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Radiation Oncology. Biology. Physics October 1982, Volume 8, Sup. 1
PRESIDENTIAL ADDRESS Monday October 25, 11:05 am, CARCINOMA OF THE PROSTATE, A VEXING BIOLOGICAL AND CLINICAL ENIGMA Carlos A. Perez, M.D. Division of Radiation Oncology, Mallinckrodt Institute of Radiology Carcinoma of the prostate poses a multiplicity of puzzling biological questions and clinical challenges. Its incidence increases with age and its behavior is closely related to the extent of involvement and microscopic characteristics of the tumor. It is a tumor of great contrasts, the prognosis ranging from extremely good in patients with well-differentiated lesions with minimal prostate involvement to extremely poor in cases of poorly differentiated, more extensive lesions. Radical prostatectomy has limited application in selected groups of patients, and frequently results in sexual impotence. The preservation of sexual potency should be a major consideration in maintaining the quality of life for patients with prostatic cancer. Though it is known that some prostatic tumors respond to hormonal manipulation, this dependence is not well understood and this therapeutic approach is besieged by empiricism. Hormonal receptors may be difficult to use as predictors of tumor response, since they are also present in the normal prostate cells. Despite some interesting observations in experimental animal models, cytotoxic agents are presently of little or no benefit in treating carcinoma of the prostate. Since 1916 there has been a great deal of interest in using irradiation to treat carcinoma of the prostate. The application of this modality has increased greatly in the past twenty years, heightened by the prospect of preserving sexual function. . The optimal doses of irradiation and volume to be treated (depending on the stage of the disease) are currently under investigation. Our inability to detect biological damage in morphologically intact cells casts strong doubts on the validity of post-irradiation biopsies and reinforces the need for the accuracy of careful clinical evaluation in the detection of local recurrences. Because of the persistence of microscopic tumor in about 20% of the irradiated prostate specimens, there is some question whether irradiation is an effective long-term antitumor agent. Correlation of histological and clinical data do suggest, however, that at least 90% of the patients with stage Band 80% of those with stage C may have prolonged tumor control in the pelvis and survival that is comparable to that obtained with other therapeutic modalities. Implantation of the prostate with r 125 following staging lymphadenectomy is a relatively po~lar procedure in the treatment of patients with stage B tumors because of its reported improved preservation of sexual function. Although staging lymphadenectomy has not been proven to have therapeutic effectiveness, it is used as an aid in patient characterization (determining status of pelvic lymph nodes). Further trials will be required to assess the therapeutic value of this approach over external irradiation. Careful patient selection and technical skills are essential in achieving optimal therapeutic results. In order to better understand the natural history of carcinoma of the prostate and the effectiveness of current therapies, further investigation of the inter-relationship of the biological behavior.of the tumor, h~rmonal milieu, and immunological status of the patient is necessary. Only then can more.ratlonal and effectlve therapeutic approaches be developed. The radiation oncologist must playa major role ln the study and treatment of this disease.
Radiation Oncology. Biology. Physics October 1982, Volume 8, Sup. 1
PRESIDENTIAL ADDRESS Monday October 25, 11:05 am, CARCINOMA OF THE PROSTATE, A VEXING BIOLOGICAL AND CLINICAL ENIGMA Carlos A. Perez, M.D. Division of Radiation Oncology, Mallinckrodt Institute of Radiology Carcinoma of the prostate poses a multiplicity of puzzling biological questions and clinical challenges. Its incidence increases with age and its behavior is closely related to the extent of involvement and microscopic characteristics of the tumor. It is a tumor of great contrasts, the prognosis ranging from extremely good in patients with well-differentiated lesions with minimal prostate involvement to extremely poor in cases of poorly differentiated, more extensive lesions. Radical prostatectomy has limited application in selected groups of patients, and frequently results in sexual impotence. The preservation of sexual potency should be a major consideration in maintaining the quality of life for patients with prostatic cancer. Though it is known that some prostatic tumors respond to hormonal manipulation, this dependence is not well understood and this therapeutic approach is besieged by empiricism. Hormonal receptors may be difficult to use as predictors of tumor response, since they are also present in the normal prostate cells. Despite some interesting observations in experimental animal models, cytotoxic agents are presently of little or no benefit in treating carcinoma of the prostate. Since 1916 there has been a great deal of interest in using irradiation to treat carcinoma of the prostate. The application of this modality has increased greatly in the past twenty years, heightened by the prospect of preserving sexual function. . The optimal doses of irradiation and volume to be treated (depending on the stage of the disease) are currently under investigation. Our inability to detect biological damage in morphologically intact cells casts strong doubts on the validity of post-irradiation biopsies and reinforces the need for the accuracy of careful clinical evaluation in the detection of local recurrences. Because of the persistence of microscopic tumor in about 20% of the irradiated prostate specimens, there is some question whether irradiation is an effective long-term antitumor agent. Correlation of histological and clinical data do suggest, however, that at least 90% of the patients with stage Band 80% of those with stage C may have prolonged tumor control in the pelvis and survival that is comparable to that obtained with other therapeutic modalities. Implantation of the prostate with r 125 following staging lymphadenectomy is a relatively po~lar procedure in the treatment of patients with stage B tumors because of its reported improved preservation of sexual function. Although staging lymphadenectomy has not been proven to have therapeutic effectiveness, it is used as an aid in patient characterization (determining status of pelvic lymph nodes). Further trials will be required to assess the therapeutic value of this approach over external irradiation. Careful patient selection and technical skills are essential in achieving optimal therapeutic results. In order to better understand the natural history of carcinoma of the prostate and the effectiveness of current therapies, further investigation of the inter-relationship of the biological behavior.of the tumor, h~rmonal milieu, and immunological status of the patient is necessary. Only then can more.ratlonal and effectlve therapeutic approaches be developed. The radiation oncologist must playa major role ln the study and treatment of this disease.