PET after Chemotherapy in Rhabdomyosarcoma Connective Tissue Oncology Society November 19, 2005 Michelle L. Klem, Leonard H. Wexler, Ravinder Grewal, Heiko Schoder, Paul A. Meyers, Suzanne L. Wolden Memorial Sloan-Kettering Cancer Center

Background Rhabdomyosarcoma (RMS) is the most common soft tissue sarcoma of childhood. Staging system is clinical and radiographic. PET for initial staging –Identify involved LN, distant metastases –Determine involvement of CT/MRI equivocal sites

Chest wall embryonal RMS (SUV 5.1) Supraclavicular LN (SUV 2.8) PET at Diagnosis

Hypothesis Initial treatment will result in a decreased SUV at the primary site of disease Study design- retrospective review of RMS patients who had PET scans at diagnosis and after receiving initial therapy

Methods PET scans performed on Biograph PET/CT scanner (Siemens) Discovery LS PET/CT scanner (General Electric) GE ADVANCE PET scanner (General Electric) SUV at primary, regional, distant sites, and areas of clinical suspicion Scans obtained 1 hour after iv 18 F-FDG

Patient Characteristics All patients with RMS treated at MSKCC from 2/02 till 12/04 were reviewed 20 had PET at the time of diagnosis and after receiving chemotherapy –11 patients had PET prior to any chemo –9 patients within first cycle of chemotherapy (13 days)

Patient Characteristics 13 females, 7 males Median age 12.3 years (range 2-38 years) 10 embryonal, 10 alveolar Stage –Stage II: 1 –Stage III: 14 –Stage IV: 5 Group –Group 3: 15 –Group 4: 5

Primary Site

Treatment Prior to PET All patients received 2-8 cycles of chemotherapy prior to follow up PET 5 patients completed radiation prior to PET

Rapid Response of PET to Chemotherapy

Initial SUV Median SUV SUV range All patients (n=20) Baseline PET prior to chemo (n=11) Baseline PET within 1 cycle of chemo (n=9) 4.1* *p=0.006

Results First follow up PET –median of 2.8 months after chemotherapy ( m) –median of 4 cycles of chemotherapy 18 patients had a decrease in SUV –Median decrease 3.7, range ( )

Results 12 patients with normal PET by first follow up –3 had completed radiation 18 had eventual normalization of PET No correlation of early normalization of PET with –primary site of disease, histology, stage, group –gender, age at diagnosis –SUV at diagnosis

Time to Normalization

Pathologic correlation

Response on PET 3 year old boy with alveolar RMS in the gluteal and pelvic regions

Response on PET Irinotecan/ Carboplatin 3 year old boy with alveolar RMS in the gluteal and pelvic regions

Response on PET 14 year old female with an alveolar paranasal RMS

Response on PET 14 year old female with an alveolar paranasal RMS Irinotecan/ Carboplatin

Conclusions PET has potential utility in monitoring response to treatment. SUV at primary site is higher when initial PET is prior to therapy. PET should be performed prior to chemotherapy when possible. A decrease in SUV was seen with therapy. Most patients had normalization by first follow up PET. Normalization of PET correlated with pathologic response to therapy. Further work is needed to assess if response on PET can be used to guide therapy and predict response in RMS.