Early Prostate-Specific Antigen Kinetics for Low- and Intermediate-Risk Prostate Cancer Treated With Definitive Radiation Therapy.

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.

A Pooled Toxicity Analysis of Moderately Hypofractionated Proton Beam Therapy and Intensity Modulated Radiation Therapy in Early-Stage Prostate Cancer Patients.

PURPOSE: Data comparing moderately hypofractionated intensity modulated radiation therapy (IMRT) and proton beam therapy (PBT) are lacking. We aim to compare late toxicity profiles of patients with early-stage prostate cancer treated with moderately hypofractionated PBT and IMRT. METHODS AND MATERIALS: This multi-institutional analysis included patients with low- or intermediate-risk biopsy-proven prostate adenocarcinoma from 7 tertiary referral centers treated from 1998 to 2018. All patients were treated with moderately hypofractionated radiation, defined as 250 to 300 cGy per daily fraction given for 4 to 6 weeks, and stratified by use of IMRT or PBT. Primary outcomes were late genitourinary (GU) and gastrointestinal (GI) toxicity. Adjusted toxicity rates were calculated using inverse probability of treatment weighting, accounting for race, National Comprehensive Cancer Network risk group, age, pretreatment International Prostate Symptom Score (GU only), and anticoagulant use (GI only). RESULTS: A total of 1850 patients were included: 1282 IMRT (median follow-up 80.0 months) and 568 PBT (median follow-up 43.9 months). Overall toxicity rates were low, with the majority of patients experiencing no late GU (56.6%, n = 1048) or late GI (74.4%, n = 1377) toxicity. No difference was seen in the rates of late toxicity between the groups, with late grade 3+ GU toxicity of 2.0% versus 3.9% (odds ratio [OR] 0.47; 95% confidence interval 0.17-1.28) and late grade 2+ GI toxicity of 14.6% versus 4.7% (OR 2.69; confidence interval 0.80-9.05) for the PBT and IMRT cohorts, respectively. On multivariable analysis, no factors were significantly predictive of GU toxicity, and only anticoagulant use was significantly predictive of GI toxicity (OR 1.90; P = .008). CONCLUSIONS: In this large, multi-institutional analysis of 1850 patients with early-stage prostate cancer, treatment with moderately hypofractionated IMRT and PBT resulted in low rates of toxicity. No difference was seen in late GI and GU toxicity between the modalities during long-term follow-up. Both treatments are safe and well tolerated.

Medical oncology consultation and minimization of overtreatment in men with low-risk prostate cancer.

PURPOSE: Specialist bias, in which specialists recommend the therapy that they are capable of delivering, is thought to influence the treatment of patients with localized prostate cancer and to contribute to overtreatment of men with limited life expectancy. Consequently, rates of active surveillance, the preferred management modality per the National Comprehensive Cancer Network (NCCN) for patients with low- and very low-risk disease and a life expectancy of less than 10 and less than 20 years, respectively, are low. We sought to determine whether consultation with a medical oncologist is associated with increased rates of active surveillance in men with low-risk prostate cancer. METHODS: We identified 188 patients with low-risk prostate cancer undergoing active surveillance at one of three referral centers in Boston, MA in 2009. Multivariable logistic regression was used to determine whether consultation with a medical oncologist was associated with selection of active surveillance. The data were reanalyzed for patients with low- and very low-risk disease and a life expectancy of less than 10 and less than 20 years, respectively. RESULTS: Consultation with a medical oncologist was associated with increased rates of active surveillance (37% v 21%, P = .01), an association that remained significant on multivariable logistic regression (odds ratio [OR] = 2.70; 95% CI, 1.27 to 5.75; P = .01). When applied to patients with limited life expectancy, this finding remained significant (OR = 4.74; 95% CI, 1.17 to 19.25; P = .03). CONCLUSION: Consultation with a medical oncologist is associated with increased rates of active surveillance, adherence to NCCN guidelines, and minimization of overtreatment in men with early prostate cancer and limited life expectancy.

Models of care and NCCN guideline adherence in very-low-risk prostate cancer.

NCCN Guidelines recommend active surveillance as the primary management option for patients with very-low-risk prostate cancer and an expected survival of less than 20 years, reflecting the favorable prognosis of these men and the lack of perceived benefit of immediate, definitive treatment. The authors hypothesized that care at a multidisciplinary clinic, where multiple physicians have an opportunity to simultaneously review and discuss each case, is associated with increased rates of active surveillance in men with very-low-risk prostate cancer, including those with limited life expectancy. Of 630 patients with low-risk prostate cancer managed at 1 of 3 tertiary care centers in Boston, Massachusetts in 2009, 274 (43.5%) had very-low-risk classification. Patients were either seen by 1 or more individual practitioners in sequential settings or at a multidisciplinary clinic, in which concurrent consultation with 2 or more of the following specialties was obtained: urology, radiation oncology, and medical oncology. Patients seen at a multidisciplinary prostate cancer clinic were more likely to select active surveillance than those seen by individual practitioners (64% vs 30%; P<.001), an association that remained significant on multivariable logistic regression (odds ratio [OR], 4.16; P<.001). When the analysis was limited to patients with an expected survival of less than 20 years, this association remained highly significant (72% vs 34%, P<.001; OR, 5.19; P<.001, respectively). Multidisciplinary care is strongly associated with selection of active surveillance, adherence to NCCN Guidelines and minimization of overtreatment in patients with very-low-risk prostate cancer.