Beam Focal Spot Offset Determination for Linear Accelerators: A Phantom less Method

The effectiveness of radiotherapy treatment is influenced by the position of beam focal spot; therefore, it is important to verify the beam focal spot periodically. In this study the beam focal spot offset is measured using an electronic portal imaging (EPID) based technique and co- rotational penumbra modulation technique(CPM).

MATERIALS AND METHODS

This method utilizes one set of jaws and the multileaf collimator (MLC) to form a symmetric field and then a 180o collimator rotation was utilized to determine the radiation isocenter defined by the jaws and the MLC, respectively. The difference between these two isocentres is then directly correlated with the beam focal spot offset of the linear accelerator. In the current study, the method has been used for Varian ClinaciX and Elekta Versa HD linear accelerators. Since an Elektalinac with the Agility® head does not have two set of jaws, a modified method that making use of one set of diaphragms, the MLC and a full 360o collimator rotation is implemented.

RESULT

The method is validated against CPM and found to be in agreement within 0.00923± 0.009360 mm ( SD) also the method has been found to be reproducible to within 0.0365 mm (SD).

CONCLUSION

The method could be used for routine quality assurance (QA) to ensure that the beam focal spot offset is in tolerance.

Radiotherapy for Pediatric Malignancies: An Experience from a Tertiary Cancer Centre

Background: Incidences of pediatric malignancies are increasing. In management of various childhood malignancies like hematological, bone and soft tissue tumors radiotherapy plays a crucial role. RT treatment planning and delivery poses a challenge to clinicians. Hence with this study we wanted to know the radiotherapy practices in our institution. Materials and Methods: This was a retrospective study analyzing case records and RT charts of all pediatric malignancies who received radiation treatment for a period of 3 years from January 2018 to December 2021. Demographic details, RT details, toxicity details were carefully recorded. Results: Details of 73 pediatric malignancy cases who received RT were analyzed. Median age was 10 years and the majority were males (66%). Commonest malignancies which received RT treatment were ALL (30%), Brain tumors (26%) and bone and soft tissue tumors (22%). Radiotherapy was given as a part of radical intent treatment including neo adjuvant, definitive, adjuvant and prophylactic in 92% of patients. Conformal RT techniques in the form of 3DCRT and VMAT were used in majority (91%) cases. A significant proportion (27%) of cases required anesthesia for RT treatment delivery. 16% of patients had treatment break and common reasons for treatment break being infections (COVID, respiratory) and neutropenia. Grade 3 or more acute toxicities were observed in 14% of patients and hematological toxicity was the most frequent. Conclusion: Hematological and bone & soft tissue tumors are the most common pediatric malignancies requiring RT as a part of multimodality treatment. For RT treatment delivery anesthesia services may be required in pediatric malignancies. Acute Grade 3 or more toxicities and treatment breaks are a concern and these pediatric cases require a properly coordinated supportive care during treatment.

Volumetric Estimation of Lung Dose and Its Association with Pneumonitis Following Radiotherapy in Breast Cancer Patients

Introduction: Lung is a major organ at risk during Post Mastectomy RadioTherapy (PMRT), because of the risk of Radiation Pneumonitis (RP). In countries like India 2D RT is widely used due to limited access to advanced technologies. We estimated the lung dose volumetrically in breast cancer patients treated with 2D tangential techniques, the incidence of acute RP and its association with lung dose. Methodology: Retrospective study of patients who underwent PMRT was done. The images with structure sets of cases planned using 2D technique were transferred to TPS and 3 D plans were generated. CLD, MLD, LL were measured from the 2D plan in the CT simulator. LDmean and V20 were measured from from DVH, in the TPS. Correlation between V20 and LDmean was done with CLD, MLD and LL. The incidence of radiation pneumonitis and its association with lung dose also was studied. Result: Total 50 patients were analyzed of which 3 patients had radiation pneumonitis. The mean CLD was 2.28 cm ± 0.54cm, MLD was 2.32 ± 0.6cm and LL was 12.52 ±2cm. V20 for two fields (MT+LT) was 17.04 ± 5.6 Gy and for three field (MT,LT and SCF) was 28.75 ± 8.6 Gy. Positive correlation was found between for V20 & LDmean and CLD, MLD & LL (p<0.05) 6% of patients developed Radiation pneumonitis but did not have association with V20 or MLD. Conclusion: Radiation pneumonitis is major concern after chest wall irradiation and the incidence is expected to be high with conventional technique where the volume is not accurately measured. It is still an option in countries like India with resource constraints by planning cautiously with the indicators of irradiated lung, like CLD and MLD within limits thus minimizing the incidence of radiation induced lung injury.    

