Risk of contralateral breast and ipsilateral lung cancer induction from forward-planned IMRT for breast carcinoma

Dose comparison between hybrid volumetric modulated arc therapy, volumetric modulated arc therapy, and three-dimensional conformal radiotherapy for breast/chest wall irradiation, including regional lymph node irradiation using deep inspiration breath-hold technique

PURPOSE

Breast radiation treatment has been linked to complications such as pneumonitis and cardiac toxicity, necessitating dose optimization. This study aims to determine the optimal integration plan of volumetric modulated arc therapy (VMAT) and three-dimensional conformal radiotherapy (3DCRT) in a deep inspiration breath-hold regimen.

MATERIALS AND METHODS

CT imaging data from twenty patients with breast or chest wall cancer, either right or left-sided, and with supraclavicular and internal mammary chain lymph nodes were retrieved. The CT data planned with a hybrid VMAT of three different weighting proportions: 30 % using 3DCRT and 70 % using VMAT, 50 % using 3DCRT and 50 % using VMAT, and 70% using 3DCRT and 30 % using VMAT and compared with full 3DCRT and full VMAT plan (classic and five arc design).

RESULTS

The homogeneity and conformity indices were better in the hybrid VMAT plans than in plans using VMAT or 3DCRT alone (P<0.005). Results of all hybrid VMAT plans showed a considerable drop of volumes receiving more than 4Gy, 8Gy or 16Gy in the ipsilateral lung compared to the full VMAT plan (P<0.001). There was a noticeable decrease in the mean dose to the heart and the dose in 5% of the contralateral breast in the plan using 70 % 3DCRT and 30 % VMAT compared to full VMAT (P<0.001). The plan using 70 % 3DCRT and 30% VMAT achieved a balance between the target and surrounding areas, compared to using only 3DCRT or VMAT.

CONCLUSION

A hybrid plan using 70 % 3DCRT contribution achieved a balanced outcome for breast or chest wall irradiation, considering both planning target volume and organs at risk. Utilizing our VMAT arc design, incorporating one shortened arc can significantly reduce doses to organs at risk further. It is important to consider the patient's anatomy when making this decision.

Comparative dosimetric study of h-IMRT and VMAT plans for breast cancer after breast-conserving surgery

AIM

To compare the dosimetric advantages and disadvantages between hybrid intensity-modulated radiation therapy (h-IMRT) and the volumetric modulated arc therapy (VMAT) technique in hypofractionated whole-breast irradiation (HF-WBI) for early-stage breast cancer (BC).

METHODS

The dose distribution of h-IMRT and VMAT plans was compared in 20 breast cancer patients. This comparison included evaluation of dosimetric parameters using dose volume histograms (DVHs) for the planning target volume (PTV) and organs-at-risk (OARs). Additionally, the study examined the normal tissue complication probability (NTCP), the second cancer complication probability (SCCP) and the tumor control probability (TCP) based on different models.

RESULTS

Significant differences were detected between the two plans, in terms of Machine units (MUs), the control points, 95 % volume (V95 %), dose homogeneity index (DHI) and conformity index (CI). The endpoint of grade II radiation pneumonitis and cardiac death due to ischemic heart disease were assessed. In h-IMRT plan, the NTCP values were marginally lower for radiation pneumonitis and slightly higher for cardiac death compared to VMAT plan, as determined by the Lyman-Kutcher-Burman model. The Schneider model was employed to predict the SCCP for both the bilateral lungs and contralateral breast, the results demonstrate that the h-IMRT plan outperforms the VMAT plan, with statistical significance. Additionally, the LQ-Poisson model was employed to forecast the TCP of the PTV, showing that the h-IMRT plan outperformed the VMAT plan (P > 0.05).

CONCLUSION

The h-IMRT technique, offering superior dose coverage and better therapeutic efficacy with fewer side effects as calculated by models, is more suitable for HF-WBI compared to the VMAT technique.

