ESTRO 2024 - Abstract Book

S82 ESTRO 2024 the additional time and resources required to perform these treatments. Moreover, the dosimetric advantages of OART for gynecological tumors will be presented. Invited Speaker

3459

Postoperative radiotherapy in high-risk and advanced NMSC

Nikhil Joshi

Rush University Medical Center, Radiation Oncology, Chicago, USA

Abstract:

Non-melanoma skin cancer (squamous cell carcinoma, basal cell carcinoma) is very common. Most cases are managed with surgery or definitive radiation. A small proportion of patients undergoing surgery will be deemed at high risk for local, regional or distant metastases. These patients may benefit from adjuvant radiation. Several risk stratification strategies are available. The most commonly used risk stratification tools include the 8 th edition of the AJCC staging system (head and neck primaries) and Brigham and Woman’s Hospital staging system (BWH). Genomic risk stratification tools are also emerging (decision Dx or 40-GEP test). High risk squamous cell carcinoma generally maybe defined by AJCC staging as T3/T4, persistently positive margin not amenable to further surgical revision, named cranial nerve involvement on pathology, recurrent primaries after prior optimal treatment, node positive disease (single node > 3 cm or multiple positive nodes), extra-capsular invasion, background of immunosuppression, poorly differentiated carcinoma, sarcomatoid carcinoma or other high risk histologies like clear cell carcinoma. BWH staging T2b, T3 tumors are similarly considered high risk for local and regional metastases and may benefit from adjuvant treatment. 40-GEP class 2A and class 2B correspond to high-risk skin cancers as well. High risk basal cell carcinoma generally includes very large, often neglected primary tumors with deep muscle, bone invasion where negative resection margins are difficult to obtain or close/positive margins that cannot be corrected with further surgery. This category also includes recurrent cases after prior optimal management. Patients should be discussed at a multidisciplinary tumor board to decide optimal management. The decision to offer adjuvant radiation including the site, extent and dose/fractionation will depend upon the surgery and nodal management. All patient, tumor and surgical treatment factors should therefore be considered before designing the optimal adjuvant radiation treatment plan. Intensity modulated radiation therapy (IMRT) is considered standard for high-risk head and neck skin cancer, when complex treatment volumes are to be treated. Treatment with electrons can be considered for sites amenable to this technique. Three-dimensional conformal photon radiation may be used for non-head and neck sites; IMRT might be necessary for certain complex treatment volumes. Brachytherapy is also acceptable depending upon the site to be treated. Several radiation dose-fractionation schemes may be used. These include conventional fractionation (1.8-2.0 Gy per fraction) as well hypofractionated (2.1-5.0 Gy per fraction) schedules. Generally, a BED-10 of 59.5-79.2 and BED-10 of 56-70.2 may be used for conventional and hypofractionated treatment courses, respectively. Concurrent systemic therapy is generally not recommended. Adjuvant immunotherapy is being explored in prospective clinical trials.

3463

Preclinical imaging studies of proton RBE in normal tissue: What are the mechanisms?