Purpose

This study used a patient-specific model to characterize and compare ideal prostate-specific antigen (PSA) kinetics for low- and intermediate-risk prostate cancer after definitive radiation treatment with conventionally fractionated, hypofractionated, stereotactic body radiation therapy, or brachytherapy, both high-dose and low-dose rate.

Methods and Materials

This retrospective analysis includes low- and intermediate-risk patients with prostate cancer treated between 1998 and 2018 at an National Cancer Institute–designated comprehensive cancer center. Demographics and treatment characteristics were prospectively collected. Patients had at least 2 PSA measurements within 24 months of treatment and were free from biochemical recurrence. The incidence of, time to, and risk factors for PSA nadir (nPSA) and bounce (bPSA) were analyzed at 24 months after radiation therapy. Ideal PSA kinetics were characterized for each modality and compared.

Results

Of 1042 patients, 45% had low-risk cancer, 37% favorable intermediate risk, and 19% unfavorable intermediate risk. nPSAs were higher for ablative modalities, both as absolute nPSA and relative to initial PSA. Median time to nPSA ranged from 14.8 to 17.1 months. Over 50% treated with nonablative therapy (conventionally fractionated, hypofractionated, and low-dose rate) reached an nPSA threshold of ≤0.5 ng/mL compared with 23% of stereotactic body radiation therapy and 33% of high-dose rate cohorts. The incidence of bPSA was 13.3% and not affected by treatment modality, Gleason score, or prostate volume. PSA decay rate was faster for ablative therapies in the 6- to 24-month period.

Conclusions

Analysis of PSA within 24 months after radiation therapy revealed ablative therapies are associated with a latent PSA response and higher nPSA. Multivariable logistics modeling revealed younger age, initial PSA above the median, presence of bPSA, and ablative therapy as predictors for not achieving nPSA ≤0.5 ng/mL. PSA decay rate appears to be faster in ablative therapies after a latent period. Understanding the different PSA kinetic profiles is necessary to assess treatment response and survey for disease recurrence.

中文翻译：

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根治性放射治疗低危和中危前列腺癌的早期前列腺特异性抗原动力学

目的

本研究使用患者特异性模型来描述和比较低危和中危前列腺癌在采用常规分割、大分割、立体定向放射治疗或近距离放射治疗进行根治性放射治疗后的理想前列腺特异性抗原 (PSA) 动力学，两者均具有高-剂量和低剂量率。

方法和材料

这项回顾性分析包括 1998 年至 2018 年间在国家癌症研究所指定的综合癌症中心接受治疗的低危和中危前列腺癌患者。前瞻性地收集了人口统计学和治疗特征。患者在治疗后 24 个月内至少进行了 2 次 PSA 测量，并且没有生化复发。在放射治疗后 24 个月时分析 PSA 最低点 (nPSA) 和反弹 (bPSA) 的发生率、时间和危险因素。对每种模式的理想 PSA 动力学进行了表征并进行了比较。

结果

在 1042 名患者中，45% 患有低风险癌症，37% 患有有利的中度风险，19% 患有不利的中度风险。nPSA 对于消融方式而言更高，无论是绝对 nPSA 还是相对于初始 PSA。nPSA 的中位时间范围为 14.8 至 17.1 个月。超过 50% 的非消融治疗（常规分割、大分割和低剂量率）达到了 ≤0.5 ng/mL 的 nPSA 阈值，而立体定向放射治疗组和高剂量率组的这一比例分别为 23% 和 33%。bPSA 的发生率为 13.3%，并且不受治疗方式、格里森评分或前列腺体积的影响。在 6 至 24 个月期间，消融疗法的 PSA 衰减速度更快。

结论

放射治疗后 24 个月内的 PSA 分析显示消融治疗与潜在的 PSA 反应和更高的 nPSA 相关。多变量逻辑模型显示年龄较小、初始 PSA 高于中值、存在 bPSA 和消融治疗是未达到 nPSA ≤0.5 ng/mL 的预测因素。在潜伏期后，PSA 衰减率在消融疗法中似乎更快。了解不同的 PSA 动力学特征对于评估治疗反应和调查疾病复发是必要的。