Better View of Melanoma Lymph Nodes With SPECT/CT

Kate Johnson

September 11, 2012

September 11, 2012 — In patients with primary melanoma, improved metastatic detection and disease-free survival rates can be achieved by adding a recently introduced technique to standard preoperative sentinel lymph node (SLN) scintigraphy, according to a study published in the September 12 issue of JAMA: The Journal of the American Medical Association.

The technique — hybrid single-photon emission computed tomography/computed tomography (SPECT/CT) imaging — could help overcome a false-negative rate that can be as high as 44% with lymphoscintigraphy, the current gold standard, say the researchers, headed by Ingo Stoffels, MD, from the University of Essen-Duisburg, in Essen, Germany.

Results from what they believe is the largest study to compare the 2 techniques show that, after a mean follow-up of 28.8 months, the hybrid SPECT/CT technique resulted in a lower local relapse rate than standard lymphoscintigraphy (6.8% vs 23.8%; P = .03). It also improved the calculated 4-year disease-free survival rate (93.9% vs 79.2%; P = .02).

"Preeoperative visualization of SLN with SPECT/CT is technically feasible and facilitates the detection of additional positive SLNs," the researchers conclude.

"Our results demonstrate clear advantages of adding the described preoperative SLN imaging by SPECT/CT to the current practice of preoperative lymphoscintigraphy in patients with melanoma," they add.

These findings should prompt a fundamental change in melanoma investigation, according to an expert not involved in the study. Renato Valdés Olmos, MD, PhD, from the Department of Nuclear Medicine at the Netherlands Cancer Institute, Antoni van Leeuwenhoek Hospital, in Amsterdam, told Medscape Medical News that "in the light of these findings, a necessary adjustment of the current protocols in melanoma appears to be mandatory."

Study Details

The study was conducted in 403 melanoma patients (mean age, 58.6 years; 60.5% male) who were drawn from the prospective computerized Skin Cancer Center database at University Hospital Essen.

All patients had a melanoma Breslow thickness of at least 1.0 mm (mean, 2.69 mm), and were defined as lymph-node-negative after clinical examination and preoperative ultrasound.

A total of 254 patients underwent standard preoperative planar sentinel node scintigraphy from March 2003 to October 2008 and another 149 underwent SPECT/CT from November 2008 to April 2011. There were no differences between groups in terms of sex, age, or tumor depth.

All patients were treated in accordance with German Association of Dermatology guidelines, which recommend regional lymph node dissection for patients with a positive SLN and adjuvant chemotherapy for patients with stage IV disease.

In total, 833 SLNs were removed from the 403 patients: 358 from the 149 SPECT/CT patients and 475 from the 254 standard lymphoscintigraphy patients (2.4 vs 1.9 per patient; P < .001).

More histologically positive SLNs were detected with SPECT/CT than with standard lymphoscintigraphy (27.5% vs 18.9%; P < .001), and SPECT/CT identified significantly more positive SLNs per patient (0.34 vs 0.21; P = .04).

SPECT/CT allowed more frequent SLN excision in the head and neck than standard lymphoscintigraphy (23.5% vs 2.0%; P < .001), and provided information that changed the surgical approach in 22% of cases — usually the location of the incision (73%) — the researchers report.

There were no major complications in either group, and no statistical difference between the rate of minor complications with SPECT/CT and standard lymphoscintigraphy (4.0% vs 7.9%; P > .05). "The additional SLNs excised in the SPECT/CT cohort resulted in no increase in morbidity," write the researchers. "On the contrary, in the SPECT/CT cohort, we demonstrated a lower morbidity than in the standard cohort."

Accuracy in Obese Patients

Additionally, SPECT/CT was reliable in overweight patients and in patients with torso or extremity melanomas — 2 groups in which the effectiveness of this technique has previously been questioned.

The researchers note that obesity "has been reported as a cause for the nonvisualization of SLNs on preoperative planar lymphoscintigraphy," but found no suggestion of this problem with SPECT/CT.

In a subgroup of 31 patients classified as obese (body mass index of 30 kg/m² or higher), positive histology was detected in 25% of SLNs (5 of 20) with SPECT/CT (7 patients) and in 9.1% of SLNs (4 of 44) with standard lymphoscintigraphy (24 patients) (P < .001).

More positive SLNs per obese patient were detected with SPECT/CT than with standard lymphoscintigraphy (0.71 vs 0.16; P < .001).

The current literature recommends against preoperative SPECT/CT for patients with torso or extremity melanoma, the researchers note. However, "in our study, we were able to demonstrate the reliability and effectiveness of preoperative SPECT/CT imaging for all [SLN excisions] without preselection by anatomical site," they write.

"Basically, this study confirms the improved identification of SLN in overweight melanoma patients, as well as those with tumors in the head and neck area. This does not mean that obese patients more frequently metastasize to the lymph nodes," Dr. Stoffels told Medscape in an email.

The fact that the study showed prolonged disease-free survival but not overall survival is likely related to the short follow-up time of 28.8 months, the researchers note.

Change in Melanoma Investigation?

Dr. Valdés Olmos, who was approached by Medscape Medical News for comment, said that "the universal use of SPECT/CT as recommended by the investigators will lead to the application of this modality in all nuclear medicine departments."

In the past few years, "standard gamma cameras have been progressively replaced by modern hybrid cameras with the possibility to acquire SPECT/CT in addition to standard planar images. However, SPECT/CT for the SLN procedures is only incidentally used in many nuclear medicine departments."

Dr. Valdés Olmos and his group has published extensively on the subject of SPECT/CT imaging of SLN in melanoma, and recently reported similar findings in a smaller cohort (Ann Surg Oncol. 2012;19:1018-1023).

SPECT/CT provides "an anatomical roadmap enabling surgeons to know more precisely the location of SLN before the operation," he explained in an email. This can lead to the detection of more SLNs "in the vicinity of the primary lesions, in aberrant drainage locations, and in lymph node basins not depicted by standard planar scintigraphic images."

He added that "initial reports on the use of SPECT/CT for SLN detection in melanoma were principally positive for the head and neck.... [The study by Dr. Stoffels and colleagues] the first to demonstrate this advantage of SPECT/CT for all melanoma sites, making the SLN procedure more reliable and effective."

Additionally, their evaluation of a small number of obese patients demonstrates the ability of SPECT/CT to improve the detection of weak-signal SLNs that are frequently seen in obese patients, he noted. This might be "due to the correction for tissue attenuation, which can be applied with this modality."

The study was not supported by any grant or sponsor. Coauthor Dirk Schadendorf, MD, PhD, from University Hospital Essen, reports receiving consultancy fees, having board membership, and receiving lecture fees from GlaxoSmithKline, Novartis, Amgen, Bristol-Myers Squibb, Roche, Genentech, and MSD. Dr. Valdés Olmos has disclosed no relevant financial relationships.

JAMA. 2012;308:1007-1014. Abstract