Comparative analysis of simultaneous integrated boost and sequential boost radiotherapy in node-positive cervical cancer: dosimetric and radiobiological considerations

For locally advanced cervical cancer, the standard therapeutic approach involves concomitant chemoradiation therapy, supplemented by a brachytherapy boost. Moreover, an external beam radiotherapy (RT) boost should be considered for treating gross lymph node (LN) volumes. Two boost approaches exist with Volumetric Intensity Modulated Arc Therapy (VMAT): Sequential (SEQ) and Simultaneous Integrated Boost (SIB). This study undertakes a comprehensive dosimetric and radiobiological comparison between these two boost strategies. The study encompassed ten patients who underwent RT for cervical cancer with node-positive disease. Two sets of treatment plans were generated for each patient: SIB-VMAT and SEQ-VMAT. Dosimetric as well as radiobiological parameters including tumour control probability (TCP) and normal tissue complication probability (NTCP) were compared. Both techniques were analyzed for two different levels of LN involvement - only pelvic LNs and pelvic with para-aortic LNs. Statistical analysis was performed using SPSS software version 25.0. SIB-VMAT exhibited superior target coverage, yielding improved doses to the planning target volume (PTV) and gross tumour volume (GTV). Notably, SIB-VMAT plans displayed markedly superior dose conformity. While SEQ-VMAT displayed favorable organ sparing for femoral heads, SIB-VMAT appeared as the more efficient approach for mitigating bladder and bowel doses. TCP was significantly higher with SIB-VMAT, suggesting a higher likelihood of successful tumour control. Conversely, no statistically significant difference in NTCP was observed between the two techniques. This study's findings underscore the advantages of SIB-VMAT over SEQ-VMAT in terms of improved target coverage, dose conformity, and tumour control probability. In particular, SIB-VMAT demonstrated potential benefits for cases involving para-aortic nodes. It is concluded that SIB-VMAT should be the preferred approach in all cases of locally advanced cervical cancer.

Comparative analysis of toxicity in patients with anal cancer undergoing definitive simultaneous integrated boost (SIB) or sequential integrated boost (SeqB) radiotherapy

PURPOSE

To compare toxicity of radiotherapy (RT) with concomitant chemotherapy (CHT) in patients (pts) with anal cancer treated with simultaneous integrated boost (SIB) versus sequential boost (SeqB).

METHODS

Sixty-six patients were treated from 2007 to 2021. Thirty patients underwent to SeqB concurrent to CHT and 37 to SIB-group. Toxicity assessment has been considered in acute and in late toxicities for gastrointestinal (GI), genitourinary (GU), cutaneous (CU) districts, according to Common Terminology Criteria for Adverse Events (CTCAE), Version 5.0. The Wexner scale among summary scoring systems has been used as a tool to measure fecal incontinence. The chi-square test for ordinal variables were used to evaluate the association between patient and treatment characteristics and acute or late severe toxicity. Univariable logistic regression models were fit to evaluate predictive factors associated with fecal incontinence.

RESULTS

Median follow-up was 61.5 months (IQR, 27.1-121.7 months) for all patients. Severe acute toxicity (≥ G2) was observed in 49 patients (74.2%). Late toxicity (≥ G2) occurred in 13 cases (19.6%). In assessment of cutaneous toxicity, there was also a significant reduction in ≥ G1 in SIB group with 29 patients (80.5%) vs SeqB group with 29 patients (96.6%) (p-value = 0.046). Of both groups 11 patients (16.6%) developed fecal incontinence, 8 (22%) in the SIB group and 3 (10%) in the SeqB.

CONCLUSION

SIB for anal cancer treatment results in reduced acute and late cutaneous toxicity compared to SeqB. According to our results the rate of other acute and late toxicities are low and comparable between the two groups.

Dosimetric benefits of 3D-printed modulated electron bolus following lumpectomy and whole-breast radiotherapy for left breast cancer

Radiotherapy with electrons is commonly applied to the tumor bed after whole-breast radiotherapy following breast conservation surgery for breast cancer patients. However, the radiation dose to adjacent organs-at-risk (OARs) and conformity of planning target volume (PTV) cannot be optimized. In this study, we examine the feasibility of using modulated electron bolus (MEB) to improve PTV conformity and reduce the dose to these OARs. Twenty-seven patients with left breast cancer were retrospectively selected in this study. For each patient, a tangential photon plan in RayStation treatment planning system with prescription of 26 Gy in 5 fractions was created as base plan. Two electron plans, one without bolus and one with MEB using Adaptiiv software based on the PTV were created. Various dosimetric parameters of OARs including left lung, heart, left anterior descending artery (LAD) and ribs and the conformity indices of PTV of these 2 electron plans together with the base plans were compared. Statistically significant decreases in the dosimetric parameters (V_5Gy, V_10Gy, V_20Gy, and mean dose) of the ipsilateral left lung and the heart were observed with MEB. The median maximum dose to the LAD and the ribs decreased by 6.2% and 4.5% respectively. The median conformity index was improved by 14.3% with median increases of monitor units by 1.7%. Our results show that MEB is feasible resulting in reduction of doses to the predefined OARs and an improved conformity of PTV. By using 3D printing, MEB might be considered as an alternative to conventional electron boost.

Comparing simultaneous integrated boost vs sequential boost in anal cancer patients: results of a retrospective observational study

Background

To evaluate clinical outcomes of simultaneous integrated boost (SIB) - intensity modulated radiotherapy (RT) in patients with non metastatic anal cancer compared to those of a set of patients treated with 3-dimensional conformal RT and sequential boost (SeqB).

