Can Fdg-pet Scanning Detect Melanoma Metastases to the Spleen?

May 24, 2007
Surgical Rounds®, April 2007, Volume 0, Issue 0

Katherine Y. Kane, Resident in Surgery, Department of Surgery; Jason B. Fleming, Associate Professor of Surgery, Department of Surgery; Irfan M. Farukhi, Assistant Professor of Radiology, Department of Radiology; Carlton C. Barnett, Jr, Assistant Professor of Surgery, Department of Surgery, UT Southwestern Medical Center, Dallas, TX

Katherine Y. Kane, MD

Resident in Surgery

Department of Surgery

Jason B. Fleming, MD

Associate Professor of Surgery

Department of Surgery

Irfan M. Farukhi, MD

Assistant Professor of Radiology

Department of Radiology

Carlton C. Barnett, Jr, MD

Assistant Professor of Surgery

Department of Surgery

UT Southwestern Medical Center

Dallas, TX

Isolated melanoma metastases to the spleen are encountered infrequently, although they have been detected with concomitant disseminated malignant melanoma or at autopsy.1 Scanning with F-18 fluorodeoxyglucose (FDG) positron emission tomography (PET) has been shown to be quite sensitive in detecting melanoma metastases2 and providing guidance for appropriate surgical intervention.3 Because there is a paucity of effective systemic therapies for disseminated malignant melanoma, metastectomy or even oligo-metastectomy remain viable treatment options. The authors report a case of isolated splenic metastasis discovered by FDG-PET scanning that was amenable to complete extirpation by laparoscopic-assisted splenectomy.

The spleen is an uncommon but recognized site for hematogenous metastases in patients with advanced melanoma.1 Advances in imaging techniques such as computed tomography (CT) and F-18 fluorodeoxyglucose (FDG) positron emission tomography (PET) can help identify isolated lesions and result in the provision of more effective local and regional therapies.2,3 FDG-PET scanning revealed isolated metastases in our patient’s spleen more than 5 months after he was classified as having treated stage IIIB melanoma. We present this patient’s case and review the literature regarding isolated splenic melanoma and the associated use of FDG-PET scanning.

Case report

A 55-year-old white man presented to our clinic 1 month after having an incisional biopsy to remove a primary melanoma from his mid-back. The melanoma was 6.4 mm in depth and without ulceration.

On physical examination, obvious swelling was noted in the patient’s left posterior neck, and he reported intermittent left subcostal pain. Other than palpable nodes in the left neck, the examination was unremarkable. A fine needle aspiration of the neck mass revealed metastatic melanoma. Blood chemistry revealed a normal lactate dehydrogenase.

The patient underwent magnetic resonance imaging of his head; CT scanning of his chest, abdomen, and pelvis; and FDG-PET scanning for preoperative staging. The FDG-PET scan showed disease in the left neck and left colon.

During a subsequent colonoscopy, a large pedunculated adenomatous polyp in the left colon was removed, and no other abnormalities were observed. Following the colonoscopy, the patient underwent a wide local excision with 2-cm margins at the primary site and a modified radical left neck dissection. Because the patient had obvious macroscopic nodal involvement, he received adjuvant radiotherapy. At this point, the patient was identified as treated stage IIIB melanoma (T4a N2b M0). He declined interferon-based chemotherapy but was considered later as a potential candidate for a therapeutic trial. More than 5 months after his initial staging, the patient was restaged using CT axial imaging and FDG-PET scanning. This FDG-PET scan identified significant uptake of 2-deoxy-2[F-18] fluoro-D-glucose in the spleen, with a standard uptake value (SUV) of 6.4 above baseline (Figure 1), which represented a change from his previous FDG-PET scan (Figure 2). The rest of his work up showed no other evidence of metastatic disease.

It was thought that the patient would benefit from a splenectomy, and a laparoscopic approach was used. The spleen had obvious peripheral abnormalities on initial inspection but was removed without difficulty (Figure 3). No other intra-abdominal disease was observed. The patient tolerated the procedure well and was discharged home on postoperative day 3. The patient was alive and had no evidence of disease 9 months after his splenectomy.

Discussion

A statistical analysis of approximately 18,000 patients with localized melanoma determined that the two most powerful predictors of recurrence and death are tumor thickness and ulceration. Patient age, anatomic site, and sex are additional statistically significant prognostic factors.4,5 Because our patient is a male with a deep melanoma on the trunk, he is clearly at high risk of distant failure.

