A 2-stage genome-wide association study to identify single nucleotide polymorphisms associated with development of urinary symptoms after radiotherapy for prostate cancer.

PURPOSE: We identified single nucleotide polymorphisms associated with change in the AUA Symptom Score after radiotherapy for prostate cancer. MATERIALS AND METHODS: A total of 723 patients treated with brachytherapy with or without external beam radiation therapy were assessed at baseline and annually after radiotherapy using the AUA Symptom Score. A 2-stage genome-wide association study was performed with the primary end point of change in AUA Symptom Score from baseline at each of 4 followup periods. Single nucleotide polymorphism associations were assessed using multivariable linear regression adjusting for pre-radiotherapy AUA Symptom Score severity category and clinical variables. Fisher's trend method was used to calculate combined p values from the discovery and replication cohorts. RESULTS: A region on chromosome 9p21.2 containing 8 single nucleotide polymorphisms showed the strongest association with change in AUA Symptom Score (combined p values 8.8×10(-6) to 6.5×10(-7) at 2 to 3 years after radiotherapy). These single nucleotide polymorphisms form a haplotype block that encompasses the inflammation signaling gene IFNK. These single nucleotide polymorphisms were independently associated with change in AUA Symptom Score after adjusting for clinical predictors including smoking history, hypertension, α-blocker use and pre-radiotherapy AUA Symptom Score. An additional 24 single nucleotide polymorphisms showed moderate significance for association with change in AUA Symptom Score. Several of these single nucleotide polymorphisms were more strongly associated with change in specific AUA Symptom Score items, including rs13035033 in the MYO3B gene, which was associated with straining (beta coefficient 0.9, 95% CI 0.6-1.2, p = 5.0×10(-9)). CONCLUSIONS: If validated, these single nucleotide polymorphisms could provide insight into the biology underlying urinary symptoms following radiotherapy and could lead to development of an assay to identify patients at risk for experiencing these effects.

A Phase 1 Study of Afatinib in Combination with Postoperative Radiation Therapy with and Without Weekly Docetaxel in Intermediate- and High-Risk Patients with Resected Squamous Cell Carcinoma of the Head and Neck.

PURPOSE: To determine the maximum tolerated dose and tolerability of (1) afatinib in combination with postoperative radiation therapy (PORT) for patients with intermediate-risk squamous cell carcinoma of the head and neck (SCCHN) and (2) afatinib in combination with PORT and weekly docetaxel for high-risk SCCHN. METHODS AND MATERIALS: An open-label, multicenter, 2-cohort, phase 1 dose-escalation trial was conducted using a 3 + 3 design. Eligible patients had definitive surgery for SCCHN, including the oral cavity, oropharynx, larynx, or hypopharynx and had intermediate- or high-risk pathologic features. Afatinib was given for a 1-week lead in before PORT and daily during 6 to 6.5 weeks of PORT with or without weekly docetaxel. The starting dose was 30 mg and could be escalated to 40 mg or de-escalated to 20 mg. The primary objective was to determine the maximum tolerated dose of afatinib with PORT or PORT + docetaxel. RESULTS: Between April 2013 and November 2017, 27 patients were enrolled and started study treatment, including 16 intermediate-risk patients and 11 high-risk patients, all with Eastern Cooperative Oncology Group performance status of 0 to 1. Most patients (n = 25) had oral cavity cancer and were treated to a median total dose of 60 Gy in the intermediate-risk arm and 65 Gy in the high-risk arm. There was 1 grade 4 event, but no deaths. The maximum tolerated dose was not established owing to dose-limiting toxicities (DLTs) in both arms. In the high-risk arm, DLTs were grade 3 mucositis (n = 3) and grade 3 diarrhea/hypokalemia (n = 1). In the intermediate-risk arm, DLTs were grade 3 mucositis (n = 4) and grade 3 diarrhea (n = 2). CONCLUSIONS: Afatinib in combination with PORT for mucosal SCCHN was difficult to tolerate because of grade 3 toxicity, mostly mucositis, in a cohort of patients requiring high-dose PORT to the oral cavity. This regimen may be better tolerated for a non-oral cavity site or if given in a different schedule.

A 2-stage genome-wide association study to identify single nucleotide polymorphisms associated with development of erectile dysfunction following radiation therapy for prostate cancer.

PURPOSE: To identify single nucleotide polymorphisms (SNPs) associated with development of erectile dysfunction (ED) among prostate cancer patients treated with radiation therapy. METHODS AND MATERIALS: A 2-stage genome-wide association study was performed. Patients were split randomly into a stage I discovery cohort (132 cases, 103 controls) and a stage II replication cohort (128 cases, 102 controls). The discovery cohort was genotyped using Affymetrix 6.0 genome-wide arrays. The 940 top ranking SNPs selected from the discovery cohort were genotyped in the replication cohort using Illumina iSelect custom SNP arrays. RESULTS: Twelve SNPs identified in the discovery cohort and validated in the replication cohort were associated with development of ED following radiation therapy (Fisher combined P values 2.1×10(-5) to 6.2×10(-4)). Notably, these 12 SNPs lie in or near genes involved in erectile function or other normal cellular functions (adhesion and signaling) rather than DNA damage repair. In a multivariable model including nongenetic risk factors, the odds ratios for these SNPs ranged from 1.6 to 5.6 in the pooled cohort. There was a striking relationship between the cumulative number of SNP risk alleles an individual possessed and ED status (Sommers' D P value=1.7×10(-29)). A 1-allele increase in cumulative SNP score increased the odds for developing ED by a factor of 2.2 (P value=2.1×10(-19)). The cumulative SNP score model had a sensitivity of 84% and specificity of 75% for prediction of developing ED at the radiation therapy planning stage. CONCLUSIONS: This genome-wide association study identified a set of SNPs that are associated with development of ED following radiation therapy. These candidate genetic predictors warrant more definitive validation in an independent cohort.

Genome-wide association study identifies a region on chromosome 11q14.3 associated with late rectal bleeding following radiation therapy for prostate cancer.

BACKGROUND AND PURPOSE: Rectal bleeding can occur following radiotherapy for prostate cancer and negatively impacts quality of life for cancer survivors. Treatment and clinical factors do not fully predict rectal bleeding, and genetic factors may be important. MATERIALS AND METHODS: A genome-wide association study (GWAS) was performed to identify SNPs associated with the development of late rectal bleeding following radiotherapy for prostate cancer. Logistic regression was used to test the association between 614,453 SNPs and rectal bleeding in a discovery cohort (79 cases, 289 controls), and top-ranking SNPs were tested in a replication cohort (108 cases, 673 controls) from four independent sites. RESULTS: rs7120482 and rs17630638, which tag a single locus on chromosome 11q14.3, reached genome-wide significance for association with rectal bleeding (combined p-values 5.4×10(-8) and 6.9×10(-7) respectively). Several other SNPs had p-values trending toward genome-wide significance, and a polygenic risk score including these SNPs shows a strong rank-correlation with rectal bleeding (Sommers' d=5.0×10(-12) in the replication cohort). CONCLUSIONS: This GWAS identified novel genetic markers of rectal bleeding following prostate radiotherapy. These findings could lead to the development of a predictive assay to identify patients at risk for this adverse treatment outcome so that dose or treatment modality could be modified.