High Local Control Following Pre-Operative Radiotherapy for Adult Deep Soft Tissue Sarcoma of the Head and Neck.

PURPOSE/OBJECTIVE(S): Local control (LC) of head and neck (HN) soft tissue sarcoma (STS) is generally lower than the > 90% rate expected in extremity STS. We report outcomes of high-risk adult HN STS [defined as requiring surgery and radiotherapy (RT) after joint in-person assessment by a HN surgeon and radiation oncologist with expertise in sarcoma management] using pre-operative (Pre-op) RT to reduce target volumes adjacent to optic or other vulnerable anatomy.

MATERIALS/METHODS: A prospective series of newly diagnosed adult HN STS patients who underwent Pre-op RT between 1989-2019 was analyzed. Angiosarcoma, fibromatosis, and embryonal/alveolar rhabdomyosarcoma were not included due to natural history requiring different management paradigms; other histologies were excluded due to the anticipated favorable control rates in these subtypes (i.e., dermatofibrosarcoma protuberans, HN sinonasal solitary fibrous tumor/hemangiopericytoma). Actuarial rates of LC, distant control (DC), and overall survival (OS) were analyzed by resection margin status. Important wound complications, defined according to a published randomized trial evaluating Pre-op RT in extremity STS, were also reported.

RESULTS: Eligibility comprised 59 cases arising from neck/supraclavicular (n = 23), sinonasal (n = 16), oral (n = 11), parapharyngeal (n = 7), and scalp (n = 2) regions. UICC/AJCC TNM-8 cT-categories were: T1 (n = 10), T2 (n = 20), T3 (n = 20), and T4 (n = 9). Neoadjuvant chemotherapy was given to 3 patients (2 rhabdomyosarcomas and 1 synovial sarcoma). Pre-op RT included: 50 Gy in 25 fractions over 5 weeks (n = 53) or 60 Gy in 30 fractions over 6 weeks (n = 6). Median interval from pre-op RT to surgery was 7.3 weeks (range: 2.9-19.6). Four patients (6.7%) had wound complications considered important according to the defined criteria. One healed following flap debridement and the remainder only required conservative management. Resection margins were grossly positive (gross+) in 4 (7%), microscopically positive (micro+) in 16 (27%), and negative in 39 (68%) patients. Six received a post-op boost of 10 Gy in 5 fractions (1 for micro+ and 5 for < 10 mm resection margins). Median follow-up was 6.5 years (0.8-28.6 years). Local failure occurred in 1/39 negative, 2/16 micro+, and 4/4 gross+ resection margin groups. Five-year LC, DC and OS for negative vs micro+ vs gross+ resection margin groups were: 97% vs 93% vs 25% (P < 0.001, micro+ vs negative: P = 0.083); 78% vs 75% vs 75% (P = 0.97), 83% vs 87% vs 25% (P < 0.001). No patient developed significant toxicity (e.g., blindness) related to RT.

CONCLUSION: HN STS patients requiring combined modality local management with moderate dose Pre-op RT in a sarcoma-focused multidisciplinary clinic setting have excellent LC and functional outcomes that parallel extremity cases, but with less wound complications. Micro+ margins without postop boost RT does not seem to compromise LC when managed within a collaborative environment.