Additional cell damage after transpupillary thermotherapy in choroidal malignant melanoma

Non-Therapeutic Laser Retinal Injury

BACKGROUND:

As lasers have become an increasingly important component of commercial, industrial, military, and medical applications, reported incidents of non-therapeutic laser eye injuries have increased. The retina is particularly vulnerable due to the focusing power and optical transparency of the eye. Continued innovations in laser technology will likely mean that lasers will play an increasingly important and ubiquitous role throughout the world. Critical evaluation should thus be paid to ensure that non-therapeutic injuries are minimized, recognized, and treated appropriately.

METHODS:

A comprehensive literature review on the PubMed database was conducted to present case reports and case series representative of the variety of laser eye injuries in different injury circumstances, tissue types, and biological damage mechanisms.

RESULTS:

A general summary of non-therapeutic laser retina injuries is presented, including information about growth of the industry, increasingly accessible online markets, inconsistent international regulation, laser classifications, laser wavelengths, and laser power, mechanisms of tissue injury, and a demonstration of the variety of settings in which injury may occur. Finally, 68 cases found in the literature are summarized to illustrate the presentations and outcomes of these patients.

CONCLUSIONS:

As non-therapeutic laser eye injuries increase in frequency, there is a greater need for public health, policy, diagnosis, and treatment of these types of injuries.

Primary transpupillary thermotherapy for choroidal indeterminate melanocytic lesions

OBJECTIVE

This study aimed to assess the ocular and metastatic outcomes of patients with choroidal indeterminate melanocytic lesions treated by primary transpupillary thermotherapy (TTT).

DESIGN

Retrospective case series.

PARTICIPANTS

Eight patients presenting choroidal indeterminate melanocytic lesions treated by primary TTT.

METHODS

A retrospective chart review was conducted for patients with a newly diagnosed choroidal indeterminate melanocytic lesion treated by at least 3 TTT sessions from 2002 to 2011. Best-corrected visual acuity and lesion dimensions were measured at baseline and during follow-up. Complications were recorded including lesion growth, metastasis, melanoma-related mortality, and treatment-related complications.

RESULTS

Mean initial thickness was 2.0 ± 0.8 mm. Patients had an average of 3.0 ± 0.9 risk factors for lesion growing. Three patients (38%) had lesion growth. Two patients (25%) had severe visual loss (>1.0 logMAR) directly related to TTT treatment. There were no fatalities due to metastasis.

CONCLUSIONS

Despite careful patient selection and systematic treatment with at least 3 TTT sessions, the use of primary TTT to treat patients with choroidal indeterminate melanocytic lesions with ≥ 1 risk factor for lesion growth yielded poor local lesion control and the possibility for severe ocular complications.

TRANSPUPILLARY THERMOTHERAPY

PURPOSE

To correlate changes in primate fundus after transpupillary thermotherapy (TTT) at two wavelengths.

METHODS

Twelve primate eyes were treated with TTT using a wavelength of 635 nm (n=7) or 810 nm (n=5). Laser parameters were as follows: 635 nm (spot size, 1 mm; duration, 30-8 seconds; and fluence [power over time], 20-91.4 J/cm) and 810 nm (spot size, 2 mm; duration, 60 seconds; and fluence, 96-436 J/cm). Fundus photography, fluorescein and indocyanine green angiography, and enucleation were performed at time 0 or 2 weeks after TTT for histologic analysis.

RESULTS

Threshold for fundus lesions (91.4 J/cm at 635 nm and 191 J/cm at 810 nm), acute and chronic retinal damage shown by histologic analysis (79.2 J/cm at 635 nm and 96 J/cm at 810 nm), and choroidal vessel occlusion (50 J/cm at 635 nm and 96 J/cm at 810 nm) were lower at 635 nm. Disorganization of the retina and retinal pigment epithelium was seen for both wavelengths at time 0 and 2 weeks after TTT. Occlusion of the choriocapillaris and choroidal stromal vessels was noted only in specimens obtained 2 weeks after TTT.

CONCLUSIONS

TTT resulted in acute and delayed damage to the neurosensory retina that persisted at 2 weeks. The 635-nm wavelength demonstrated a lower threshold fluence for visible fundus lesions, retinal damage, and choroidal vascular occlusion than the 810-nm laser.

Transscleral thermotherapy with laser-induced and conductive heating in hamster Greene melanoma

The purpose of this study was to investigate the cytotoxic effect of heat as induced by transscleral thermotherapy (TSTT), which may be of interest in the treatment of patients with choroidal melanoma. The aim of TSTT is to heat both the sclera and the tumor up to a cytotoxic temperature of about 60 degrees C. TSTT was performed in hamsters with subcutaneously implanted Greene melanoma covered by a specimen of human donor sclera of thickness 0.5, 0.7 or 0.9 mm. A newly developed applicator, which combines conductive episcleral heating at 60 degrees C with laser-induced heating, was used at laser powers ranging from 500 to 1500 mW delivered by an 810 nm diode laser, beam diameter 3 mm, and exposure time 1 min. Temperatures were measured at the scleral surface and at the sclera-tumor interface. The extent of tumor necrosis was examined by light microscopy and the sclera was examined by polarized light microscopy. Maximal depth of tumor necrosis without scleral damage was 4.4 (SD 1.5) mm. The temperature at the scleral surface after TSTT was 58.8 (SD 2.4) degrees C. The temperature at the sclera-tumor interface ranged from 56.4 (SD 3.7) degrees C at 500 mW to 65.3 (SD 4.4) degrees C at 1250 mW laser power. Structural changes to the scleral collagen started to develop at 1250 mW. TSTT with combined laser-induced and conductive heating caused cytotoxic temperatures in the tumor and the sclera, which were well tolerated by the scleral collagen.

