The utility of initial staging PET-CT as a baseline scan for surveillance imaging in stage II and III melanoma

A comprehensive analysis of metastatic disease following surgery for clinically localized cutaneous melanoma

BACKGROUND

The National Comprehensive Cancer Network considers "baseline staging" (whole body computed tomography or positron emission tomography scans with or without brain magnetic resonance imaging scans) for all patients with asymptomatic melanoma who had a positive sentinel lymph node biopsy result. The true yield of these workups is unknown.

METHODS

We created cohorts of adult patients with malignant melanoma using the National Cancer Database (2012-2020) to mimic 3 common scenarios: 1) clinically node-negative disease, with positive sentinel lymph node biopsy results; 2) clinically node-negative disease, with negative sentinel lymph node biopsy results; and 3) clinically node-positive disease, with confirmed lymph node metastases. Multivariable regression, supervised decision trees, and nomograms were constructed to assess the risk of metastases based on key features.

RESULTS

In total, 10 371 patients were in scenario 1, 55 172 were in scenario 2, and 4012 were in scenario 3. The proportion of patients with any metastatic disease (brain metastases) were as follows: 1.4% (0.3%) in scenario 1, 0.3% (<0.1%) in scenario 2, and 11.6% (1.6%) in scenario 3. On multivariable regression, Breslow depth greater than 4, ulceration, and lymphovascular invasion were associated with greater risk of metastatic disease. A supervised decision tree for patients in scenarios 1 and 2 found that the only groups with more than 2% risk of metastases were groups with T4 tumors or T2/T3 tumors with ulceration and lymphovascular invasion. Most groups had a negligible risk (<0.1%) of brain metastases.

CONCLUSION

This study is the first large analysis to guide the use of imaging for cutaneous melanoma. Among patients with clinically node negative disease, metastatic disease is uncommon, and brain metastases are exceedingly rare. Further investigation could promote a tailored approach to metastatic workups guided by individual risk factors.

Effectiveness of clinical and instrumental follow-up for cutaneous melanoma

INTRODUCTION

Follow-up guidelines for melanoma greatly differ in the methods of screening for recurrence, and timing and duration of the follow up, with many areas of controversy and a lack of general consensus. The aims of this study are to present our protocol and case series for follow up and to summarize and discuss current literature on melanoma follow-up guidelines/recommendations in different countries.

METHODS

We retrospectively reviewed 539 patients operated for melanoma between 2004 and 2013 at the same Institution. Data on the diagnostic role of the different clinical and instrumental detection methods were adjusted for sex, age at diagnosis, staging and evaluated by Fisher's exact test and multivariate analysis. Recommendations from the literature were summarized and discussed.

RESULTS

Local recurrences and second melanoma were always identified through physical examination, irrespectively of melanoma staging. Regional metastases were most often identified through physical examination and ultrasound, being more frequent in stage II and III, while distant metastases were most often identified through CT scans. Surveillance follow-up schedules vary significantly depending on country, physician specialty, and stage of disease, with a lack of evidence on the efficacy of the different schemes. Similarities and controversies in the different follow-up protocols are presented and discussed.

CONCLUSION

Our clinical series showed that physical examination is very powerful in identifying local recurrences and second melanomas. Physical examination and ultrasound are equally powerful in identifying regional metastases, and alternating them over time could allow to reduce the number of follow-up visits. CT scans, differently from chest x-ray, showed a high power in identifying distant metastases. Surveillance follow-up schedules in the literature vary significantly depending on country, physician specialty, and stage of disease, with a lack of evidence on the efficacy of the different schemes. Standard protocols are desirable for a better evaluation of results.

"The Benefit Of Positron Emission Tomography/Computed Tomography In Stage I And Stage II Melanomas With High-Risk Decisiondx-Melanoma Scores"

INTRODUCTION

Early detection of melanoma is instrumental as the 5-year survival decreases from 93.3% to <50% when metastases are present.^1-3 Distinguishing which patients require closer follow-up can be difficult for melanoma patients. Developments by Castle Biosciences' (Friendswood, TX) DecisionDx-Melanoma (DDx-M) use 31 melanoma associated genes to stratify melanomas into 4 classes with 1A having lowest risk of morbidity and mortality and 2B the highest.⁵ We assessed the benefit of providing additional ¹⁸FDG-PET-CT and brain MRI to genetically high-risk patients who may have otherwise been overlooked.

METHODS

297 patients at our institution had biopsies sent for DDx-M between 2014 and 2021. Patients found to have Class 2 melanomas received additional screening with yearly ¹⁸FDG-PET-CT scans and brain MRIs. Patients with Class 2 DDx-M scores and negative SLNB were included in the study. 66 met inclusion criteria and received imaging.

RESULTS

Within 3 years of follow-up, 8/66 (12.1%) patients had metastases detected by ¹⁸FDG-PET-CT scans. No patients with stage IA or IB went on to develop metastases.

DISCUSSION

¹⁸FDG-PET-CT scans detect metastases in < 3% of the time when all stage I and II patients are scanned; however, by using DDx-M in our screening protocols, we achieved a detection rate of 12.1%.^6,7 These patients went on to receive treatment and would have otherwise progressed undetected, leading to higher morbidity and mortality.

CONCLUSION

We suggest all patients with initial stage II or above melanomas receive a DDx-M score and those with class 2 receive yearly ¹⁸FDG-PET-CT/brain MRI imaging.

Yield of baseline imaging for distant metastases in high-risk primary melanoma

BACKGROUND

The yield of baseline imaging in patients presenting with higher risk primary tumours, at least American Joint Committee on Cancer 8th edition stage IIC or III melanoma, is unclear.

METHODS

This retrospective study included patients referred to the Victorian Melanoma Service from January 2017 to April 2020, diagnosed with at least stage IIC or stage III melanoma. Patients with a T4b tumour and no sentinel lymph node biopsy were included as 'T4bNX'.

RESULTS

One hundred and sixty-four patients (median age 65 years) with baseline imaging (T4bNX: 19, IIC: 30, IIIA: 21, IIIB: 43, IIIC: 50, IIID: 1) were included. The majority were male (73%), and those with T4bNX melanoma tended to be older (median age 79 years). Distant metastases were detected in 21% (4/19) of T4bNX, 3% (1/30) of stage IIC, 0% (0/21) of stage IIIA, and 6% (6/94) of stages IIIB-D melanoma patients. All stage III patients with distant metastases had palpable lymphadenopathy a presentation. Two patients had brain metastases, both of whom had T4bNX melanoma and synchronous extra-cranial metastases.

CONCLUSIONS

Compared to stage IIC, baseline imaging detects higher rates of extra-cranial distant disease in stages IIIB-D and T4bNX melanoma. Intracranial imaging has greater yield in patients with distant extra-cranial disease.