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Post mastectomy linac IMRT irradiation of chest wall and regional nodes: dosimetry data and acute toxicities.

Ma J, Li J, Xie J, Chen J, Zhu C, Cai G, Zhang Z, Guo X, Chen J - Radiat Oncol (2013)

Bottom Line: As compared to segmented plans, integrated plans typically increased V5 of ipsilateral lung (p=0.005), and heart (p=0.001) in patients with left-sided lesions.The difference in occurrence of ≥ grade 2 RD between integrated and segmented plans was statistically insignificant (X2=0.35, p=0.55).Only 2 were found to have grade 2 radiation pneumonitis.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Radiation Oncology, Fudan University Shanghai Cancer Center, Cancer Institute of Fudan University, Shanghai, 200032, China.

ABSTRACT

Background: Conventional post-mastectomy radiation therapy is delivered with tangential fields for chest wall and separate fields for regional nodes. Although chest wall and regional nodes delineation has been discussed with RTOG contouring atlas, CT-based planning to treat chest wall and regional nodes as a whole target has not been widely accepted. We herein discuss the dosimetric characteristics of a linac IMRT technique for treating chest wall and regional nodes as a whole PTV after modified radical mastectomy, and observe acute toxicities following irradiation.

Methods: Patients indicated for PMRT were eligible. Chest wall and supra/infraclavicular region +/-internal mammary nodes were contoured as a whole PTV on planning CT. A simplified linac IMRT plan was designed using either integrated full beams or two segments of half beams split at caudal edge of clavicle head. DVHs were used to evaluate plans. The acute toxicities were followed up regularly.

Results: Totally, 85 patients were enrolled. Of these, 45 had left-sided lesions, and 35 received IMN irradiation. Planning designs yielded 55 integrated and 30 segmented plans, with median number of beams of 8 (6-12). The integrated and segmented plans had similar conformity (1.41±0.14 vs. 1.47±0.15, p=0.053) and homogeneity indexes (0.13±0.01 vs. 0.14±0.02, p=0.069). The percent volume of PTV receiving >110% prescription dose was <5%. As compared to segmented plans, integrated plans typically increased V5 of ipsilateral lung (p=0.005), and heart (p=0.001) in patients with left-sided lesions. Similarly, integrated plans had higher spinal cord Dmax (p=0.009), ipsilateral humeral head (p<0.001), and contralateral lung Dmean (p=0.019). During follow-up, 36 (42%) were identified to have ≥ grade 2 radiation dermatitis (RD). Of these, 35 developed moist desquamation. The median time to onset of moist desquamation was 6 (4-7) weeks from start of RT. The sites of moist desquamation were most frequently occurred in anterior axillary fold (32/35), and secondly chest wall (12/35). The difference in occurrence of ≥ grade 2 RD between integrated and segmented plans was statistically insignificant (X2=0.35, p=0.55). Only 2 were found to have grade 2 radiation pneumonitis.

Conclusions: The linac IMRT technique applied in PMRT with chest wall and regional nodes as a whole PTV was dosimetrically feasible, and the treatment was proved to be well-tolerated by most patients.

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Related in: MedlinePlus

A 10-beam segmented plan designed for a patient with right breast cancer: (a) 4 beams (0, 35, 215, and 330 degrees) for supra/infraclavicular region; (b) six beams (35, 45, 55, 220, 235, and 245 degrees) for chest wall; (c): lateral BEV of the PTV with MLC-defined port displayed.
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Figure 2: A 10-beam segmented plan designed for a patient with right breast cancer: (a) 4 beams (0, 35, 215, and 330 degrees) for supra/infraclavicular region; (b) six beams (35, 45, 55, 220, 235, and 245 degrees) for chest wall; (c): lateral BEV of the PTV with MLC-defined port displayed.

