Technical Aspects of Focal Therapy in Localized Prostate Cancer

© Springer-Verlag France 2015

Eric Barret and Matthieu Durand (eds.)Technical Aspects of Focal Therapy in Localized Prostate Cancer10.1007/978-2-8178-0484-2_1

1. Rationale for Focal Therapy

Franck Bladou¹  

(1)

H.Black Chair in Surgical Oncology, Chief of Urology Department, Jewish General Hospital, McGill University, Pavilion E-941, 3755 Chemin de la Cote Sainte Catherine, Montreal, QC, H3T 1E2, Canada

Franck Bladou

Email: [email protected]

1.1 Increasing Incidence of Low-Risk Prostate Cancer

Incidence rates for prostate cancer have been increasing for the last three decades, and this is mainly due to earlier diagnoses of asymptomatic diseases by the use of the prostate-specific antigen (PSA) test and PSA screening. In the pre-PSA era, during the decade before 1976, prostate cancer incidence was increasing slowly (2 % per year), when half of all prostate cancers were incidentally detected in transurethral resection chips for benign prostatic hyperplasia treatment or diagnosed by clinical symptoms and digital rectal examination in more advanced diseases [1, 2]. Early detection efforts were associated with a rapid increase in prostate cancer incidence after 1986, from 2 to 12 % per year, with a peak in 1992 (237.2 per 100,000 men in the USA) [3]. In the subsequent 3 years, from 1992 to 1995, a 10 % per year decline occurred. During the following decade (1995–2005), prostate cancer incidence stabilized, but to a higher level (150.5 per 100,000) than those in 1986 (119 per 100,000). USA prostate cancer incidence was estimated at 238,590 in 2013 [4].

In European countries, the incidence of prostate cancer almost doubled from 1995 to 2008, with an age-standardized rate of 47.4–93.4 when PSA testing has been widely used [5]. Meanwhile, the mortality rate decreased in Europe, from an age-standardized rate of 23.5 in 1995 to 20.7 in 2008 [5]. The same trend of mortality rate even before this date occurred in the USA, from 38 per 100,000 in 1995 to 22 per 100,000 in 2006 [6].

Parallel to the increase in prostate cancer incidence, a significant downward risk migration occurred over time, with fewer high-risk diseases (from 40.9 % in 1990 to 14.8 % in 2002) and an increase in low-risk prostate cancers (from 31.2 % in 1990 to 47.7 % in 2002) [7]. Early detection of asymptomatic prostate cancer has increased the number of low-risk diseases and, as a consequence, has increased the treatment of such diseases. In prostatectomy series, the proportion of low-risk patients, stratified according to the D’Amico risk group classification for disease progression, in European radical prostatectomy cohorts was up to 66 % in 2004 [8] and up to 75 % in a large series of radical prostatectomies from the USA [9].

1.2 PSA Screening: Facts and Lessons Learned

Overdiagnosis, overtreatment, numbers needed to treat: the price to pay for cost of saving lives.

PSA screening is Janus-like (two-faced), where one positive side allows a cancer-specific mortality reduction and the other a negative side, called overdiagnosis. Overdiagnosis means a diagnosis of prostate cancer with no specific risk for the patient, a cancer that would not progress to symptoms or death. However, due to the lack of pertinent prognostic factors and of precise diagnostic tools, the only certainty that the cancer diagnosed will become a nonthreatening disease is when the patient dies of competitive morbidity while his prostate cancer is not treated or still in place. Most patients and physicians would not take the risk of underdiagnosis and undertreatment with such a lack of crucial information concerning the disease progression risk. The direct drawbacks of overdiagnosis are, therefore, the treatment of all patients, low- and high-risk diseases using the same aggressive treatments, leading to overtreatment in a significant proportion of low-risk, nonaggressive prostate cancers (the truly negative side of PSA screening).

The question raised is whether, even when such a dramatic rise in the incidence rate has occurred during the same period of time, the decrease in prostate cancer mortality rates should be attributed to the results of PSA screening. One answer could be the effect of the lead-time in prostate cancer, that is the interval from screen detection to the time of clinical diagnosis, when the tumor would have surfaced without screening. The vast majority of prostate cancers have a low-growth profile, and the lead-time for prostate cancer is estimated to be between 5 and 12 years, depending on the patient’s age at screening. For example, in the European Randomized Study of Screening for Prostate Cancer (ERSPC), it has been estimated that for a single screening test, the mean lead-time was 12 years at age 55 and 6 years at age 75 [10].

