Clinical Investigation
Breast Intensity-Modulated Radiation Therapy Reduces Time Spent With Acute Dermatitis for Women of All Breast Sizes During Radiation

https://doi.org/10.1016/j.ijrobp.2008.08.071Get rights and content

Purpose

To study the time spent with radiation-induced dermatitis during a course of radiation therapy for breast cancer in women treated with conventional or intensity-modulated radiation therapy (IMRT).

Methods and Materials

The study population consisted of 804 consecutive women with early-stage breast cancer treated with breast-conserving surgery and radiation from 2001 to 2006. All patients were treated with whole-breast radiation followed by a boost to the tumor bed. Whole-breast radiation consisted of conventional wedged photon tangents (n = 405) earlier in the study period and mostly of photon IMRT (n = 399) in later years. All patients had acute dermatitis graded each week of treatment.

Results

The breakdown of the cases of maximum acute dermatitis by grade was as follows: 3%, Grade 0; 34%, Grade 1; 61%, Grade 2; and 2%, Grade 3. The breakdown of cases of maximum toxicity by technique was as follows: 48%, Grade 0/1, and 52%, Grade 2/3, for IMRT; and 25%, Grade 0/1, and 75%, Grade 2/3, for conventional radiation therapy (p < 0.0001). The IMRT patients spent 82% of weeks during treatment with Grade 0/1 dermatitis and 18% with Grade 2/3 dermatitis, compared with 29% and 71% of patients, respectively, treated with conventional radiation (p < 0.0001). Furthermore, the time spent with Grade 2/3 toxicity was decreased in IMRT patients with small (p = 0.0015), medium (p < 0.0001), and large (p < 0.0001) breasts.

Conclusions

Breast IMRT is associated with a significant decrease both in the time spent during treatment with Grade 2/3 dermatitis and in the maximum severity of dermatitis compared with that associated with conventional radiation, regardless of breast size.

Introduction

Breast-conserving surgery and radiation therapy are the standard alternatives to mastectomy for eligible patients with Stage 0, I, or II invasive breast cancer 1, 2. Postoperative whole-breast radiation therapy is associated with long-term local control on the order of 85% to 95%, with survival outcomes equivalent to those seen in women who undergo mastectomy 3, 4, 5. Postoperative radiation therapy for invasive breast cancer has also been associated with improved local control 4, 6 and overall survival (7) compared with breast-conserving surgery alone.

Despite this success, there is room for improvement in conventional tangential breast radiation therapy, which is often associated with a greater than 10% dose inhomogeneity across the target volume, which may in turn increase the incidence of acute side effects and negatively impact the long-term cosmesis that is a particular benefit of treatment 8, 9, 10, 11. In particular, the increase in dose inhomogeneity is associated with acute skin toxicity that increases in severity with increasing breast size 9, 12. Acute dermatitis, including moist desquamation of the skin during or within 6 weeks of radiation, is seen in 30% to 50% of women treated with conventional radiation therapy 13, 14. Moist desquamation is associated with decreased quality of life during radiation treatment (14). The dose inhomogeneity associated with conventional radiation, in which the target receives significantly greater doses than the doses prescribed, could also result in an increased incidence of long-term complications. For example, a worse long-term cosmetic outcome and a greater complication rate have been associated with doses greater than 50 Gy or a daily dose per fraction of 2.5 Gy or greater delivered using conventional radiation therapy 15, 16, 17.

Intensity-modulated radiation therapy (IMRT) involves the use of optimized, nonuniform radiation beam intensities to create more conformal dose distributions around the targets of irradiation. The IMRT technique involves many aspects already established as a part of three-dimensional conformal radiation: patient immobilization; definition of target volumes and organs and normal structures in three dimensions by drawing contours on cross-sectional images using CT simulation; optimization of treatment plans based upon isodose coverage of target structures; and multi-leaf collimation. However, IMRT also requires more advanced radiation therapy treatment planning which depends on computer algorithms for inverse dose planning. The IMRT technique also has special physics requirements, including the requirement for new protocols for acceptance testing, commissioning, and rigorous quality assurance. Initial experiences with IMRT for breast cancer have shown that it is associated with improved dose distributions in the treated breast, lower doses delivered to normal heart or lung tissue, a low incidence of acute toxicity, and a reduced incidence of subacute complications such as breast edema and of undesirable cosmetic changes compared with those associated with standard techniques 18, 19, 20, 21, 22, 23, 24, 25.

All of these previous prospective and retrospective studies of breast IMRT have looked at the incidence of acute dermatitis only in terms of maximum grade occurring during a course of radiation therapy. Given that a typical course of adjuvant radiation therapy for breast cancer lasts 6 weeks, the reporting of only the maximally occurring grade of acute dermatitis could obscure large differences in patient experience with that toxicity. For example, although 2 patients may have Grade 2 dermatitis, in 1 patient this may occur only in Week 5 of treatment and in the other patient in Weeks 3 through 6 of treatment. We hypothesized that this difference in the onset and duration of acute toxicity is a more important determinant of quality of life during treatment than whether a patient experiences Grade 2 toxicity at all.

This study is the first, to our knowledge, to analyze the incidence of acute dermatitis separately during each week of a course of radiation therapy for breast cancer. We also examined the respective effects of IMRT and wedged tangential irradiation on both the incidence of radiation dermatitis and the time spent with Grade 2 or greater radiation dermatitis.

Section snippets

Methods and Materials

In this retrospective study, the study population consisted of 804 consecutive women with early-stage breast cancer treated with breast-conserving surgery and radiation therapy from 2001 to 2006. Inclusion criteria were that the patient have Stage 0, I, or II breast cancer as defined by the American Joint Committee on Cancer (26); received radiation therapy at the Fox Chase Cancer Center, and completed radiation therapy. Exclusion criteria included male breast cancer, T3 to T4 disease, Stage IV

Results

Patient characteristics are shown in Table 2. There were 405 patients treated with conventional radiation and 399 patients treated with IMRT. Significant differences were seen between groups in terms of breast size, chest wall separation, tumor stage, treatment energy, use of chemotherapy before radiation, and use and timing of tamoxifen. There were no significant differences in nodal stage, whole-breast dose, or total dose, which consisted of the whole-breast plus boost dose.

In terms of the

Discussion

This study of more than 800 patients treated for breast cancer is unique in assessing the degree of skin toxicity each week during a course of radiation therapy as opposed to only the maximum degree of toxicity. We observed that IMRT reduces the incidence of dermatitis of Grade 2 or greater in women of all breast sizes, which prior studies have also shown. However, we also found that IMRT reduced the absolute number of weeks spent with this degree of acute dermatitis. In particular, women

Acknowledgment

The authors thank Cindy Rosser for her collection and management of the data for the study population.

References (29)

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Abstract presented at the scientific session of the 49th annual meeting of the American Society for Therapeutic Radiology and Oncology in Los Angeles, CA October 28-Novermber 1, 2007.

Conflict of Interest: none.

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