Dosimetric considerations in treating mediastinal disease with mantle fields: characterization of the dose under mantle blocks

Grid/lattice therapy: consideration of small field dosimetry

Small-field dosimetry used in special procedures such as gamma knife, Cyberknife, Tomotherapy, IMRT, and VMAT has been in evolution after several radiation incidences with very significant (70%) errors due to poor understanding of the dosimetry. IAEA-TRS-483 and AAPM-TG-155 have provided comprehensive information on small-fields dosimetry in terms of code of practice and relative dosimetry. Data for various detectors and conditions have been elaborated. It turns out that with a suitable detectors dose measurement accuracy can be reasonably (±3%) achieved for 6 MV beams for fields >1×1 cm2. For grid therapy, even though the treatment is performed with small fields created by either customized blocks, multileaf collimator (MLC), or specialized devices, it is multiple small fields that creates combined treatment. Hence understanding the dosimetry in collection of holes of small field is a separate challenge that needs to be addressed. It is more critical to understand the scattering conditions from multiple holes that form the treatment grid fields. Scattering changes the beam energy (softer) and hence dosimetry protocol needs to be properly examined for having suitable dosimetric parameters. In lieu of beam parameter unavailability in physical grid devices, MLC-based forward and inverse planning is an alternative path for bulky tumours. Selection of detectors in small field measurement is critical and it is more critical in mixed beams created by scattering condition. Ramification of small field concept used in grid therapy along with major consideration of scattering condition is explored. Even though this review article is focussed mainly for dosimetry for low-energy megavoltage photon beam (6 MV) but similar procedures could be adopted for high energy beams. To eliminate small field issues, lattice therapy with the help of MLC is a preferrable choice.

[Secondary breast cancer after treatment for Hodgkin's disease. About seven cases]

OBJECTIVE

Therapeutic results of Hodgkin disease (HD) have improved by the use of combined radio-chemotherapy. However, this association can increase the risk of on-term effects including secondary cancers. In a retrospective study, we collected secondary breast cancer (BC) in patients previously treated with chemoradiotherapy for Hodgkin disease at Salah-Azaïz institute of Tunis.

PATIENTS AND METHODS

Between 1975 and 2003, seven patients (six women and one man) treated for HD subsequently developed BC. Mean age at diagnosis of HD was 21 years (12-29). The first treatment was combined chemotherapy (MOPP-ABVD) and radiotherapy for all patients. Radiotherapy was delivered with cobalt 60 with large fields. The median dose was 41.3 Gy (2 Gy/fraction in 6 patients and 3.3 Gy in one).

RESULTS

The breast tumours occurred after a median delay of 204 months (132-276). According to the TNM classification, we showed two stage T2, one stage T3, two stage T4b and two stage T4d. The mean clinical size was 47 mm (25-80 mm). All patients had infiltrating carcinoma. Axillary node histological involvement was found in 6 cases. All patients were treated by mastectomy and chemotherapy. Only one patient had a locoregional irradiation. Median survival was 26.5 months (12-48). Four patients died and three are still alive at respectively 24, 31 and 144 months.

DISCUSSION AND CONCLUSION

According to the previous data, breast cancer represents 6.3 to 9% of all second cancers occurring after HD treatment. We conclude that especially young women and girls treated for HD should be carefully monitored. We suggest that secondary BC be sometimes treated by conservative radiosurgical approach.

Evolving role of radiation therapy for hematologic malignancies

Radiation therapy continues to play a paramount role in the therapy of hematologic malignancies, whether as definitive therapy, as consolidation after chemotherapy, as part of bone marrow transplantation protocols, or in palliation. During the past 2 decades, significant advances in radiation therapy have occurred, including the evolution of involved-field irradiation and the adoption of conformal radiation administration. It is hoped that modern techniques will reduce the long-term sequelae associated with radiation-based treatments.