Hybrid Treatment Planning for Chest Wall Irradiation Utilizing Three-Dimensional Conformal Radiotherapy (3DCRT), Intensity-Modulated Radiation Therapy (IMRT), and Volumetric Modulated Arc Therapy (VMAT): A Systematic Review

Novel hybrid approaches for chest wall irradiation show promising outcomes regarding target coverage and sparing organs at risk (OARs). In this systematic review, we compared hybrid volumetric modulated arc therapy (H-VMAT) or hybrid intensity-modulated radiotherapy (H-IMRT) techniques with non-hybrid techniques, such as three-dimensional conformal radiation therapy (3DCRT), field-in-field (FIF), intensity-modulated arc therapy (IMRT), and volumetric modulated arc therapy (VMAT), for breast cancer patients with mastectomy. Our focus was the plan quality and dose distribution to the OARs. Using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) checklist, we performed a systematic review and quality appraisal of primary studies evaluating hybrid therapy to the chest wall and the OARs. An extensive online search of PubMed and Scopus databases was conducted using appropriate keywords. The dose to the OARs (lung, heart, and contralateral breast), planning target volume (PTV), homogeneity index (HI), and conformity index (CI) were extracted. The data were then tabulated and compared for the outcomes between modalities among the studies. Nine studies that met the search criteria were selected to evaluate the PTV coverage and dosimetric results of hybrid and non-hybrid techniques. In terms of 95% PTV coverage, among nine reviewed studies, the largest difference between the two techniques was between VMAT (47.6 Gy) and H-VMAT (48.4 Gy); for the conformity index, the largest difference was noted between 3DCRT (0.58) and H-VMAT (0.79). In both cases, differences were statistically significant (P < 0.005). Two studies showed dose homogeneity improvement within the treatment target in H-VMAT (0.15 and 0.07) compared with 3DCRT (0.41 and 0.12), with a P value of <0.001. Two studies did not report on the homogeneity index, and three others observed no statistical difference. Regarding OARs, in the comparison of H-VMAT and VMAT, the largest significant change was in the volume receiving 5 Gy (V5Gy) of the ipsilateral lung and the V10Gy of the contralateral lung. For the ipsilateral lung, V5Gy was 90.7% with VMAT versus 51.45% with H-VMAT. For the contralateral lung, V10Gy was 54.9% with VMAT versus 50.5% with H-VMAT. In six studies, the mean dose of the contralateral breast was lower in hybrid techniques than in single modalities: VMAT (4.2%, 6.0%, 1.9%, 7.1%, 4.57%) versus H-VMAT (1.4%, 3.4%, 1.8%, 3.5%, 2.34%) and IMRT (9.1%) versus H-IMRT (4.69%). Although most studies did not report on monitor units and treatment time, those that included them showed that hybrids had lower monitor units and shorter treatment times. Hybrid techniques in radiotherapy, such as combining two modalities, can indeed facilitate lower doses to OARs for patients with a high risk of toxicities. Prospective clinical studies are needed to determine the outcomes of breast cancer treated with hybrid techniques.

Clinical and sociodemographic risk factors associated with the development of second primary cancers among postmenopausal breast cancer survivors

BACKGROUND

Advancement in breast cancer (BC) diagnosis and treatment have increased the number of long-term survivors. Consequently, primary BC survivors are at a greater risk of developing second primary cancers (SPCs). The risk factors for SPCs among BC survivors including sociodemographic characteristics, cancer treatment, comorbidities, and concurrent medications have not been comprehensively examined. The purpose of this study is to assess the incidence and clinicopathologic factors associated with risk of SPCs in BC survivors.

METHODS

We analyzed 171, 311 women with early-stage primary BC diagnosed between January 2000 and December 2015 from the Medicare-linked Surveillance Epidemiology and End Results (SEER-Medicare) database. SPC was defined as any diagnosis of malignancy occurring within the study period and at least 6 months after primary BC diagnosis. Univariate analyses compared baseline characteristics between those who developed a SPC and those who did not. We evaluated the cause-specific hazard of developing a SPC in the presence of death as a competing risk.

