Background
Retrospective NCDB (National Cancer Data Base) analysis. 4,056 patients who underwent surgery for thymoma or thymic carcinoma at NCDB-participating facilities, 2004–2012. Compared OS with vs without PORT. Patients categorized by Masaoka-Koga stage (I–IIA, IIB, III, IV). Excluded non-surgical patients and those who received preoperative RT.
Interventions and follow up
Arm A: PORT (N=2,001, 49%)
Arm B: No PORT (N=2,055, 51%)
Primary endpoint: OS
mFollow up: NR (2004–2012 NCDB data)
Arm B: No PORT (N=2,055, 51%)
Primary endpoint: OS
mFollow up: NR (2004–2012 NCDB data)
Results
OS (multivariable, thymoma cohort): PORT HR 0.72 (95% CI NR), P=.001 — PORT associated with superior OS
Propensity score-matched analysis: Confirmed OS advantage for PORT
Stage IIB (PORT vs no PORT): HR 0.61, P=.035
Stage III: HR 0.69, P=.020
Positive margins (R1): HR 0.53, P<.001
Stage I–IIA: HR 0.76, P=.156 — not significant
Propensity score-matched analysis: Confirmed OS advantage for PORT
Stage IIB (PORT vs no PORT): HR 0.61, P=.035
Stage III: HR 0.69, P=.020
Positive margins (R1): HR 0.53, P<.001
Stage I–IIA: HR 0.76, P=.156 — not significant
Adverse events
Main adverse events: Retrospective NCDB — RT toxicity data not systematically available.
Conclusions
PORT was associated with superior OS in thymoma (HR 0.72) on multivariable and propensity score analyses, with greatest benefit for stage IIB, stage III, and positive margins. No statistically significant benefit was demonstrated for stage I–IIA. This large NCDB analysis provides the strongest registry-level evidence supporting PORT for intermediate- and high-risk thymoma.
Key Limitations
Key Limitations: Retrospective NCDB analysis — selection bias (clinician selection of PORT patients by stage, histology, and margin status). RT dose, technique, and field not captured in NCDB. Masaoka-Koga staging may be inconsistently applied across NCDB institutions. Chemotherapy use (a confounder) was adjusted for but residual confounding remains. No prospective RCT has evaluated PORT for thymoma, and one is unlikely given rarity of the disease. The lack of significance for stage I–IIA may reflect true absence of benefit or insufficient statistical power for subgroup analysis.
Clinical Context
Jackson 2017 is the largest NCDB analysis on PORT for thymoma and provides the most compelling evidence that PORT improves OS, particularly for stage IIB, III, and R1 disease. Combined with Forquer SEER (no benefit for stage I), current NCCN recommendations: PORT after complete resection (R0) is recommended for stage II–III thymoma; PORT is strongly recommended for R1–R2 resection or any thymic carcinoma. For stage I thymoma with R0 resection, PORT can be omitted. Typical PORT dose: 45–50 Gy (R0), 54–60 Gy (R1), with IMRT to minimize cardiac, pulmonary, and esophageal toxicity.
References