A Study on Set Up Variations During Treatment, and Assessment of Adequacy of Current CTV-PTV Margins in Head and Neck Radiotherapy

Introduction: 3DCRT and IMRT demands high accuracy in patient positioning and accurate and faithful reproducibility of the treatment position right from the day of acquisition of planning scans and throughout the entire duration of radiation treatment delivery. Inadequacies in the accurate reproduction of the treatment positions during each fraction can lead to setup variations which can significantly compromise the ultimate precision of idealized treatment delivery. Materials and methodology: We retrospectively analysed the daily setup variations in patients with head and neck malignancies who received radical or adjuvant radiotherapy from January 2018 to June 2018. A CTV-PTV margin of 0.5 cm is used at our centre. The average displacement from the reference treatment position in lateral, longitudinal and vertical directions were calculated based on CBCT shifts recorded during the entire course of treatment. Results: 101 patients were included in the study (45.54% radical radiotherapy and 54.45% postoperative radiotherapy). The mean shift in any direction was between 0.13 cm and 0.19 cm in the study population as a whole, in radically treated patients and postoperative patients. The shift in any direction of more than 0.5 cm occurred only once or twice during the entire treatment period per patient, except one postoperative patient. The frequency of shift was more in postoperative patients. The mean shifts in the lateral and longitudinal directions were significantly more for postoperative patients (p 0.008 and 0.014 respectively). Conclusions: The CTV to PTV expansion margin used at our institute is adequate for radically treated patients with head and neck cancers both in definitive and postoperative settings. The smaller mean shifts (<2mm) and low frequency of shifts points to the potential for reducing the current CTV to PTV expansion, which needs to be validated in larger studies.

CT and MRI Based Gross Tumor Volume Comparison in Pharyngeal and Laryngeal Carcinoma

Background: Different other imaging modalities help in accurate gross tumor volume delineation. Studies have shown conflicting results for intermodality GTV comparison. Since in our institute we routinely take planning CT and planning MRI for laryngeal and pharyngeal tumors treated with definitive radiotherapy, with this study we intent to compare the gross tumor volume (GTV) with these modalities in these tumors. Materials & Methods: Study population included pharyngeal and laryngeal carcinoma patients treated. Planning CT and planning MRI images of these patients were retrieved. Gross tumor volume (GTV) was delineated by a Radiation Oncologist in both these image sets and GTVs were documented. Results: Out of 87 patients analysed, the overall median GTV with planning CT and planning MRI were 20.4 cc & 18.2 cc respectively. Median GTV with planning CT & MRI for different sites like Nasopharynx, Oropharynx, Larynx and Hypopharynx were 32.85 & 27.75 cc, 22.1 & 20.9 cc, 8.25 & 10.35cc and 20.55 & 20.6 cc respectively with no statistically significant difference. Median GTVs with CT & MRI for different primary tumor stages like T2, T3, T4a, T4b were 14.3 & 14.3 cc, 20.45 & 19 cc, 16.55 & 27.45 cc and 50.75 & 52.4 cc respectively. Analysis showed 94.6 % correlation between GTVs with CT & MRI. Conclusion: This study showed comparable median GTVs with planning CT & MRI for pharyngeal and laryngeal carcinomas. Subset analysis did not show any significant difference in GTVs with two modalities for different primary tumor site. As expected there was good correlation between GTVs of two modalities. Even though the results does not show significant intermodality variation for GTV delineation. With the results of this study we cannot question the use of multiple modalities for GTV delineation as subtle variation in GTV can result in differences in target volumes resulting in differences in toxicity profile.