Mentions: For each patient, a multi-beam simplified IMRT plan was generated using Pinnacle treatment planning software (version 8.0). The IMRT plans were designed using either integrated full beams or two segments of half beams split at caudal edge of clavicle head, the latter technique require that the length of chest wall PTV should not exceed 19 cm so as to be fully covered by the half beams at caudal side. Although the selection of beam angles was at discretion of the responsible dosimetrist, basically, an integrated plan employs full beam to cover the whole PTV, whereas a segmented plan uses different beam angles in the cranial half beams to cover the upper part of PTV (supra/infraclavicular region), and caudal half beams to cover the lower part (chest wall±IMN), respectively. The angles sectors covered by multiple beams are shown in Figures 1 and 2 for representative integrated and segmented plans, respectively. All plans were optimized to cover the whole PTVs and spare surrounding normal tissues as much as possible. To ensure a sufficient skin dose, a daily 3-mm bolus was placed on chest wall of each patient. The optimization process started with dose-volume constraints as follows: 90% of PTV to receive 50Gy in 25 fractions; ipsilateral mean lung dose ≤20Gy, and ≤30% of the ipsilateral lung to receive ≤20Gy; ≤5% of the heart to receive ≤30Gy, mean heart dose ≤8Gy for left-sided lesions, and ≤10Gy if IMN was included; spinal cord maximum dose ≤45Gy; contralateral breast mean dose ≤1.5Gy. Priority was high for the PTV, heart and lung constraints relative to other structures. Optimization proceeded with these settings until no further improvement was seen. Priority was then increased for other structures until a balance was reached between PTV coverage and normal tissues sparing. During optimization, a simplified IMRT plan was defined to have ≤5 segments/beam, ≥ 10 cm2/segment, and ≥10 MU/segment [8]. After optimization, a final dose calculation using the collapsed cone convolution superposition (CCCS) algorithm was performed. Dose grid size used for calculations was 0.2 cm by 0.2 cm by 0.2 cm. Once PTV and normal tissues dose constraints were met, the dosimetrist would expand the anterior border of chest wall field 1.5-2 cm beyond the skin surface to ensure chest wall coverage.


Post mastectomy linac IMRT irradiation of chest wall and regional nodes: dosimetry data and acute toxicities.

Ma J, Li J, Xie J, Chen J, Zhu C, Cai G, Zhang Z, Guo X, Chen J - Radiat Oncol (2013)

A 10-beam segmented plan designed for a patient with right breast cancer: (a) 4 beams (0, 35, 215, and 330 degrees) for supra/infraclavicular region; (b) six beams (35, 45, 55, 220, 235, and 245 degrees) for chest wall; (c): lateral BEV of the PTV with MLC-defined port displayed.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3643842&req=5

Figure 2: A 10-beam segmented plan designed for a patient with right breast cancer: (a) 4 beams (0, 35, 215, and 330 degrees) for supra/infraclavicular region; (b) six beams (35, 45, 55, 220, 235, and 245 degrees) for chest wall; (c): lateral BEV of the PTV with MLC-defined port displayed.
Mentions: For each patient, a multi-beam simplified IMRT plan was generated using Pinnacle treatment planning software (version 8.0). The IMRT plans were designed using either integrated full beams or two segments of half beams split at caudal edge of clavicle head, the latter technique require that the length of chest wall PTV should not exceed 19 cm so as to be fully covered by the half beams at caudal side. Although the selection of beam angles was at discretion of the responsible dosimetrist, basically, an integrated plan employs full beam to cover the whole PTV, whereas a segmented plan uses different beam angles in the cranial half beams to cover the upper part of PTV (supra/infraclavicular region), and caudal half beams to cover the lower part (chest wall±IMN), respectively. The angles sectors covered by multiple beams are shown in Figures 1 and 2 for representative integrated and segmented plans, respectively. All plans were optimized to cover the whole PTVs and spare surrounding normal tissues as much as possible. To ensure a sufficient skin dose, a daily 3-mm bolus was placed on chest wall of each patient. The optimization process started with dose-volume constraints as follows: 90% of PTV to receive 50Gy in 25 fractions; ipsilateral mean lung dose ≤20Gy, and ≤30% of the ipsilateral lung to receive ≤20Gy; ≤5% of the heart to receive ≤30Gy, mean heart dose ≤8Gy for left-sided lesions, and ≤10Gy if IMN was included; spinal cord maximum dose ≤45Gy; contralateral breast mean dose ≤1.5Gy. Priority was high for the PTV, heart and lung constraints relative to other structures. Optimization proceeded with these settings until no further improvement was seen. Priority was then increased for other structures until a balance was reached between PTV coverage and normal tissues sparing. During optimization, a simplified IMRT plan was defined to have ≤5 segments/beam, ≥ 10 cm2/segment, and ≥10 MU/segment [8]. After optimization, a final dose calculation using the collapsed cone convolution superposition (CCCS) algorithm was performed. Dose grid size used for calculations was 0.2 cm by 0.2 cm by 0.2 cm. Once PTV and normal tissues dose constraints were met, the dosimetrist would expand the anterior border of chest wall field 1.5-2 cm beyond the skin surface to ensure chest wall coverage.

