Tags

Type your tag names separated by a space and hit enter

Dose-response characteristics of low- and intermediate-risk prostate cancer treated with external beam radiotherapy.
Int J Radiat Oncol Biol Phys. 2005 Mar 15; 61(4):993-1002.IJ

Abstract

PURPOSE

In this era of dose escalation, the benefit of higher radiation doses for low-risk prostate cancer remains controversial. For intermediate-risk patients, the data suggest a benefit from higher doses. However, the quantitative characterization of the benefit for these patients is scarce. We investigated the radiation dose-response relation of tumor control probability in low-risk and intermediate-risk prostate cancer patients treated with radiotherapy alone. We also investigated the differences in the dose-response characteristics using the American Society for Therapeutic Radiology and Oncology (ASTRO) definition vs. an alternative biochemical failure definition.

METHODS AND MATERIALS

This study included 235 low-risk and 387 intermediate-risk prostate cancer patients treated with external beam radiotherapy without hormonal treatment between 1987 and 1998. The low-risk patients had 1992 American Joint Committee on Cancer Stage T2a or less disease as determined by digital rectal examination, prostate-specific antigen (PSA) levels of < or =10 ng/mL, and biopsy Gleason scores of < or =6. The intermediate-risk patients had one or more of the following: Stage T2b-c, PSA level of < or =20 ng/mL but >10 ng/mL, and/or Gleason score of 7, without any of the following high-risk features: Stage T3 or greater, PSA >20 ng/mL, or Gleason score > or =8. The logistic models were fitted to the data at varying points after treatment, and the dose-response parameters were estimated. We used two biochemical failure definitions. The ASTRO PSA failure was defined as three consecutive PSA rises, with the time to failure backdated to the mid-point between the nadir and the first rise. The second biochemical failure definition used was a PSA rise of > or =2 ng/mL above the current PSA nadir (CN + 2). The failure date was defined as the time at which the event occurred. Local, nodal, and distant relapses and the use of salvage hormonal therapy were also failures.

RESULTS

On the basis of the ASTRO definition, at 5 years after radiotherapy, the dose required for 50% tumor control (TCD(50)) for low-risk patients was 57.3 Gy (95% confidence interval [CI], 47.6-67.0). The gamma50 was 1.4 (95% CI, -0.1 to 2.9) around 57 Gy. A statistically significant dose-response relation was found using the ASTRO definition. However, no dose-response relation was noted using the CN + 2 definition for these low-risk patients. For the intermediate-risk patients, using the ASTRO definition, the TCD(50) was 67.5 Gy (95% CI, 65.5-69.5) Gy and the gamma50 was 2.2 (95% CI, 1.1-3.2) around TCD(50). Using the CN + 2 definition, the TCD(50) was 57.8 Gy (95% CI, 49.8-65.9) and the gamma50 was 1.4 (95% CI, 0.2-2.5). Recursive partitioning analysis identified two subgroups within the low-risk group, as well as the intermediate-risk group: PSA level <7.5 vs. > or =7.5 ng/mL. Most of the benefit from the higher doses for the low- and intermediate-risk group was derived from the patients with the higher PSA values. For the low-risk group, the dose-response curves essentially plateaued at 78 Gy.

CONCLUSION

A dose-response relation was found using the ASTRO definition for low-risk prostate cancer. However, we found only marginal or no dose-response relation when the CN + 2 definition was used. Most of the benefit from the higher doses derived from low-risk patients with higher PSA levels. In all cases, little projected gain appears to exist at doses >78 Gy for these patients. A dose-response relation was noted for the intermediate-risk patients using either the CN + 2 or ASTRO definition. Most of the benefit from the higher doses also derived from the intermediate-risk patients with higher PSA levels. Some room for improvement appears to exist with additional dose increases in this group.

Authors+Show Affiliations

Department of Radiation Oncology, The University of Texas M. D. Anderson Cancer Center, 1515 Holcombe Blvd., Box 97, Houston, TX 77030, USA. mrcheung@mdanderson.orgNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info available

Pub Type(s)