Methods

A retrospective cohort of 190 anal cancer patients treated at 3 academic centers with concurrent chemo-RT employing either SIB or SeqB was analysed. The SIB-group consisted of 87 patients, treated with 2 cycles of Mitomycin (MMC) and 5-Fluorouracil (5FU) using SIB-IMRT delivering 42-45Gy/28–30 fractions to the elective pelvic lymph nodes and 50.4-54Gy/28-30fractions to the primary tumor and involved nodes, based on pre-treatment staging. The SeqB group comprised 103 patients, treated with MMC associated to either 5FU or Capecitabine concurrent to RT with 36 Gy/20 fractions to a single volume including gross tumor, clinical nodes and elective nodal volumes and a SeqB to primary tumor and involved nodes of 23.4 Gy/13 fractions. We compared colostomy-free survival (CFS), overall survival (OS) and the cumulative incidence of colostomy for each radiation modality. Cox proportional-hazards model addressed factors influencing OS and CFS.

Results

Median follow up was 34 (range 9–102) and 31 months (range 2–101) in the SIB and SeqB groups. The 1- and 2-year cumulative incidences of colostomy were 8.2% (95%CI:3.6–15.2) and 15.0% (95%CI:8.1–23.9) in the SIB group and 13.9% (95%CI: 7.8–21.8) and 18.1% (95%CI:10.8–27.0) in the SeqB group. Two-year CFS and OS were 78.1% (95%CI:67.0–85.8) and 87.5% (95%CI:77.3–93.3) in the SIB group and 73.5% (95%CI:62.6–81.7) and 85.4% (95%CI:75.5–91.6) in the SeqB, respectively. A Cox proportional hazards regression model highlighted an adjusted hazard ratio (AdjHR) of 1.18 (95%CI: 0.67–2.09;p = 0.560), although AdjHR for the first 24 months was 0.95 (95%CI: 0.49–1.84;p = 0.877) for the SIB approach.

Conclusions

SIB-based RT provides similar clinical outcomes compared to SeqB-based in the treatment of patients affected with non metastatic anal cancer.

A comparative analysis between sequential boost and integrated boost intensity-modulated radiation therapy with concurrent chemotherapy for locally-advanced head and neck cancer

BACKGROUND

Planning and delivery of IMRT for locally advanced head and neck cancer (LAHNC) can be performed using sequential boost or simultaneous integrated boost (SIB). Whether these techniques differ in treatment-related outcomes including survival and acute and late toxicities remain largely unexplored.

METHODS

We performed a single institutional retrospective matched cohort analysis on patients with LAHNC treated with definitive chemoradiotherapy to 69.3 Gy in 33 fractions. Treatment was delivered via sequential boost (n = 68) or SIB (n = 141). Contours, plan evaluation, and toxicity assessment were performed by a single experienced physician. Toxicities were graded weekly during treatment and at 3-month follow up intervals. Recurrence-free survival, disease-free survival, and overall survival were estimated via Kaplan-Meier statistical method.

RESULTS

At 4 years, the estimated overall survival was 69.3% in the sequential boost cohort and 76.8% in the SIB cohort (p = 0.13). Disease-free survival was 63 and 69% respectively (p = 0.27). There were no significant differences in local, regional or distant recurrence-free survival. There were no significant differences in weight loss (p = 0.291), gastrostomy tube placement (p = 0.494), or duration of gastrostomy tube dependence (p = 0.465). Rates of acute grade 3 or 4 dysphagia (82% vs 55%) and dermatitis (78% vs 58%) were significantly higher in the SIB group (p < 0.001 and p = 0.012 respectively). Moreover, a greater percentage of the SIB cohort did not receive the prescribed dose due to acute toxicity (7% versus 0, p = 0.028).

CONCLUSIONS

There were no differences in disease related outcomes between the two treatment delivery approaches. A higher rate of grade 3 and 4 radiation dermatitis and dysphagia were observed in the SIB group, however this did not translate into differences in late toxicity. Additional investigation is necessary to further evaluate the acute toxicity differences.

Simultaneous integrated vs. sequential boost in VMAT radiotherapy of high-grade gliomas

BACKGROUND

In 20 patients with high-grade gliomas, we compared two methods of planning for volumetric-modulated arc therapy (VMAT): simultaneous integrated boost (SIB) vs. sequential boost (SEB). The investigation focused on the analysis of dose distributions in the target volumes and the organs at risk (OARs).

METHOD

After contouring the target volumes [planning target volumes (PTVs) and boost volumes (BVs)] and OARs, SIB planning and SEB planning were performed. The SEB method consisted of two plans: in the first plan the PTV received 50 Gy in 25 fractions with a 2-Gy dose per fraction. In the second plan the BV received 10 Gy in 5 fractions with a dose per fraction of 2 Gy. The doses of both plans were summed up to show the total doses delivered. In the SIB method the PTV received 54 Gy in 30 fractions with a dose per fraction of 1.8 Gy, while the BV received 60 Gy in the same fraction number but with a dose per fraction of 2 Gy.

RESULTS

All of the OARs showed higher doses (Dmax and Dmean) in the SEB method when compared with the SIB technique. The differences between the two methods were statistically significant in almost all of the OARs. Analysing the total doses of the target volumes we found dose distributions with similar homogeneities and comparable total doses.

CONCLUSION

Our analysis shows that the SIB method offers advantages over the SEB method in terms of sparing OARs.