Background

The objective of this study was to validate a simple predictive model for survival of patients with advanced cancer.

Methods

Previous studies with training and validation datasets developed a model predicting survival of patients referred for palliative radiotherapy using three readily available factors: primary cancer site, site of metastases and Karnofsky performance score (KPS). This predictive model was used in the current study, where each factor was assigned a value proportional to its prognostic weight and the sum of the weighted scores for each patient was survival prediction score (SPS). Patients were also classified according to their number of risk factors (NRF). Three risk groups were established. The Radiation Therapy and Oncology Group (RTOG) 9714 data was used to provide an additional external validation set comprised of patients treated among multiple institutions with appropriate statistical tests.

Results

The RTOG external validation set comprised of 908 patients treated at 66 different radiation facilities from 1998 to 2002. The SPS method classified all patients into the low-risk group. Based on the NRF, two distinct risk groups with significantly different survival estimates were identified. The ability to predict survival was similar to that of the training and previous validation datasets for both the SPS and NRF methods.

Conclusions

The three variable NRF model is preferred because of its relative simplicity.

Purpose

To report the long-term outcome of patients with prostate cancer treated with external beam radiation therapy and high dose rate (HDR) brachytherapy from a prospective multi-institutional trial conducted by NRG Oncology/RTOG.

Methods and materials

Patients with clinically localized (T1c-T3b) prostate cancer without prior history of transurethral resection of prostate or hip prosthesis were eligible for this study. All patients were treated with a combination of 45 Gy in 25 fractions from external beam radiation therapy and one HDR implant delivering 19 Gy in 2 fractions. Adverse events (AE) were collected using Common Toxicity Criteria for Adverse Events, version 3. Cumulative incidence was used to estimate time to severe late gastrointestinal (GI)/genitourinary (GU) toxicity, biochemical failure, disease-specific mortality, local failure, and distant failure. Overall survival was estimated using the Kaplan-Meier method.

Results

One hundred and twenty-nine patients were enrolled from July 2004 to May 2006. AE data was available for 115 patients. Patients were National Comprehensive Cancer Network (NCCN) intermediate to very high risk. The median age was 68, T1c-T2c 91%, T3a-T3b 9%, PSA ≤10 70%, PSA >10 to ≤20 30%, GS 6 10%, GS 7 72%, and GS 8 to 10 18%. Forty-three percent of patients received hormonal therapy. At a median follow-up time of 10 years, there were 6 (5%) patients with grade 3 GI and GU treatment-related AEs, and no late grade 4 to 5 GI and GU AEs. At 5 and 10 years, the rate of late grade 3 gastrointestinal and genitourinary AEs was 4% and 5%, respectively. Five- and 10-year overall survival rates were 95% and 76%. Biochemical failure rates per Phoenix definition at 5 and 10 years were 14% and 23%. The 10-year rate of disease-specific mortality was 6%. At 5 and 10 years, the rates of distant failure were 4% and 8%, respectively. The rates of local failure at 5 and 10 years were 2% at both time points.

Conclusions

Combined modality treatment using HDR prostate brachytherapy leads to excellent long-term clinical outcomes in this prospective multi-institutional trial.