In 2006, a large unselected autopsy series involving 8,563 patients showed splenic metastases were relatively uncommon, occurring in approximately 3% of the 1,898 patients discovered to have solid tumors.1 Patients with splenic metastases were generally younger and had an average of six separate metastatic sites. After lung cancer, malignant melanoma was the second most common solid tumor to metastasize to the spleen, but this still occurred relatively infrequently, affecting only nine patients (15.8% of all splenic metastases in this series).1 It can be concluded that the spleen is a rare but known site for hematogenous metastases in patients with advanced-stage melanoma. The prognosis for these patients is poor; patients with non-lung visceral metastases have a 1-year survival rate of 40%, with a median survival of 6 to 8 months.5

Theoretically, improved imaging techniques (ie, CT and FDG-PET scanning) should help identify new, isolated lesions so local and/or regional therapies can be employed more frequently and effectively. In particular, it appears that FDG-PET scanning is quite sensitive (92%), specific (88%), and accurate (91%) on a lesion-by-lesion basis for evaluating patients with stage III and stage IV melanoma.2 At this time, FDG-PET scanning does not accurately identify microscopic disease and cannot assist in determining treatment for patients with stage I and stage II melanoma.2

FDG-PET scanning has been particularly useful in determining treatment for asymptomatic patients. The finding of metastatic disease, especially multiple non-lung visceral metastases, might lead one to forgo a potentially morbid therapy such as lymphadenectomy. Tyler and colleagues reported that FDG-PET scanning affected patient care in 15% of cases where operations were considered for stage III patients,3 whereas Mijnhout and associates reported a change in therapy for up to 40% of patients in their series who were suspected to have recurrent melanoma.5

Despite the poor prognosis for patients with isolated splenic metastases, surgery may provide long-term benefits in terms of overall and disease-free survival. A study from the Sydney Melanoma Unit included 113 patients treated for splenic melanoma between 1990 and 2001.6 Fifteen (13%) of these patients underwent splenectomy with acceptable rates of morbidity and no mortalities. Median survival of patients in the group that underwent surgery with intention to cure was 23 months, compared with 4 months for patients in the conservatively treated group.

Moreover, resection of the first metastatic lesion may delay the metastatic cascade that leads to involvement of new organ sites. It is postulated that macroscopic metastases elaborate immunosuppressive factors that blunt the host response and allow for dissemination of additional metastatic disease.6 Metastectomy removes the inimical tumor microenvironment and restores immune function.6 Complete surgical resection of all clinically evident disease with tumor-negative margins can yield a median survival of 20 months and increase the overall survival rate by 20%. These numbers compare favorably with conventional nonoperative management, where the median survival is 6 to 8 months with an overall survival rate of 6%.6 In addition to potential survival benefits, surgical resection of distant metastases confined to a single site may yield better quality of life compared with the systemic toxicities belonging to chemotherapeutic and biochemical therapies.6 Besides the possible oncologic benefits, splenectomy for bulky metastatic disease is recommended for palliation of visceral pain and to prevent spontaneous splenic rupture.7

Conclusion

With the use of appropriate imaging modalities for staging, such as CT and FDG-PET scanning, and laparoscopic techniques, patients with isolated splenic melanoma likely will benefit from laparoscopic-assisted splenectomy. As operative techniques become more refined and imaging techniques improve, aggressive treatment of solitary splenic metastases and metastectomies likely will increase.

References

Pathol Res Pract

1. Schon CA, Gorg C, Ramaswamy A, et al. Splenic metastases in a large unselected autopsy series. . 2006;202(5): 351-356.

Mol Imaging Biol

2. Harris MT, Berlangieri SU, Cebon JS, et al. Impact of 2-deoxy-2[F-18]fluoro-D-glucose positron emission tomography on the management of patients with advanced melanoma. . 2005;7(4):304-308.

Cancer

3. Tyler DS, Onaitis M, Kherani A, et al. Positron emission tomography scanning in malignant melanoma. . 2000; 89(5):1019-1025.

J Clin Oncol

4. Balch CM, Soong SJ, Gershenwald JE, et al. Prognostic factors analysis of 17,600 melanoma patients: validation of the American Joint Committee on Cancer melanoma staging system. . 2001;19(16): 3622-3634.

Nucl Med Commun

5. Mijnhout GS, Comans EF, Raijmakers P, et al. Reproducibility and clinical value of 18F-fluorodeoxyglucose positron emission tomography in recurrent melanoma. . 2002; 23(5):475-481.

J Clin Oncol

6. Hsueh EC, Essner R, Foshag LJ, et al. Prolonged survival after complete resection of disseminated melanoma and active immunotherapy with a therapeutic cancer vaccine. . 2002;20(23):4549-4554.

Tumori

7. Buzbee TM, Legha SS. Spontaneous rupture of spleen in a patient with splenic metastasis of melanoma. A case report. . 1992;78(1):47-48.

Self-assessment questions

Choose the best answer for each of the following questions.

1. Cutaneous melanoma with a depth greater than 4 mm needs a margin size greater than or equal to:

a) 0.5 cm

b) 1.0 cm

c) 1.5 cm

d) 2.0 cm

2. What is the proper melanoma staging for skin lesions that are 6.4 mm deep and associated with palpable lymph nodes?

a) Stage I

b) Stage II

c) Stage III

d) Stage IV

3. Cutaneous melanomas with organ metastases appear to benefit from:

a) Immediate surgery

b) Radiation therapy

c) Radiation therapy and surgery

d) There is no survival benefit with added therapy

4. FDG-PET scanning:

a) Possesses sensitivity close to 100% for abdominal organ metastases

b) Can detect earlier tumor activity than more conventional studies, including CT scanning

c) Works best for stage III and stage IV disease

d) All of the above

5. Surgical therapy for spleen metastases:

a) Increases overall survival rate

b) Has minimal effect on overall survival rate

c) Has no effect on overall survival rate

d) Produces better results than radiation or chemotherapy

»click to view answer