Patterns of Failure in Node Positive Cervical Cancer Patients Treated with Radical Radiotherapy

Background: Chemoradiation plays an important role in cervical cancer treatment but dose to organs at risk (OAR) is the limitation while escalating dose to target. With conformal techniques dose escalation is made possible without increase in toxicities. Though node positive cervical cancers have poorer prognosis delivering higher dose to the involved nodes have shown benefit. We aim to determine the patterns of failure in node positive cervical cancer patients treated with chemoradiation and to determine the grade III and IV toxicities associated with it.Methods and Materials: In this retrospective study node positive cervical cancer patients treated with conformal radiotherapy were analysed. 45 Gy -50.4 Gy was given to the pelvis and 55 Gy to positive nodes with sequential or simultaneous integrated boost (SIB) in 25 -28 fractions with weekly cisplatin 40mg/m2 followed by brachy therapy. Extended fields were used to treat patients with positive para aortic lymph nodes. Treatment toxicities were recorded as per CTCAE version 4.3. Results: Of the 62 patients 87.1% had squamous cell carcinoma and majority were in stage II (38.7%). At a median follow up of 33 months two (3.2%) patients had local recurrence, eight (12.9 %) had distant failure and one (1.6%) had loco regional recurrence. Lung was the most common site of metastasis followed by the supraclavicular region. The 3 year overall and disease free survival were 91.4 % and 77.2 % respectively. Stage of the disease (p=0.001) and residue at the end of therapy (p-0.010) showed significant association with DFS but not with OS. 21 (33%) had Grade III –IV toxicities, nine (13%) having acute toxicities and 12 (19.4%) had late toxicities. Conclusion: Though node positive cervical cancers have poor prognosis our study showed that aggressive management improves the outcome without increase in toxicities.

Clinical Outcomes of Head and Neck Cancer Patients Treated with Palliative Oral Metronomic Chemotherapy at a Tertiary Cancer Center in Kerala, India

BACKGROUND

Cetuximab-based chemotherapy is the standard palliative chemotherapy in head and neck cancers, but there is a limitation due to financial and logistic reasons, and where oral metronomic chemotherapy can be a successful alternate. Oral metronomic chemotherapy (MCT) can either be with Methotrexate alone or a combination of Methotrexate and Erlotinib. The study was aimed to assess the clinical outcome of oral MCT in head and neck cancer patients.

MATERIALS AND METHODS

This was a retrospective review done at a tertiary cancer centre in India. The clinical outcomes of head and neck cancers patients started on palliative oral MCT from 1st August 2016 to 31st December 2017 were analyzed. The demographic details, toxicity profiles, response to MCT, disease progression status were analyzed. Univariate analysis was done to assess the factors associated with disease progression. Kaplan Meier curve was used for estimating progression free survival (PFS).

RESULTS

Of the total 104 patients, the most common primary site of head and neck cancer was oral cavity (52%). MCT scheduled with Methotrexate and Erlotinib in 80 patients. Toxicity rate was 61%, with Grade 3-4 toxicity in 21%. Response rate was 56% and clinically meaningful response rate was 69%. Disease progression was observed in 55% patients. Median PFS rate was 134 Days. Oral MCT was permanently stopped in 73%, the most common reason being disease progression.

DISCUSSION

Patients who underwent palliative oral MCT had a median PFS of 134 days which is considered as promising treatment method. Results confirmed more than 50% response rate with lower Grade 3-4 toxicities.

CONCLUSION

Palliative oral MCT either with Methotrexate and Erlotinib or Methotrexate alone will be a feasible treatment option in patients with head and neck cancers treated with palliative intent.

