Purpose: Our goal was to evaluate the safety and toxicity of combining a PARP inhibitor, olaparib, with cetuximab and fractionated intensity-modulated radiotherapy for patients with locally advanced head and neck cancer and heavy smoking histories.Patients and Methods: Patients with ≥10 packs/year history of smoking were treated with olaparib at doses ranging from 25-200 mg orally twice daily beginning approximately 10 days prior to initiation of and with concurrent radiation (69.3 Gy in 33 fractions) using a time-to-event continual reassessment method model. Cetuximab was administered starting approximately 5 days prior to radiation per standard of care.Results: A total of 16 patients were entered onto the study, with 15 evaluable for acute toxicity. The most common treatment-related grade 3-4 side effects were radiation dermatitis and mucositis (38% and 69%, respectively). The MTD was determined to be 50 mg orally twice daily, but the recommended phase II dose was deemed to be 25 mg orally twice daily. At a median follow-up of 26 months, the actuarial median overall survival was 37 months, but was not reached for other endpoints. Two-year overall survival, progression-free survival, local control, and distant control rates were 72%, 63%, 72%, and 79%, respectively. Patients who continued to smoke during therapy experienced higher recurrence rates. MYC and KMT2A were identified as potential correlatives of response on gene amplification and mutational analysis.Conclusions: Olaparib at 25 mg orally twice daily with concurrent cetuximab and radiation was well tolerated with reduced dermatitis within the radiation field. Response rates were promising for this high-risk population. Clin Cancer Res; 24(20); 4949-59. ©2018 AACR.

Reports regarding the frequency of SMAD4 loss in human head and neck squamous cell carcinoma (HNSCC) vary significantly. We have shown that SMAD4 deletion contributes to HNSCC initiation and progression. Therefore, accurately detecting genetic SMAD4 loss is critical to determine prognosis and therapeutic interventions in personalized medicine. We developed a SMAD4 fluorescence in situ hybridization (FISH) assay to identify chromosomal SMAD4 loss at the single cell level of primary HNSCC specimens and patient derived xenograft (PDX) tumors derived from HNSCCs. SMAD4 heterozygous loss was detected in 35% of primary HNSCCs and 41.3% of PDX tumors. Additionally, 4.3% of PDX tumors had SMAD4 homozygous loss. These frequencies of SMAD4 loss were similar to those in The Cancer Genome Atlas (TCGA). However, we identified significant heterogeneities of SMAD4 loss (partial or complete) among cells within each tumor. We also found that aneuploidy (monosomy and polysomy) contributed greatly to how to define chromosomal SMAD4 deletion. Furthermore, in cultured PDX tumors, SMAD4 mutant cells outcompeted SMAD4 wildtype cells, resulting in establishing homogenous SMAD4 mutant HNSCC cell lines with partial or complete genomic SMAD4 loss, suggesting a survival advantage of SMAD4 mutant cells. Taken together, our study reveals inter- and intra-tumor heterogeneities of SMAD4 chromosomal loss in HNSCCs. Further, SMAD4 FISH assay provides a platform for future clinical diagnosis of SMAD4 chromosomal loss that potentially serves as a molecular marker for prognosis and therapeutic intervention in cancer patients.