation of PCMost patients with prostate cancer are asymptomatic, particularly in the early stages of disease. Only a minor part of men with urinary disorders seek medical help35. Two independent studies has found that concern for prostate cancer, rather than the degree of urinary disorders, determines whether one is seeking a doctor36,37. As such, many patients are still asymptomatic at the time of diagnosis, as patient requested screenings by PSA measurements with the following biopsies are commonly performed. Detection of elevated PSA in general health controls in healthy men has been an increasing cause of referral to an urologist, and as of 2016, elevated PSA was the main reason for a diagnosis of PC in Norway38. Local progression may result in lower urinary tract obstruction associated with BPH, and symptoms such as weak stream, hesitancy, urgency, frequency, nocturia, straining, intermittency, incomplete emptying, and various degrees of incontinence may occur. PC tumors may bleed, presenting hematuria. Approximately 90 % of all new incidents in the United States have been reported as localized or regional PCs39. Although not as common, around 7 % of PC patients in Norway are initially diagnosed with metastatic PC, where bone pain may be the presenting symptom6. 1.1.6 Diagnosis, staging and prognosisPSA discussionThe measurements of PSA levels revolutionized the ability to diagnose PC at an early stage40. In addition, a serum PSA level before treatment of more than 100 ng/ml has been found to be strongest indicator of metastatic disease with a positive predictive value of 100 % in a prospective study of 60 patients with newly diagnosed PC41. However, mass screening of the asymptomatic patient with PSA measurements remains a controversial subject, and argumentations are complex. Briefly summarized, PSA screening for PC has not shown a gain in overall survival although the European Randomized Study of Screening for Prostate Cancer (ERSPC) study has shown that PSA screening reduced the risk of death from PC42,43. The benefit of reduced mortality of PC must be weighed against potential adverse effects of overdiagnosis and complications of treatment such as urinary leakage, erection failure and dysfunction of the intestine. It is estimated that 23 – 42 % of PCs detected as a result of PSA screening has been overdiagnosed44,45. This is based on estimated expected life of the diagnosis and estimated chance that the disease will produce clinical symptoms from prostate cancer without PSA screening. In conclusion, PSA testing of potentially healthy men for prostate cancer will probably lead to reduced mortality, but at the cost of over diagnosis and overtreatment of tumors that may not give symptoms throughout the man’s life. An American study found that the proportion of men who wanted to undergo PSA testing was halved after being given extensive information46. In conjuction with the recommendations of the European Association of Urology (EAU) and US Preventive Services Task Force, population-based screening is not recommended and this has been implemented in the Norwegian national guidelines for diagnosis, treatment and follow-up of PC. There is still no level 1 evidence that PSA mass screening is cost-effective in reducing PC mortality47. Exceptions should be made for middle-aged men with family disposition for PC or other high risk groups such as patients with known mutations in BRCA2. PSA tests can be offered to the patient on an individual basis, but should not be taken without the patient being fully informed of the pros and cons.Table 1 1. Frequency of PC accoring to low PSA levels in 2950 patients48. PSA level (ng/ml) Risk of PC0.0 – 0.5 6.6 %0.6 – 1.0 10.1 %1.1 – 2.0 17.0 %2.1 – 3.0 23.0 %3.1 – 4.0 26.9 %The PC diagnosis is most often determined by the appearance of cancer tissue in biopsies from the prostate or from TUR-P tissue, while some patients are primarily diagnosed with metastasis and highly elevated PSA. The general practitioners tools for detection of PC are PSA and DRE. In conjuction with the patient, the practitioner decides whether to refer the patient to a specialist for biopsy following a thorough examination, evaluation of current and prior serum PSA values and DRE findings. The need for prostate biopsy is based on PSA level and/or suspicious DRE, while age, potential comorbidity, and therapeutic consequences should also be considered49. Limited PSA elevation alone should not prompt immediate biopsy. Prostate specific antigen level should be verified after a few weeks using the same assay under standardised conditions. However, DRE is limited because it only allows the posterior surface of the gland to be digitally examined, and the examination is highly subjective with poor inter-examination reliability. On the other hand, some types of PC only mildly increase PSA levels, justifying the DRE as an important examination. In asymptomatic men with moderately elevated PSA and with life expectancy below 10 years and negative DRE, one can be reluctant regarding biopsies.The tissue sampling is usually done under local anesthetics guided by a transrectal ultrasound (TRUS) probe49. The majority of tissue sampling is in the peripheral zone, with the number of biopsies ranging from eight to 16. In the case of repeated benign biopsies and persistent elevated PSA levels, a multiparametric magnetic resonance imaging (MRI) of the prostate and targeted biopsies can be considered. While CT and TRUL are not recommended for local staging for any risk group, for intermediate-risk patients ISUP Grade 3 or high-risk localized for locally advanced PC patients, MRI is recommended.Grading refers to the microscopic description of cancer aggressiveness. The biopsies are graded according to the Gleason Scoring system50. The Gleason grading system consists of histopathological patterns graded from well-differentiated grade 1 to poorly-differentiated grade 5, where grade 1 and 2 are not considered to be cancer and are rarely used. The two most dominant Gleason grades are summed to obtain a Gleason Score. More than 40 years after Gleason’s grading score was invented by Douglas Gleason, this is still one of the most important prognostic factors in PC.The primary assessment of PC stage is usually done with DRE, measurement of PSA, and for men with higher risk disease skeletal scintigraphy, optionally supplemented by computer tomography (CT) or MRI. Local T-staging is based on the findings on DRE and optionally MRI. N-stage is of outmost importance for patients considered for curative treatment, where the most accurate method for determination of N-stage is an operative extended lymphadenectomi. M-stage is best assessed with MRI or skeletal scintigraphy due to its predominant metastatic spread to skeletal tissue. The TNM classification for adenocarsinomas of the prostate is presented in Error! Reference source not found.Table 1 4.  Risk stratification to separate PC patients with a potential curative disease and patients in a palliative setting is imperative regarding choice of therapy. The division of these groups is not crystal clear, but several risk stratification tools mostly based on PSA, Gleason Score and T stage are used to help risk stratification51-53. The EAU Guidelines of 2017 uses the 2017 TNM classification of PC and the EAU risk group classification, which is essentially based on D’Amico’s classification system for PC49. The EAU risk group for biochemical recurrence of localized and locally advanced PC is presented in Error! Reference source not found.Table 1 2.Table 1 2. EAU risk groups for biochemical recurrence of localised and locally advanced prostate cancer. GS=Gleason score; ISUP=International Society for Urologcal Pathology; PSA=prostate-specific antigen.DefinitionLow-risk Intermediate-risk High-riskPSA < 10 ng/mLand GS < 7    (ISUP grade 1)and cT1-2a PSA 10-20 ng/mLor GS 7        (ISUP grade 2/3)or cT2b PSA > 20 ng/mLor GS > 7    (ISUP grade 4/5)or cT2c any PSAany GS                               (Any ISUP) cT3-4 or cN+