A semiempirical method for the description of off-center ratios at depth from linear accelerators

A semiempirical method for the description of the off-center ratios (OCR) at depth from linear accelerators is presented, which is based on a method originally developed for cobalt-60 (60)Co units. The OCR profile is obtained as the sum of 2 components: the first describes an OCR similar to that from a (60)Co unit, which approximates that resulting from the modification of the original x-ray intensity distribution by the flattening filter; the second takes into account the variable effect of the flattening filter on dose profile for different depths and field sizes, by considering the existence of a block and employing the negative field concept. The above method is formulated in a mathematical expression, where the parameters involved are obtained by fitting to the measured OCRs. Using this method, OCRs for various depths and field sizes, from a Philips SL-20 for the 6 MV x-ray beam and a Siemens Primus 23, for both the 6-MV and 23-MV x-ray beams, were reproduced with good accuracy. Furthermore, OCRs for other fields and depths that were not included in the fitting procedure were calculated using linear interpolation to estimate the values of the parameters. The results indicate that this method can be used to calculate OCR profiles for a wide range of depths and field sizes from a measured set of data and may be used for monitor unit calculations for off-axis points using a standard geometry. It may also be useful as a quality control tool to verify the accuracy of lacking profiles calculated by a treatment planning system.

Breast cancer occurred after treatment for Hodgkin's disease: analysis of 133 cases

PURPOSE

To assess the clinical and histological characteristics of breast cancer (BC) occurring after Hodgkin's disease (HD) and give possible therapies and prevention methods.

MATERIALS AND METHODS

In a retrospective multicentric analysis, 117 women and two men treated for HD subsequently developed 133 BCs. The median age at diagnosis of HD was 24 years. The HD stages were stage I in 25 cases (21%), stage II in 70 cases (59%), stage III in 13 cases (11%), stage IV in six cases (5%) and not specified in five cases (4%). Radiotherapy (RT) was used alone in 74 patients (63%) and combined modalities with chemotherapy (CT) was used in 43 patients (37%).

RESULTS

BC occurred after a median interval of 16 years. TNM classification (UICC, 1978) showed 15 T0 (11.3%), 44 T1 (33.1%), 36 T2 (27.1%), nine T3 (6.7%), 15 T4 (11.3%) and 14 Tx (10.5%). Ductal infiltrating carcinoma and ductal carcinoma in situ (DCIS) represented 81.2 and 11.3% of the cases, respectively. Among the infiltrating carcinoma, the axillary involvement rate was 50%. Seventy-four tumours were treated by mastectomy without (67) or with (ten) RT. Forty-four tumours had lumpectomy without (12) or with (32) RT. Another four received RT alone, and one CT alone. Sixteen patients (12%) developed isolated local recurrence. Thirty-nine patients (31.7%) developed metastases and 34 died; 38 are in complete remission whereas five died of intercurrent disease. The 5-year disease-specific survival rate was 65.1%. The 5-year disease-specific survival rates for the pN0, pN1-3 and pN>3 groups were 91, 66 and 15%, respectively (P<0.0001), and 100, 88, and 64% for the TIS, T1 and T2. For the T3 and T4, the survival rates decreased sharply to 32 and 23%, respectively. These secondary BC are of two types: a large number of aggressive tumours with a very unfavourable prognosis (especially in the case of pN>3 and/or T3T4), and many tumours with a 'slow spreading' such as DCIS and microinvasive lesions. These lesions developed especially in patients treated exclusively by RT.

CONCLUSIONS

The young women and girls treated for HD should be carefully monitored in the long-term by clinical examination, mammography and ultrasonography. We suggest that a baseline mammography is performed 5-8 years after supradiaphragmatic irradiation (complete mantle or involved field) in patients who were treated before 30 years of age. Subsequent mammographies should be performed every 2 years or each year, depending on the characteristics of the breast tissue (e.g. density) and especially in the case of an association with other BC risk factors. This screening seems of importance due to excellent prognosis in our T(1S)T(1) groups, and the possibility of offering these young women a conservative treatment.

[Bilateral breast cancer after Hodgkin disease. Clinical and pathological characteristics and therapeutic possibilities: an analysis of 13 cases]

PURPOSE

Though Hodgkin's disease (HD) is one of the malignancies in which considerable progress has been made, long-term side effects have been observed, second primary cancer being the most significant. Several recent reports have indicated an increased risk of breast cancer (BC) in girls and young women among HD patients.

