KEY POINTS
- Investigators retrospectively selected 20 patients with pleural dissemination of thymic tumors requiring ipsilateral whole-pleural irradiation. Three plans were generated for every patient using helical tomotherapy, VMAT, and dynamic multileaf collimator IMRT; all patients were ultimately treated with tomotherapy.
- Prescription schedules were individualized and heterogeneous. They included simultaneous integrated boost regimens delivering 34.5–50 Gy in 10–20 fractions to gross disease with 20–36 Gy to the pleural cavity, or elective pleural irradiation followed by a 20 Gy in 10 fractions sequential boost.
- Tomotherapy achieved the highest prescription-dose coverage, with mean PTV coverage of 95.12% ± 2.76% and significant differences from both alternative techniques (p < 0.0001). It also provided better hotspot control and a slightly sharper extracapsular dose gradient.
- Ipsilateral lung V20 was 60.15% with tomotherapy, compared with 72.61% with VMAT and 72.03% with dynamic IMRT, an absolute reduction exceeding 12 percentage points. Ipsilateral lung mean dose, V5, and V10 were also significantly lower.
- Contralateral lung V5 was 34.07% with tomotherapy, versus 45.91% with VMAT and 44.57% with dynamic IMRT. The reduction is relevant because low-dose spread can become substantial during irradiation of the entire pleural surface.
- For both lungs combined, tomotherapy produced a mean dose of 13.45 ± 2.99 Gy, V5 of 61.82%, V10 of 45.10%, and V20 of 27.82%. Most lung metrics were significantly lower than with the other techniques, while differences for the heart, liver, and whole body were generally not significant.
- All patients completed treatment without interruption, with a mean beam-on time of 10.0 ± 3.1 minutes per fraction. However, respiratory motion was managed mainly through geometric margins rather than routine four-dimensional CT, gating, or breath-hold, and comparative pneumonitis or disease-control outcomes were not reported.
CLINICAL TAKEAWAY
Helical tomotherapy may be particularly useful for the long, concave targets encountered in whole-pleural irradiation for disseminated thymic tumors. The planning advantage is convincing, but the authors’ recommendation to use tomotherapy as first-line treatment is stronger than the evidence: prospective toxicity and control data are still needed.