Interim Analysis of a Non-Randomized Prospective Trial Comparing Hypofractionated Post-Mastectomy Radiotherapy (HF-PMRT) to Conventional Post-Mastectomy Radiotherapy (CF-PMRT) for Breast Cancer (BC) Patients

PURPOSE/OBJECTIVE(S)

The standard of care for treatment for LABC patients who have undergone modified radical mastectomy (MRM) is PMRT. Post-mastectomy RT (PMRT) for LABC patients has been established in three trials to improve locoregional control and overall survival (OS). A published trial from China showed that HF-PMRT was non-inferior to CF-PMRT. This study was conducted to determine if HF-PMRT can provide similar efficacy and toxicity.

MATERIALS/METHODS

A non-randomized prospective trial design was employed to compare HF-PMRT and CF-PMRT in post-MRM BC patients. Patients with pathologically proven BC who underwent MRM without positive margins and with less than 8 positive nodes were included. Informed consent was obtained. Patients decided which treatment they will receive. They received either HF-PMRT of 43.2 Gy in 16 fractions (fx) [2.7 Gy/fx] or CF-PMRT of 50-50.4 Gy in 1.8-2.0 Gy/fx to both chest wall and regional nodes (axillary and supraclavicular) in both regimens. Primary endpoints were 2-year OS and 2-year local recurrence free survival (LRFS). Secondary endpoints include acute and late toxicities. Analysis was done as intention-to treat. An interim analysis of 2-year results is presented.

RESULTS

A total of 37 patients were enrolled in two separate cohorts: a single-arm cohort that recruited 10 HF-PMRT patients from 2014-2015 and a two-arm prospective trial that started recruitment last 2019 and included 12 HF-PMRT and 15 CF-PMRT patients. Median follow-up was 35 months. There were more Stage IIB and Stage III for the CF-PMRT arm [p = 0.040]. Treatment interruptions were more frequent in the CF-PMRT arm (100% vs 68%, p = 0.028). The duration of interruption was also longer in CF-PMRT (median 8 vs 3 days) [p < 0.003]. Acute and late toxicities were not statistically different. There was one patient each with RTOG Grade 2 acute skin toxicity in the HF-PMRT (4.55%) and CF-PMRT arms (6.67%) [p = 0.703]. For late toxicities, the HF-PMRT arm had 6 Grade 1 late skin toxicities and 1 Grade 3 late skin toxicity vs 1 Grade 1 late skin toxicity for CF-PMRT arm [p = 0.196]. 2-year OS rate (86.3% vs 100%, p = 0.403) 2-year DFS rate (68.18% and 73.33%, p = 0.126) were both not statistically different. There were no reported locoregional recurrences (LCR).

CONCLUSION

In terms of local control, both arms have showed no LCRs. 2-year OS and DFS rate were no different. As the study has not yet reached the adequate sample size, the non-inferiority of HF-PMRT cannot be definitively concluded. Acute and late toxicities were no different. There was a significantly higher rate of treatment interruptions in the CF-PMRT compared to the HF-PMRT arm. The results of this interim analysis prove to be promising and patients will continue to be accrued. The final results of this study might have tremendous implications in local practice.

Significance of Hypofractionated Radiotherapy in Postoperative Irradiation for Breast Cancer: An Asian Multi-institutional Prospective Study

AIMS

There is a need for the adequate distribution of healthcare resources in Southeast Asia. Many countries in the region have more patients with advanced breast cancer who are eligible for postmastectomy radiotherapy (PMRT). Therefore, it is critical that hypofractionated PMRT is effective in most of these patients. This study investigated the significance of postoperative hypofractionated radiotherapy in patients with breast cancer, including advanced breast cancer, in these countries.

MATERIALS AND METHODS

Eighteen facilities in 10 Asian countries participated in this prospective, interventional, single-arm study. The study included two independent regimens: hypofractionated whole-breast irradiation (WBI) for patients who had undergone breast-conserving surgery and hypofractionated PMRT for patients who had undergone total mastectomy at a dose of 43.2 Gy in 16 fractions. In the hypofractionated WBI group, patients with high-grade factors received additional 8.1 Gy boost irradiation sessions for the tumour bed in three fractions.