MATERIALS AND METHODS

In a retrospective multicenter analysis, 63 women treated for HD subsequently developed BC. Results that were obtained in 13 women (21%) who developed either synchronous (five cases) or metachronous (eight cases) BC were analyzed. The median age at diagnosis of HD was 19 years. Seven patients underwent exclusive radiotherapy (RT) (including "mantle" supradiaphragmatic irradiation) and six received concomittant radiation therapy and chemotherapy.

RESULTS

The first breast tumor occurred after a median delay of 16 years. According to the TNM classification, we showed nine stage T0 (non palpable lesions), four stage T1, five stage T2, one stage T3, two stage T4 and five stage Tx BC. Seventeen infiltrating carcinomas, two fibrosarcomas and seven ductal carcinomas in situ were observed. Among 15 axillary dissections performed for invasive carcinomas, histological involvement was found in 10 cases. Seventeen tumors were treated by mastectomy and nine patients underwent conservative surgical treatment. With a 70-month median follow-up (range: 15-125), three patients developed locoregional recurrence and four other metastases. At present, eight are alive with no evidence of disease and one died of intercurrent disease.

CONCLUSION

According to previous works, BC represents 6.3 to 9% of all second cancers occurring after HD treatment. The risk is higher in young women treated before 20 years of age, especially before 15 years of age. Factors that favour the development of secondary BC are: supradiaphragmatic irradiation, very young age at treatment, chemotherapy with alkylating agents, and probably genetic factors. We conclude that young women and girls treated for HD should be carefully monitored at least 10 years after the end of the treatment for HD, using clinical examination, mammography and ultrasonography. The optimal rythm of this follow-up is not yet clearly defined. Moreover, after multidisciplinary concertation, we suggest that secondary BC be sometimes treated by conservative radiosurgical approach.

Breast cancer in patients treated for Hodgkin's disease: clinical and pathological analysis of 76 cases in 63 patients

In a retrospective multicentric analysis, 63 women treated between 1941 to 1988 for Hodgkin's disease (HD) subsequently developed 76 breast cancers (BC). The median age at diagnosis of HD was 26 years (range 7-67), and 22 women (35%) were 20 years old or less. Exclusive radiotherapy (RT) was used in 36 women (57%) and combined modalities with chemotherapy (CT) in 25 (39%). Breast cancer occurred after a median interval of 16 years (range 2-40) and the median age at diagnosis of the first BC was 42 years (range 25-73). TNM classification (UICC, 1978) showed 10 T0 (non-palpable lesions) (13%), 20 T1 (26%), 22 T2 (29%), 8 T3 (11%), 7 T4 (9%) and 9 Tx (12%), giving altogether a total of 76 tumours, including, respectively, 5 and 8 bilateral synchronous and metachronous lesions. Among the 68 tumours initially discovered, 53 ductal infiltrating, one lobular infiltrating and two medullary carcinomas were found. Moreover, two fibrosarcomas and 10 ductal carcinoma in situ (DCIS) were also found. Among 50 axillary dissections for invasive carcinomas, histological involvement was found in 31 cases (62%). 45 tumours were treated by mastectomy, without (n = 35) or with (n = 10) RT. 27 tumours had lumpectomy, without (n = 7) or with RT (n = 20). 2 others received RT only, and one only CT. 7 patients (11%) developed isolated local recurrence. 20 patients (32%) developed metastases and all died; 38 are in complete remission, whereas 5 died of intercurrent disease. The 5-year disease-specific survival rate by the Kaplan-Meier method was 61%. The 5-year disease-specific survival rate for pN0, pN1-3 and pN > or = 3 groups were 91%, 66% and 0%, respectively (P < 0.0001) and 100%, 88%, 64% and 23% for the T0, T1, T2 and T3T4 groups, respectively. These secondary BCs seem to be of two types: a large number of aggressive tumours with a very unfavourable prognosis (especially in the case of pN > 3 and/or T3T4); and many tumours with a 'slow development' such as DCIS and microinvasive lesions, especially in patients treated exclusively by RT. Moreover, a very unusual rate of bilateral tumours (21%) was observed. These secondary BC could be 'in field', in 'border of field' or 'out of field'. However, a complete analysis of doses delivered by supradiaphragmatic irradiation was often very difficult, due to large variations in several parameters. We conclude that young women and girls treated for HD should be carefully monitored by clinical examination, mammography and ultrasonography.