Radiation-induced equilibrium is a balance between tumor cell proliferation and T cell-mediated killing.

Local failures following radiation therapy are multifactorial, and the contributions of the tumor and the host are complex. Current models of tumor equilibrium suggest that a balance exists between cell birth and cell death due to insufficient angiogenesis, immune effects, or intrinsic cellular factors. We investigated whether host immune responses contribute to radiation-induced tumor equilibrium in animal models. We report an essential role for immune cells and their cytokines in suppressing tumor cell regrowth in two experimental animal model systems. Depletion of T cells or neutralization of IFN-γ reversed radiation-induced equilibrium, leading to tumor regrowth. We also demonstrate that PD-L1 blockade augments T cell responses, leading to rejection of tumors in radiation-induced equilibrium. We identify an active interplay between tumor cells and immune cells that occurs in radiation-induced tumor equilibrium and suggest a potential role for disruption of the PD-L1/PD-1 axis in increasing local tumor control.

Chemoreirradiation for recurrent salivary gland malignancies.

BACKGROUND AND PURPOSE: To report our experience in treating recurrent salivary gland malignancies using concurrent chemotherapy and reirradiation. MATERIALS AND METHODS: Between 1986 and 2007, 14 patients with locoregionally recurrent salivary gland cancer underwent maximal surgical resection followed by adjuvant 5-fluorouracil and hydroxyurea-based chemotherapy concurrently with 1.5Gy twice daily or 2Gy daily reirradiation. Each cycle consisted of chemoreirradiation for 5 consecutive days followed by a 9-day break. The median reirradiation dose was 66Gy (R 30-72Gy) after a mean radiation treatment interval of 48 months. RESULTS: The median follow-up for all patients was 18 months (R 2-125 months) and 41 months for survivors. The parotid gland (n=6) and minor salivary glands (n=6) were involved more commonly than the submandibular gland (n=2). Locoregional control at 1 and 3years was 72.2% and 51.6%, respectively. Actuarial overall survival at 3 and 5 years was 35.7% and 26.8%, respectively. Tracheostomies and feeding tubes were placed in 2 and 8 patients, respectively. Six patients had feeding tubes at last follow-up or death. CONCLUSIONS: Concurrent chemotherapy and reirradiation for recurrent salivary malignancies result in promising locoregional control for patients with recurrent salivary gland malignancies.

Chemoradiotherapy for locoregionally advanced squamous cell carcinoma of the base of tongue.

BACKGROUND: Our aim was to report the outcomes of base of tongue cancers treated with chemoradiotherapy. METHODS: Between 1990 and 2004, 127 patients with stage III or IV base of tongue cancer were treated with chemoradiotherapy on protocol. Indications included nodal involvement, T3/T4 tumors, positive margins, those patients refusing surgery, or were medically inoperable. The most common regimen was paclitaxel (100 mg/m2 on day 1), infusional 5-fluorouracil (600 mg/m2/day × 5 days), hydroxyurea (500 mg prescribed orally [PO] 2 × daily [BID]), and 1.5 Gy twice daily irradiation followed by a 9-day break without treatment. RESULTS: Median follow-up was 51 months. The median dose to gross tumor was 72.5 Gy (range, 40-75.5 Gy). Five-year locoregional progression-free survival, overall survival, and disease-free survival was 87.0%, 58.2%, and 46.0%, respectively. CONCLUSION: Concurrent chemoradiotherapy results in promising locoregional control for base of tongue cancer. As distant relapse was common, further investigation of systemic therapy with novel agents may be warranted.

Twice-daily reirradiation for recurrent and second primary head-and-neck cancer with gemcitabine, paclitaxel, and 5-fluorouracil chemotherapy.

PURPOSE: We previously demonstrated the efficacy of concurrent gemcitabine, paclitaxel, and 5-fluorouracil in conjunction with twice-daily (1.5-Gy) radiotherapy delivered on alternating weeks (TFGX(2)) in locally advanced head-and-neck cancer. Here, we report the clinical outcome and late toxicity of TFGX(2) in a subset of patients previously irradiated to the head and neck. METHODS AND MATERIALS: Twenty-nine previously irradiated patients, presenting with recurrent or second primary head-and-neck cancer, underwent TFGX(2). Twelve patients underwent attempted surgical resection before chemoradiotherapy, 10 of whom were left with no measurable disease. Patients with measurable disease received a median radiation dose of 72 Gy; those with no measurable disease received a median dose of 61 Gy. The cumulative dose ranged from 74.4 to 156.4 Gy (mean, 125.7 Gy; median, 131.0 Gy). RESULTS: The median follow-up was 19.1 months (50.9 months for living patients). The 5-year overall survival rate was 34.5%, and the locoregional control rate was 54.5%. In patients with measurable disease at treatment, the 5-year overall survival and locoregional control rate was 26.3% and 45.1%, respectively, compared with 50.0% (p = 0.14) and 70% (p = 0.31), respectively, for those with no measurable disease. Measurable disease and radiation dose were highly statistically significant for overall survival and locoregional control on multivariate analysis. Of 14 patients assessable for late toxicity, 3 developed Grade 4-5, 8 Grade 2-3, and 3 Grade 0-1 toxicity. CONCLUSION: Aggressive reirradiation with chemotherapy in locally advanced head-and-neck cancer provides a chance for long-term cure at the expense of toxicity. Attempted surgical resection before chemoradiotherapy improved disease control and survival.