A word of explanation must preface any statistics on cancer of the prostate. The figures which follow deal with the disease as it is ordinarily thought of-a clinically manifest and diagnosable entity capable of causing significant morbidity and mortality.

It will be pointed out that for every case of carcinoma of the prostate that fits this description there are apparently many others that are undetectable by any readily applicable clinical means and are diagnosed only by microscopic examination of the gland.

The significance of this so-called latent cancer is debatable at present; the various aspects of this controversy will be considered later in this chapter.

Meanwhile, the figures cited deal only with clinically manifest prostatic cancer.

Incidence

31,000 new cases per year 12% of male cancer incidence

Mortality

15,400 deaths per year

10.6% of male cancer mortality

Rates And Ratio

Age

Trend Last Ten Years

Geographic Distribution

The mortality rates for prostatic cancer are remarkably constant for most of the reporting countries (Table 12). In sharp contrast are the high rate for non-white males in the United States and the low rate for males in Japan. Recent studies in Japan have revealed latent prostatic cancer in 18% of men over 50 years of age dying of other causes, a rate comparable to those reported for the United States. This observation is consistent with the theory that differences in intrinsic, perhaps hormonally controlled, factors determine the rate of clinically active and ultimately fatal prostatic cancer.

Etiology

Nothing is known of the etiology of carcinoma of the prostate at present. The profound effect of alteration of the hormonal environment on the established disease by medical or surgical means suggests an endocrine background. However, beyond this inference, little can be said.

Pathology. Clinical Vs. Latent Disease

An impressive number of papers have been published in recent years on this subject. The salient facts might be summarized as follows.

Table 12. Geographic Distribution Of Cancer Of The Prostate (Annual Mortality Rates Per 100,000-1956-1957)

•Age-adjusted on combined population of forty-six countries in 1950. *From Segi, M.: Cancer Mortality for Selected Sites in Twenty-Four Countries (1950-1957), Sendai, Japan, Tohoku University School of Medicine.

1. At autopsy or routine open surgical biopsy, depending upon how intensively the search is made, from 14 to 46% of all males over the age of 50 years can be shown to have microscopic evidence of latent cancer of the prostate.

2. The incidence of this finding increases sliarply with age and is said to be present in 80% of men 90 years of age or over.

3. No clinical evidence of the disease is apparent in these men. The diagnosis is based on microscopic evidence only.

4. On the basis of such statistics, it has been estimated that:

(a) Right now in the United States there are 10 million men harboring microscopic evidence of prostate cancer.

(b) In the future some 40 million of the 85 million American males alive at present will develop such evidence.

Such alarming figures raise certain pertinent questions:

1. Are the microscopic criteria for the diagnosis of prostate cancer valid?

2. Assuming that such criteria are valid:

(a) Will all such microscopic foci become clinically significant if the patients live long enough?

(b) Will any such foci become significant, or does prostate cancer have different beginnings? 3. Since it seems likely that the truth lies somewhere in between, i.e., some, but by no means all, of such microscopic foci will become clinically significant:

(a) What causes one focus to become aggressive while another lies dormant?

(b) How can the potentially dangerous latent lesion be distinguished from its more "benign" counterpart?

(c) What should be the clinical management of the patient found to have latent prostatic cancer?

As might be suspected, there are no clear-cut answers to these questions and few, if any, hard and fast rules to go by.

An attempt will be made to furnish some guidance in subsequent paragraphs.

Gross And Microscopic Considerations

1. Virtually all prostate cancers are adenocarcinomas.

2. The great majority of these tumors are located in the posterior lobe of the gland, making them readily accessible to palpation by the index finger through the rectum.

3. As has been pointed out, it is impossible to make any distinction, even on microscopic appearance, between latent and indolent prostate cancer with a relatively good prognosis and its much more aggressive and lethal counterpart. Such judgment takes the form of an educated guess when all of the clinical findings are available. Only the hindsight provided by observation of the clinical course of the disease can make this distinction with any degree of certainty. The therapeutic dilemmas that result from this fact are familiar to all.

4. The conventional type of resection of the prostate for relief of obstructive symptoms due to benign disease affords no protection against the development of subsequent prostatic cancer. The portion of gland removed by such a procedure is situated centrally, whereas cancer arises almost exclusively posteriorly. Thus a man with a history of the usual prostatic surgery is by no means free of the risk of cancer of this organ.

Clinical Stages

Prostatic cancer has been divided into four clinical stages by Whitmore. (Table 13).

Several facts are emphasized by Table 13:

1. Only a small proportion of prostate cancer is now diagnosed in the "early" or localized stage.

2. Latent prostatic cancer is not detectable clinically.

3. Symptomatic cancer of the prostate is not usually "early" or curable.

Table 13. Stages Of Prostatic Cancer According To Whitmore