On the one hand, it has been estimated that more than a million men have been diagnosed and treated for prostate cancer due to the introduction of PSA screening, and therefore the increase in diagnosis has led to an increase in treatment with exposure to known risks of impotence, incontinence, and radiation-induced lesions, particularly in younger males [11]. On the other hand, recent large, randomized clinical trials have shown a significant reduction in metastasis and cancer-specific mortality in the PSA screening group compared to the control group with no screening [12, 13]. It has been estimated, by using projection models, that almost 50 % of the observed decline in prostate cancer mortality in the last decades can be attributed to PSA screening [14]; it has been also speculated that survival improvement may be due to more effective treatment of early high-risk and advanced prostate cancer patients [15].

Because mortality rates in North America have decreased significantly (by 40 %) since the use of PSA testing in the late 1980s, both in younger populations and in the elderly since 2000, while in other European countries the decrease in the mortality rate was noted only in middle-aged populations, these results suggest that in the USA, PSA screening and aggressive treatments were both offered to the two age groups, whereas in other countries, it was preferred to do PSA testing on men under age 70 and/or the elderly, who were less likely to receive aggressive treatments [16].

Finally, if overdiagnosis is not something negative (knowing that a patient harbors the disease), it bears its own negative consequences, i.e., overtreatment (cancer treated by aggressive management with potential morbidity for a disease that would not otherwise result in symptoms or death, exposing the patient to unneeded side effects): the treatment does more harm for the patient than his disease does, against the background of Hippocrates’s primum non nocere [first, do no harm] dictum, which is at the root of our daily practice of medicine.

An extensive debate, still ongoing, has led to numerous publications since the initial results of the ERSPC and US Prostate, Lung, Colorectal and Ovarian (PLCO) cancer screening trials were first released in the same issue of the New England Journal of Medicine in 2010 [17, 18]. Over 78,000 men in the USA and 240,000 men in Europe have participated in these unique trials, whose initial results after 10–12 years of follow-up are still maturing. However, the published results of these two large studies have motivated the US Preventive Services Task Force (USPSTF) to recommend against PSA screening for prostate cancer, creating a storm in the medical community [19, 20]. The results of the two trials are controversial: In the US PLCO trial, there was no significant difference in prostate cancer mortality between the screening and control groups, with a 22 % increase in prostate cancer detection in the screened group. The main drawback of this study was that, in the control group, almost half of the participants had a screening test at some point during the study. In the ERSPC trial, there was a 20 % mortality reduction in the screened group, with a 50–60 % increase in prostate cancer detection in the screened group.

If controversy is still ongoing regarding the pros and cons of PSA screening, data maturation of the two large trials will possibly help to better define the ideal number of patients needed to treat (NTT) and benefit, versus the harm of such screening. If it is clearly demonstrated that PSA screening is efficient enough to detect prostate cancer and even reduce prostate cancer mortality, the actual cost linked to it is the great number of patients needed to treat for each cancer death avoided (48 in the initial ERSPC study results) and its negative consequences –overtreatment [21]. The value of the critical number of NTT has been extensively studied and is still controversial in the literature, with values widely varying – from 48 in the initial ERSPC study to 33 in a second analysis of the same study [12], to 12 in the sub-analysis of the Swedish trial [13], to 5 in the subgroup of men with no life-shortening comorbidities in a post-randomization analysis of the PLCO study [22].

Number to treat means the number of patients to expose to the reality of treatment-related morbidity and side effects with potential quality-of-life impairment. The 15-year outcomes of radical prostatectomy and radiation therapy have been recently published from a population-based longitudinal cohort, allowing a close-to-reality picture of patient-reported, disease-specific, health-related, quality-of-life mature outcomes [23]. The prevalence of erectile dysfunction universally affected 90 % of the treated men in this cohort at 15 years, of whom 37–43 % reported being bothered with respect to sexual symptoms. Other publications reported similar results, with 7–14 % of men suffering from urinary incontinence after surgery or radiation therapy [24], 84 % suffering from erectile dysfunction, and 48 % suffering from sexual distress in the prostatectomy group of the Scandinavian Prostate Cancer Group 4 trial at a median follow-up of 12.2 years [25]. It states clearly that men who have undergone prostatectomy or radiotherapy for localized prostate cancer suffer from declines in all functional outcomes throughout early, intermediate, and long-term follow-up.