Transpupillary thermotherapy versus plaque radiotherapy for suspected choroidal melanomas

PURPOSE

To examine the outcomes and complications of transpupillary thermotherapy for treatment of small choroidal melanomas.

DESIGN

Retrospective case-matched comparative study and retrospective observational study.

PARTICIPANTS

The case-matched study consisted of 36 patients treated with either transpupillary thermotherapy or plaque radiotherapy (18 patients per group). The observational study consisted of 21 patients treated with transpupillary thermotherapy alone (primary transpupillary thermotherapy) and 9 patients treated with transpupillary thermotherapy plus plaque radiotherapy (adjuvant transpupillary thermotherapy).

MAIN OUTCOME MEASURES

Visual acuity, local tumor control, and metastasis.

RESULTS

The case-matched groups did not differ significantly with respect to age, gender, initial visual acuity, tumor location, or length of follow-up (mean, 33 months for transpupillary thermotherapy vs. 40 months for plaque radiotherapy). There was no significant difference in final visual acuity (P = 0.810) or postoperative visual acuity change (P = 0.919) between the 2 groups. In the observational study, the mean follow-up was 32 months (range, 4-58 months). Indications for primary transpupillary thermotherapy included documented growth (10 patients) and the presence of >/=3 risk factors for growth (11 patients). Retinal complications occurred in 16 patients (76%). The mean posttreatment visual acuity change was minus 2 lines (range, minus 9 to plus 7 lines). Local failure occurred in 6 patients (29%). Local failure was associated with an increased number of transpupillary thermotherapy spots per session (P = 0.023) and decreased tumor pigmentation (P = 0.001). Indications for adjuvant transpupillary thermotherapy included tumor radioresistance (6 patients) and the presence of risk factors for local failure (3 patients). All 9 tumors that received adjuvant transpupillary thermotherapy regressed rapidly, with no local failures. The mean postoperative visual acuity change was -1.9 lines (range, -9 to +5 lines). No patient in either study developed metastasis.

CONCLUSIONS

The recent interest in transpupillary thermotherapy as primary therapy for choroidal melanoma is based largely on the assumption that transpupillary thermotherapy may provide better visual outcomes than plaque radiotherapy. However, this study found no significant difference in visual outcomes between transpupillary thermotherapy and plaque radiotherapy. Further, the local failure rate with transpupillary thermotherapy was substantially higher than with plaque radiotherapy. The most promising role for transpupillary thermotherapy seems to be as an adjunct to plaque radiotherapy. The appropriate indications for transpupillary thermotherapy in the management of choroidal melanoma need to be re-evaluated.

Clinicopathologic findings in choroidal melanomas after failed transpupillary thermotherapy

PURPOSE

To review the clinicopathologic features of eyes enucleated after failed transpupillary thermotherapy.

DESIGN

Retrospective review.

METHODS

Pathology reports in the L.F. Montgomery Laboratory between 1998 and 2002 were searched for enucleated eyes with choroidal melanoma that had been treated only by transpupillary thermotherapy (TTT) prior to enucleation. The clinical features of the patients, including ultrasonography examination, were reviewed and compared with the pathologic findings.

RESULTS

Seven eyes from seven patients had been enucleated, representing 8% of eyes treated with TTT at our institute during the period studied. The primary indication for enucleation was tumor growth. The melanomas tended to grow laterally, with minimal if any increase in thickness. Five of the seven eyes histologically demonstrated extrascleral extension, which was detected by ultrasonography prior to enucleation in only one of those eyes.

CONCLUSIONS

Choroidal melanoma may continue to grow along a path of least resistance after TTT. The melanoma may extend laterally in the choroid and through emissary canals. Early extrascleral extension may be difficult to detect by ultrasonography.

Thermotherapy in the management of choroidal melanoma

During the past 20 years of enucleation, which was the standard treatment for choroidal melanoma over more than a century, has largely been replaced by eye salvaging therapies such as radiotherapy or local resection. In 1995 transpupillary thermotherapy (TTT) using an infrared diode laser was introduced as a new conservative therapy for patients with choroidal melanoma. TTT can be defined as a heat treatment modality, which is delivered through a dilated pupil to the tumour surface. The technique uses a wide diode laser beam diameter with a low irradiance and a long exposure time. TTT induces tumour necrosis at sub-photocoagulation levels by a direct cell destructive effect with only a few ocular complications. TTT can be performed as sole therapy or combined with plaque radiotherapy, thus permitting a lower radiation dose. For amelanotic tumours dye-enhanced TTT with indocyanine green can be used. In this paper we review the role of sole or combined TTT, related to the current other treatment modalities for choroidal melanoma.