Late toxicities among laryngopharyngeal cancers patients treated with different schedules of concurrent chemoradiation at a rural tertiary cancer care center

Background:

Concurrent chemoradiation is the treatment of choice for laryngeal-pharyngeal cancers. Apart from survival organ preservation remains major aims of the treatment. Advanced radiation techniques like VMAT have shown to reduce morbidity. The purpose of our study is to assess the late toxicities in patients treated with concurrent chemoradiation and its association with dose to organs at risk.

Aims:

Assessment of late toxicities following concurrent chemoradiation in patients with laryngopharyngeal cancers.

Materials and Methods:

Retrospective study at a tertiary cancer centre on patients with laryngeal and pharyngeal cancers treated with concurrent chemoradiation with VMAT upto a total dose of 69.3 -70 Gy in 33-35 fractions and concurrent chemotherapy with Cisplatin was done. Severe late toxicities and its association with demographic and clinical parameters and dose to OAR were studied. Data was analysed using EpiData analysis v2.2.2.182.

Results:

Of the 93 patients studied majority were males above 55 years. Oropharynx was the commonest site (58%) with T3 and N2 in majority. Late dysphagia and odynophagia was seen in 18(21%) and 23(27%) patients respectively. 16 (17%) had tube dependence and nine (9.6%) had aspiration pneumonia. D60, V50 and V60 along with site, node positivity and weight loss were found to be significantly associated with severe late toxicity.

Conclusion:

Oropharyngeal cancers, node positivity and weight loss were found to have significant grade III and above toxicities including tube dependency. Dose to larynx showed association with severe late toxicities, though dose to constrictors could not.

Improved survival among oral cancer patients: findings from a retrospective study at a tertiary care cancer centre in rural Kerala, India

BACKGROUND

Oral cancer is very common in India. The reported 5-year survival of such patients is around 50% after treatment with surgery and radiotherapy, much lower than most of the developed countries.

METHODS

A retrospective study of a prospective database of oral cancer patients undergoing surgery from June 2009 to June 2013 was conducted. Follow-up details were updated from case records and by phone calls. Data were double entered in EpiData Entry version 3.1 and were analysed using EpiData Analysis software 2.1.0.73.

RESULTS

Two-hundred and twenty patients were analysed (136 males); 85% were consuming tobacco, mainly in chewable form. The majority (51.1%) had tongue cancer, of whom 75 patients (34.1%) had T4 tumours. Postoperative radiotherapy was given to 108 patients (49.1%). Forty had recurrence, of which 23 were in early stage. Of these, 19 showed node positivity (p < 0.01). Node-negative patients had 79% 5-year survival while node positive had 59% which is comparable to that reported in developed countries. Median disease-free survival duration was 48.2 months.

CONCLUSIONS

Node positivity is the single factor affecting recurrence and survival. The overall survival and disease-free survival is better in patients without lymph node involvement and in patients with early stage of cancer as compared to the patients with node involvement and in advanced stages.

En Bloc Resection with Partial Sacrectomy Helps to Achieve R0 Resection in Locally Advanced Rectal Cancer, Experience from a Tertiary Cancer Center

Partial sacrectomy is a radical procedure that benefits a select group of patients with locally advanced primary or recurrent rectal cancer with posterior extension and carries potential for significant morbidity. This study was done to evaluate the morbidity and oncological outcome of patients who underwent partial sacral resection for rectal cancer in a tertiary cancer center. Seventeen patients underwent partial sacrectomy during the period from 2011 to 2015. Eleven patients had primary and six had recurrent rectal cancer. All patients were evaluated with MRI pelvis and metastatic evaluation with CT scan of the chest and abdomen and PET scan in patients with recurrent cancer. All patients had resection below the level of S2/S3 junction or lower. Three patients were females and the remaining were males. Median age was 56 years. Overall morbidity was 76% and most common morbidity was wound related. The mean estimated relapse-free survival (RFS) for patients treated for primary rectal cancer was 20.3 months (95% confidence interval (CI), 12.8-27.9) and the mean estimated overall survival (OS) 23.9 months. Estimated mean RFS for patients who were operated for recurrent rectal cancer was 25.6 months (95% CI, 17.7-33.5) and the median RFS was yet to reach. Estimated mean OS was 29.7 months (95% CI, 15.5-43.8) and the median OS was 39.6 months. Partial sacrectomy below the level of S2/S3 junction is a safe approach to facilitate en bloc resection of locally advanced primary and recurrent rectal cancer extending posteriorly with loss of plane with sacrum. In selected patients, this approach can improve survival at the cost of high morbidity.