As always, the controversy is balanced between two extremes – the pros and cons of PSA testing for early detection of prostate cancer. We have the potential to substantially reduce the incidence of prostate cancer and save thousands of lives but at a considerable risk of overtreatment for a large portion of the population. The answer given by the USPSTF against PSA testing has been seen as a negative extreme, as stated in several publications [21, 26, 27], with the feeling that there should not be a black or white answer to this important question. PSA screening, along with information about the risks (overtreatment) and benefits of such a test, should allow to screen and treat only the men at high risk, who are most likely to benefit.

The field of urology will be judged on how it deals with early detection and treatment of prostate cancer. Let’s leave a legacy we can be proud of. [26]

1.3 Active Surveillance: One of the Answers to Overtreatment

Many efforts have been made over the last few decades to decrease the morbidity of whole-gland treatments, in the fields of both urology and radiotherapy. A better selection of ideal candidates for curative treatment is clearly shown in recent series of both surgical and radiation management. Radical prostatectomy procedure has drastically improved in terms of side effects with the introduction of open nerve-sparing procedure, minimally invasive and robot-assisted surgeries. Amongst the main improvements achieved by these procedures are a decreased operative bleeding, a postsurgical recovery improvement, a better urinary continence and erectile function preservation. On the other hand, a more precise delivery of higher doses of radiation to an individual-based target with a better control of organ motion during radiation exposure is one of the improvements made in these fields.

Active surveillance is another important answer to overtreatment, by reducing treatment – and treatment-induced harm – for minimal-risk disease. In the 2000s a few teams in various parts of the world showed that selected patients with initial parameters of low-risk prostate cancer could be followed without any initial treatment and that a treatment could be proposed when there happened to be progression parameters in recurrent prostate biopsy specimens over time. The most mature data on active surveillance comes from Toronto, where a cohort of 453 patients has been followed for more than 10 years with a 10-year actuarial prostate cancer mortality of 3 % [28]. Five patients in this series died of prostate cancer; three of them had initial occult metastasis, one refused treatment, and only one would probably have had a better outcome with initial treatment [21]. The results on conservative management have been supported by those of the Prostate Cancer Intervention versus Observation Trial (PIVOT), which did not show differences in prostate cancer-specific mortality between low-risk patients managed conservatively versus definitively [29].

For these reasons, the National Institutes of Health endorsed active surveillance as an option for all men with low-risk prostate cancer [30] and the NCCN Guidelines favored active surveillance in patients with very low-risk prostate cancer (defined as stage T1c, Gleason 6, PSA less than 10 ng/mL with fewer than three positive biopsy cores and less than 50 % of any core involved with cancer, and PSA density of less than 0.15 ng/mL/g) and a life expectancy of less than 20 years, as well as in elderly patients with low-risk disease (stage T1c-2a, Gleason less or equal to 6, PSA less or equal to 10 ng/mL) and less than 10 years’ life expectancy.

However, several concerns raised by active surveillance include the initial downgrading of the tumor (almost 30 % of men with initial Gleason scores of 3 + 3 harbor higher grade cancer, particularly in the largest glands and among more elderly men) [31]; a lack of definition of optimal criteria for surveillance and treatment decision-making; the risk of disease progression during the surveillance period; the morbidity and cost of recurrent prostate biopsies with an increased risk of severe infection; the quality of life/anxiety of non-treated cancers (knowing that the suicide rate is higher in men diagnosed with prostate cancer [32]); and so forth.

Two large randomized trials are ongoing and will compare active surveillance versus surgical treatment or radiation therapy: in the UK, the ProtecT study (Prostate Testing for Cancer and Treatment trial, ClinicalTrials.gov identifier NCT00632983) and in North America, the START study (Surveillance Therapy Against Radical Treatment trial, ClinicalTrials.gov identifier NCT00499174). Results from these studies will help define the best candidates for active surveillance and analyze the efficacy of such management in this population of men; however, the maturation of these results will take years [33].