RESULTS

Of the study cohort, 21,510 (13%) of BC survivors developed a SPC and BC was the most common SPC type (28%). The median time to SPC was 44 months. Women who were white, older, and with fewer comorbidities were more likely to develop a SPC. While statins [hazard ratio (HR) 1.066 (1.023-1.110)] and anti-hypertensives [HR 1.569 (1.512-1.627)] increased the hazard of developing a SPC, aromatase inhibitor therapy [HR 0.620 (0.573-0.671)] and bisphosphonates [HR 0.905 (0.857-0.956)] were associated with a decreased hazard of developing any SPC, including non-breast SPCs.

CONCLUSION

Our study shows that specific clinical factors including type of cancer treatment, medications, and comorbidities are associated with increased risk of developing SPCs among older BC survivors. These results can increase patient and clinician awareness, target cancer screening among BC survivors, as well as developing risk-adapted management strategies.

Lifetime radiation-induced sarcoma risk in patients subjected to IMRT or VMAT for uterine cervix carcinoma

This study was conducted to estimate the lifetime radiation-induced bone and soft tissue sarcoma risks from intensity modulated radiation therapy (IMRT) and volumetric modulated arc therapy (VMAT) for uterine cervix carcinoma. 13 cervical cancer patients were included. The bone and soft tissue structures were defined on patients' treatment planning computed tomography (CT) scans. Both CT-based IMRT and VMAT plans with 6 MV photons delivering 45 Gy to the target site were designed for each patient. The organ equivalent dose (OED) and the lifetime attributable risk (LAR) for developing bone or soft tissue sarcoma were estimated using treatment planning data and a non-linear mechanistic model. The estimation method did not consider the survival rates following radiotherapy and the use of brachytherapy treatments. The patient-specific OEDs of the bone structure from IMRT and VMAT were 2.33-2.83 and 2.34-2.82 Gy, respectively. The corresponding values for the soft tissue structure were 1.27-1.70 and 1.32-1.73 Gy. An insignificant difference was found between the patient-specific OEDs and the directly proportional sarcoma risks (bone: P = 0.07; soft tissue: P = 0.38). The LAR for the development of a bone sarcoma varied from 0.05 to 0.16% by the patient's age during irradiation and the applied treatment delivery technique. The corresponding LAR range for radiation-induced soft-tissue sarcoma was 0.08-0.27%. The above LARs resulted in a relative risk of more than 1.20 indicating that IMRT or VMAT may lead to a considerable risk increase of developing bone or soft tissue sarcoma exceeding 20% in respect to the current incidence of these malignancies in unexposed population.

A radiobiological comparison of hypo-fractionation versus conventional fractionation for breast cancer 3D-conformal radiation therapy

BACKGROUND

The present research was aimed to compare the toxicity and effectiveness of conventional fractionated radiotherapy versus hypo-fractionated radiotherapy in breast cancer utilizing a radiobiological model.

MATERIALS AND METHODS

Thirty-five left-sided breast cancer patients without involvement of the supraclavicular and axillary lymph nodes (with the nodal stage of N0) that had been treated with conventional or hypo-fractionated were incorporated in this study. A radiobiological model was performed to foretell normal tissue complication probability (NTCP) and tumor control probability (TCP).

RESULTS

The data represented that TCP values for conventional and hypo-fractionated regimens were 99.16 ± 0.09 and 95.96 ± 0.48, respectively (p = 0.00). Moreover, the NTCP values of the lung for conventional and hypo-fractionated treatment were 0.024 versus 0.13 (p = 0.035), respectively. Also, NTCP values of the heart were equal to zero for both regimens.

CONCLUSION

In summary, hypo-fractionated regimens had comparable efficacy to conventional fraction radiation therapy in the case of dosimetry parameters for patients who had left breast cancer. But, utilizing the radiobiological model, conventional fractionated regimens presented better results compared to hypo-fractionated regimens.

The risk for developing a secondary cancer after breast radiation therapy: Comparison of photon and proton techniques

BACKGROUND AND PURPOSE

To compare secondary malignancy risks of modern proton and photon therapy techniques for locally advanced breast cancer.

