Lung Tissue Damage Caused by Heat Accumulation from Adjacent Laser Application: Surgical Implications

There is a robust body of evidence that the use of laser may facilitate a lobe-sparing precision resection of a large number of metastases and therefore improve complete resection. The latter is the most important prognostic factor and thus functional and technical resectability should be the central criteria of eligibility in these cases.[1] [2] In the experience reported by Rolle et al,[1] when complete resection is gained, a 5-year survival of 41% is observed, irrespective of the primary tumor histology.

In this context, we have read with great interest the recent experimental study performed by Kirschbaum et al,[3] investigating—in the swine model—the lung tissue damage caused by heat accumulation from adjacent laser application. In this very interesting study, the authors observed at histological evaluation that in the 0.5-cm quadrants that lay distant from the “center” of the laser application, the tissue presented with cell vacuolization and membrane destruction. Otherwise, in the 1-cm quadrants, no signs of thermal cell damage were observed. The authors, translating this experimental data in the daily clinical practice, correctly suggested that: (1) laser lesions that sit further than 1 cm apart do not entail the risk of heat accumulation; (2) if two separate lung metastases are closer than 1 cm to each other, the surgeon should either wait 3 to 5 minutes for spontaneous tissue cooling before resecting the next metastasis to avoid applying the second laser shot on a surface of pulmonary parenchyma already interested and potentially damaged by the first application.

Although we are perfectly in line with these considerations, we believe that clinical implications with a higher tier of significance could—and should—be kept in mind when undertaking clinical indecisions at the time of surgery by analyzing the preliminary results reported by Kirschbaum et al.

Indeed, the histological evidence of lung parenchyma damage/destruction in the area within a radius of 0.5 cm from the laser application may represent an advantage of this method of resection because even the microscopic (not detectable) residual neoplastic cells (spreading from the metastatic lesion to the adjacent “healthy” parenchyma) could potentially be eradicated. Inspired by this assumption, we have reviewed the clinical records of patients with pulmonary metastases who underwent at our institution a “laser-assisted sublobar resection” adopting the same Nd:YAG 1,318 nm laser device (LIMAX-120, Gebrüder Martin GmbH & Co. KG, Tuttlingen, Germany) equipped with innovative characteristics (power up to 120 W; cut-line temperature up to 700°C).

From August 2012 to December 2013, a total of 19 patients with pulmonary metastases underwent “laser-assisted sublobar resection.” Multiple lesions were observed in eight cases (median, 2; range, 0–4). Surgical procedures mean time was 120 minutes (range, 50–380 minutes). No intraoperative complication as such as no remarkable bleeding or air leaks were observed. Early postoperative complications occurred in five patients (22.7%) but none of them was laser related apart from two cases of temporary diaphragmatic supraelevation. During the follow-up period (mean time, 18 months), six patients experienced a recurrence of disease (three widespread, two contralateral pulmonary, and one liver). Thus, none of the recurrences was observed at the level of pulmonary laser-assisted resection borders (“local relapse”). On the contrary, the risk of local relapse after pulmonary resection using the standard stapler devices (“stump relapse”) is not negligible even in patients who have undergone a presumptively radical resection: 10% in Saisho et al's experience.[4] Similarly, Kanai et al[5] observed a “stump relapse” in 23% of patients (in a cohort of 62 wedge resections), concluding that a diameter more than 10 mm and a distance between the pleura and the deepest end of the tumor (depth value) more than 14 mm were significant risk factors correlated with the “stump relapse.”

Although a direct comparison is obviously not methodologically correct and the data are only preliminary (this makes any clinical assumption avoid), we could speculate on the fact that the laser-assisted resection of pulmonary lesions is potentially associated with a low risk of “local relapse” when compared with standard sublobar lung resection performed via stapler devices.

In this sense, we greatly appreciate the authors' reflections and reactions of the points raised. Finally, we strongly advocate further experimental studies in the animal model but also extended retrospective comparative analyses investigating the degree of “local relapse” risk in patients who underwent a laser-assisted resection versus those where a stapler-assisted pulmonary sublobar resection was performed.

• References

• 1 Rolle A, Pereszlenyi A, Koch R, Richard M, Baier B. Is surgery for multiple lung metastases reasonable? A total of 328 consecutive patients with multiple-laser metastasectomies with a new 1318-nm Nd:YAG laser. J Thorac Cardiovasc Surg 2006; 131 (6) 1236-1242
• 2 Rolle A, Pereszlenyi A, Koch R, Bis B, Baier B. Laser resection technique and results of multiple lung metastasectomies using a new 1,318.  nm Nd:YAG laser system. Lasers Surg Med 2006; 38 (1) 26-32
• 3 Kirschbaum A, Rexin P, Pehl A, Bartsch D, Quint K. Laser Resection of Lung Tissue: Heat Accumulation from Adjacent Laser Application and How to Cool It Down. Thorac Cardiovasc Surg 2013; (e-pub ahead of print)
• 4 Saisho S, Nakata M, Sawada S , et al. Evaluation of video-assisted thoracoscopic surgery for pulmonary metastases: 11-years of experience. Surg Endosc 2009; 23 (1) 55-61
• 5 Kanai Y, Mitsuda S, Nakano T , et al. Stump recurrence after pulmonary metastasectomy from colorectal cancer [in Japanese]. Kyobu Geka 2013; 66 (4) 284-287