A nomogram for individualized estimation of survival among patients with brain metastasis

Abstract

Purpose: An estimated 24%-45% of patients with cancer develop brain metastases. Individualized estimation of survival for patients with brain metastasis could be useful for counseling patients on clinical outcomes and prognosis.

Methods: De-identified data for 2367 patients with brain metastasis from 7 Radiation Therapy Oncology Group randomized trials were used to develop and internally validate a prognostic nomogram for estimation of survival among patients with brain metastasis. The prognostic accuracy for survival from 3 statistical approaches (Cox proportional hazards regression, recursive partitioning analysis [RPA], and random survival forests) was calculated using the concordance index. A nomogram for 12-month, 6-month, and median survival was generated using the most parsimonious model.

Results: The majority of patients had lung cancer, controlled primary disease, no surgery, Karnofsky performance score (KPS) ≥ 70, and multiple brain metastases and were in RPA class II or had a Diagnosis-Specific Graded Prognostic Assessment (DS-GPA) score of 1.25-2.5. The overall median survival was 136 days (95% confidence interval, 126-144 days). We built the nomogram using the model that included primary site and histology, status of primary disease, metastatic spread, age, KPS, and number of brain lesions. The potential use of individualized survival estimation is demonstrated by showing the heterogeneous distribution of the individual 12-month survival in each RPA class or DS-GPA score group.

Conclusion: Our nomogram provides individualized estimates of survival, compared with current RPA and DS-GPA group estimates. This tool could be useful for counseling patients with respect to clinical outcomes and prognosis.

Fig. 1.

Overall Kaplan-Meier observed survival for all RTOG patients with brain metastasis with 95% CI lines. The dotted lines above and below solid line are the 95% CI lines. Numbers above the x axis are number of patients at risk at each time point.

Fig. 2.

Nomogram for 6- and 12-month survival and median survival for RTOG brain metastases patients. BA, Breast and Adenocarcinoma; BO, Breast and Other; LA, Lung and Adenocarcinoma; LL, Lung and Large cell; LO, Lung and Other; LSM, Lung and Small cell; LSQ, Lung and Squamous cell; OA, Other and Adenocarcinoma; OG, Other and GI; OR, Other and Renal; OSQ, Other and Squamous cell; SMM, Skin-Melanoma; OO, Other and Other; PR, Partial Resection; CGTR, Complete/Gross total resection.

Fig. 3.

Calibration curve based on 12-month survival prediction. Patients were grouped into quintiles of the predicted 12-month survival probabilities. The vertical bars represent 95% confidence intervals.

Fig. 4.

Distribution of nomogram 12-month survival probabilities within each RPA class. Values in parentheses indicate the number of patients. Class I: KPS ≥ 70, primary tumor controlled, age <65 years and brain metastasis only; class III: KPS < 70; class II: all others, including KPS ≥ 70 and primary uncontrolled, KPS ≥ 70 primary controlled and age ≥ 65, and KPS ≥ 70 primary controlled, age ≥ 65 and brain and other metastases.

Fig. 5.

Distribution of nomogram 12-month survival probabilities within each DS-GPA class. Values in parentheses indicate the number of patients in each DS-GPA class.