1.4 Rationale of Focal Therapy for Localized Prostate Cancer

The increase in prostate cancer incidence, mainly attributed to the use of PSA testing, has resulted in a greater proportion of low-risk cancers occurring in younger men. This population of newly diagnosed prostate cancer men is the one where the risk of complications associated with curative treatments, i.e., incontinence and impotence, has the highest impact. This risk has to be weighted to the small absolute risk reduction of approximately 5 % over 10 years that is associated with surgery, compared to watchful waiting in this population of low-risk disease [34, 35]. Management options for this population therefore lie between the extremes of radical, potentially harmful therapies and active surveillance. On the one hand, there is a maximum chance of cure, together with sexual and/or urinary morbidity, and on the other, a preservation of genitourinary functions with the psychological and health care burdens of absence of treatment and active surveillance.

Focal therapy aims at directing ablative sources of treatment – such as heat, cold, radiation, vascular necrosis – to the only focus of cancer surrounded by the safety margin of a normal gland. Its goals are to control the disease without explicitly eradicating it, to carry out active surveillance of the non-treated gland that could harbor other foci of cancer, and to limit side effects and morbidity of whole-gland treatment while allowing a partial treatment and a decrease of potential anxiety due to the absence of treatment.

This concept follows the one adopted for other malignancies, such as breast, colon, or kidney cancers in selected patients.

Focal therapy, as with every innovation in oncology, raises a lot of questions, hopes, and concerns [36]. In its infancy, this concept’s adaptation for prostate cancer has just begun its initial phase study level [37]. Who will be the ideal patients for focal therapy; which source of ablation will emerge from the options available nowadays; what will be the optimal targeting and follow-up (multiparametric prostate MRI being the most advanced tool used to date for this purpose [38]);, what will be the percentage of salvage treatments to perform after focal treatment; what type of salvage options will there be; and how important will the morbidity of such salvage treatments be? These are just a few of the unanswered questions that we will have to address in order to bring focal therapy for prostate cancer to the level of standard treatment options for selected men with localized prostate cancer in the near future – beginning now.

References

1.

Meigs JB, Barry MJ, Giovannucci E, et al. High rates of prostate-specific antigen testing in men with evidence of benign prostatic hyperplasia. Am J Med. 1998;104:517–25.PubMedCrossRef

2.

Brawley OW. Trends in prostate cancer in the United States. J Natl Cancer Inst Monogr. 2012;45:152–6.CrossRef

3.

Quaglia A, Lillini R, Crocetti E, Buzzoni C, Vercelli M, AIRTUM Working Group. Incidence and mortality trends for four major cancers in the elderly and middle-aged adults: an international comparison. Surg Oncol. 2013;22(2):e31–8.PubMedCrossRef

4.

Siegel R, Naishadham D, Jemal A. Cancer statistics, 2013. CA Cancer J Clin. 2013;63(1):11–30.PubMedCrossRef

5.

Ferlay J, Parkin DM, Steliarova-Foucher E. Estimates of cancer incidence and mortality in Europe in 2008. Eur J Cancer. 2010;46(4):765–81.PubMedCrossRef

6.

Jemal A, Siegal R, Xu J, XU J. CA statistics, 2010. CA Cancer J Clin. 2010;60:277–300.PubMedCrossRef

7.

Cooperberg MR, Lubeck DP, Mehta SS, Carroll PR, CaPSURE. Time trends in clinical risk stratification for prostate cancer: implications for outcomes (data from CaPSURE). J Urol. 2003;170(6 Pt 2):S21–5; discussion S26–7. Erratum in: J Urol. 2004 Feb;171(2 Pt 1):811.PubMedCrossRef

8.

Budäus L, Spethmann J, Isbarn H, Schmitges J, Beesch L, Haese A, Salomon G, Schlomm T, Fisch M, Heinzer H, Huland H, Graefen M, Steuber T. Inverse stage migration in patients undergoing radical prostatectomy: results of 8916 European patients treated within the last decade. BJU Int. 2011;108(8):1256–61.PubMedCrossRef

9.

