Chemical disease-free survival in localized carcinoma of prostate treated with external beam irradiation: Comparison of American Society of Therapeutic Radiology and Oncology Consensus or 1 ng/ml as endpoint

Purpose: To compare postirradiation biochemical disease-free survival using the American Society of Therapeutic Radiology and Oncology (ASTRO) Consens us or elevation of postirradiation prostate-specific antigen (PSA) level be yond 1 ng/mL as an endpoint and correlate chemical failure with subsequent appearance of clinically detected local recurrence or distant metastasis. Methods and Materials: Records of 466 patients with histologically confirme d adenocarcinoma of the prostate treated with irradiation alone between Jan uary 1987 and December 1995 were analyzed; 339 patients were treated with b ilateral 120 degrees are rotation and, starting in 1992, 117 with three-dim ensional conformal irradiation. Doses were 68-77 Gy in 1.8 to 2 Gy daily fr actions. Minimum follow-up is 4 years (mean, 5.5 years; maximum, 9.6 years) . A chemical failure was recorded using the ASTRO Consensus or when postirr adiation PSA level exceeded 1 ng/ml at any time. Clinical failures were det ermined by rectal examination, radiographic studies, and,,when clinically i ndicated, biopsy. Results: Six-year chemical disease-free survival rates using the ASTRO Cons ensus according to pretreatment PSA level for T1 tumors were: less than or equal to 4 ng/mL, 100%; 4.1-20 ng/mL, 80%; and > 20 ng/mL, 50%. For T2 tumo rs the rates were: less than or equal to 4 ng/mL, 91%; 4.1-10 ng/mL, 81%; 1 0.1-20 ng/mL, 55%; 20.1-40 ng/mL, 63%; and > 40 ng/mL, 46%. When postirradi ation PSA levels higher than 1 ng/mL were used, the corresponding 6-year ch emical disease-free survival rates for T1 tumors were 92% for pretreatment PSA levels of less than or equal to 4 ng/mL, 58-60% for levels of 4.1-20 ng /mL, and 30% for levels > 20 ng/mL. For T2 tumors, the 6-year chemical dise ase-free survival rates were 78% in patients with pretreatment PSA levels o f 4-10 ng/mL, 45% for 10.1-40 ng/mL, and 25% for > 40 ng/mL. Of 167 patient s with TI tumors, 30 (18%) developed a chemical failure, 97% within 5 years from completion of radiation therapy; no patient has developed a local rec urrence or distant metastasis. In patients with T2 tumors, overall 45 of 23 6 (19%) had chemical failure, 94% within 5 years of completion of radiation therapy; 4% have developed a local recurrence, and 10%, distant metastasis . In patients with T3 tumors, overall, 24 of 65 (37%) developed a chemical failure, 100% within 3.5 years from completion of radiation therapy; 4% of these patients developed a local recurrence,within 2 years, and 12% develop ed distant metastasis within 4 years of completion of irradiation. The aver age time to clinical appearance of local recurrence or distant metastasis a fter a chemical failure was detected was 5 years and 3 years, respectively. Conclusion: There was a close correlation between the postirradiation nadir PSA and subsequent development of a chemical failure. Except for patients with T1 tumors and pretreatment PSA of 4.1-20 ng/mL, there is good agreemen t in 6-year chemical disease-free survival using the ASTRO Consensus or PSA elevations above 1 ng/mL as an endpoint. Although the ASTRO Consensus tend s to give a higher percentage of chemical disease-free survival in most gro ups, the differenced with longer follow-up are not statistically significan t (p > 0.05). It is important to follow these patients for at least 10 gear s to better assess the significance of and the relationship between chemica l and clinical failures. (C) 2001 Elsevier Science Inc.