Bottom Line: As compared to segmented plans, integrated plans typically increased V5 of ipsilateral lung (p=0.005), and heart (p=0.001) in patients with left-sided lesions.The difference in occurrence of ≥ grade 2 RD between integrated and segmented plans was statistically insignificant (X2=0.35, p=0.55).Only 2 were found to have grade 2 radiation pneumonitis.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Radiation Oncology, Fudan University Shanghai Cancer Center, Cancer Institute of Fudan University, Shanghai, 200032, China.

ABSTRACT

Background: Conventional post-mastectomy radiation therapy is delivered with tangential fields for chest wall and separate fields for regional nodes. Although chest wall and regional nodes delineation has been discussed with RTOG contouring atlas, CT-based planning to treat chest wall and regional nodes as a whole target has not been widely accepted. We herein discuss the dosimetric characteristics of a linac IMRT technique for treating chest wall and regional nodes as a whole PTV after modified radical mastectomy, and observe acute toxicities following irradiation.

Methods: Patients indicated for PMRT were eligible. Chest wall and supra/infraclavicular region +/-internal mammary nodes were contoured as a whole PTV on planning CT. A simplified linac IMRT plan was designed using either integrated full beams or two segments of half beams split at caudal edge of clavicle head. DVHs were used to evaluate plans. The acute toxicities were followed up regularly.

Results: Totally, 85 patients were enrolled. Of these, 45 had left-sided lesions, and 35 received IMN irradiation. Planning designs yielded 55 integrated and 30 segmented plans, with median number of beams of 8 (6-12). The integrated and segmented plans had similar conformity (1.41±0.14 vs. 1.47±0.15, p=0.053) and homogeneity indexes (0.13±0.01 vs. 0.14±0.02, p=0.069). The percent volume of PTV receiving >110% prescription dose was <5%. As compared to segmented plans, integrated plans typically increased V5 of ipsilateral lung (p=0.005), and heart (p=0.001) in patients with left-sided lesions. Similarly, integrated plans had higher spinal cord Dmax (p=0.009), ipsilateral humeral head (p<0.001), and contralateral lung Dmean (p=0.019). During follow-up, 36 (42%) were identified to have ≥ grade 2 radiation dermatitis (RD). Of these, 35 developed moist desquamation. The median time to onset of moist desquamation was 6 (4-7) weeks from start of RT. The sites of moist desquamation were most frequently occurred in anterior axillary fold (32/35), and secondly chest wall (12/35). The difference in occurrence of ≥ grade 2 RD between integrated and segmented plans was statistically insignificant (X2=0.35, p=0.55). Only 2 were found to have grade 2 radiation pneumonitis.

Conclusions: The linac IMRT technique applied in PMRT with chest wall and regional nodes as a whole PTV was dosimetrically feasible, and the treatment was proved to be well-tolerated by most patients.

Show MeSH
Related in: MedlinePlus