Clinical implications of different calculation algorithms in breast radiotherapy: a comparison between pencil beam and collapsed cone convolution.

BACKGROUND: This investigation focused on the clinical implications of the use of the Collapsed Cone Convolution algorithm (CCC) in breast radiotherapy and investigated the dosimetric differences as respect to Pencil Beam Convolution algorithm (PBC). MATERIAL AND METHODS: 15 breast treatment plans produced using the PBC algorithm were re-calculated using the CCC algorithm with the same MUs. In a second step, plans were re-optimized using CCC algorithm with modification of wedges and beam weightings to achieve optimal coverage (CCCr plans). For each patient, dosimetric comparison was performed using the standard tangential technique (SWT) and a forward-planned IMRT technique (f-IMRT). RESULTS: The CCC algorithm showed significant increased dose inhomogeneity. Mean and minimum PTV doses decreased by 1.4% and 2.8% (both techniques). Mean V95% decreased to 83.7% and 90.3%, respectively for the SWT and f-IMRT. V95% was correlated to the ratio of PTV and lung volumes into the treatment field. The re-optimized CCCr plans achieved similar target coverage, but high-dose volume was significantly larger (V107%: 7.6% vs 2.3% (SWT), 7.1% vs 2.1% (f-IMRT). There was a significantly increase in the ipsilateral lung volume receiving low doses (V5 Gy: 31.3% vs 26.2% in SWT, 27.0% vs 23.0% in f-IMRT). MUs needed for PTV coverage in CCCr plans were higher by 3%. CONCLUSIONS: The PBC algorithm overestimated PTV coverage in terms of all important dosimetric metrics. If previous clinical experience are based on the use of PBC model, especially needed is discussion between medical physicists and radiation oncologists to fully understand the dosimetric changes.

Planning comparison between standard and conformal 3D techniques in post-operative radiotherapy of gastric cancer: a systematic review.

The objective of this study was to establish the impact of three-dimensional conformal radiotherapy (3D-CRT) technique in post-operative radiotherapy of gastric cancer. A bibliographical research was performed using the PubMed. On the database, Search was carried out using Medical Subject Heading (MeSH) database; the algorithm for search was ''Radiotherapy" (MeSH) AND ''Stomach Neoplasms" (MeSH). Only planning comparative studies on conformal techniques vs standard techniques in post-operative radiotherapy of gastric cancer were included in the review process. We identified 185 papers, five of them fulfilling the inclusion criteria. A great inhomogeneity was observed regarding the analysed dosimetric end points. Three of the five studies reported a benefit in favour of 3D-CRT for target irradiation despite a minimal advantage in most cases. The liver was better spared from irradiation by the traditional technique in all studies. No univocal result was obtained for the right kidney: the traditional technique performed better in two studies, 3D-CRT yielded better results in two others, whereas in the fifth study, each technique was either better or worse according to the different considered end point. 3D-CRT, however, allowed for better sparing of the left kidney in four studies. There is no absolute reason to prefer 3D-CRT with multiple beams in every patient. It may be preferable to choose the technique based on individual patient characteristics. Because there is no proof of superiority for 3D-CRT, there is no absolute reason to exclude patients who are treated in centres equipped with only the two-dimensional technique from the potential benefit of post-operative chemoradiation.

Mammography before post-operative radiotherapy in conservatively managed breast cancer patients: is it useful?

OBJECTIVE: The aim of this study was to evaluate the role of bilateral mammography undertaken before adjuvant radiotherapy in patients with conservatively managed invasive carcinoma of the breast. METHODS: Patients with invasive breast cancer referred to the Radiotherapy Unit of the Università Cattolica del Sacro Cuore, in Campobasso, Italy, between March 2002 and September 2006 were retrospectively reviewed. Patients were referred to our facility from other local and regional hospitals where they received breast-conserving surgery and adjuvant chemotherapy. They presented to our department for post-operative whole-breast radiotherapy. All patients underwent physical examination and bilateral mammography prior to adjuvant irradiation. RESULTS: 201 patients met the selection criteria as delineated. Of these 201 patients who underwent pre-radiotherapy mammography, 3 had suspicious findings on mammography. In two of those cases, the histopathological examination confirmed the presence of residual disease within the residual mammary gland. In one case, the pre-radiotherapy mammogram allowed for the detection of disease persistence which was not otherwise appreciated on physical exam. In the other case, the diagnostic imaging confirmed only the findings of the physical exam. In both cases of residual disease, the tumour was found elsewhere in the breast and not at the primary site. In one patient, the radiological re-assessment led to a false-positive result. No cases of contralateral synchronous breast cancer were observed. The overall adjunctive cost of this strategy including a routine mammography besides the clinical visit was €7012 for all patients. CONCLUSIONS: No clear recommendation exists regarding post-operative mammography before adjuvant radiotherapy. In our experience, this strategy allowed for the detection of gross disease persistence after surgery which was not appreciated at clinical examination in 1 case out of 201. In this patient, adjuvant radiotherapy up to a total dose of 50 Gy would have been inadequate. Given the low cost of mammography, further investigation about its role in pre-radiotherapy evaluation is warranted.

Volumetric modulated arc therapy with simultaneous integrated boost for locally advanced rectal cancer.

AIMS: To report the feasibility of volumetric modulated arc therapy (VMAT) for neoadjuvant radiotherapy in locally advanced rectal cancer in a dose-escalation protocol and simultaneous integrated boost (SIB) approach. Moreover, the VMAT technique was compared with three-dimensional conformal radiotherapy (3D-CRT) and fixed-field intensity modulated radiotherapy (IMRT), in terms of target coverage and irradiation of organs at risk. MATERIALS AND METHODS: Eight patients with locally advanced rectal cancer were treated with the SIB-VMAT technique. The VMAT plans were compared with 3D-CRT and IMRT techniques in terms of several clinically dosimetric parameters. The number of monitor units and the delivery time were analysed to score the treatment efficiency. All plans were verified in a dedicated solid water phantom using a two-dimensional array of ionisation chambers. RESULTS: All techniques meet the prescription goal for planning target volume coverage, with VMAT showing the highest level of conformality. VMAT is associated with 40, 53 and 58% reduction in the percentage of volume of small bowel irradiated to 30, 40 and 50Gy, compared with 3D-CRT. No significant differences were found with respect to SIB-IMRT. VMAT plans showed a significant reduction of monitor units by nearly 20% with respect to IMRT and reduced treatment time from 14 to 5min for a single fraction. CONCLUSIONS: SIB-VMAT plans can be planned and carried out with high quality and efficiency for rectal cancer, providing similar sparing of organs at risk to SIB-IMRT and resulting in the most efficient treatment option. SIB-VMAT is currently our standard approach for radiotherapy of locally advanced rectal cancer.