Determining optimal follow-up in the management of human papillomavirus-positive oropharyngeal cancer.

BACKGROUND: Determining the optimal follow-up for patients can help maximize the use of health care resources. This is particularly true in a growing epidemic such as human papillomavirus-positive oropharyngeal squamous cell carcinoma (HPV+OPSCC). The objective of the current study was to evaluate time to disease recurrence or late toxicity in this cohort of patients to optimize patient management. METHODS: An institutional database identified 232 patients with biopsy-proven, nonmetastatic HPV+OPSCC who were treated with radiotherapy. A retrospective review was conducted in patients who were followed every 3 months for the first year, every 4 months in year 2, and every 6 months in years 3 to 5. Late toxicity (grade ≥ 3; toxicity was scored based on National Cancer Institute Common Terminology Criteria for Adverse Events [version 4]), locoregional control, distant control, and overall survival were assessed. RESULTS: The median follow-up was 33 months. Based on Radiation Therapy Oncology Group (RTOG) 0129 study risk groupings, patients were either considered to be at low (162 patients; 70%) or intermediate (70 patients; 30%) risk. Concurrent systemic therapy was used in 85% of patients (196 patients). The 3-year locoregional control, distant control, and overall survival rates were 94%, 91%, and 91%, respectively. Late toxicity occurred in 9% of patients (21 patients). Overall, 64% of toxicity and failure events occurred within the first 6 months of follow-up, with a < 2% event incidence noted at each subsequent follow-up. Only 4 patients experienced their first event after 2 years. CONCLUSIONS: HPV+OPSCC has a low risk of disease recurrence and late toxicity after treatment; approximately two-thirds of events occur within the first 6 months of follow-up. These data suggest that it may be reasonable to reduce follow-up in patients with HPV+OPSCC to every 3 months for the first 6 months, every 6 months for the first 2 years, and annually thereafter.

Clinical Benefits of Proton Beam Therapy for Tumors of the Skull Base.

BACKGROUND: The unique radiobiological properties of protons have been understood for many years. In addition, many of the clinical benefits of radiotherapy were first noted in tumors involving the skull base. More public attention has been given to proton beam therapy due to the increasing number of centers now in operation or in the planning stages for offering this treatment option. METHODS: We reviewed the physical properties of protons and the clinical studies performed to justify their use in the management of skull-base tumors and determine the benefits of proton beam therapy. RESULTS: Published reports suggest a benefit to proton beam therapy for use in tumors of the skull base, including craniopharyngiomas, chordomas, skull-base sarcomas, and unresectable meningiomas. CONCLUSIONS: Use of proton beam therapy may be beneficial in select patients. Surgical and medical oncologists should have a general understanding of such cases to facilitate their appropriate referral.

Defective DNA repair and cell cycle arrest in cells expressing Merkel cell polyomavirus T antigen.

The pathways by which Merkel cell polyomavirus (MCV) infection contributes to the formation of Merkel cell carcinomas are important for understanding the pathogenesis of these cancers. We hypothesized that MCV T antigen suppresses normal responses to ultraviolet radiation (UVR)-induced DNA damage. An MCV-infected cell line (MKL-1) exhibited UVR hypersensitivity, impaired repair of DNA lesions and cell cycle arrest after UVR, as well as reduced levels of the DNA damage recognition protein, XPC. When ectopically expressed in uninfected UISO cells, mutant but not wild-type T antigen resulted in loss of repair of UVR-induced cyclobutane pyrimidine dimers and reductions in XPC, p53 and p21 levels, whereas both wild-type and mutant T antigen inhibited cell cycle arrest after UVR. Similarly, only mutant T antigen in normal fibroblasts inhibited DNA repair and XPC expression, while both mutant and wild-type T antigens produced cell cycle dysregulation. Wild-type T antigen expression produced large T, 57 kT and small T antigens while mutant T antigen was only detectable as a truncated large T antigen protein. Expression of wild-type large T antigen but not small T antigen inhibited the G1 checkpoint in UISO cells, but neither wild-type large T nor small T antigens affected DNA repair, suggesting that large T antigen generates cell cycle defects, and when mutated may also impair DNA repair. These results indicate that T antigen expression by MCV can inhibit key responses to UVR-induced DNA damage and suggest that progressive MCV-mediated abrogation of genomic stability may be involved in Merkel cell carcinogenesis.

Deficient Nucleotide Excision Repair in Squamous Cell Carcinoma Cells.

Squamous cell carcinomas (SCCs) are associated with ultraviolet radiation and multiple genetic changes, but the mechanisms leading to genetic instability are unclear. SCC cell lines were compared to normal keratinocytes for sensitivity to ultraviolet radiation, DNA repair kinetics and DNA repair protein expression. Relative to normal keratinocytes, four SCC cell lines were all variably sensitive to ultraviolet radiation and, except for the SCC25 cell line, were deficient in global repair of cyclobutane pyrimidine dimers, although not 6-4 photoproducts. Impaired DNA repair of cyclobutane pyrimidine dimers was associated with reduced mRNA expression from XPC but not DDB2 genes which each encode key DNA damage recognition proteins. However, levels of XPC or DDB2 proteins or both were variably reduced in repair-deficient SCC cell lines. p53 levels did not correlate with DNA repair activity or with XPC and DDB2 levels, but p63 levels were deficient in cell lines with reduced global repair. Repair-proficient SCC25 cells depleted of p63 lost XPC expression, early global DNA repair activity and UV resistance. These results demonstrate that some SCC cell lines are deficient in global nucleotide excision repair and support a role for p63 as a regulator of nucleotide excision repair in SCCs.