Adaptive splenic radiotherapy for symptomatic splenomegaly management in myeloproliferative disorders. Tumori. 2015;101:84-90. [PMID: 25702680 DOI: 10.5301/tj.5000221]

Adaptive radiation therapy of breast cancer by repeated imaging during irradiation

Breast cancer is the most frequent cancer among females and also a leading cause of cancer related mortality worldwide. A multimodality treatment approach may be utilized for optimal management of patients with combinations of surgery, radiation therapy (RT) and systemic treatment. RT composes an integral part of breast conserving treatment, and is typically used after breast conserving surgery to improve local control. Recent years have witnessed significant improvements in the discipline of radiation oncology which allow for more focused and precise treatment delivery. Adaptive radiation therapy (ART) is among the most important RT techniques which may be utilized for redesigning of treatment plans to account for dynamic changes in tumor size and anatomy during the course of irradiation. In the context of breast cancer, ART may serve as an excellent tool for patients receiving breast irradiation followed by a sequential boost to the tumor bed. Primary benefits of ART include more precise boost localization and potential for improved normal tissue sparing with adapted boost target volumes particularly in the setting of seroma reduction during the course of irradiation. Herein, we provide a concise review of ART for breast cancer in light of the literature.

A feasibility study of dynamic adaptive radiotherapy for nonsmall cell lung cancer

PURPOSE

The final state of the tumor at the end of a radiotherapy course is dependent on the doses given in each fraction during the treatment course. This study investigates the feasibility of using dynamic adaptive radiotherapy (DART) in treating lung cancers assuming CBCT is available to observe midtreatment tumor states. DART adapts treatment plans using a dynamic programming technique to consider the expected changes of the tumor in the optimization process.

METHODS

DART is constructed using a stochastic control formalism framework. It minimizes the total expected number of tumor cells at the end of a treatment course, which is equivalent to maximizing tumor control probability, subject to the uncertainty inherent in the tumor response. This formulation allows for nonstationary dose distributions as well as nonstationary fractional doses as needed to achieve a series of optimal plans that are conformal to the tumor over time, i.e., spatiotemporally optimal plans. Sixteen phantom cases with various sizes and locations of tumors and organs-at-risk (OAR) were generated using in-house software. Each case was planned with DART and conventional IMRT prescribing 60 Gy in 30 fractions. The observations of the change in the tumor volume over a treatment course were simulated using a two-level cell population model. Monte Carlo simulations of the treatment course for each case were run to account for uncertainty in the tumor response. The same OAR dose constraints were applied for both methods. The frequency of replanning was varied between 1, 2, 5 (weekly), and 29 times (daily). The final average tumor dose and OAR doses have been compared to quantify the potential dosimetric benefits of DART.

RESULTS

The average tumor max, min, mean, and D95 doses using DART relative to these using conventional IMRT were 124.0%-125.2%, 102.1%-114.7%, 113.7%-123.4%, and 102.0%-115.9% (range dependent on the frequency of replanning). The average relative maximum doses for the cord and esophagus, mean doses for the heart and lungs, and D05 for the unspecified tissue resulting 84%-102.4%, 99.8%-106.9%, 66.9%-85.6%, 58.2%-78.8%, and 85.2%-94.0%, respectively.

CONCLUSIONS

It is feasible to apply DART to the treatment of NSCLC using CBCT to observe the midtreatment tumor state. Potential increases in the tumor dose and reductions in the OAR dose, particularly for parallel OARs with mean or dose-volume constraints, could be achieved using DART compared to nonadaptive IMRT.

Splenic irradiation for splenomegaly: A systematic review

Splenic irradiation (SI) is a palliative treatment option for symptomatic splenomegaly (i.e. for pain, early satiety, pancytopenia from sequestration) secondary to hematologic malignancies and disorders. The purpose of the current article is to review the literature on SI for hematologic malignancies and disorders, including: (1) patient selection and optimal technique; (2) efficacy of SI; and (3) toxicities of SI. PICOS/PRISMA methods are used to select 27 articles including 766 courses of SI for 486 patients from 1960 to 2016. The most common cancers treated included chronic lymphocytic leukemia and myeloproliferative disorders; the most common regimen was 10Gy in 1Gy fractions over two weeks, and 27% of patients received retreatment. A partial or complete response (for symptoms, lab abnormalities) was obtained in 85-90% of treated patients, and 30% were retreated within 6-12months. There was no correlation between biologically equivalent dose of radiation therapy and response duration, pain relief, spleen reduction, or cytopenia improvement (r2 all <0.4); therefore, lower doses (e.g. 5Gy in 5 fractions) may be as effective as higher doses. Grade 3-4 toxicity (typically leukopenia, infection) was noted in 22% of courses, with grade 5 toxicity in 0.7% of courses. All grade 5 toxicities were due to either thrombocytopenia with hemorrhage or leukopenia with sepsis (or a combination of both); they were sequelae of cancer and not directly caused by SI. In summary, SI is generally a safe and efficacious method for treating patients with symptomatic splenomegaly.