METHODS AND MATERIALS

We utilized dosimetric data from 34 [10 photon-VMAT, 10 photon-3DCRT, 14 pencil beam scanning proton (PBS)] breast cancer patients who received comprehensive nodal irradiation. Employing a model based on organ equivalent dose to account for both inhomogeneous organ dose distributions and non-linear functional dose relationships, we estimated excess absolute risk, excess relative risk, and lifetime attributable risk (LAR) for secondary malignancies. The model uses dose distribution, number of fractions, age at exposure, attained age, the linear-quadratic dose response relationship for cell survival, repopulation factor, as well as gender specific age dependencies, and initial slopes of dose response curves.

RESULTS

The LAR for carcinoma at age 70 was estimated to be up to 3.64% for esophagus with an advantage of 3DCRT over PBS and VMAT. For the ipsilateral lung, risks were lowest for PBS (up to 5.56%), followed by 3DCRT (up to 6.54%) and VMAT (up to 7.7%). For the contralateral lung, there is a clear advantage of 3DCRT and PBS techniques (risk <0.86%) over VMAT (up to 4.4%). The risk for the contralateral breast is negligible for 3DCRT and PBS but was estimated as up to 1.2% for VMAT. Risks for the thyroid are overall negligible. Independently performed comparative treatment plans on 10 patients revealed that the risk for the contralateral lung and breast using VMAT can be more than an order of magnitude higher compared to PBS. Sarcoma risks were estimated as well showing similar trends but were overall lower compared to carcinoma.

CONCLUSION

Conventional (3DCRT) techniques led to the lowest estimated risks of, thyroid and esophageal secondary cancers while PBS demonstrated a benefit for secondary lung and contralateral breast cancer risks, with the highest risks overall associated with VMAT techniques.

Secondary bladder and rectal cancer risk estimates following standard fractionated and moderately hypofractionated VMAT for prostate carcinoma

PURPOSE

To estimate the risk for bladder and rectal cancer induction due to standard fractionated (SF) and moderately hypofractionated (HF) volumetric modulated arc therapy (VMAT) for prostate carcinoma.

METHODS

Twelve patients with low or intermediate-risk of prostate cancer referred for external-beam radiotherapy were included in this study. Three computed tomography-based VMAT plans were created for each study participant. The first plan was generated by assuming patient's irradiation with SF-VMAT (78 Gy in 39 fractions). The second and third plans were created on the basis of two different HF schedules (HF-VMAT₁ : 70 Gy in 30 fractions, HF:VMAT₂ : 60 Gy in 20 fractions). Data from differential dose-volume histograms obtained by the above treatment plans were employed to calculate the organ equivalent dose (OED) of the bladder and rectum with the aid of a nonlinear model accounting for fractionation and proliferation effects. The calculated OED values were used to estimate the average lifetime attributable risk (LAR_av ) for the appearance of radiotherapy-induced secondary bladder and rectal malignancies. The lifetime risk of radiation carcinogenesis was compared with the respective organ-, and age-dependent lifetime intrinsic risk (LIR) of cancer development for unexposed males.

RESULTS

The average OED of the rectum from SF-VMAT, HF-VMAT₁ and HF-VMAT₂ for prostate cancer was 972.0, 900.2, and 815.7 cGy, respectively. The corresponding values for bladder were 73.4, 72.3, and 71.0 cGy. The LAR_av for rectal cancer induction varied from 0.06% to 0.4% by the fractionation schedule used for irradiation and by the age of the patient at the time of treatment. The corresponding risk range related to the development of secondary bladder malignancies was 0.06-0.33%. The SF-VMAT, HF-VMAT₁ and HF-VMAT₂ led to an increase of the lifetime rectal cancer risk with respect to LIR by 2.2-9.8%, 2.0-9.1% and 1.8-8.2%, respectively, depending upon the patient's age. The corresponding elevation for bladder cancer induction was up to 8.0%, 7.9% and 7.7%.

CONCLUSIONS

The use of VMAT for prostate carcinoma leads to a noteworthy increase of the lifetime risk for bladder and rectal cancer induction compared to that of unexposed people irrespective of the patient's age at the time of treatment and the applied fractionation scheme. The cancer risk data presented in this study may be taken into account by radiation oncologists and medical physicists in the selection of the optimal radiation therapy plan.