Gallina A, Chun FKH, Suardi N, Eastham JA, Perrotte P, Graefen M, Hutterer G, Huland H, Klein EA, Reuther A, Montorsi F, Briganti A, Shariat SF, Roehrborn CG, delaTaille A, Salomon L, Karakiewicz PI. Comparison of stage migration patterns between Europe and the USA: an analysis of 11 350 men treated with radical prostatectomy for prostate cancer. BJU Int. 2008;101:1513–8.PubMedCrossRef

10.

Draisma G, Boer R, Otto SJ, van der Cruijsen IW, Damhuis RA, Schröder FH, de Koning HJ. Lead times and overdetection due to prostate-specific antigen screening: estimates from the European Randomized Study of Screening for Prostate Cancer. J Natl Cancer Inst. 2003;95(12):868–78.PubMedCrossRef

11.

Welch HG, Albertsen PC. Prostate cancer diagnosis and treatment after the introduction of prostate-specific antigen screening: 1986–2005. J Natl Cancer Inst. 2009;101(19):1325–9.PubMedCentralPubMedCrossRef

12.

Schroder FH, Hugosson J, Roobol MJ, et al. Prostate-cancer mortality at 11 years of follow-up. N Engl J Med. 2012;366:981–90.PubMedCrossRef

13.

Hugosson J, Carlsson S, Aus G, et al. Mortality results from the Göteborg randomised population-based prostate-cancer screening trial. Lancet Oncol. 2010;11:725–32.PubMedCentralPubMedCrossRef

14.

Etzioni R, Tsodikov A, Mariotto A, et al. Quantifying the role of PSA screening in the US prostate cancer mortality decline. Cancer Causes Control. 2008;19:175–81.PubMedCentralPubMedCrossRef

15.

Kvåle R, Auvinen A, Adami HO, Klint A, Hernes E, Møller B, Pukkala E, Storm HH, Tryggvadottir L, Tretli S, Wahlqvist R, Weiderpass E, Bray F. Interpreting trends in prostate cancer incidence and mortality in the five Nordic countries. J Natl Cancer Inst. 2007;99(24):1881–7.PubMedCrossRef

16.

Quaglia A, Parodi S, Grosclaude P, Martinez-Garcia C, Coebergh JW, Vercelli M. Differences in the epidemic rise and decrease of prostate cancer among geographical areas in Southern Europe: an analysis of differential trends in incidence and mortality in France, Italy and Spain. Eur J Cancer. 2003;39:654–65.PubMedCrossRef

17.

Schröder FH, Hugosson J, Roobol MJ, Tammela TL, Ciatto S, Nelen V, Kwiatkowski M, Lujan M, Lilja H, Zappa M, Denis LJ, Recker F, Berenguer A, Määttänen L, Bangma CH, Aus G, Villers A, Rebillard X, van der Kwast T, Blijenberg BG, Moss SM, de Koning HJ, Auvinen A, ERSPC Investigators. Screening and prostate-cancer mortality in a randomized European study. N Engl J Med. 2009;360(13):1320–8.PubMedCrossRef

18.

Andriole GL, Crawford ED, Grubb 3rd RL, Buys SS, Chia D, Church TR, Fouad MN, Gelmann EP, Kvale PA, Reding DJ, Weissfeld JL, Yokochi LA, O’Brien B, Clapp JD, Rathmell JM, Riley TL, Hayes RB, Kramer BS, Izmirlian G, Miller AB, Pinsky PF, Prorok PC, Gohagan JK, Berg CD, PLCO Project Team. Mortality results from a randomized prostate-cancer screening trial. N Engl J Med. 2009;360(13):1310–9. Erratum in: N Engl J Med. 2009 Apr 23;360(17):1797.PubMedCentralPubMedCrossRef

19.

Lin K, Lipsitz R, Miller T, Janakiraman S, U.S. Preventive Services Task Force. Benefits and harms of prostate-specific antigen screening for prostate cancer: an evidence update for the U.S. Preventive Services Task Force. Ann Intern Med. 2008;149:192–9.PubMedCrossRef

20.

Moyer VA, U.S. Preventive Services Task Force. Screening for prostate cancer: U.S. Preventive Services Task Force recommendation statement. Ann Intern Med. 2012;157(2):120–34.PubMedCrossRef

21.