RESULTS

Between February 2013 and October 2019, 227 and 222 patients were enrolled in the hypofractionated WBI and hypofractionated PMRT groups, respectively. The median follow-up periods in the hypofractionated WBI and hypofractionated PMRT groups were 61 and 60 months, respectively. The 5-year locoregional control rates were 98.9% (95% confidence interval 97.4-100.0) and 96.3% (95% confidence interval 93.2-99.4) in the hypofractionated WBI and hypofractionated PMRT groups, respectively. Regarding adverse events, grade 3 acute dermatitis was observed in 2.2% and 4.9% of patients in the hypofractionated WBI and hypofractionated PMRT groups, respectively. However, no other adverse events were observed.

CONCLUSION

Although further follow-up is required, hypofractionated radiotherapy regimens for postoperative patients with breast cancer in East and Southeast Asian countries are effective and safe. In particular, the proven efficacy of hypofractionated PMRT indicates that more patients with advanced breast cancer can receive appropriate care in these countries. Hypofractionated WBI and hypofractionated PMRT are reasonable approaches that can contain cancer care costs in these countries. Long-term observation is required to validate our findings.

Preliminary survey of 3D image-guided brachytherapy for cervical cancer at representative hospitals in Asian countries

3D image-guided brachytherapy (3D-IGBT) has become a standard therapy for cervical cancer. However, the use of 3D-IGBT is limited in East and Southeast Asia. This study aimed to clarify the current usage patterns of 3D-IGBT for cervical cancer in East and Southeast Asia. A questionnaire-based survey was performed in 11 countries within the framework of the Forum for Nuclear Cooperation in Asia. The questionnaire collected the treatment information of patients with cervical cancer who underwent 3D-IGBT. The cumulative external beam radiotherapy and 3D-IGBT doses were summarized and normalized to a biological equivalent dose of 2 Gy per fraction (EQD2) using a linear-quadratic model. Of the 11 institutions representing the participating countries, six (55%) responded to the questionnaire. Overall, data of 36 patients were collected from the six institutions. Twenty-one patients underwent whole-pelvic irradiation and 15 underwent whole-pelvic irradiation with central shielding. Patients received a median of four treatment sessions of 3D-IGBT (range, 2-6). All 3D-IGBT sessions were computed tomography (CT)-based and not magnetic resonance image-based. The median doses to the high-risk clinical target volume D90, bladder D2cc, rectum D2cc and sigmoid colon D2cc were 80.9 Gy EQD2 (range, 58.9-105.9), 77.7 Gy EQD2 (range, 56.9-99.1), 68.0 Gy EQD2 (range, 48.6-90.7) and 62.0 Gy EQD2 (range, 39.6-83.7), respectively. This study elucidated the current patterns of 3D-IGBT for the treatment of cervical cancer in East and Southeast Asia. The results indicate the feasibility of observational studies of CT-based 3D-IGBT for cervical cancer in these countries.

Multicentre dose audit for clinical trials of radiation therapy in Asia

A dose audit of 16 facilities in 11 countries has been performed within the framework of the Forum for Nuclear Cooperation in Asia (FNCA) quality assurance program. The quality of radiation dosimetry varies because of the large variation in radiation therapy among the participating countries. One of the most important aspects of international multicentre clinical trials is uniformity of absolute dose between centres. The National Institute of Radiological Sciences (NIRS) in Japan has conducted a dose audit of participating countries since 2006 by using radiophotoluminescent glass dosimeters (RGDs). RGDs have been successfully applied to a domestic postal dose audit in Japan. The authors used the same audit system to perform a dose audit of the FNCA countries. The average and standard deviation of the relative deviation between the measured and intended dose among 46 beams was 0.4% and 1.5% (k = 1), respectively. This is an excellent level of uniformity for the multicountry data. However, of the 46 beams measured, a single beam exceeded the permitted tolerance level of ±5%. We investigated the cause for this and solved the problem. This event highlights the importance of external audits in radiation therapy.

Irradiation synchronized with respiration gate

A respiratory gating technique was developed for radiotherapy of tumors unable to remain stable due to respiration. Irradiation was started and stopped with a microwave oscillator of a linear accelerator controlled by gating signals at specific points in the respiratory cycle. This technique was tested in a phantom specially designed to simulate a patient with lung cancer and in clinical therapy for lung tumors of seven patients. A mask was used to check ventilation in the phantom and airbags were used to measure thoracoabdominal pressure in patients and in the phantom; this enabled us to detect the excursion of the tumors. Low sensitivity film for verification demonstrated the efficacy of this technique. The gated irradiation was proved to ensure more precise radiotherapy for tumors located close to the diaphragm.