PracticeUpdate Oncology May 2019

ACRO 2019 25

Recurrence Outside Treatment Field A ChallengeWith SBRT for Recurrent Head and Neck Squamous Cell Carcinoma Additional research is needed to determine which patients are most likely to benefit from this treatment modality. S tereotactic Body Radiation Ther- apy (SBRT) is a useful treatment for patients with recurrent head and neck

squamous cell carcinoma, but it has its limi- tations with regard to nodal re-occurrences outside of the radiation treatment field. Resection is the current treatment of choice for patients with recurrent head and neck squamous cell carcinoma, a disease with poor survival. But concurrent comorbidities and encasement of major vascular or neu- rological structures in the neck make some patients poor candidates for resection. SBRT has gained increasing acceptance as an alternative to conventional re-irra- diation in these patients, demonstrating a tolerable toxicity profile. " …treatment failure following SBRT was primarily from regional recurrences outside the treatment field. " “SBRT is a technique for delivering radi- ation therapy that, compared with most other modalities, delivers a relatively high dose of radiation for a relatively short period of time,” presenter Clark M. Hathe- way, a medical student at the University of Pittsburgh School of Medicine told Elsevi- er’s PracticeUpdate . “So, where a regular treatment might give 1 or 2 Gy of radiation every day for 30 days, SBRT will deliver more like 10 Gy in five or so treatments. It is a very focused and targeted treatment, so it delivers radiation to just the tumor with very little coverage of healthy, normal tissue.” In this study, 62 patients with previously irradiated nodal recurrent head and neck squamous cell carcinoma were treated with SBRT at 40 to 50 Gy in five fractions deliv- ered on non-consecutive days. Patients could also receive concurrent cetuxi- mab with or without docetaxel. Overall, 9 patients (14.5%) received SBRT alone; 8 (12.9%) received surgery with adjuvant SBRT; 38 (61.3%) received SBRT and con- current cetuximab (2 given additional docetaxel); and 7 (11.3%) received SBRT, surgery, and cetuximab. “For these patients, SBRT was considered the best option because most of them

were inoperable at this point,” explained Mr. Hatheway. “The specific concern for these patients is that if they have lymph node involvement, it is difficult to know whether their disease is too advanced to receive something as targeted as SBRT. So, we were interested in seeing where the disease would recur after treatment in the head and neck or outside of the head and neck.” Locoregional recurrence was defined recurrence within the head and neck, including at another nodal station, in-field at the treated node, or at a mucosal site. Distant recurrence was defined as those occurring outside the head and neck. After a median follow-up period of 177 days from end of treatment, 10 patients (16.1%) had persistent or progressive disease within the treatment area following SBRT, and 21 (33.9%) had locoregional recurrence outside of the SBRT treatment field. Of these latter patients, 11 experienced recur- rence in regional nodal stations, and 2 at both previously treated nodes and neigh- boring nodes. Seven experienced mucosal recurrences (including 4 at the original

primary site), and 1 had a cutaneous recur- rence. An additional 7 patients (11.3%) had distant metastases, including 5 with con- comitant locoregional disease. Toxicity rates were consistent with prior experience with SBRT. Four patients (6.5%) experienced grade ≥3 acute tox- icities including dysphagia, trismus, and laryngeal dysfunction, with one grade 4 lingual artery bleed. Eight patients (12.9%) experienced late grade ≥3 toxicities, most commonly dysphagia, while one suffered a fatal carotid injury. The authors concluded that treatment failure following SBRT was primarily from regional recurrences outside the treat- ment field. This raises concerns about the presence of undetectable disease and emphasizes the importance of developing improved imaging strategies and sensitiz- ing systemic therapy. Mr. Hatheway noted that further study should determine what factors are rele- vant in the success or failure of SBRT in this patient group. www.practiceupdate.com/c/81263

VOL. 3 • NO. 2 • 2019