Klotz L. Prostate cancer overdiagnosis and overtreatment. Curr Opin Endocrinol Diabetes Obes. 2013;20(3):204–9.PubMedCrossRef

22.

Crawford ED, Grubb 3rd R, Black A, et al. Comorbidity and mortality results from a randomized prostate cancer screening trial. J Clin Oncol. 2011;29:355–61.PubMedCentralPubMedCrossRef

23.

Resnick MJ, Koyama T, Fan KH, Albertsen PC, Goodman M, Hamilton AS, Hoffman RM, Potosky AL, Stanford JL, Stroup AM, Van Horn RL, Penson DF. Long-term functional outcomes after treatment for localized prostate cancer. N Engl J Med. 2013;368(5):436–45.PubMedCentralPubMedCrossRef

24.

Sanda MG, Dunn RL, Michalski J, et al. Quality of life and satisfaction with outcome among prostate-cancer survivors. N Engl J Med. 2008;358:1250–61.PubMedCrossRef

25.

Johansson E, Steineck G, Holmberg L, et al. Long-term quality-of-life outcomes after radical prostatectomy or watchful waiting: the Scandinavian Prostate Cancer Group-4 randomised trial. Lancet Oncol. 2011;12:891–9.PubMedCrossRef

26.

Glass AS, Cooperberg MR, Carroll PR. Early detection of prostate cancer: more information, more clarity. Eur Urol. 2012;62(5):753–5; discussion 755–6.PubMedCrossRef

27.

Schröder FH, Hugosson J, Carlsson S, et al. Screening for prostate cancer decreases the risk of developing metastatic disease: findings from the European Randomized Study of Screening for Prostate Cancer (ERSPC). Eur Urol. 2012;62:745–52.PubMedCrossRef

28.

Klotz L, Zhang L, Lam A, et al. Clinical results of long-term follow-up of a large, active surveillance cohort with localized prostate cancer. J Clin Oncol. 2010;28:126–31.PubMedCrossRef

29.

Wilt TJ, Brawer MK, Jones KM, et al. Radical prostatectomy versus observation for localized prostate cancer. N Engl J Med. 2012;367:203–13.PubMedCentralPubMedCrossRef

30.

NIH State-of-the-Science Conference. Role of active surveillance in the management of men with localized prostate cancer. 2011. Available at: http://​consensus.​nih.​gov/​2011/​prostate.​htm. Accessed 21 Dec 2011.

31.

Lecornet E, Ahmed HU, Hu Y, et al. The accuracy of different biopsy strategies for the detection of clinically important prostate cancer: a computer simulation. J Urol. 2012;188:974–80.PubMedCrossRef

32.

Carlsson S, Sandin F, Fall K, Lambe M, Adolfsson J, Stattin P, Bill-Axelson A. Risk of suicide in men with low-risk prostate cancer. Eur J Cancer. 2013;49:1588–99.PubMedCrossRef

33.

Fung-Kee-Fung SD, Porten SP, Meng MV, Kuettel M. The role of active surveillance in the management of prostate cancer. J Natl Compr Canc Netw. 2013;11(2):183–7.PubMed

34.

Bill-Axelsen A, Holmberg L, Mirrja R, et al. Watchful waiting and prostate cancer. NEJM. 2005;352:1977–84.CrossRef

35.

Merrill RM, Stephenson RA. Trends in mortality rates in patients with prostate cancer during the era of prostate specific screening. J Urol. 2000;163:503–10.PubMedCrossRef

36.

Eggener SE, Scardino PT, Carroll PR, Zelefsky MJ, Sartor O, Hricak H, Wheeler TM, Fine SW, Trachtenberg J, Rubin MA, Ohori M, Kuroiwa K, Rossignol M, Abenhaim L, International Task Force on Prostate Cancer and the Focal Lesion Paradigm. Focal therapy for localized prostate cancer: a critical appraisal of rationale and modalities. J Urol. 2007;178(6):2260–7.PubMedCrossRef

37.

Ahmed HU, Hindley RG, Dickinson L, Freeman A, Kirkham AP, Sahu M, Scott R, Allen C, Van der Meulen J, Emberton M. Focal therapy for localised unifocal and multifocal prostate cancer: a prospective development study. Lancet Oncol. 2012;13(6):622–32.PubMedCentralPubMedCrossRef

38.

