Analysis of loco-regional failures in head and neck cancer after radical radiation therapy.
OBJECTIVE
To investigate the anatomical distribution of loco-regional treatment failures (LRF) in patients with head and neck squamous cell carcinoma (HNSCC) in relation to clinical target volume (CTV) delineation.


METHODS
56 patients with LRF were retrospectively identified. Patients were previously treated with radical intensity modulated radiotherapy (IMRT) +/- chemotherapy. Target volumes include gross tumour volume (GTV), its volumetric expansion of 10mm (GTV-HD), CTV high dose (CTV-HD) delineated by anatomic expansion from GTV and CTV low dose (CTV-LD) defined to receive a prophylactic dose. LRF were evaluated by PET-CT or CT scan. We analysed the association between sites of LRF and target volumes and dosimetry, using image co-registration. Based on percentage of volume that received 95% of prescribed dose, LRF were classified as in-field, marginal or out-field.


RESULTS
Median interval time from end of treatment to LRF was 186days. 65 (95.6%) LRF were classified as in-field. Considering primary target volumes, 40 (58.8%) LRF occurred inside GTV, 13 (19.1%) in GTV-HD and 7 (10.3%) in CTV-HD. The overall 1-year and 2-year post-failure survival (PFS) was 45.8% and 24.2%, respectively. Post radiation LRF managed with salvage surgery had a significantly higher median PFS when compared with palliative treatments (p=0.003).


CONCLUSIONS
The majority of LRF occurred within GTV/GTV-HD, suggesting it is safe to reduce the CTV to a volumetric expansion. Given the low incidence of geographical misses, future studies should be directed towards dose escalation of high-risk volumes. Potential reduction of RT-related toxicity with volumetric expansion could facilitate salvage surgery.
Department of Clinical Oncology, Guy's and St Thomas' NHS Foundation Trust, London, UK; Department of Radiotherapy, Policlinico Umberto I, "Sapienza" University of Rome, Rome, Italy.
Francesca
F
De Felice
Department of Medical Physics, Guy's and St Thomas' NHS Foundation Trust, London, UK.
Christopher
C
Thomas
PET Imaging Centre, St Thomas' Hospital, Division of Imaging Sciences and Biomedical Engineering, King's College London, King's Health Partners, London, UK.
Sally
S
Barrington
Department of Clinical Oncology, Guy's and St Thomas' NHS Foundation Trust, London, UK.
Angela
A
Pathmanathan
Department of Clinical Oncology, Guy's and St Thomas' NHS Foundation Trust, London, UK.
Mary
M
Lei
Department of Clinical Oncology, Guy's and St Thomas' NHS Foundation Trust, London, UK. Electronic address: Teresa.GuerreroUrbano@gstt.nhs.uk.
Teresa Guerrero
TG
Urbano
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002294:Carcinoma, Squamous Cell / Q000453:epidemiology* / Q000532:radiotherapy* / Q000601:surgery; D006258:Head and Neck Neoplasms / Q000453:epidemiology* / Q000532:radiotherapy* / Q000601:surgery; D006801:Humans; D008875:Middle Aged; D009364:Neoplasm Recurrence, Local / Q000453:epidemiology*; D011879:Radiotherapy Dosage; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods*; D012189:Retrospective Studies; D012307:Risk Factors; D016879:Salvage Therapy / Q000706:statistics & numerical data; D017211:Treatment Failure; D047368:Tumor Burden
CTV; Head and neck cancer; IMRT; Loco-regional failure; Persistence; Radiation; Radical; Radiotherapy; Recurrence; Volumetric