The recent development of intensity modulated radiation therapy (IMRT) allows the dose distribution to be tailored to match the tumour's shape and position, avoiding damage to healthy tissue to a greater extent than previously possible. Traditional treatment plans assume that the target structure remains in a fixed location throughout treatment. However, many studies have shown that because of organ motion, inconsistencies in patient positioning over the weeks of treatment, etc, the tumour location is not stationary. We present a probabilistic model for the IMRT inverse problem and show that it is identical to using robust optimization techniques, under certain assumptions. For a sample prostate case, our computational results show that this method is computationally feasible and promising-compared to traditional methods, our model has the potential to find treatment plans that are more adept at sparing healthy tissue while maintaining the prescribed dose to the target.

ObjectiveTo compare demographics and disease characteristics in dogs in which peritoneopericardial diaphragmatic hernia (PPDH) had been diagnosed and report outcomes after surgical treatment (ST) or conservative treatment (CT).Study designRetrospective study.Sample populationOne hundred twenty‐eight dogs (91 ST, 37 CT) in which PPDH had been diagnosed.MethodsMedical records were reviewed for demographics, perioperative findings, and outcomes. Follow‐up was obtained via telephone interview and email correspondence with owners and referring veterinarians. Baseline variables were compared between treatment groups.ResultsDogs treated surgically were younger (P < .001), more likely to be sexually intact (P = .002), more likely to have clinical signs from PPDH vs an incidental diagnosis (P < .001), and more likely to have other congenital abnormalities (P = .003) compared with dogs treated conservatively. Ninety‐seven percent of ST dogs were discharged from hospitals. Intraoperative and postoperative complications were reported in 22% and 41% of dogs, respectively, although most complications were classified as low grade (75% and 83%, respectively). Follow‐up was available in 87 dogs, at a median of 1062 days. Hernia recurrence was not reported in any surgically treated dog. The deaths of nine dogs (five ST, four CT) could be attributed to PPDH, and long median survival times were observed in both the ST and CT groups (8.2 and 5 years, respectively).ConclusionPreoperative characteristics differed between dogs treated conservatively vs surgically. Surgical treatment was associated with low operative mortality, and both ST and CT dogs had good long‐term survival.Clinical significanceA diagnosis of PPDH can confer a good long‐term prognosis for both ST and CT dogs.

OBJECTIVE To determine whether conservative lateral surgical margins (equal to tumor diameter for tumors < 2 cm in diameter or 2 cm for larger tumors) were noninferior to wide (3-cm) lateral surgical margins for achieving tumor-free histologic margins following excision of grade I and II cutaneous mast cell tumors (MCTs) in dogs. ANIMALS 83 grade I and II MCTs excised with a deep surgical fascial margin and requisite lateral surgical margins from 68 dogs from 2007 to 2017. Tumors representing scar revision or local recurrence were excluded. PROCEDURES A pathology department database was searched to identify qualifying MCTs, and medical records were cross-referenced to obtain data regarding patients and tumors. Outcome (complete vs incomplete excision as histologically determined) was compared between conservative- and wide-margin groups. A noninferiority margin of ≥ 0.9 was used for the risk ratio (probability of complete excision for the conservative- vs wide-margin group), implying that noninferiority would be established if the data indicated that the true risk of complete excision with the conservative-margin approach was at worst 90% of that for the wide-margin approach. RESULTS The proportion of excised MCTs with tumor-free histologic margins was similar between the conservative- (43/46 [93%]) and wide- (34/37 [92%]) margin groups. There were no differences in tumor diameter or location between treatment groups. The risk ratio (1.02; 95% confidence interval, 0.89 to 1.19) met the criterion for noninferiority. CONCLUSIONS AND CLINICAL RELEVANCE The conservative-margin approach appeared to be noninferior to the wide-margin approach for achieving tumor-free histologic margins in the dogs of this study, and its use could potentially reduce the risk of postoperative complications. (J Am Vet Med Assoc 2020;256:567-572

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