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Schueler and associates describe their experience with thermochemotherapy (TCT) in bilateral retinoblastoma.1 The reported results of transpupillary thermotherapy used in combination with chemotherapy are encouraging, with 86–96% tumour control.2,3 In the current series, however, local recurrence occurred in 38%.
The dosage of carboplatin used in the current series was 10 mg/kg body weight, which is lower than the standard dosage of 18.6 mg/kg body weight.4 Lower dose of carboplatin, the key drug in the chemotherapy regimen for retinoblastoma, could have influenced the higher recurrence rate.
The authors mention that they treated submacular tumours with TCT. However, in our experience, tumours located in the macular area are better treated initially with chemotherapy for 3–6 cycles in order to achieve maximum possible reduction in tumour size before considering thermotherapy. Chemotherapy reduced macular tumours tend to shrink away from the fovea towards one of the major arcades or the optic nerve, thus exposing the foveal region. Residual tumours beyond 3–6 cycles of chemotherapy could be treated with thermotherapy. A smaller scar thus produced may optimise residual central vision.
The high mean total duration of thermotherapy in the current series is probably because of a smaller spot size of 0.4 mm. The diode laser (Iris Medical Inc, Mountain View, CA, USA) with an operating microscope adapter allows for a spot size of 0.8, 1.2, and 2.0 mm.3 The relatively newer large spot indirect ophthalmoscope delivery system provides a 1.2 mm spot size.3 A larger spot size will indeed reduce the duration of thermotherapy and allow for a more uniform coverage. Corneal, iris, and lens complications are minimised with better convergent beam optical systems currently available.
We believe that with higher dose of carboplatin, staggered thermotherapy for submacular tumours, use of better optical systems for delivery and a larger spot size for thermotherapy, and judicious selection of cases, the tumour regression and vision salvage with TCT could be further optimised.
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