Long Term Cosmetic Outcomes and Toxicities of Proton Compared to Photon 3-D - Conformal Accelerated Partial Breast Irradiation (3-D - APBI)
Reporter: Lauren Hertan
The Abramson Cancer Center of the University of Pennsylvania
Last Modified: October 4, 2013
Presenter: Sigolene Galland
Presenter Affiliation: Massachusetts General Hospital, Boston, MA
- Accelerated partial breast irradiation (APBI) has been used increasingly over the past few years. Benefits include shorter treatment time and decreased radiation dose to surrounding tissues. However, there is the possibility that microscopic cancer elsewhere in the breast would not be treated.
- Research is currently being done comparing APBI to whole breast radiation, however, ASTRO has published consensus guidelines regarding the appropriate use of APBI (Smith et al. Int J Rad Biol Phys 2009).
- The physical properties of proton beam therapy (PBT) make it an appealing modality for accelerated partial breast irradiation
- The primary goal of the study was to evaluate the long-term outcomes in women treated accelerated partial breast irradiation using protons versus photons.
- 98 patients with stage I breast cancer were treated with 3D-APBI, 19 with protons (1-3 fields, with a single field used per treatment) and 79 with photons or mixed photon and electrons (3 or more fields, all beams treated each day).
- The prescribed dose was 32 Gy delivered in 8 twice-daily fractions.
- At each visit, both physician and patient toxicity and satisfaction evaluations were performed.
- The four-point scale for cosmetic scoring and RTOG/EORTC Late Radiation Morbidity systems were used for evaluation of skin, subcutaneous and non-cutaneous toxicities.
- Median follow-up was 82.5 months (range, 2-104 months).
- At 7 years, the overall local control was 94%.
- There was no difference in local control between the two groups, with 3 local recurrences in the group treated with PBT versus 2 treated with photons.
- Physician assessment of cosmetic outcome varied between the two treatment groups, with 94% of photon patients versus 62% of proton patients being rated as good or excellent (p= 0.03).
- However, there was no difference in patient reported outcomes with 96% of photon patients versus 92% of proton patients reporting good or excellent cosmetic outcome.
- The patients treated with PBT had a higher incidence of skin toxicity with telangiectasia 69% for proton and 16% for photon (p = 0.0013), pigmentation change 54% for proton and 22% for photon (p = 0.02) and late skin toxicity 61.5% for proton and 18% for photon (p = 0.029).
- There were no significant differences between the groups in the incidences of breast pain, edema, fibrosis, fat necrosis, skin desquamation, rib pain, or rib fracture.
- Proton 3D-APBI, with a single field used per treatment, provided similar long term clinical outcomes compared to photon 3D-APBI, but led to higher rates of telangiectasia, skin color change and atrophy.
- Further work should be done as to the best way to optimize proton APBI to reduce late toxicity.
- This study was an important first step in comparing photon and proton treatment for APBI.
- Although proton therapy does appear to have theoretical benefit over photon therapy for APBI, this study highlighted the need for further optimization in order to decrease the long-term toxicity.
- One limitation of this study was potentially the difference in skin dose between the two groups. The physical properties of PBT often lead to higher skin doses than with photon therapy. This, combined with the fact the PBT patients were only treated with one field daily, could lead to a significantly higher skin dose in the PBT patients, although this data was not reported.
- Encouragingly, patients reported high satisfaction with their cosmetic outcome regardless of treatment modality, suggesting that they may be less critical than physicians regarding cosmesis.