Dickinson L, Ahmed HU, Allen C, et al. Magnetic resonance imaging for the detection, localisation, and characterisation of prostate cancer: recommendations from a European consensus meeting. Eur Urol. 2011;59:477–94.PubMedCrossRef

© Springer-Verlag France 2015

Eric Barret and Matthieu Durand (eds.)Technical Aspects of Focal Therapy in Localized Prostate Cancer10.1007/978-2-8178-0484-2_2

2. The Concept of the Index Lesion

Ian A. Donaldson¹, ², Mark Emberton¹, ², Alex Freeman³ and Hashim U. Ahmed¹, ²  

(1)

Division of Surgery and Interventional Science, University College London, London, UK

(2)

Department of Urology, University College London Hospitals NHS Foundation Trust, London, UK

(3)

Department of Histopathology, University College London Hospitals NHS Foundation Trust, London, UK

Hashim U. Ahmed

Email: [email protected]

2.1 Introduction

Prostate cancer is a multifocal disease, but not all of these lesions will cause harm. Recent evidence has been building to suggest that it is the largest and highest-grade cancer which drives the disease to grow, invade, metastasise and lead to premature death (Fig. 2.1). This tumour has been popularly coined the index lesion and, arguably, is central to the entire discipline of focal therapy.

Fig. 2.1

The index lesion hypothesis states that the largest and highest-grade tumour (usually one and the same) is alone capable of metastases

The introduction of PSA has shifted the landscape in which prostate cancer is now detected [1]. Whilst the ability to screen for prostate cancer before it is clinically apparent is of obvious benefit to men who have aggressive disease, there is a real risk of detecting and treating smaller lower-grade cancers that may never cause harm [2]. As such, if not all cancer lesions are clinically significant, one can contemplate changing the management of prostate cancer from treatment directed to the whole gland to treatment directed only to disease that will cause a reduction in either quality or length of life. This represents a radical shift in how we treat the disease, but it certainly is in tune with the paradigm shifts we have witnessed in breast, thyroid, kidney and liver cancers to just name a few. The concept of the index lesion therefore runs to the very core of attempts to reduce the harms of screening and treatment of prostate cancer, since systematic biopsies which inadvertently detect indolent disease will need to be replaced by targeted precision biopsies directed at a lesion of concern [3].

2.2 Clinically Significant Disease and Tumour Multifocality

Tumour multifocality in solid organs is not a novel phenomenon. It is not only found in prostate cancer (Fig. 2.2), but it is also well recognised at various rates of incidence in the breast, thyroid, lung and even renal cancers. In these cancers physicians have taken an approach to treat only the cancer that will cause harm, leave small indolent tumours (often unknown of) and preserve healthy tissue. In breast cancer, lumpectomy and localised radiotherapy might now be favoured over whole breast adjuvant radiotherapy as recurrences predominantly occur in the area of surgical resection after lumpectomy [4]. The importance of preservation of healthy thyroid tissue is well recognised by colleagues in head and neck oncology leading to renaming the clinically insignificant disease papillary microcarcinoma [5]. The high rates of small lung tumours found at autopsy that would have caused more harm by investigation and treatment are commonly called pseudo-disease in recognition of their non-malignant behaviour. Such a concept is made easier because the diagnostic pathway in those malignancies involves detection of the clinical phenotype, either visually, with palpation or by imaging. In other words, diagnosis and treatment are directed at measurable disease.

Fig. 2.2

Sections taken from radical prostatectomy specimens (a–e) and pathology diagram showing dominant Gleason pattern 4 + 3 lesion with secondary satellite Gleason pattern 3 + 3 prostate cancer (f)

In stark contrast to this, prostate cancer is typically detected by a somewhat random deployment of 10–12 transrectal needles, and the disease is confirmed histologically on these microscopic samples. This technique has been deemed adequate as the presence of disease in the prostate was all that was required to inform treatment directed at a whole gland level. By virtue of finding lots of lesions through this biopsy strategy, the multifocality of the disease has been used as a rationale to treat the entire prostate. However, informed treatment decisions based on biochemical and pathological