Journal Article

Language

eng

PubMed ID

15752878

Citation

Cheung, Rex, et al. "Dose-response Characteristics of Low- and Intermediate-risk Prostate Cancer Treated With External Beam Radiotherapy." International Journal of Radiation Oncology, Biology, Physics, vol. 61, no. 4, 2005, pp. 993-1002.
Cheung R, Tucker SL, Lee AK, et al. Dose-response characteristics of low- and intermediate-risk prostate cancer treated with external beam radiotherapy. Int J Radiat Oncol Biol Phys. 2005;61(4):993-1002.
Cheung, R., Tucker, S. L., Lee, A. K., de Crevoisier, R., Dong, L., Kamat, A., Pisters, L., & Kuban, D. (2005). Dose-response characteristics of low- and intermediate-risk prostate cancer treated with external beam radiotherapy. International Journal of Radiation Oncology, Biology, Physics, 61(4), 993-1002.
Cheung R, et al. Dose-response Characteristics of Low- and Intermediate-risk Prostate Cancer Treated With External Beam Radiotherapy. Int J Radiat Oncol Biol Phys. 2005 Mar 15;61(4):993-1002. PubMed PMID: 15752878.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Dose-response characteristics of low- and intermediate-risk prostate cancer treated with external beam radiotherapy. AU - Cheung,Rex, AU - Tucker,Susan L, AU - Lee,Andrew K, AU - de Crevoisier,Renaud, AU - Dong,Lei, AU - Kamat,Ashish, AU - Pisters,Louis, AU - Kuban,Deborah, PY - 2004/03/23/received PY - 2004/07/19/revised PY - 2004/07/23/accepted PY - 2005/3/9/pubmed PY - 2005/4/21/medline PY - 2005/3/9/entrez SP - 993 EP - 1002 JF - International journal of radiation oncology, biology, physics JO - Int J Radiat Oncol Biol Phys VL - 61 IS - 4 N2 - PURPOSE: In this era of dose escalation, the benefit of higher radiation doses for low-risk prostate cancer remains controversial. For intermediate-risk patients, the data suggest a benefit from higher doses. However, the quantitative characterization of the benefit for these patients is scarce. We investigated the radiation dose-response relation of tumor control probability in low-risk and intermediate-risk prostate cancer patients treated with radiotherapy alone. We also investigated the differences in the dose-response characteristics using the American Society for Therapeutic Radiology and Oncology (ASTRO) definition vs. an alternative biochemical failure definition. METHODS AND MATERIALS: This study included 235 low-risk and 387 intermediate-risk prostate cancer patients treated with external beam radiotherapy without hormonal treatment between 1987 and 1998. The low-risk patients had 1992 American Joint Committee on Cancer Stage T2a or less disease as determined by digital rectal examination, prostate-specific antigen (PSA) levels of < or =10 ng/mL, and biopsy Gleason scores of < or =6. The intermediate-risk patients had one or more of the following: Stage T2b-c, PSA level of < or =20 ng/mL but >10 ng/mL, and/or Gleason score of 7, without any of the following high-risk features: Stage T3 or greater, PSA >20 ng/mL, or Gleason score > or =8. The logistic models were fitted to the data at varying points after treatment, and the dose-response parameters were estimated. We used two biochemical failure definitions. The ASTRO PSA failure was defined as three consecutive PSA rises, with the time to failure backdated to the mid-point between the nadir and the first rise. The second biochemical failure definition used was a PSA rise of > or =2 ng/mL above the current PSA nadir (CN + 2). The failure date was defined as the time at which the event occurred. Local, nodal, and distant relapses and the use of salvage hormonal therapy were also failures. RESULTS: On the basis of the ASTRO definition, at 5 years after radiotherapy, the dose required for 50% tumor control (TCD(50)) for low-risk patients was 57.3 Gy (95% confidence interval [CI], 47.6-67.0). The gamma50 was 1.4 (95% CI, -0.1 to 2.9) around 57 Gy. A statistically significant dose-response relation was found using the ASTRO definition. However, no dose-response relation was noted using the CN + 2 definition for these low-risk patients. For the intermediate-risk patients, using the ASTRO definition, the TCD(50) was 67.5 Gy (95% CI, 65.5-69.5) Gy and the gamma50 was 2.2 (95% CI, 1.1-3.2) around TCD(50). Using the CN + 2 definition, the TCD(50) was 57.8 Gy (95% CI, 49.8-65.9) and the gamma50 was 1.4 (95% CI, 0.2-2.5). Recursive partitioning analysis identified two subgroups within the low-risk group, as well as the intermediate-risk group: PSA level <7.5 vs. > or =7.5 ng/mL. Most of the benefit from the higher doses for the low- and intermediate-risk group was derived from the patients with the higher PSA values. For the low-risk group, the dose-response curves essentially plateaued at 78 Gy. CONCLUSION: A dose-response relation was found using the ASTRO definition for low-risk prostate cancer. However, we found only marginal or no dose-response relation when the CN + 2 definition was used. Most of the benefit from the higher doses derived from low-risk patients with higher PSA levels. In all cases, little projected gain appears to exist at doses >78 Gy for these patients. A dose-response relation was noted for the intermediate-risk patients using either the CN + 2 or ASTRO definition. Most of the benefit from the higher doses also derived from the intermediate-risk patients with higher PSA levels. Some room for improvement appears to exist with additional dose increases in this group. SN - 0360-3016 UR - https://www.unboundmedicine.com/medline/citation/15752878/Dose_response_characteristics_of_low__and_intermediate_risk_prostate_cancer_treated_with_external_beam_radiotherapy_ L2 - https://linkinghub.elsevier.com/retrieve/pii/S0360-3016(04)02129-7 DB - PRIME DP - Unbound Medicine ER -