Fractionated HDR brachytherapy moulds for carcinoma of the pinna
ForSuperficial BCC/SCC of the pinna, no cartilage invasion
TL;DR13 pts with superficial pinna carcinoma treated with HDR moulds, 45 Gy/8 fx: complete resolution in all, no recurrences at minimum 18 mo f/u.
The transferable parameter is ultrasound-guided mould height: measuring tumour depth (0.84 mm in one case) lets the 80% isodose cover disease while leaving cartilage outside, which electrons cannot do for lesions thinner than 12 mm. Full-thickness cases needed a sandwich mould at reduced dose (42.5 Gy), so cartilage sparing is the selection criterion.
In superficial BCC or SCC confined to pinna skin without cartilage invasion on ultrasound, this supports an HDR surface mould as a cartilage-sparing RT option; it does not address lesions requiring full-thickness pinna irradiation.
The transferable parameter is ultrasound-guided mould height: measuring tumour depth (0.84 mm in one case) lets the 80% isodose cover disease while leaving cartilage outside, which electrons cannot do for lesions thinner than 12 mm. Full-thickness cases needed a sandwich mould at reduced dose (42.5 Gy).
13 details
Retrospective single-institution series of 13 pts treated at the Christie Hospital up to July 1996. Technique description with three illustrative cases.
9 BCC, 3 SCC, 1 intraepidermal carcinoma. Lesion confined to pinna skin; dermal ultrasound confirmed cartilage not invaded in all but one.
HDR microselectron with single stepping iridium source via custom vacuum-formed mould. 45 Gy in 8 fx over 5 days prescribed to the surface, mould height set so tumour depth lies within the 80% isodose. Sandwich mould case reduced to 42.5 Gy.
Complete tumour resolution in all pts, barely perceptible scar. No recurrences and no late complications over minimum 18 mo f/u.
Moderate cutaneous erythema limited to the high-dose area, settled by the 6 wk visit. No discernible reaction on the contralateral pinna skin.
Authors position moulds against electrons (poor fall-off for thin lesions, cartilage necrosis risk), 30 kVp X-rays (dose inhomogeneity on curved surfaces, limited availability) and surgery (amputation or excision with graft). No head-to-head data.
Outcomes reported as a blanket statement without per-pt f/u, actuarial LC, or a validated cosmesis scale. Late cartilage toxicity can emerge beyond 18 mo, and the LQ-based BED rationale assumes complete repair between fractions.
The contribution is technique, not efficacy: ultrasound depth measurement plus tunable source height makes the plan conformal to sub-millimetre tumour thickness. Whether a higher late-tissue BED is tolerated because of the small volume is asserted, not shown.
Single-institution case series of 13 selected pts, no comparator, 18 mo minimum f/u too short for late cartilage effects; outcomes descriptive only.
- Late cartilage toxicity beyond 18 months
- Local control vs surgery or electrons in matched pts
📚 Sources · 📄 1 paper
The longer read
This paper is best read as a technique report with an outcome footnote rather than as efficacy evidence. Its real argument is physical. Thin cutaneous lesions on the pinna sit directly over avascular cartilage, and the modality chosen has to drop off steeply within a few millimetres. The authors make a coherent case that electrons cannot do this for small fields or thin lesions, that low-energy kilovoltage beams have become hard to source and dose evenly over a curved ear, and that a mould built at a chosen source-to-skin height lets the planner place the 80% isodose just beyond the measured tumour depth. Pairing this with transdermal ultrasound, validated against excised specimens in a separate small group, is what turns the mould from a historical Manchester-system device into a conformal tool.
The clinical outcome claims deserve much less weight. Thirteen selected pts, all with superficial disease and intact cartilage, is a population in which almost any competent local therapy would control the tumour. Complete resolution and no recurrence at a minimum of 18 months is reassuring but not discriminating, and the paper offers no per-patient follow-up distribution, no actuarial local control, and no structured cosmesis assessment. The excellent cosmesis is an investigator impression.
The fractionation choice is the part a modern reader should examine most carefully. Moving from low dose rate to HDR, the authors picked 45 Gy in 8 fractions, twice daily on the middle days, and justify it with an LQ comparison against familiar regimens. They concede the late-tissue BED is higher than conventional schedules and argue the tiny irradiated volume makes this acceptable. That is plausible, but late cartilage and skin effects are exactly the events an 18-month window is too short to capture. The one sandwich case, where full-thickness irradiation was unavoidable, received a reduced dose, which reflects the authors' own concern about cartilage tolerance.
What the paper changes is narrow: it supports offering a surface mould, or by extension a modern applicator approach with depth-guided prescription, to pts with superficial pinna BCC or SCC who are poor candidates for excision or graft. It does not settle durable control, late toxicity, or how the technique compares with surgery or electrons in matched pts. It would be wrong if late cartilage necrosis or deformity emerged after the reported window, or if the uniformly good outcomes reflected selection rather than technique.