Does the use of induction chemotherapy in oral cavity cancer compromise subsequent loco-regional treatment delivery: Results from a matched pair analysis

BACKGROUND

Neoadjuvant chemotherapy is being increasingly used in patients with unresectable oral cavity cancers to make them resectable. However, its impact on locoregional treatment delivery in such setting remains poorly studied.

AIMS

To evaluate the impact of neoadjuvant chemotherapy on delivery of further locoregional treatment.

SETTINGS AND DESIGN

Mono institutional retrospective audit of patients with oral cavity squamous cell cancers treated with neoadjuvant triplet chemotherapy in India.

MATERIALS AND METHODS

Patients receiving neoadjuvant chemotherapy (n = 14) from May 2012 to April 2014 were matched 1:2 to patients undergoing upfront surgery (n = 28) based on age (>60 or 60 and less), gender (male or female) and subsite site (tongue and floor of mouth or buccoalveolar complex). Data regarding factors related to the delivery of locoregional treatment and toxicities were compiled.

STATISTICAL ANALYSIS

Descriptive analysis in the form of median (range) for continuous variables and frequencies for categorical variables.

RESULTS

Patients undergoing neoadjuvant chemotherapy required more extensive resections and had greater operative time (460 vs. 415 min, P < 0.001). A greater incidence of locoregional wound complications was seen as a consequence (57.1% vs. 14.3%, P, 0.01). However, toxicities during radiotherapy were not substantially different between the two groups and compliance to radiation was also similar. Total package time of 100 days or less, was maintained in 90% of patients in both groups.

CONCLUSIONS

Delivery of neoadjuvant chemotherapy does not impair the ability to deliver locoregional treatment.

Locoregional recurrences after post-operative volumetric modulated arc radiotherapy (VMAT) in oral cavity cancers in a resource constrained setting: experience and lessons learned

OBJECTIVE

The conformal nature of dose distribution produced by volumetric modulated arc radiotherapy (VMAT) increases the risk of geographic miss. Data regarding patterns of failure after VMAT in oral cavity cancers in resource-constrained settings are scarce. The aim of the present study was to ascertain the patterns of failure in patients receiving adjuvant VMAT intensity-modulated radiotherapy (IMRT) for oral cavity cancer in Malabar Cancer Center, Kerala, India.

METHODS

Data of patients with oral cavity cancer receiving adjuvant VMAT IMRT between April 2012 and March 2014 were collected. Recurrent volumes were delineated on the treatment planning images and classified as defined by Dawson et al (Dawson LA, Anzai Y, Marsh L, Martel MK, Paulino A, Ship JA, et al. Patterns of local-regional recurrence following parotid-sparing conformal and segmental intensity-modulated radiotherapy for head and neck cancer. Int J Radiat Oncol Biol Phys 2000; 46: 1117-26).

RESULTS

75 patients with a median follow-up of 24 months were analysed. 41 (55%) patients had oral tongue cancers and 52 (69%) of the patients had Stage IVA cancers. The 2-year locoregional recurrence-free survival, disease-free survival and overall survival were 88.9%, 82.1% and 80.5%, respectively. With a median time to failure of 6.5 months, five infield and three outfield failures were identified.

CONCLUSION

A relatively low rate of outfield failure and lack of marginal failure attests to the efficacy of VMAT in such patients. Modifications to our existing target delineation policy have been proposed.

ADVANCES IN KNOWLEDGE

The use of standardized target delineation methods allows safe use of VMAT IMRT even in resource-constrained settings.