Sub-stage specific surveillance imaging detects relapses in melanoma

Source: healio.com/hematology-oncology, May 2015

CHICAGO — Disease sub-stage specific PET imaging effectively detected relapses in stage III melanoma, according to findings presented at the ASCO Annual Meeting.

Jeremy Howard Lewin, MD, of Peter MacCallum Cancer Center in East Melbourne, Australia, and colleagues conducted this retrospective study to assess disease sub-stage specific PET surveillance in a cohort of 86 patients with resected stage III melanoma.

Researchers conducted whole body PET/CT scans at a single center in Australia between 2009 and 2013.

“Variation among countries and disciplines exists with regard to radiological surveillance,” Lewin said. “Most data looking at radiological surveillance has been retrospective. However, technology has been evolving and PET/CT has shown increased specificity and sensitivity compared with CT for the detection of metastatic disease.”

Patients with stage IIIA disease underwent scanning at 6 and 18 months, whereas those with stage IIIB disease underwent screening at 6, 12, 18, 24, 36, 48 and 60 months and those in the stage IIIC group underwent screening at 6, 12, 18, 24, 36 months.

Eleven patients in the stage IIIA arm, 50 in the stage IIIB arm and 25 in the stage IIIC arm underwent PET surveillance according to the schedule

The median follow-up duration was 28 months after surgery.

The overall relapse rate was 29%, which represented 4% of patients in the IIIA group, 56% in the IIIB group and 40% in the IIIC group. Eighty-eight percent of the patients who relapsed were asymptomatic at the time of scanning.

Clinicians observed incidental secondary malignancies in 7% of the cohort.

Loco-regional relapse rates were higher among patients with stage IIIA and IIIB disease than for those with IIIC disease (40% vs. 10%).

Thirty-six percent of patients who relapsed — one patient from the IIIA group, six from the IIIB group and two from the IIIC group —  underwent potentially curative resection. Five of those patients (one IIIA and four IIIB) were disease-free after 32 months of median follow-up.

An individual PET scan yielded a positive predictive value for detecting relapse at the time of scanning of 69% (95% CI, 43-87) and a negative predictive value of 99% (95% CI, 95-100) in stage IIIB disease. For stage IIIC disease, the positive predictive value was 73% (95% CI, 39-94) and the negative predictive value was 97% (95% CI, 90-100).

For detecting any relapse per patient, the surveillance protocol was associated with a positive predictive value of 68% (95% CI, 43-87) and a negative predictive value of 97% (95% CI, 83-99) in stage IIIB disease. Further, there was a positive predictive value of 73% (95% CI, 39-94) and a negative predictive value of 86% (95% CI, 57-98) in stage IIIC disease.

The sensitivity of the sub-stage specific imaging approach for detecting relapses was 88% (95% CI, 69-97) and the specificity was 84% (95% CI, 72-92).

“We identified a favorable sensitivity and specificity of sub-stage specific PET/CT imaging after resected stage 3 melanoma,” Lewin concluded. “The negative predictive value can be reassuring for patients.” — by Rob Volansky

Perspective
This gives us some justification for doing fluorodeoxyglucose PET as part of routine follow-up for stage III melanoma to detect occult metastases. The efficacy of metastatectomy may be improved by this approach. The very high negative predictive value will also provide relief from anxiety regarding recurrence. It is not known whether this will translate to an improved OS, but in context of local surgical, radiation or systemic therapy, DFS would be expected to be better. At face value, this study supports the use of PET scan evidence to support the follow-up schedule used, with a 6-month interval initially. In melanoma, 6 months is a long time, and PET scans are frequently necessary at shorter intervals or more frequently based on clinical grounds if there is high suspicion for recurrence. A definitive answer requires a prospective randomized study, perhaps as part of an adjuvant therapy trial.
Sanjay Awasthi, MD
City of Hope