Preoperative radiotherapy in the management of retroperitoneal liposarcoma.

BACKGROUND: Histological subtype influences both prognosis and patterns of treatment failure in retroperitoneal sarcoma. Previous studies on the efficacy of neoadjuvant radiotherapy (NRT) have incorporated multiple histological types with heterogeneous tumour biology. The survival impact of NRT specifically for patients with retroperitoneal liposarcoma is poorly defined. METHODS: Patients who underwent resection with curative intent for retroperitoneal liposarcoma and who received NRT or surgery alone were identified in the US National Cancer Data Base (2004-2013). Cox regression was used to identify co-variables associated with overall survival. NRT and surgery-alone cohorts were matched 1 : 1 by propensity scores based on the survival hazard on Cox modelling. Overall survival was compared by Kaplan-Meier estimates. RESULTS: A total of 2082 patients with retroperitoneal liposarcoma were identified; 1908 underwent surgery alone and 174 received NRT before surgical resection. Median tumour size was 22·0 cm and 34·9 per cent of tumours were high grade. In the unmatched cohort, NRT was not associated with improved overall survival (χ2 = 3·49, P = 0·062). In the propensity score-matched cohort, NRT was associated with an improvement in survival (median overall survival 129·2 versus 84·3 months; P = 0·046; hazard ratio (HR) 1·54, 95 per cent c.i. 1·01 to 2·36). This effect appeared most pronounced for tumours with adjacent organ invasion (median overall survival not reached versus 63·8 months; P = 0·044; HR 1·79, 1·01 to 3·19). CONCLUSION: NRT improved survival in patients undergoing surgery for retroperitoneal liposarcoma, particularly those with high-risk pathological features.

Proton beam therapy.

Conventional radiation therapy directs photons (X-rays) and electrons at tumours with the intent of eradicating the neoplastic tissue while preserving adjacent normal tissue. Radiation-induced damage to healthy tissue and second malignancies are always a concern, however, when administering radiation. Proton beam radiotherapy, one form of charged particle therapy, allows for excellent dose distributions, with the added benefit of no exit dose. These characteristics make this form of radiotherapy an excellent choice for the treatment of tumours located next to critical structures such as the spinal cord, eyes, and brain, as well as for paediatric malignancies.

Comparative treatment planning between proton and X-ray therapy in pancreatic cancer.

With the utilization of new biologic agents and experimental chemotherapy in the treatment of pancreatic cancer, the issue of local-regional control will become increasingly important. This study was undertaken to determine the feasibility of dose escalation using proton therapy, as compared to conventional 3-dimensional conformal radiation, by minimizing the dose to normal tissues. The photon treatment plans of 4 patients with unresectable pancreatic cancer treated on a biologic therapy trial were utilized. Each patient was treated using a 3- or 4-field photon plan with 45 Gy to the clinical target volume (CTV), followed by a boost of 14.4 Gy to the gross target volume (GTV). Using a Helax treatment planning system, proton plans were generated to encompass the same CTV and GTV to the same prescribed dose. Dose-volume histograms (DVHs) were generated for the GTV, CTV, spinal cord, liver, and right and left kidneys. Each DVH was compared between the photon and proton plans. Proton plans utilized either a 2- or 3-field technique. Available energies included 130 or 180 MeV. Range modulators and bolus were used as needed to conform to the target volume. With the CTV and GTV receiving the same dose from the proton and photon plans, all individual proton plans were superior to the photon plans in reduction of normal tissue dose. For the 4 patients, the average dose reduction to 50% of the organ at risk was 78% to spinal cord (p = 0.003), 73% to left kidney (p = 0.025), 43% to right kidney (p = 0.059), and 55% to liver (p = 0.061). These comparative treatment plans show proton therapy results in significant reductions of dose to normal tissue compared to conventional photons while treating the same target volumes. This allows for the design of dose-escalation protocols using protons in combination with new biologic therapies and chemotherapy.