SPECT/CT lymphoscintigraphy of sentinel node(s) for superselective prophylactic irradiation of the neck in cN0 head and neck cancer patients: a prospective phase I feasibility study.

BACKGROUND: Clinically node negative HNSCC patients have a risk ranging between 18 and 45% of occult metastases, making prophylactic irradiation mandatory. Selective irradiation of nodal target volume based on international guidelines is practice. Anyway, about half the tumours lying in an anatomical subsite known to potentially drain bilaterally effectively do so, leading to unnecessary large volume irradiation. Moreover, 15% of the tumours show drainage outside of predicted basin, increasing the risk for potential geographical misses. Three-dimensional SPECT/CT lymphoscintigraphy (LS) of sentinel node(s) may help to individualize nodal target volume selection. This prospective phase I study explores its feasibility and the dosimetric impact. METHODS: Ten cN0 HNSCC patients eligible for definitive radiotherapy were imaged with SPECT/CT after 99mTc nanocolloid injection around the tumour. The neck levels containing up to four hottest nodes were identified and selected for prophylactic irradiation (CTVn-LS) by volumetric modulated arc therapy. A comparative virtual planning was performed with volumes selected according to international guidelines (CTVn-IG). RESULTS: Migration was observed in all patients (one with gamma probe only). 2.9 sentinel nodes were detected per patient on average. In some patients, accurate localization was difficult when not using thermoplastic mask for SPECT/CT. CTVn-LS was totally encompassed by CTVn-IG in all patients but one (unpredicted drainage in retropharyngeal level). On average, CTVn-LS and related planning target volumes were two times smaller than IG ones. This led to significant dose decrease in identified organs at risk as well as remaining volume at risk. CONCLUSIONS: SPECT/CT LS is a promising tool to individualize prophylactic node CTV in cN0 HNSCC patients eligible for definitive radiotherapy. Oncological safety must be confirmed by ongoing phase II study.

(18)F-fluoride PET for monitoring therapeutic response in Paget's disease of bone.

UNLABELLED: A prospective study was undertaken to evaluate PET with (18)F-fluoride for monitoring the response to bisphosphonates in Paget's disease of bones. METHODS: Fourteen patients with a monostotic (n = 9) or a polyostotic form (n = 5) of Paget's disease were scanned at baseline and at 1 and 6 mo after the beginning of treatment. Dynamic acquisition and arterial blood sampling were used to calculate the influx constant Ki (by both the Patlak [Ki-PAT] method and the nonlinear regression [Ki-NLR] method). Kinetic modeling was compared with maximal standardized uptake values (SUV(max)) and biochemical markers of bone remodeling. RESULTS: Baseline uptake of (18)F-fluoride by pagetic bones was significantly higher than in normal bones (P < 0.05). One month after the start of treatment, SUV(max), Ki-PAT, Ki-NLR, and K(1) (the unidirectional clearance of fluoride from plasma to the whole of the bone tissue) decreased significantly by 27.8%, 27.9%, 27.5%, and 23.6%, respectively. Biochemical markers were already normalized in 6 of 9 patients with monostotic disease, although all had high (18)F-fluoride uptake values. Six months after the start of treatment, (18)F-fluoride uptake further diminished by 22.3%-25.6%. Biochemical markers were normal in all but 2 patients, although 10 of 14 patients still showed high (18)F-fluoride uptake. One patient did not respond to treatment and maintained high uptake of (18)F-fluoride throughout the study. SUV(max) correlated with both Ki-PAT and Ki-NLR at baseline, 1 mo, and 6 mo (P < 0.05). Moreover, the change of SUV(max) between baseline and 1 mo, as well as between baseline and 6 mo, also correlated with the change of Ki-PAT and Ki-NLR (P < 0.05). CONCLUSION: Our results show that (18)F-fluoride PET can be used to noninvasively and accurately monitor the efficacy of treatment with bisphosphonates in Paget's disease of bones. SUV(max) correlates with Ki-PAT and Ki-NLR and, interestingly, varies in the same manner as kinetic indices. Therefore, the use of SUV(max) could avoid the need for dynamic acquisition and arterial blood sampling and would facilitate the use of whole-body PET in a clinical setting.